5 Chapter 5: Nutritional Requirements – General Information

Tracy Everitt; Brittany Yantha; and Megan Davies

Introduction

This chapter provides an in-depth review of the micronutrients necessary during lifespan development to give students a better understanding of how micronutrient needs change as a person ages. The following chapter, Aging Information, provides a more specific look at the changing nutrient requirements in older age. This chapter is meant to give students a refresher of HNU 351 Nutrition Assessment and summarizes this information for those who did not take this class 

5.1 Fat-Soluble Vitamins

Learning Objectives

  • Explore the functions and dietary sources of fat-soluble vitamins.
  • Describe the risks associated with deficiencies and excesses of fat-soluble vitamins.

Vitamin A

Vitamin A is a generic term for a group of similar compounds called retinoids. Retinol is the form of Vitamin A found in animal-derived foods and is converted in the body to the biologically active forms of Vitamin A: retinal and retinoic acid (thus, retinol is sometimes referred to as “preformed Vitamin A”). About 10% of plant-derived carotenoids, including beta-carotene, can be converted in the body to retinoids and are another source of functional Vitamin A. Carotenoids are pigments synthesized by plants that give them their yellow, orange, and red colour. Over six hundred carotenoids have been identified, with just a few exceptions; all are found in the plant kingdom. There are two classes of carotenoids—the xanthophylls, which contain oxygen, and the carotenes, which do not.

 

In plants, carotenoids absorb light for use in photosynthesis and act as antioxidants. Beta-carotene, alpha-carotene, and beta-cryptoxanthin are converted to retinol in the body. The other carotenoids, such as lycopene, are not. Many biological actions of carotenoids are attributed to their antioxidant activity, but they likely act by other mechanisms, too.

 

Vitamin A is fat-soluble and is packaged into chylomicrons in the small intestine and transported to the liver. The liver stores and exports Vitamin A as needed; it is released into the blood and transported to cells. Carotenoids are not absorbed as well as Vitamin A, but like Vitamin A, they require fat in the meal for absorption. In intestinal cells, carotenoids are packaged into lipid-containing chylomicrons and then transported to the liver. In the liver, carotenoids are repackaged into lipoproteins, which transport them to cells.

 

The retinoids are aptly named as their most notable function is in the retina of the eye, where they aid in vision, particularly in seeing under low-light conditions. Therefore, night blindness is the most definitive sign of Vitamin A deficiency. Vitamin A has several vital functions in the body, including maintaining vision and a healthy immune system. Many of Vitamin A’s roles are like hormone functions  (for example, Vitamin A can interact with DNA, causing a change in protein function). Vitamin A helps maintain healthy skin, the linings and coverings of tissue, and regulates growth and development. As an antioxidant, Vitamin A protects cellular membranes, helps maintain glutathione levels, and influences enzyme activity in detoxifying free radicals. 

Vision

Retinol circulating in the blood is taken up by cells in the eye retina, where it is converted to retinal and is involved in the eye’s ability to see under low light conditions. A deficiency in Vitamin A thus, results in a decrease in the detection of low-level light, a condition referred to as night blindness.

 

Insufficient intake of dietary Vitamin A over time can also cause complete vision loss. Vitamin A deficiency is the number one cause of preventable blindness worldwide. Vitamin A not only supports the vision function of the eyes but also maintains the covers and linings of the eyes. Vitamin A deficiency can lead to the dysfunction of the linings and coverings of the eye (e.g., bitot spots), causing dryness of the eyes, a condition called xerophthalmia. The progression of this condition can cause ulceration of the cornea and eventually blindness.

Figure 5.1.1: Bitot Spot caused by vitamin A deficiency. Malnutrition-Bitot’s Spots/ Bitot’s Spots caused by vitamin A deficiency by CDC / Nutrition Program.

Immunity

The common occurrence of advanced xerophthalmia in children who died from infectious diseases led scientists to hypothesize that supplementing Vitamin A in the diet for children with xerophthalmia might reduce disease-related mortality. In Asia in the late 1980s, targeted populations of children were administered Vitamin A supplements, and the death rates from measles and diarrhea declined by up to 50 percent (Sommer, 2008). Vitamin A supplementation in these deficient populations did not reduce the number of children who contracted these diseases, but it did decrease the severity of the diseases so that they were no longer fatal. Soon after the results of these studies were communicated to the rest of the world, the World Health Organization (W.H.O.) and the United Nations Children’s Fund (U.N.I.C.E.F.) commenced worldwide campaigns against Vitamin A deficiency. U.N.I.C.E.F. estimates that the distribution of over half a billion Vitamin A capsules prevents 350,000 childhood deaths annually (Sommer, 2008).

 

In the twenty-first century, science has demonstrated that Vitamin A greatly affects the immune system. We still need clinical trials investigating the proper doses of Vitamin A required to help ward off infectious disease and how much Vitamin A supplementation affects populations that are not deficient (Sommer, 2008). Micronutrient deficiencies may contribute to a disease’s development, progression, and severity, but this does not mean an increased intake of these micronutrients will solely prevent or cure disease. The effect, as usual, is cumulative and depends on the diet, among other things.

Growth and Development

Vitamin A acts similarly to some hormones in that it can change the number of proteins in cells by interacting with DNA. This is the primary way that Vitamin A affects growth and development. Vitamin A deficiency in children is linked to growth retardation; however, Vitamin A deficiency is often accompanied by protein malnutrition and iron deficiency, thereby confounding the investigation of Vitamin A’s specific effects on growth and development.

 

In the fetal stages of life, Vitamin A is important for limb, heart, eye, and ear development and in both deficiency and excess, Vitamin A causes congenital disabilities. Further, males and females require Vitamin A in the diet to reproduce effectively.

Cancer

Vitamin A’s role in regulating cell growth and death, especially in tissues that line and cover organs, suggests it may be effective in treating certain lung, neck, and liver cancers. It has been shown in some observational studies that Vitamin A-deficient populations have a higher risk for some cancers. However, Vitamin A supplements have been found to increase the risk of lung cancer in people at high risk for the disease (i.e., smokers, ex-smokers, and workers exposed to asbestos). The Beta-Carotene and Retinol Efficacy Trial (C.A.R.E.T.) involved over eighteen thousand participants at high risk for lung cancer. This trial found that people who took supplements containing very high doses of Vitamin A (25,000 international units) and beta-carotene had a 28 percent higher incidence of lung cancer midway through the study, which was consequently stopped (Goodman, 2004).

Vitamin A Toxicity

Vitamin A toxicity, or hypervitaminosis A, is rare. Typically, it requires intakes ten times the RDA of preformed Vitamin A in the form of supplements (it would be hard to consume such high levels from a regular diet) for a substantial amount of time. However, some people may be more susceptible to Vitamin A toxicity at lower doses. The signs and symptoms of Vitamin A toxicity include dry, itchy skin, loss of appetite, swelling of the brain, and joint pain. In severe cases, Vitamin A toxicity may cause liver damage and coma.

 

Vitamin A is essential during pregnancy, but doses above 3,000 micrograms per day (10,000 international units) have been linked to an increased incidence of congenital disabilities. Pregnant women should check the amount in any prenatal or pregnancy multivitamin she takes to ensure the amount is below the UL.

Dietary Reference Intakes for Vitamin A

There is more than one source of Vitamin A in the diet. There is preformed Vitamin A, abundant in many animal-derived foods, and carotenoids, found in high concentrations in vibrantly coloured fruits and vegetables and some oils.

 

Intestinal and liver cells convert some carotenoids to retinol. However, only small amounts of certain carotenoids are converted to retinol, meaning fruits and vegetables are not necessarily good sources of Vitamin A.

 

The RDA for Vitamin A includes all sources of Vitamin A. The RDA for Vitamin A is given in mcg of retinol activity requirements (RAE) to consider its available forms. The human body converts all dietary sources of Vitamin A into retinol. Therefore, 1 mcg of retinol is equivalent to 12 mcg of beta-carotene, and 24 mcg of alpha-carotene or beta-cryptoxanthin. For example, 12 micrograms of fruit- or vegetable-based beta-carotene will yield 1 microgram of retinol. Vitamin A is currently listed in food and supplement labels using international units (IU). The following conversions are listed below (Dietary Supplement Fact Sheet, 2018):

1 IU retinol = 0.3 mcg R.A.E.

1 IU beta-carotene from dietary supplements = 0.15 mcg RAE

1 IU beta-carotene from food = 0.05 mcg RAE

1 IU alpha-carotene or beta-cryptoxanthin = 0.025 mcg RAE

The RDA for Vitamin A is sufficient to support growth and development, reproduction, vision, and immune system function while maintaining adequate liver stores (for four months).

 

Table 5.1.1: Dietary Reference Intakes for Vitamin A (ug/day RAE) for adolescents and adults.

Age Group
RDA Males and Females
UL
Adolescents (14-18 years)
Males: 700
2800
Adolescents (14-18 years)
Females: 700
2800
Adults (>19 years)
Males: 900
3000
Adults (>19 years)
Females: 700
3000

Dietary Sources of Vitamin A and Beta-Carotene

Preformed Vitamin A is found only in foods of animal origin, with the liver being the richest source because that’s where Vitamin A is stored. Table 5.1.2 provides the Vitamin A content of foods containing preformed Vitamin A.

 

Table 5.1.2: Vitamin A Content of Foods Containing Preformed Vitamin A

Food Serving Vitamin A (ug RAE)
Beef liver 3 oz.
8,163 
Chicken liver 3 oz.
3,701 
Milk, skim 1 c.
150 
Milk, whole 1 c.
75 
Cheddar cheese 1 oz.
85 

In North America, the most consumed carotenoids are alpha-carotene, beta-carotene, beta-cryptoxanthin, lycopene, lutein, and zeaxanthin. See Table 5.1.3 for the carotenoid content of various foods.

 

Table 5.1.3: Vitamin A Content of Various Carotenoid-containing Foods

Vitamin D

Vitamin D refers to a group of fat-soluble Vitamins derived from cholesterol. Vitamins D2 (ergocalciferol) and D3 (calcitriol) are the only ones that have biological actions in the human body. The skin synthesizes Vitamin D when exposed to sunlight. In fact, for most people, more than 90 percent of their Vitamin D3 comes from casual exposure to UVB rays in sunlight. Anything that reduces exposure to the sun’s UVB rays decreases the amount of Vitamin D3 your skin synthesizes. That would include long winters, your home’s altitude, whether you are wearing sunscreen, and skin colour (including tanned skin). Do you ever wonder about an increased risk of skin cancer by spending too much time in the sun? Do not fret. Less than thirty minutes of sun exposure to the arms and legs will increase blood levels of Vitamin D3 more than taking 10,000 I.U. (250 micrograms) of Vitamin D3.

Vitamin D’s Functional Role

Activated Vitamin D3 (calcitriol) regulates blood calcium levels in concert with the parathyroid hormone and is critical for bone health. Less than 15 percent of calcium is absorbed from foods or supplements without adequate Vitamin D intake.  A deficiency of Vitamin D in children causes a bone disease called nutritional rickets. Rickets is very common among children in developing countries and is characterized by soft, weak, deformed bones that are exceptionally susceptible to fracture. Vitamin D deficiency may also cause a similar disease called osteomalacia, characterized by low bone mineral density (BMD). Osteomalacia has the same symptoms and consequences as osteoporosis and often coexists with osteoporosis. Vitamin D deficiency may be common in the population, especially in the elderly population, dark-skinned populations, and in the many people who live in the northern latitudes where sunlight exposure is much decreased during the long winter season.

Health Benefits

Observational studies have shown that people with low levels of Vitamin D in their blood have lower bone mineral density and an increased incidence of osteoporosis. In contrast, diets with high intakes of salmon, which contain a large amount of Vitamin D, are linked with better bone health. Unfortunately, current evidence does not demonstrate that large doses of supplemental Vitamin D improve bone density (Bolland, Grey & Avenell, 2018).  Safe sun exposure (10-30 minutes of mid-day sun on the arms and legs two to three times per week) and food sources of Vitamin D are your best plan of action.

 

Many other health benefits have been linked to Vitamin D, from decreased cardiovascular disease to infection prevention. Furthermore, evidence from laboratory studies conducted in cells, tissues, and animals suggests Vitamin D prevents the growth of certain cancers, blocks inflammatory pathways, reverses atherosclerosis, increases insulin secretion, and blocks viral and bacterial infection and many other things. Vitamin D deficiency has been linked to an increased risk of autoimmune diseases. Immune diseases, rheumatoid arthritis, multiple sclerosis, and Type 1 diabetes have been observed in populations with inadequate Vitamin D levels. Additionally, Vitamin D deficiency is linked to an increased incidence of hypertension. Most scientific evidence describing other health benefits of Vitamin D is from laboratory and observational studies and requires confirmation in clinical intervention studies. This is an example of how the findings in observational and lab studies may not be the same as intervention studies. To date, interventional studies have been inconclusive regarding supplementation and the other potential roles of Vitamin D in the body (Bolland, Grey & Avenell, 2018).

Vitamin D Toxicity

Although Vitamin D toxicity is rare, too much can cause calcium concentrations or hypercalcemia. Hypercalcemia can lead to a large amount of calcium being excreted through the urine, which can cause kidney damage. Calcium deposits may also develop in soft tissues such as the kidneys, blood vessels, cardiovascular system. However, it is important to know that synthesizing Vitamin D from the sun does not cause Vitamin D toxicity because the skin production of Vitamin D3 is a tightly regulated process.

Dietary Reference Intake for Vitamin D

The Institute of Medicine RDA for Vitamin D is listed in Table 5.1.4. The National Osteoporosis Foundation recommends slightly higher levels and that adults under age fifty get between 400 and 800 international units of Vitamin D every day, and adults fifty and older get between 800 and 1,000 international units of Vitamin D every day. Toxicity from excess Vitamin D is rare, but certain diseases such as hyperparathyroidism, lymphoma, and tuberculosis make people more sensitive to the increases in calcium caused by high intakes of Vitamin D.

 

Table 5.1.4: Dietary Reference Intakes for Vitamin D (mcg/day) for adolescents and adults.

Age Group RDA Males and Females UL
Adolescents (14-18 years) 15 50
Adults (19-70 years) 15 50
Adults (>70 years) 20 50

Source: https://www.canada.ca/en/health-canada/services/food-nutrition/healthy-eating/dietary-reference-intakes/tables/reference-values-vitamins-dietary-reference-intakes-tables-2005.html

 

Table 5.1.5: Dietary Sources of Vitamin D (IU; conversion 1IU = 0.025 mcg).

Food Serving Vitamin D (IU)
Swordfish 3 oz. 566
Salmon 3 oz. 447
Tuna fish, canned in water, drained 3 oz. 154
Orange juice fortified with Vitamin D 1 c. 137
Milk, non-fat, reduced fat and whole, Vitamin D fortified 1 c. 115-124
Margarine, fortified 1 Tbsp 60
Sardines, canned in oil, drained 2 e. 46
Beef liver 3 oz. 42
Egg, large 1 e. 41

Source: Dietary Supplement Fact Sheet: Vitamin D. National Institutes of Health, Office of Dietary Supplements. Updated September 5, 2012. Accessed October 22, 2017.

Vitamin E

Vitamin E occurs in eight chemical forms, of which alpha-tocopherol appears to be the only form recognized to meet human requirements. Alpha-tocopherol and Vitamin E’s other constituents are fat-soluble and primarily responsible for protecting cell membranes against lipid destruction caused by free radicals, making it an antioxidant. When alpha-tocopherol interacts with a free radical, it can no longer act as an antioxidant unless it is enzymatically regenerated. Vitamin C helps to regenerate some of the alpha-tocopherol, but the remainder is eliminated from the body. Therefore, to maintain Vitamin E levels, you must ingest it as part of your diet.

 

Insufficient levels are rare (signs and symptoms of such conditions are not always evident) but primarily the cause of nerve degeneration. People with malabsorption disorders, such as Crohn’s disease or cystic fibrosis, and babies born prematurely, are at higher risk for Vitamin E deficiency (Goodman et al., 2011).

 

Vitamin E has many other important roles and functions in the body, such as boosting the immune system by helping to fight off bacteria and viruses. It also enhances the dilation of blood vessels and inhibits the formation of blood clotting. Despite Vitamin E’s numerous beneficial functions when taken in recommended amounts, large studies do not support the idea that taking higher doses of this Vitamin will increase its power to prevent or reduce disease risk (McGinley, Shafat & Donnelly, 2009).

 

Fat in the diet is required for Vitamin E absorption as it is packaged into lipid-rich chylomicrons in intestinal cells and transported to the liver. The liver stores some of the Vitamin E or packages it into lipoproteins, which deliver it to cells.

Cardiovascular Disease

Vitamin E reduces the oxidation of LDLs, and it was therefore hypothesized that Vitamin E supplements would protect against atherosclerosis. However, large clinical trials have not consistently found evidence to support this hypothesis. In the “Women’s Angiographic Vitamin and Estrogen Study,” postmenopausal women who took 400 international units (264 milligrams) of Vitamin E and 500 milligrams of Vitamin C twice per day had higher death rates from all causes (Waters et al., 2002).

 

Other studies have not confirmed the association between increased Vitamin E intake from supplements and increased mortality. There is more consistent evidence from observational studies that a higher intake of Vitamin E from foods is linked to a decreased risk of dying from a heart attack.

Cancer

The large clinical trials that evaluated whether there was a link between Vitamin E and cardiovascular disease risk also looked at cancer risk. These trials, called the HOPE-TOO Trial and Women’s Health Study did not find that Vitamin E at doses of 400 international units (264 milligrams) per day or 600 international units (396 milligrams) every other day reduced the risk of developing any form of cancer (Lonn et al., 2005; Lee et al., 2005).

Vitamin E Toxicity

Researchers have not found any adverse effects from consuming Vitamin E in food. Although that may be the case, supplementation of alpha-tocopherol in animals has been shown to cause hemorrhage and disrupt blood coagulation. Extremely high levels of Vitamin E can interact with Vitamin K-dependent clotting factors causing inhibition of blood clotting (Dietary Supplement Fact Sheet: Vit.E, 2018).

 

Vitamin E supplements often contain more than 400 international units, almost twenty times the RDA. The UL for Vitamin E is set at 1,500 international units for adults. There is some evidence that taking Vitamin E supplements at high doses has negative health effects. As mentioned, Vitamin E inhibits blood clotting and a few clinical trials have found that people taking Vitamin E supplements have an increased risk of stroke. In contrast to Vitamin E from supplements, there is no evidence that consuming foods containing Vitamin E compromises health.

Dietary Reference Intakes for Vitamin E

The Recommended Dietary Allowance (RDA) and Tolerable Upper Intake Level (UL) for older adults for Vitamin E are given in Table 5.1.6.

 

Table 5.1.6: Dietary Reference Intakes for Vitamin E (mg/day) for adolescents and adults.

Age Group RDA Males and Females UL
Adolescents (14-18 years) 15 800
Adults (>19 years) 15 1000

Dietary Sources of Vitamin E

Add some nuts to your salad and make your own dressing to get a healthy dietary dose of Vitamin E.

Vitamin E is found in many foods, especially those higher in fat, such as nuts and oils. Some spices, such as paprika and red chili pepper, and herbs, such as oregano, basil, cumin, and thyme, also contain Vitamin E. (Keep in mind spices and herbs are commonly used in small amounts in cooking and therefore are a lesser source of dietary Vitamin E.) See Table 5.1.7 for a list of foods and their Vitamin E content.

Everyday Connection

To increase your dietary intake of Vitamin E from plant-based foods try a spinach salad with tomatoes and sunflower seeds, and add a dressing made with sunflower oil, oregano, and basil.

 

Table 5.1.7: Dietary Sources of Vitamin E

Food Serving Vitamin E (mg)
Sunflower seeds 1 oz. 7.4
Almonds 1 oz. 6.8
Sunflower oil 1 Tbsp 5.6
Hazelnuts 1 oz. 4.3
Peanut butter 2 Tbsp 2.9
Corn oil 1 Tbsp 1.9
Kiwi 1 medium 1.1
Tomato 1 medium 0.7
Spinach 1 c. raw 0.6

Source: Dietary Supplement Fact Sheet: Vitamin E. National Institutes of Health, Office of Dietary Supplements. http://ods.od.nih.gov/factsheets/VitaminE-QuickFacts/. Updated August 17, 2018. Accessed June 30, 2019.

Vitamin K

Vitamin K refers to a group of fat-soluble vitamins that are similar in chemical structure. Vitamin K is critical for blood function, acting as coenzymes which play an essential role in blood coagulation (aka blood clotting). Blood-clotting proteins are continuously circulating in the blood. Upon injury to a blood vessel, platelets stick to the wound forming a plug. Without Vitamin K, blood would not clot.

 

A deficiency in Vitamin K causes bleeding disorders. It is relatively rare, but people who have liver or pancreatic disease, celiac disease, or malabsorption conditions are at higher risk for Vitamin K deficiency. Signs and symptoms include nosebleeds, easy bruising, broken blood vessels, bleeding gums, and heavy menstrual bleeding in women. The function of the anticoagulant drug warfarin is impaired by excess Vitamin K intake from supplements. Calcium additionally plays a role in the activation of blood-clotting proteins.

Bone Health

Vitamin K is also required for maintaining bone health. It modifies the protein osteocalcin, which is involved in the bone remodelling process. All the functions of osteocalcin and the other Vitamin K-dependent proteins in bone tissue are not well understood and are under investigation. Some studies show that people with diets low in Vitamin K also have an increased risk for bone fractures.

Dietary Reference Intake and Food Sources for Vitamin K

The Food and Nutrition Board (FNB) has not established a UL for Vitamin K because it has a low potential for toxicity. According to the FNB, “no adverse effects associated with Vitamin K consumption from food or supplements have been reported in humans or animals” (Institute of Medicine, 2001).

 

Table 5.1.8: Dietary Reference Intakes for Vitamin K (mcg/day) for adolescents and adults.

Age Group RDA Males and Females
Adolescents (14-18 years) 75
Adults (>19 years) Males: 120
Adults (>19 years) Females: 90

Dietary Sources of Vitamin K

Vitamin K is present in many foods. It is found in the highest concentrations in green vegetables such as broccoli, cabbage, kale, parsley, spinach, and lettuce. Additionally, Vitamin K can be synthesized via bacteria in the large intestine. The amount of Vitamin K synthesized by bacteria and absorbed in the lower intestine is unknown but likely contributes less than 10 percent of the recommended intake. Newborns have low Vitamin K stores, and it takes time for their sterile gut to acquire the bacteria to produce Vitamin K. It has become a routine practice to give newborns a single intramuscular or oral dose of Vitamin K. This practice has eliminated Vitamin K-dependent bleeding disorders in babies. In populations where parents refuse this practice, physicians are seeing increased rates of blood clotting problems in newborns (Schulte et al., 2014).

 

Table 5.1.9: Dietary Sources of Vitamin K.

 

Summary of Fat-soluble Vitamins

Table 5.1.10 provides a summary of the fat-soluble vitamins.

 

Table 5.1.10: Fat-soluble Vitamins Summary Table

Vitamin
Sources
Recommended Intake for older adults
Major functions
Deficiency diseases and symptoms
Groups at risk of deficiency
Toxicity
UL
Vitamin A (retinol, retinal, retinoic acid, carotene, beta-carotene)
Retinol: beef and chicken liver, skim milk, whole milk, cheddar cheese; Carotenoids: pumpkin, carrots, squash, collards, peas
700-900 mcg/day
Antioxidant, vision, cell differentiation, reproduction, immune function
Xerophthalmia, night blindness, eye infections; poor growth, dry skin, impaired immune function
People living in poverty (especially infants and children), premature infants, pregnant and lactating women people who consume low-fat or low-protein diets
Hypervitaminosis A: Dry, itchy skin, hair loss, liver damage, joint pain, fractures, congenital disabilities, swelling of the brain
3000 mcg/day
Vitamin D
Swordfish, salmon, tuna, orange juice (fortified), milk (fortified), sardines, egg, synthesis from sunlight
800 I.U./day (15-20 mcg/day)
Absorption and regulation of calcium and phosphorus, maintenance of bone
Rickets in children: abnormal growth, misshapen bones, bowed legs, soft bones; osteomalacia in adults
Breastfed infants, older adults, people with limited sun exposure, people with dark skin
Calcium deposits in soft tissues, damage to the heart, blood vessels, and kidneys
4000 I.U./day (100 mcg/day)
Vitamin E
Sunflower seeds, almonds, hazelnuts, peanuts
15 mg/day
Antioxidant, protects cell membranes
Broken red blood cells, nerve damage

People with poor fat absorption, premature infants

Inhibition of Vitamin K clotting factors

1000 mcg/day from supplemental sources

Vitamin K
Vegetable oils, leafy greens, synthesis by intestinal bacteria
90-120 mcg/day
Synthesis of blood clotting proteins and proteins needed for bone health and cell growth
Hemorrhage
Newborns, people on long-term antibiotics
Anemia, brain damage
N D

Key Takeaways

See the Table above for a summary of the fat-soluble vitamins.

Contributors

University of Hawai’i at Mānoa Food Science and Human Nutrition Program: Allison Calabrese, Cheryl Gibby, Billy Meinke, Marie Kainoa Fialkowski Revilla, and Alan Titchenal

5.2 Water-Soluble Vitamins

Learning Objectives

  • Explore the functions and dietary sources of water-soluble vitamins.
  • Describe the risks associated with deficiencies and excesses of water-soluble vitamins.

Most water-soluble vitamins play a different role in energy metabolism; they are required as functional parts of enzymes involved in energy release and storage. Vitamins and minerals that make up a part of enzymes are referred to as coenzymes and cofactors, respectively. Enzymes require coenzymes and cofactors to catalyze (speed up) specific reactions. They assist in converting a substrate to an end product. Coenzymes and cofactors are essential in catabolic (to breakdown) pathways and play a role in many anabolic (to build up) pathways. In addition to being essential for metabolism, many vitamins and minerals are required for blood renewal and function. At insufficient levels in the diet, these vitamins and minerals impair the health of blood and consequently the delivery of nutrients in and wastes out, amongst its many other functions. In this section, we will focus on the vitamins that take part in metabolism, blood function, and renewal.

Vitamin C

Vitamin C, also called ascorbic acid, is a water-soluble micronutrient essential in the diet for humans, although most other mammals can readily synthesize it. Vitamin C’s ability to donate electrons easily makes it a highly effective antioxidant. It is effective in scavenging free radicals. It protects lipids by disabling free radicals and aiding in the regeneration of Vitamin E.

 

In addition to its role as an antioxidant, Vitamin C is a required part of several enzymes like signaling molecules in the brain, some hormones, and amino acids. Vitamin C is also essential for the synthesis and maintenance of collagen. Collagen is the most abundant protein in the body and is used for various functions, such as forming the structure for ligaments, tendons, blood vessels and scars that bind wounds together. Vitamin C is the glue that holds the collagen fibers together; without sufficient levels in the body, collagen strands are weak and abnormal.

 

Vitamin C levels in the body are affected by the amount in the diet, which influences how much is absorbed and excreted, such that the higher the intake, the more Vitamin C is excreted. Vitamin C is not stored in any significant amount in the body, but once it has been reduced to a free radical, it is very effectively regenerated, and therefore it can exist in the body as an active antioxidant for many weeks.

 

The classic condition associated with Vitamin C deficiency is scurvy. The signs and symptoms of scurvy include skin disorders, bleeding gums, painful joints, weakness, depression, and increased susceptibility to infections. An adequate intake of fruits and vegetables rich in Vitamin C prevents scurvy.

Vitamin C Toxicity

High doses of Vitamin C have been reported to cause numerous problems, but the only consistently shown side effects are gastrointestinal upset and diarrhea. To prevent these GI discomforts, the IOM has set a UL for adults at 2,000 milligrams per day (greater than twenty times the R.D.A.).

 

At very high doses in combination with iron, Vitamin C has sometimes been found to increase oxidative stress, reaffirming that getting your antioxidants from foods helps to regulate intake levels and is better than getting them from supplements. There is some evidence that taking Vitamin C supplements at high doses increases the likelihood of developing kidney stones; however, this effect is most often observed in people that already have multiple risk factors for kidney stones.

Dietary Reference Intake for Vitamin C

The dietary reference intakes for older adults for Vitamin C are listed in Table 5.2.1. They are considered adequate to prevent scurvy. Vitamin C’s effectiveness as a free radical scavenger motivated the Institute of Medicine (IOM) to increase the RDA for smokers by 35 milligrams, as tobacco smoke is an environmental and behavioural contributor to free radicals in the body.

 

Table 5.2.1: Dietary Reference Intakes for Vitamin C (mg/day) for adolescents and adults.

Dietary Sources of Vitamin C

Citrus fruits are excellent sources of Vitamin C, as are many vegetables. British sailors in the past were often referred to as “limeys” as they carried sacks of limes onto ships to prevent scurvy. Vitamin C is not found in significant amounts in animal-based foods. Because Vitamin C is water-soluble, it leaches away from foods considerably during cooking, freezing, thawing, and canning. Up to 50 percent of Vitamin C can be boiled away. Therefore, to maximize Vitamin C intake from foods, you should eat fruits and vegetables raw or lightly steamed. For the Vitamin C content of various foods, see Table 5.2.2.

 

Table 5.2.2: Vitamin C Content of Various Foods

Food Serving Vitamin C (milligrams)
Orange juice 6 oz. 93
Grapefruit juice 6 oz. 70
Orange 1 medium 70
Strawberries 1 c. 85
Tomato 1 medium 17
Sweet red pepper 1/2 c. raw 95
Broccoli 1/2 c. cooked 51
Romain lettuce 2 c. 28
Cauliflower 1 c. boiled 55

Source: Dietary Supplement Fact Sheet: Vitamin C. National Institutes of Health, Office of Dietary Supplements. Updated September 18, 2018. Accessed June 30, 2019.

Thiamin (B1)

Thiamin is essential in glucose metabolism. It acts as a cofactor for enzymes that break down glucose for energy production. Thiamin plays a key role in nerve cells as the glucose that is catabolized by thiamin is needed for an energy source. Additionally, thiamin plays a role in the synthesis of neurotransmitters and is therefore required for RNA, DNA, and A.T.P. synthesis.

 

The brain and heart are most affected by a deficiency in thiamin. Thiamin deficiency, also known as beriberi, can cause symptoms of fatigue, confusion, movement impairment, pain in the lower extremities, swelling, and heart failure. It is prevalent in societies whose main dietary staple is white rice. During the processing of white rice, the bran is removed, along with what were called in the early nineteenth century, “accessory factors,” which are vital for metabolism. Dutch physician Dr. Christiaan Eijkman cured chickens of beriberi by feeding them unpolished rice bran in 1897. By 1912, Sir Frederick Gowland Hopkins determined from experiments with animals that the “accessory factors,” eventually renamed vitamins, are needed in the diet to support growth since animals fed a diet of pure carbohydrates, proteins, fats, and minerals failed to grow. Eijkman and Hopkins were awarded the Nobel Prize in Physiology (or Medicine) in 1929 for their discoveries in the emerging science of nutrition.

Dietary Reference Intakes of Thiamin

The dietary reference intakes for older adults for thiamin are listed in Table 5.2.3. There is no UL for thiamin because there have not been any reports of toxicity when excess amounts are consumed from food or supplements.

 

Table 5.2.3: Dietary Reference Intakes for Thiamin(mg/day) for adolescents and adults.

Dietary Sources of Thiamin

Whole grains, meat, and fish are great sources of thiamin. Some countries fortify their refined bread and cereals. In Canada, there are both voluntary and mandatory guidelines for thiamine fortification to help Canadian’s increase their dietary consumption. As outlined by the Government of Canada (2022), fortification guidelines for thiamin in Canada are as follows:

VOLUNTARY MANDATORY 
·       Breakfast cereals

·       Some fruit flavoured drinks

·       Bases, concentrates and mixes that are used for making fruit flavoured drinks

·       Infant cereal products

·       Alimentary pastes

·       Infant formulas and formulated liquid diets

·       Flavoured beverage mixes and bases recommended for addition to milk

·       Some pre-cooked rice

·       “Enriched” alimentary pastes

·       Food represented for use in a very low-energy diet

·       Stimulated meat products, simulated poultry meat products, simulated poultry meat products, meat product extenders, and poultry product extenders

·       Meal replacements and nutritional supplements

·       Ready breakfast, instant breakfast and other similar breakfast replacements

·       Flour, white flour, enriched flour or enriched white flour

·       Products simulating whole egg

·       Liquid whole egg, dried whole egg, frozen whole egg, liquid yolk, dried yolk, frozen yolk, liquid egg whites, dried egg white, liquid whole egg mix, dried whole egg mix, frozen whole egg mix, liquid yolk mix, dried yolk mix, and frozen yolk mix if there is a reduction in the vitamin content during processing

 

For the thiamin content of various foods, see Table 5.2.4.

 

Table 5.2.4: Thiamin Content of Various Foods

Source: Health Professional Fact Sheet: Thiamin. National Institutes of Health, Office of Dietary. Updated February 11, 2016. Accessed October 5, 2017.

Riboflavin (B2)

Riboflavin is an essential component of flavoproteins, which are coenzymes involved in many metabolic pathways of carbohydrate, lipid, and protein metabolism. Flavoproteins aid in the transfer of electrons in the electron transport chain. Furthermore, the functions of other B-vitamin coenzymes, such as Vitamin B6 and folate, depend on flavoproteins’ actions. The “flavin” portion of riboflavin gives a bright yellow colour to riboflavin, an attribute that helped lead to its discovery as a vitamin. When riboflavin is taken in excess amounts (supplement form), the excess will be excreted through your kidneys and show up in your urine. Although the colour may alarm you, it is harmless. No adverse effects of high doses of riboflavin from foods or supplements have been reported.

 

Riboflavin deficiency sometimes referred to as ariboflavinosis, is often accompanied by other dietary deficiencies (most notably protein) and can be common in people that suffer from alcoholism. This deficiency will usually also occur in conjunction with deficiencies of other B vitamins because many B vitamins have similar food sources. The signs and symptoms of riboflavin deficiency include dry, scaly skin, cracking of the lips and corners of the mouth, sore throat, itchy eyes, and light sensitivity.

Dietary Reference Intakes of Riboflavin

The RDAs for different age groups for riboflavin are listed in Table 5.2.5. There is no UL for riboflavin because no toxicity has been reported when an excess amount has been consumed through foods or supplements.

 

Table 5.2.5: Dietary Reference Intakes for Riboflavin (mg/day) for adolescents and adults.

Dietary Sources of Riboflavin

Riboflavin can be found in various foods, but it is important to remember that sunlight can destroy it. Milk is one of the best sources of riboflavin in the diet and was once delivered and packaged in glass bottles. This packaging has changed to cloudy plastic containers or cardboard to help block the light from destroying the riboflavin in milk. For the riboflavin content of various foods see Table 5.2.6.

 

Table 5.2.6: Riboflavin Content of Various Foods

Niacin (B3)

Niacin is a component of the coenzymes NADH and NADPH, which are involved in the catabolism and/or anabolism of carbohydrates, lipids, and proteins. NADH is the predominant electron carrier and transfers electrons to the electron-transport chain to make ATP. NADPH is also required for the anabolic pathways of fatty-acid and cholesterol synthesis. In contrast to other vitamins, humans can synthesize niacin from the amino acid tryptophan in a process requiring enzymes dependent on riboflavin, Vitamin B6, and iron. Niacin is made from tryptophan only after tryptophan has met all of its other needs in the body. The contribution of tryptophan-derived niacin to niacin needs in the body varies widely. A few scientific studies have demonstrated that diets high in tryptophan have minimal effect on niacin deficiency. Niacin deficiency is commonly known as pellagra, and the symptoms include fatigue, decreased appetite, and indigestion. These symptoms are then commonly followed by the four D’s: diarrhea, dermatitis, dementia, and sometimes death.

Dietary Reference Intakes of Niacin

The RDAs and ULs for different age groups for Niacin are listed in Table 5.2.7. Because Niacin needs can be met from tryptophan, The RDA is expressed in niacin equivalents (NE). The conversions of NE, Niacin, and tryptophan are: 1 mg NE= 60 milligrams tryptophan= 1 mg niacin.

 

Table 5.2.7: Dietary Reference Intakes for Niacin (NE/day) for adolescents and adults.

Dietary Sources of Niacin

Niacin can be found in various foods such as yeast, meat, poultry, red fish, and cereal. In plants, especially mature grains, niacin can be bound to sugar molecules which can significantly decrease the niacin bioavailability. For the niacin content of various foods, see Table 5.2.8.

 

Table 5.2.8: Niacin Content of Various Foods

Source: Micronutrient Information Center: Niacin. Oregon State University, Linus Pauling Institute. Updated in July 2013. Accessed October 22, 2017.

Pantothenic Acid (B5)

Pantothenic acid forms coenzyme A, the cell’s primary carrier of carbon molecules. Acetyl-CoA is the carbon carrier of glucose, fatty acids, and amino acids in the citric acid cycle. Coenzyme A is also involved in synthesizing lipids, cholesterol, and acetylcholine (a neurotransmitter). Pantothenic Acid deficiency is exceptionally rare. Signs and symptoms include fatigue, irritability, numbness, muscle pain, and cramps. You may have seen pantothenic acid on many ingredient lists for skin and hair care products; however, there is no good scientific evidence that pantothenic acid improves human skin or hair.

 

Dietary Reference Intake for Pantothenic Acid

Because there is little information on the requirements for pantothenic acids, the Food and Nutrition Board (FNB) has developed Adequate Intakes (AI) based on the observed dietary intakes in healthy population groups. The AI for different age groups for pantothenic acid is listed in Table 5.2.9.

 

Table 5.2.9: Adequate Intakes for Pantothenic Acid (mg/day) for adolescents and adults.

Dietary Sources of Pantothenic Acid

Pantothenic Acid is widely distributed in all types of food, which is why a deficiency in this nutrient is rare. Pantothenic Acid gets its name from the Greek word “pantothen, “meaning “from everywhere.” For the pantothenic acid content of various foods, see Table 5.3.10.

 

Table 5.3.10: Pantothenic Acid Content of Various Foods

Biotin

Biotin is required as a coenzyme in the citric acid cycle and in lipid metabolism. It is also required as an enzyme to synthesize glucose and some nonessential amino acids. A specific enzyme, biotinidase, is necessary to release biotin from protein so that it can be absorbed in the gut. Some bacterial synthesis of biotin occurs in the colon; however, this is not a significant source of biotin. Biotin deficiency is rare but can be caused by eating large amounts of raw egg whites over an extended period. This is because the protein in egg whites tightly binds to biotin, making it unavailable for absorption. A rare genetic disease-causing malfunction of the biotinidase enzyme also results in biotin deficiency. Symptoms of biotin deficiency are like those of other B vitamins but may also include hair loss when severe.

Dietary Reference Intakes of Biotin

Because there is little information on the requirements for biotin, the FNB has developed Adequate Intakes (AI) based on the observed dietary intakes in healthy population groups. The AI for different age groups for biotin is listed in Table 5.2.11.

 

Table 5.2.11: Adequate Intakes for Biotin (mcg/day) for adolescents and adults.

Dietary Sources of Biotin

Biotin can be found in foods such as eggs, fish, meat, seeds, nuts, and certain vegetables. For the pantothenic acid content of various foods, see Table 5.2.12.

 

Table 5.2.12: Biotin Content of Various Foods

Food

Serving

Biotin (micrograms)

Eggs

1 large

10

Salmon, canned

3 oz.

5

Pork chop

3 oz.

3.8

Sunflower seeds

¼ c.

2.6

Sweet potato

½ c.

2.4

Almonds

¼ c.

1.5

Tuna, canned

3 oz.

0.6

Broccoli

½ c.

0.4

Banana

½ c.

0.2

Vitamin B6 (Pyridoxine)

Vitamin B6 is the coenzyme involved in a wide variety of functions in the body. One primary function is the nitrogen transfer between amino acids which plays a role in amino-acid synthesis and catabolism. Also, it functions to release glucose from glycogen in the catabolic glycogenolysis pathway and is required by enzymes to synthesize multiple neurotransmitters and hemoglobin.

 

Vitamin B6 is also a required coenzyme for the synthesis of hemoglobin. A deficiency in Vitamin B6 can cause anemia, but it is different from that caused by insufficient folate, cobalamin, or iron; although the symptoms are similar. The size of red blood cells is normal or somewhat smaller, but the hemoglobin content is lower. This means each red blood cell has less capacity for carrying oxygen, resulting in muscle weakness, fatigue, and shortness of breath. Other deficiency symptoms of Vitamin B6 can cause dermatitis, mouth sores, and confusion.

 

Transamination reactions transfer an amino acid group to a carbon group. Decarboxylation reactions remove the acid group (COOH) from an amino acid to be used for neurotransmitter synthesis. Deamination reactions remove an amino group from an amino acid to use for energy production and glucose synthesis.

 

The Vitamin B6 coenzyme is needed for many different reactions essential for amino acid synthesis, catabolism for energy, and the synthesis of glucose and neurotransmitters.

 

Vitamin B6 coenzyme is essential for converting amino acid methionine into cysteine. With low levels of Vitamin B6, homocysteine will build up in the blood. High levels of homocysteine increase the risk of heart disease.

Vitamin B6 Toxicity

Currently, no adverse effects have been associated with a high dietary intake of Vitamin B6, but large supplemental doses can cause severe nerve impairment. To prevent this from occurring, the UL for adults is set at 100 mg/day.

Dietary Reference Intakes of Vitamin B6

The RDAs and ULs for different age groups for Vitamin B6 are listed in Table 5.2.13.

 

Table 5.2.13: Dietary Reference Intakes for Vitamin B6 (mg/day) for adolescents and adults.

Age Group

RDA Males and Females

UL

Adolescents (14-18 years)

Males: 1.3

80

Adolescents (14-18 years)

Females: 1.2

80

Adults (>19 years)

1.3

100

Dietary Sources of Vitamin B6

Vitamin B6 can be found in a variety of foods. The richest sources include fish, beef liver and other organ meats, potatoes, and other starchy vegetables and fruits. For the Vitamin B6 content of various foods, see Table 5.2.14.

 

Table 5.2.14: B6 Content of Various Foods

Food

Serving

Vitamin B6 (milligrams)

Chickpeas

1 c.

1.1

Tuna, fresh

3 oz.

0.9

Salmon

3 oz.

0.6

Potatoes

1 c.

0.4

Banana

1 medium

0.4

Ground beef patty

3 oz.

0.3

White rice, enriched

1 c.

0.1

Spinach

½ c

0.1

Folate

Folate is a required coenzyme for the synthesis of the amino acid methionine, and for making RNA and DNA. Therefore, rapidly dividing cells are most affected by folate deficiency. Red blood cells, white blood cells, and platelets are continuously being synthesized in the bone marrow from dividing stem cells. When folate is deficient, cells cannot divide normally. A consequence of folate deficiency is macrocytic or megaloblastic anemia. Macrocytic and megaloblastic mean “big cell,” and anemia refers to fewer red blood cells or red blood cells containing less hemoglobin. Macrocytic anemia is characterized by larger and fewer red blood cells. It is caused by red blood cells being unable to produce DNA and RNA fast enough—cells grow but do not divide, making them large in size.

 

Folate is especially essential for the growth and specialization of cells of the central nervous system. Children whose mothers were folate-deficient during pregnancy have a higher risk of neural-tube congenital disabilities. Folate deficiency is causally linked to the development of spina bifida, a neural-tube defect that occurs when the spine does not completely enclose the spinal cord. Spina bifida can lead to many physical and mental disabilities. Observational studies show that the prevalence of neural-tube defects decreased after the fortification of enriched cereal grain products with folate in 1996 in the United States (and 1998 in Canada) compared to before grain products were fortified with folate.

 

Additionally, results of clinical trials have demonstrated that neural-tube defects are significantly less than in the offspring of mothers who began taking folate supplements one month prior to becoming pregnant and throughout the pregnancy. In response to the scientific evidence, the Food and Nutrition Board of the Institute of Medicine (I.O.M.) raised the R.D.A. for folate to 600 micrograms per day for pregnant women. Some were concerned that higher folate intake may cause colon cancer, however scientific studies refute this hypothesis.

Dietary Reference Intakes of Folate

The RDAs and ULs for different age groups for folate are listed in Table 5.2.15. Folate is a compound that is found naturally in foods. Folic acid, however, is the chemical structure form used in dietary supplements and enriched foods such as grains. The FNB has developed dietary folate equivalents (DFE) to reflect the fact that folic acid is more bioavailable and easily absorbed than folate found in food. The conversions for the different forms are listed below.

  • 1 mcg DFE = 1 mcg food folate
  • 1mcg DFE = 0.6 mcg folic acid from fortified foods or dietary supplements consumed with foods
  • 1 mcg DFE = 0.5 mcg folic acid from dietary supplements taken on an empty stomach

 

Table 5.2.15: Dietary Reference Intakes for Folate (DFE/day) for adolescents and adults.

Age Group

RDA Males and Females

UL

Adolescents (14-18 years)

400

800

Adults (>19 years)

400

1000

Dietary Sources of Folate

Folate is found naturally in a wide variety of food, especially in dark leafy vegetables (foliage), fruits, and animal products. The U.S. Food and Drug Administration (FDA) began requiring manufacturers to fortify enriched bread, cereals, flours, and cornmeal to increase the consumption of folate in the American diet. For the folate content of various foods, see Table 5.2.16.

 

Table 5.2.16: Folate Content of Various Foods

Food

Serving

Folate (micrograms, DFE)

Beef Liver

3 oz.

215

Fortified breakfast cereals

¾ c.

400

Spinach

½ c.

131

White rice, enriched

½ c.

90

Asparagus

4 spears

85

White bread, enriched

1 slice

43

Broccoli

2 spears

45

Avocado

½ c.

59

Orange juice

6 oz.

35

Egg

1 large

22

Vitamin B12 (Cobalamin)

Vitamin B12 contains cobalt, making it the only Vitamin with a metal ion. Vitamin B12 is bound to protein in food (Mahmood, 2014). In the stomach, hydrochloric acid releases Vitamin B12 from protein, combining with intrinsic factor (Mahmood, 2014). The Vitamin B12-intrinsic factor complex is absorbed through the intestinal enterocytes and enters circulation (Mahmood, 2014).

 

Vitamin B12 is an essential part of coenzymes. It is necessary for fat and protein catabolism, folate coenzyme function, and hemoglobin synthesis. A folate-dependent enzyme needs an enzyme requiring Vitamin B12 to synthesize DNA. Thus, a deficiency in Vitamin B12 has similar consequences to health as folate deficiency. In children and adults, Vitamin B12 deficiency causes macrocytic anemia. Pernicious anemia is caused by secondary intrinsic factor deficiency from loss of parietal cells, small intestine disorders, genetic mutations, or gastric surgery, which disrupts Vitamin B12 absorption (Mahmood, 2014). Red blood cells do not divide normally and are too large due to a Vitamin B12 deficiency (Maymood, 2014).  There is an increased risk for neural tube defects for babies born to cobalamin-deficient mothers. For the human body to absorb Vitamin B12, the stomach, pancreas, and small intestine must function properly.

 

Reversible symptoms of Vitamin B12 deficiency include feeling tired and weak, as the red blood cells in macrocytic anemia have a lower capacity to distribute oxygen to the body (Dietitians of Canada, 2019). Other irreversible symptoms include tingling/numbness in the limbs, motor and visual disturbances, and cognitive impairments such as memory loss and dementia (Stover, 2010). Vitamin B12 deficiency can be treated with oral Vitamin B12 supplements or intramuscular injections (Stover, 2010).

Vitamin B12 Relationship with Folate and Vitamin B6

Vitamin B12 and folate play key roles in converting homocysteine to amino acid methionine. As mentioned previously, high levels of homocysteine in the blood increase the risk of heart disease. Low levels of Vitamin B12, folate or Vitamin B6 will increase homocysteine levels, increasing the risk of heart disease.

 

When there is a deficiency in Vitamin B12, inactive folate (from food) cannot be converted to active folate and used in the body to synthesize DNA. Folic Acid, however (that comes from supplements or fortified foods), is available to be used as active folate in the body without Vitamin B12. Therefore, macrocytic anemia may occur if there is a deficiency in Vitamin B12. Fortifying foods with folate decreases the risk of an individual developing macrocytic anemia.

Dietary Reference Intakes of Vitamin B12

The RDAs and ULs for different age groups for Vitamin B12 are listed in Table 5.2.17.

 

Table 5.2.17: Dietary Reference Intakes for Vitamin B12 (mcg/day) for adolescents and adults.

Age Group

RDA Males and Females

Adolescents (14-18 years)

2.4

Adults (>19 years)

2.4

Dietary Sources of B12

Vitamin B12 is found naturally in animal products such as fish, meat, poultry, eggs, and milk products. Although Vitamin B12 is not generally present in plant foods, fortified breakfast cereals are also a good source of Vitamin B12. For the Vitamin B12 content of various foods, see Table 5.2.18.

 

Table 5.2.18: B12 Content of Various Foods

Food

Serving

B12 (micrograms)

Clams

3 oz.

84.1

Salmon

3 oz.

4.8

Tuna, canned

3 oz.

2.5

Breakfast cereals, fortified

1 serving

1.5

Beef, top sirloin

3 oz.

1.4

Milk, low-fat

8 fl oz.

1.2

Yogurt, low-fat

8 oz.

1.1

Cheese, swiss

1 oz.

0.9

Egg

1 large

0.6

Source: Dietary Fact Sheet: Vitamin B12. National Institute of Health, Office of Dietary Supplements. Updated February 11, 2016. Accessed October 28, 2017.

Choline

Choline is a water-soluble substance that is not classified as a vitamin because the body can synthesize it. However, the synthesis of choline is limited and therefore it is recognized as an essential nutrient. Choline is needed to perform functions such as lipid transport, homocysteine metabolism, synthesizing the neurotransmitter acetylcholine, and phospholipids used to make cell membranes. A deficiency in choline may lead to impaired brain development in the fetus during pregnancy, and in adults can cause fatty liver and muscle damage.

Dietary Reference Intakes of Choline

There is insufficient data on choline, so the FNB has developed AIs for all ages to prevent fatty liver disease. The AI and UL for different age groups for choline are listed in Table 5.2.19.

 

Table 5.2.19: Adequate Intakes for Choline (mg/day) for adults over 19.

Age Group

AI Males and Females

Adults (>19 years)

Males: 550

Adults (>19 years)

Females: 425

Dietary Sources of Choline

Choline can be found in a variety of different foods. The main dietary sources of choline in the United States consist of primarily animal-based products. For the Choline content of various foods, see Table 5.2.20.

 

Table 5.2.20: Choline Content of Various Foods

Food

Serving

Choline (milligrams)

Egg

1 large

147

Soybeans

½ cup

107

Chicken breast

3 oz.

72

Mushrooms, shiitake

½ c.

58

Potatoes

1 large

57

Kidney beans

½ c.

45

Peanuts

¼ c.

24

Brown rice

1 c.

19

Summary of Water-Soluble Vitamins

A table that summarizes water-soluble vitamins.

Vitamin

Sources

Recommended Intake for Older Adults

Functions

Deficiency Diseases and Symptoms

Groups at Risk of Deficiency

Toxicity

UL

Vitamin C (ascorbic acid)

Orange juice, grapefruit juice, strawberries, tomato, sweet red pepper

75-90 mg/day

Antioxidant, collagen synthesis, hormone and neurotransmitter synthesis

Scurvy, bleeding gums, joint pain, poor wound healing,

Smokers, alcoholics, elderly

Kidney stones, GI distress, diarrhea

2000 mg/day

Thiamin (B1)

Pork, enriched and whole grains, fish, legumes

Males: 1.0-1.2 mg/day

Females: 0.9-1.1 mg/day

Coenzyme: assists in glucose metabolism, RNA, DNA, and A.T.P. synthesis

Beriberi: fatigue, confusion, movement impairment, swelling, heart failure

Alcoholics, older adults, eating disorders

None reported

N D

Riboflavin (B2)

Beef liver, enriched breakfast cereals, yogurt, steak, mushrooms, almonds, eggs

Males: 1.1-1.3 mg/day

Females: 0.9-1.1 mg/day

Coenzyme: assists in glucose, fat and carbohydrate metabolism, electron carrier, other B vitamins are dependent on

Ariboflavinosis: dry scaly skin, mouth inflammation and sores, sore throat, itchy eyes, light sensitivity

None

None reported

N D

Niacin (B3)

Meat, poultry, fish, peanuts, enriched grains

Males:

12-16 mg/day

Females:

11-14 mg/day

Coenzyme: assists in glucose, fat, and protein metabolism, electron carrier

Pellagra: diarrhea, dermatitis, dementia, death

Alcoholics

Nausea, rash, tingling extremities

35 mg/day from fortified foods and supplements

Pantothenic Acid (B5)

Sunflower seeds, fish, dairy products, widespread in foods

5 mg/day

Coenzyme: assists in glucose, fat, and protein metabolism, cholesterol and neurotransmitter synthesis

Muscle numbness and pain, fatigue, irritability

Alcoholics

Fatigue, rash

N D

B6 (Pyridoxine)

Meat, poultry, fish, legumes, nuts

Males: 1.4-1.7 mg/day

Females: 1.3-1.5 mg/day

Coenzyme; assists in amino-acid synthesis, glycogneolysis, neurotransmitter and hemoglobin synthesis

Muscle weakness, dermatitis, mouth sores, fatigue, confusion

Alcoholics

Nerve damage

100 mg/day

Biotin

Egg yolks, fish, pork, nuts and seeds

30 ug/day

Coenzyme; assists in glucose, fat, and protein metabolism, amino-acid synthesis

Muscle weakness, dermatitis, fatigue, hair loss

Those consuming raw egg whites

None reported

N D

Folate

Leafy green vegetables, enriched grains, orange juice

320-400  ug/day

 

Coenzyme; amino acid synthesis, RNA, DNA, and red blood cell synthesis

Diarrhea, mouth sores, confusion, anemia, neural-tube defects

Pregnant women, alcoholics

Masks B12 deficiency

1000 ug/day from fortified foods and supplements

B12 (cobalamin)

Meats, poultry, fish

2.0-2.4 ug/day

Coenzyme; fat and protein catabolism, folate function, red-blood-cell synthesis

Muscle weakness, sore tongue, anemia, nerve damage, neural-tube defects

Vegans, elderly

None reported

N D

Choline

Egg yolk, wheat, meat, fish, synthesis in the body

Males: 550 mg/day

Females: 425 mg/day

Synthesis of neurotransmitters and cell membranes, lipid transport

Non-alcoholic fatty liver disease, muscle damage, interfered brain development in fetus

None

Liver damage, excessive sweating, hypotension

3500 mg/day

Do B-Vitamin Supplements Provide an Energy Boost?

Although some marketers claim taking a vitamin that contains one thousand times the daily value of certain B vitamins boosts energy and performance, this is a myth that is not backed by science. The “feeling” of more energy from energy-boosting supplements stems from the high number of added sugars, caffeine, and other herbal stimulants that accompany the high doses of B vitamins. As discussed, B vitamins are needed to support energy metabolism and growth but taking in more than required does not supply you with more energy. A great analogy of this phenomenon is the gas in your car. Does it drive faster with a half-tank of gas or a full one? It does not matter; the car drives as fast as it has gas. Similarly, depletion of B vitamins will cause problems in energy metabolism but having more than is required to run metabolism does not speed it up. Buyers of B-vitamin supplements beware; B vitamins are not stored in the body and all excess will be flushed down the toilet along with the extra money spent.

 

B vitamins are naturally present in numerous foods, and many other foods are enriched with them. In the United States, B-vitamin deficiencies are rare; however, in the nineteenth century, some vitamin-B deficiencies plagued many people in North America. Niacin deficiency, also known as pellagra, was prominent in poorer Americans whose main dietary staple was refined cornmeal. Its symptoms were severe and included diarrhea, dermatitis, dementia, and even death. Some of the health consequences of pellagra are the result of niacin being in insufficient supply to support the body’s metabolic functions.

Key Takeaways

See the Table above for a summary of the water-soluble vitamins.

Contributors

University of Hawai’i at Mānoa Food Science and Human Nutrition Program: Allison Calabrese, Cheryl Gibby, Billy Meinke, Marie Kainoa Fialkowski Revilla, and Alan Titchenal

5.3 Introduction to Major Minerals

Learning Objectives

  • Discuss the roles of calcium in the body
  • Describe the risks associated with deficiency or toxicity of calcium.
  • List food groups that are dietary sources of calcium.
  • Discuss the roles of phosphorus in the body
  • List food groups that are dietary sources of phosphorus.
  • Discuss the roles of magnesium in the body
  • List food groups that are dietary sources of magnesium.
  • Discuss the roles of sodium in the body
  • List foods that are dietary sources of sodium
  • Describe ways to reduce daily sodium intake.
  • Discuss the roles of potassium in the body
  • List foods that are dietary sources of potassium.

Major minerals are classified as minerals that are required in the diet each day in amounts larger than 100 milligrams. These include sodium, potassium, chloride, calcium, phosphorus, magnesium, and sulfur. These major minerals can be found in various foods. For example, in Guam, the major mineral, calcium, is consumed in the diet not only through dairy, a common source of calcium, but also through the mixed dishes, desserts, and vegetables that they consume. A varied diet significantly improves an individual’s ability to meet nutrient needs (Pobocik, Trager & Monson, 2008).

Bioavailability

Minerals are not as efficiently absorbed as most vitamins, so minerals’ bioavailability can be very low. Plant-based foods often contain factors, such as oxalate and phytate, that bind to minerals and inhibit (interfere with) their absorption. In general, minerals are better absorbed from animal-based foods. In most cases, absorption will decrease if a particular mineral’s dietary intake is increased. Some minerals influence the absorption of others. For instance, excess zinc in the diet can impair iron and copper absorption. Conversely, certain vitamins enhance mineral absorption. For example, Vitamin C boosts iron absorption, and Vitamin D boosts calcium and magnesium absorption. As is the case with vitamins, certain gastrointestinal disorders, and diseases, such as Crohn’s disease and kidney disease, as well as the aging process, impair mineral absorption, putting people with malabsorption conditions and the elderly at higher risk for mineral deficiencies.

Calcium

Calcium’s Functional Roles

Calcium is the most abundant mineral in the body, and over 99% of it is stored in bone tissue. Although only 1% of the calcium in the human body is found in the blood and soft tissues, it is here that it performs the most critical functions. Blood calcium levels are rigorously controlled so that if blood levels drop the body will rapidly respond by stimulating bone breakdown, thereby releasing stored calcium into the blood. Thus, bone tissue sacrifices its stored calcium to maintain blood calcium levels. Therefore, bone health depends on dietary calcium intake, and blood calcium levels do not always correspond to dietary intake.

 

Calcium plays a role in several different functions in the body. The most well-known calcium function is to build and strengthen bones and teeth. Recall that when bone tissue first forms during the modelling or remodelling process, it is unhardened, protein-rich tissue. In bone mineralization, calcium phosphates (salts) are deposited on the protein matrix. Calcium salts typically make up about 65% of bone tissue. When your diet is calcium deficient, the mineral content of bone decreases, causing it to become brittle and weak. Thus, increased calcium intake helps increase bone tissue’s mineralized content. Greater mineralized bone tissue corresponds to a greater bone mineral density (BMD) and greater bone strength. The remaining calcium plays a role in nerve impulse transmission by facilitating electrical impulse transmission from one nerve cell to another. Calcium in muscle cells is essential for muscle contraction because the flow of calcium ions is needed for the muscle proteins to interact. Calcium is also essential in blood clotting by activating clotting factors to fix damaged tissue.

 

In addition to calcium’s four primary functions, calcium has several other minor functions that are critical for maintaining normal physiology. For example, without calcium, the hormone insulin could not be released from cells in the pancreas, and glycogen could not be broken down in muscle cells and used to provide energy for muscle contraction.

Maintaining Calcium Levels

Because calcium performs such vital functions in the body, blood calcium level is closely regulated by the hormones parathyroid hormone (PTH), calcitriol, and calcitonin. PTH is secreted to increase blood calcium levels via three different mechanisms when blood calcium levels are low. First, PTH stimulates the release of calcium stored in the bone. Second, PTH acts on kidney cells to increase calcium reabsorption and decrease excretion in the urine. Third, PTH stimulates enzymes in the kidney that activate Vitamin D to calcitriol. Calcitriol is the active hormone that acts on the intestinal cells and increases dietary calcium absorption. When blood calcium levels become too high, the hormone calcitonin is secreted by cells in the thyroid gland and PTH secretion stops. At higher nonphysiological concentrations, calcitonin lowers blood calcium levels by increasing calcium excretion in the urine, preventing further absorption of calcium in the gut and directly inhibiting bone resorption (Birkett, 1998).

 

There are three possible routes of the parathyroid hormone when blood calcium levels are low. One is to stimulate the release of calcium from the bone to get to normal calcium levels. A second is the activation of Vitamin D which increases intestinal calcium absorption. The last route is to reduce the calcium lost in urine. These are all ways the body maintains calcium levels (Birkett, 1998).

Beware of Lead

There is public health concern about the lead content of some brands of calcium supplements, as supplements derived from natural sources such as oyster shell, bone meal, and dolomite (a type of rock containing calcium magnesium carbonate) are known to contain high amounts of lead. In one study conducted on twenty-two brands of calcium supplements, eight of the brands exceeded the acceptable limit for lead content. This was the case in supplements derived from oyster shells and refined calcium carbonate. The same study also found that brands claiming to be lead-free did show very low lead levels. Because lead levels in supplements are not disclosed on labels, it is important to know that products not derived from an oyster shell or other natural substances are generally low in lead content. In addition, it was also found that one brand did not disintegrate as is necessary for absorption, and one brand contained only 77 percent of the stated calcium content (Ross et al., 2000).

Diet, Supplements, and Chelated Supplements

In general, calcium supplements do not perform as well as dietary sources of calcium in providing many of the health benefits linked to higher calcium intake. This is partly because dietary sources of calcium supply additional nutrients with health-promoting activities. Chelated forms of calcium supplements are easier to absorb as the chelation process protects the calcium from oxalates and phytates that may bind with the calcium in the intestines. However, these are more expensive supplements and only increase calcium absorption by up to 10 percent. In people with low dietary intakes of calcium, calcium supplements have a negligible benefit on bone health without Vitamin D – Vitamin D must be activated and, in the bloodstream, promote calcium absorption. Thus, it is important to maintain an adequate Vitamin D intake for optimal calcium utilization. Limiting calcium supplementation and striving to get most of your calcium from food is best.

Dietary Reference Intake for Calcium

The recommended dietary allowances (RDAs) for calcium are listed in Table 5.3.1. The RDAs are higher for women above age fifty and men older than seventy-one, because as we age, calcium absorption in the gut decreases, Vitamin D3 activation is reduced, and maintaining adequate blood calcium levels is important to prevent accelerating bone tissue loss (especially during menopause). Currently, the dietary intake of calcium for females above age nine is, on average, below the R.D.A. for calcium. The Institute of Medicine (IOM) recommends that people not consume over 2,500 milligrams per day of calcium as it may cause adverse effects in some people.

 

Table 5.3.1: Dietary Reference Intakes for Calcium (mg/day) for adolescents and adults.

Age Group

RDA Males and Females

UL

Adolescents (14-18 years)

1300

2500

Adults (19-50 years)

1000

2500

Adult Females (50-71 years)

1200

2500

Adults (>71 years)

1200

2500

Dietary Sources of Calcium

In the typical Canadian diet, calcium is obtained mostly from dairy products, primarily cheese. A slice of cheddar or Swiss cheese contains just over 200 milligrams of calcium. One cup of nonfat milk contains approximately 300 milligrams of calcium, which is about a third of the RDA for calcium for most adults. Foods fortified with calcium, such as cereals, soy milk, and orange juice also provide one-third or greater of the calcium RDA. Although the typical American diet relies primarily on dairy products for obtaining calcium, there are other good non-dairy sources of calcium.

Tools For Change

If you need to increase calcium intake, are a vegan, or have a food allergy to dairy products, it is helpful to know that some plant-based foods are high in calcium. Tofu (made with calcium sulfate), turnip greens, mustard greens, and Chinese cabbage are good sources. For a list of non-dairy sources, you can find the calcium content for thousands of foods by visiting the USDA National Nutrient Database. When obtaining calcium from a vegan diet, it is important to know that some plant-based foods significantly impair calcium absorption. These include spinach, Swiss chard, rhubarb, beets, cashews, and peanuts. Careful planning and good selections can provide sufficient calcium for those who do not consume milk or dairy products. Table 5.3.2 shows the calcium content of various foods.

 

Table 5.3.2: Calcium Content of Various Foods

Food

Serving

Calcium (milligrams)

Yogurt, low fat

8 oz.

415

Mozzarella

1.5 oz.

333

Sardines, canned with bones

3 oz.

325

Cheddar Cheese

1.5 oz.

307

Milk, nonfat

8 oz.

299

Soymilk, calcium-fortified

8 oz.

299

Orange juice, calcium-fortified

6 oz.

261

Tofu, firm, made with calcium sulfate

½ c.

253

Salmon, canned with bones

3 oz.

181

Turnip, boiled

½ c.

99

Kale, cooked

1 c.

94

Vanilla Ice Cream

½ c.

84

White bread

1 slice

73

Kale, raw

1 c.

24

Broccoli, raw

½ c.

21

Source: Fact Sheet for Health Professionals: Calcium. National Institute of Health, Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/Calcium-HealthProfessional/. Updated September 26, 2018. Accessed June 30, 2019.

Key Takeaways

  • The most well-known role of calcium is to build and strengthen bones and teeth.
  • Calcium plays a role in nerve impulse transmission by facilitating electrical impulse transmission from one nerve cell to another.
  • Calcium in muscle cells is essential for muscle contraction because the flow of calcium ions is needed for the muscle proteins to interact.
  • Calcium is essential in blood clotting by activating clotting factors to fix damaged tissue.
  • In addition to calcium’s four primary functions calcium has several other minor functions that are critical for maintaining normal physiology. Without calcium, the hormone insulin could not be released from cells in the pancreas, and glycogen could not be broken down in muscle cells and used to provide energy for muscle contraction.
  • Sufficient dietary intake of calcium is critical for proper bone health. Calcium inadequacy is prevalent in adolescent girls and the elderly.
  • Dairy products, fortified milk alternatives and some vegetables contain calcium.
  • Consuming more calcium than is recommended can be detrimental. If you take a calcium supplement, take 500 mg or less at one time.
 Contributors

University of Hawai’i at Mānoa Food Science and Human Nutrition Program: Allison Calabrese, Cheryl Gibby, Billy Meinke, Marie Kainoa Fialkowski Revilla, and Alan Titchenal

Phosphorous

Phosphorus is present in our bodies as part of a phosphate group. These phosphate groups are essential as a structural component of cell membranes (as phospholipids), DNA and RNA, energy production (ATP), and regulation of acid-base homeostasis. Phosphorus, however, is mostly associated with calcium as a part of the mineral structure of bones and teeth. Blood phosphorus levels are not controlled as strictly as calcium, so the PTH stimulates renal excretion of phosphate so that it does not accumulate to toxic levels.

Dietary Reference Intakes for Phosphorus

In comparison to calcium, most Canadians are not at risk of having a phosphate deficiency. Phosphate is present in many foods popular in the Canadian diet including meat, fish, dairy products, processed foods, and beverages. Phosphate is added to many foods because it acts as an emulsifying agent, prevents clumping, improves texture and taste, and extends shelf-life. The average intake of phosphorus in adults ranges between 1,000 and 1,500 milligrams per day, well above the RDA of 700 milligrams per day. The UL set for phosphorous is 4,000 milligrams per day for adults and 3,000 milligrams per day for people over age seventy. Table 5.3.3 contains the RDAs for phosphorus, and table 5.3.4 shows the phosphorous content of various foods.

Table 5.3.3: Dietary Reference Intakes for Phosphorus (mg/day) for adolescents and adults.

Age Group

RDA Males and Females

UL

Adolescents (14-18 years)

1250

4000

Adults (19-70 years)

700

4000

Adults (>71 years)

700

3000

Dietary Sources of Phosphorus

Table 5.3.4: Phosphorus Content of Various Foods

Foods

Serving

Phosphorus (milligrams)

Salmon

3 oz.

315

Yogurt, nonfat

8 oz.

306

Turkey, light meat

3 oz.

217

Chicken, light meat

3 oz.

135

Beef

3 oz.

179

Lentils*

½ c.

178

Almonds*

1 oz.

136

Mozzarella

1 oz.

131

Peanuts*

1 oz.

108

Whole wheat bread

1 slice

68

Egg

1 large

86

Carbonated cola drink

12 oz.

41

Bread, enriched

1 slice

25

Micronutrient Information Center: Phosphorus. Oregon State University, Linus Pauling Institute. Updated on June 2014. Accessed June 30, 2019.

Contributors

University of Hawai’i at Mānoa Food Science and Human Nutrition Program: Allison Calabrese, Cheryl Gibby, Billy Meinke, Marie Kainoa Fialkowski Revilla, and Alan Titchenal

Magnesium

Learning Objectives

  • Discuss the roles of magnesium in the body
  • List food groups that are dietary sources of magnesium.

Magnesium’s Functional Role

Approximately 60 percent of magnesium in the human body is stored in the skeleton, making up about 1 percent of mineralized bone tissue. Magnesium is not an integral part of the hard mineral crystals, but it resides on the crystal’s surface and helps maximize the bone structure. Observational studies link magnesium deficiency with an increased risk for osteoporosis. A magnesium-deficient diet is associated with decreased levels of parathyroid hormone and the activation of Vitamin D, which may lead to an impairment of bone remodelling. A study of nine hundred elderly women and men did show that higher dietary intakes of magnesium correlated to an increased bone mineral density (BMD) in the hip.1 Only a few clinical trials have evaluated the effects of magnesium supplements on bone health, and their results suggest some modest benefits on BMD.

In addition to participating in bone maintenance, magnesium has several other functions in the body. Magnesium is required in more than three hundred enzymatic reactions, and every reaction involving the cellular energy molecule ATP. Magnesium plays a role in DNA, RNA, carbohydrate, and lipid synthesis and is essential for nerve conduction and muscle contraction. Another health benefit of magnesium is that it may decrease blood pressure.

Many Canadians do not get the recommended intake of magnesium from their diets. Some observational studies suggest mild magnesium deficiency is linked to increased risk for cardiovascular disease. Signs and symptoms of severe magnesium deficiency may include tremor, muscle spasms, loss of appetite, and nausea.

1 Tucker KL, Hannan MT, et al. Potassium, Magnesium, and Fruit and Vegetable Intakes Are Associated with Greater Bone Mineral Density in Elderly Men and Women. Am J Clin Nutr. 1999; 69(4), 727–36. Accessed June 30, 2019.

Dietary Reference Intake and Food Sources for Magnesium

The RDAs for magnesium for adults between ages nineteen and thirty are 400 milligrams per day for males and 310 milligrams per day for females. For adults above age thirty, the RDA increases slightly to 420 milligrams per day for males and 320 milligrams for females. Table 5.3.5 shows the RDA for magnesium.

Table 5.3.5: Dietary Reference Intakes for Magnesium (mg/day) for adolescents and adults.

Age Group

RDA Males and Females

UL

Adolescents (14-18 years)

410

350*

Adults (19-30 years)

400

350*

Adults (30-70 years)

420

350*

Adults (>71 years)

420

350*

*The UL is based on supplemental magnesium, not magnesium from food.

Dietary Sources of Magnesium

Magnesium is part of the green pigment, chlorophyll, vital for photosynthesis in plants; therefore, green leafy vegetables are good dietary sources for magnesium. Magnesium is also found in high concentrations in fish, dairy products, meats, whole grains, and nuts. Additionally, chocolate, coffee, and hard water contain a good amount of magnesium. Most people in America do not fulfill the RDA for magnesium in their diets. Typically, Western diets have a low fish intake and predominantly include refined grains rather than whole grains. Table 5.3.6 shows the magnesium content of various foods.

 

Table 5.3.6: Magnesium Content of Various Foods

Food

Serving

Magnesium (milligrams)

Almonds

1 oz.

80

Cashews

1 oz.

74

Soymilk

1 c.

61

Black beans

½ c.

60

Edamame

½ c.

50

Bread

2 slices

46

Avocado

1 c.

44

Brown rice

½ c.

42

Yogurt

8 oz.

42

Oatmeal, instant

1 packet

36

Salmon

3 oz.

26

Chicken breasts

3 oz.

22

Apple

1 medium

9

Source: Dietary Supplement Fact Sheet: Magnesium. National Institutes of Health, Office of Dietary Supplements. Updated September 26, 2018. Accessed June 30, 2019.

Contributors

University of Hawai’i at Mānoa Food Science and Human Nutrition Program: Allison Calabrese, Cheryl Gibby, Billy Meinke, Marie Kainoa Fialkowski Revilla, and Alan Titchenal

Sodium

Sodium is vital not only for maintaining fluid balance but also for many other essential body functions. In contrast to many minerals, sodium absorption in the small intestine is highly efficient, and in a healthy individual, all excess sodium is excreted by the kidneys. In fact, very little sodium is required in the diet (about 200 milligrams) because the kidneys actively reabsorb sodium. Kidney reabsorption of sodium is hormonally controlled, allowing for a relatively constant sodium concentration in the blood.

Needs and Dietary Sources of Sodium

Table salt is approximately 40 percent sodium and 60 percent chloride. As a reference point, just ⅔ teaspoon of salt is needed in the diet to meet the AI for sodium. The AI considers the amount of sodium lost in sweat during recommended physical activity levels and additionally provides for the sufficient intake of other nutrients, such as chloride. Sodium deficiency is not a concern, and higher intakes are associated with an increased risk of chronic disease, especially blood pressure. The Tolerable Upper Intake Level (UL) for sodium is not determined; however, it is recommended to reduce intakes to below 2,300 milligrams per day for adults, especially if a person has hypertension. Just over 1 teaspoon of salt contains 2,300 milligrams of sodium. Table 5.3.7 shows the AI for sodium.

 

Table 5.3.7: Adequate Intakes for Sodium (mg/day) for adolescents and adults.

Age Group

AI for Males and Females

UL

Adolescents (14-18 years)

1500

2300

Adults (19-50 years)

1500

2300

Adults (51-70 years)

1500

2300

Adults (>71 years)

1500

2300

Source: Dietary Reference Intakes: Water, Potassium, Sodium, Chloride, and Sulfate. Institute of Medicine. http://www.iom.edu/Reports/2004/Dietary-Reference-Intakes-Water-Potassium-Sodium-Chloride-and-Sulfate.aspx. Updated February 11, 2004. Accessed September 22, 2017.

Food Sources for Sodium

Most sodium in the typical North American diet comes from processed and prepared foods. Manufacturers add salt to foods as a preservative and to improve texture and flavour. The amount of salt in similar food products varies widely. Some foods, such as meat, poultry, and dairy foods, contain naturally occurring sodium. For example, one cup of low-fat milk contains 107 milligrams of sodium. Naturally occurring sodium accounts for less than 12 percent of dietary intake in a typical diet. For the sodium contents of various foods see Table 5.3.8.

 

Table 5.3.8: Sodium Contents of Selected Foods.

Food

Serving Size

Sodium(milligrams)

Breads, all types

1 oz.

95–210

Rice Chex cereal

1 ¼ c.

292

Raisin Bran cereal

1 c.

362

Frozen pizza, plain, cheese

4 oz

450–1200

Frozen vegetables, all types

½ c.

2–160

Salad dressing, regular fat, all types

2 Tbsp.

110–505

Salsa

2 Tbsp.

150–240

Soup (tomato), reconstituted

8 oz.

700–1260

Potato chips

1 oz. (28.4 g)

120–180

Tortilla chips

1 oz. (28.4 g)

105–160

Pork

3 oz.

59

Chicken

(½ breast)

69

Chicken fast food dinner

Not Determined

2243

Chicken noodle soup

1 c.

1107

Dill pickle

1

928

Soy sauce

1 Tbsp.

1029

Canned corn

1 c.

384

Baked beans, canned

1 c.

856

Hot dog

1

639

Burger, fast-food

1

990

Steak

3 oz.

55

Canned tuna

3 oz.

384

Fresh tuna

3 oz.

50

Dry-roasted peanuts

1 c.

986

American cheese

1 oz.

406

Tap water

8 oz.

12

Sodium on the Nutrition Facts Panel

Sodium level in milligrams is a required listing on a Nutrition Facts label.

Tools for Change

To decrease your sodium intake, become a salt-savvy shopper by reading the label and the ingredient list of processed foods and choosing those lower in salt. Even better, stay away from processed foods and control the seasoning food with salt-based seasoning. Reducing salty foods diminishes salt cravings, so you may need to try a lower sodium diet for a week or two before you will be satisfied with the less salty food. If you have been diagnosed with hypertension, consider following the D.A.S.H. diet.

Salt Substitutes

Using a salt substitute is an option for those looking to decrease salt use. However, many salt substitutes still contain sodium, just in lesser amounts than table salt. Also, remember that most salt in the diet is from proccessed foods, not from table salt. Salt substitutes often replace sodium with potassium. People with kidney disorders often have problems excreting excess potassium and are advised to avoid salt substitutes containing potassium. People with liver disorders should also avoid salt substitutes containing potassium because their treatment is often accompanied by potassium dysregulation. Table 5.3.9 contains a list of low-sodium seasonings.

 

Table 5.3.9: Salt Alternatives.

Alternative

Implementation of Alternative

Allspice

Lean ground meats, stews, tomatoes, peaches, applesauce, cranberry sauce, gravies, lean meat

Almond extract

Puddings, fruits

Caraway seeds

Lean meats, stews, soups, salads, bread, cabbage, asparagus, noodles

Chives

Salads, sauces, soups, lean-meat dishes, vegetables

Cider vinegar

Salads, vegetables, sauces

Cinnamon

Fruits, bread, pie crusts

Curry powder

Lean meats (especially lamb), veal, chicken, fish, tomatoes, tomato soup, mayonnaise,

Dill

fish sauces, soups, tomatoes, cabbages, carrots, cauliflower, green beans, cucumbers, potatoes, salads, macaroni, lamb

Garlic (not garlic salt)

Lean meats, fish, soups, salads, vegetables, tomatoes, potatoes

Ginger

Chicken, fruits

Lemon juice

Lean meats, fish, poultry, salads, vegetables

Mace

Hot bread, apples, fruit salads, carrots, cauliflower, squash, potatoes, veal, lamb

Mustard (dry)

lean ground meats, lean meats, chicken, fish, salads, asparagus, broccoli, Brussels sprouts, cabbage, mayonnaise, sauces

Nutmeg

Fruits, pie crust, lemonade, potatoes, chicken, fish, lean meatloaf, toast, veal, pudding

Onion powder

Lean meats, stews, vegetables, salads, soups

Paprika

Lean meats, fish, soups, salads, sauces, vegetables

Parsley

Lean meats, fish, soups, salads, sauces, vegetables

Peppermint extract

Puddings, fruits

Pimiento

Salads, vegetables, casserole dishes

Rosemary

Chicken, veal, lean meatloaf, lean beef, lean pork, sauces, stuffings, potatoes, peas, lima beans

Sage

Lean meats, stews, biscuits, tomatoes, green beans, fish, lima beans, onions, lean pork

Savory

Salads, lean pork, lean ground meats, soups, green beans, squash, tomatoes, lima beans, peas

Thyme

Lean meats (especially veal and lean pork), sauces, soups, onions, peas, tomatoes, salads

Turmeric

Lean meats, fish, sauces, rice

Source: Shaking the Salt Habit. American Heart Association.Updated Oct 31, 2016. Accessed June 30, 2019.

Key Takeaways

  • Sodium is vital for maintaining fluid balance, nerve impulse transmission, nutrient absorption in the small intestine, and nutrient reabsorption in the kidney.
  • The sodium-potassium pump facilitates the transport of nutrients through intestinal cells.
  • Most sodium in the typical North American diet comes from processed and prepared foods. Read labels and choose foods lower in sodium more often.

Contributors

University of Hawai’i at Mānoa Food Science and Human Nutrition Program: Allison Calabrese, Cheryl Gibby, Billy Meinke, Marie Kainoa Fialkowski Revilla, and Alan Titchenal

Potassium

Functions of Potassium in the Body

Potassium plays an essential role in managing blood pressure. Potassium balances the effects of sodium on blood pressure because the more potassium you eat, the more sodium you lose through urine. Nerve impulses also involve both sodium and potassium. A nerve impulse moves along a nerve via the movement of sodium ions into the cell. To end the impulse, potassium ions rush out of the nerve cell, thereby decreasing the positive charge inside the nerve cell. This diminishes the stimulus. The sodium-potassium pump transfers sodium ions out in exchange for potassium ions in to restore the original concentrations of ions between the intracellular and extracellular fluid. The nerve cell is ready for the next impulse once the ion concentrations are restored.  Similarly, potassium is involved in restoring the normal membrane potential and ending muscle contraction in muscle cells. Potassium is also involved in protein synthesis, energy metabolism, and platelet function and acts as a buffer in blood, playing a role in acid-base balance.

Imbalances of Potassium

Insufficient potassium levels in the body (hypokalemia) can be caused by a low dietary intake of potassium or by high sodium intakes, but more commonly, it results from medications that increase water excretion, mainly diuretics. The signs and symptoms of hypokalemia are related to the functions of potassium in nerve cells and consequently skeletal and smooth-muscle contraction, including muscle weakness and cramps, respiratory distress, and constipation. Severe potassium depletion can cause the heart to have abnormal contractions and can even be fatal. High levels of potassium in the blood, or hyperkalemia, also affect the heart, often displaying no signs or symptoms. Extremely high levels of potassium in the blood disrupt the electrical impulses that stimulate the heart and can cause the heart to stop. Hyperkalemia is usually only seen in those with kidney dysfunction. Table 5.3.10 shows the AI for potassium.

Needs and Dietary Sources of Potassium

Table 5.3.10: Adequate Intake of Potassium(mg/day) for adolescents and adults.

Age Group

AI for Males and Females

Adolescents (14-18 years)

Males: 3000

Adolescents (14-18 years)

Females: 2300

Adults (>19 years)

Males: 3400

Adults (>19 years)

Females: 2600

Food Sources for Potassium

Fruits and vegetables that contain high amounts of potassium are spinach, lettuce, broccoli, peas, tomatoes, potatoes, bananas, apples, and apricots. Whole grains, seeds, certain fish (such as salmon, cod, and flounder), and meats are also high in potassium. The Dietary Approach to Stop Hypertension (DASH diet) emphasizes potassium-rich foods.

Table 5.3.9: Potassium Contents of Selected Foods.

Food Serving Size Potassium (milligrams)
Beet greens, cooked 1 c. 1309
Swiss chard, cooked 1c. 961
Potato, with skin 1 medium 926
Yam, cooked 1 c. 911
Yogurt, plain, nonfat 8 oz. 625
White beans, cooked ½ c. 502
Orange juice, 100% 1 c. 496
Banana 1 medium 451
Grapefruit 1 fruit 415
Coconut water, unsweetened 1 c. 396
Milk, low fat (1%) 1 c. 366
Lentils, cooked ½ c. 366
Avocado ½ c. 364
Beef 3 oz. 288
Pistachio nuts 1 oz. 286
Lamb 3 oz. 285

 

Bioavailability

Greater than 90 percent of dietary potassium is absorbed in the small intestine. Although highly bioavailable, potassium is a very soluble mineral and is easily lost during the cooking and processing of foods. Fresh and frozen foods are better sources of potassium than canned.

Key Takeaways

  • Potassium plays an important role in managing blood pressure. Potassium balances the effects of sodium on blood pressure because the more potassium you eat, the more sodium you lose through urine.
  • Nerve impulses also involve both sodium and potassium. Similarly, potassium is involved in restoring the normal membrane potential and ending muscle contraction in muscle cells.
  • Potassium is involved in protein synthesis, energy metabolism, and platelet function, and acts as a buffer in blood, playing a role in acid-base balance.
  • Fruits and vegetables that contain high amounts of potassium are spinach, lettuce, broccoli, peas, tomatoes, potatoes, bananas, apples, and apricots. Whole grains, seeds, certain fish (such as salmon, cod, and flounder), and meats are also high in potassium.
  • The Dietary Approach to Stop Hypertension (DASH diet) emphasizes potassium-rich foods.

Contributors

University of Hawai’i at Mānoa Food Science and Human Nutrition Program: Allison Calabrese, Cheryl Gibby, Billy Meinke, Marie Kainoa Fialkowski Revilla, and Alan Titchenal

Table 5.3.10: Summary of Minerals

Micronutrient Sources Recommended Intake for Older Adults Functions Deficiency Diseases and Symptoms Groups at Risk of Deficiency Toxicity UL
Calcium Yogurt, cheese, sardines, milk, orange juice, turnip 1000 – 1200 mg/day Component of mineralized bone, provides structure and microarchitecture Increased risk of osteoporosis Postmenopausal women, those who are lactose intolerant, or vegan Kidney stones 2000 mg/day
Phosphorus Salmon, yogurt, turkey, chicken, beef, lentils 580-700 mg/day The structural component of bones, cell membrane, DNA and RNA, and ATP Bone loss, weak bones Older adults, alcoholics None 3000 mg/day
Magnesium Whole grains and legumes, almonds, cashews, hazelnuts, beets, collards, and kelp Males: 350-420 mg/day

Females:

265-320 mg/day

Component of mineralized bone, ATP synthesis and utilization, carbohydrate, lipid, protein, RNA, and DNA synthesis Tremor, muscle spasms, loss of appetite, nausea Alcoholics, individuals with kidney and gastrointestinal disease Nausea, vomiting, low blood pressure 350 mg/day
Sulfur Protein foods ND Structure of some vitamins and amino acids, acid-base balance None when protein needs are met None None ND
Sodium Processed foods, table salt, pork, chicken 1200 mg/day Major positive extracellular ion, nerve transmission, muscle contraction, fluid balance Muscle cramps People consuming too much water, excessive sweating, those with vomiting or diarrhea High blood pressure 2300 mg/day
Potassium Fruits, vegetables, legumes, whole grains, milk Males: 3400 mg/day

Females: 2600 mg/day

Major positive intracellular ion, nerve transmission, muscle contraction, fluid balance Irregular heartbeat, muscle cramps People consuming diets high in processed meats, those with vomiting or diarrhea Abnormal heartbeat ND
Chloride Table salt, processed foods 1800 mg/day Major negative extracellular ion, fluid balance Unlikely None None 3600 mg/day

5.4 Trace Minerals

Learning Objectives

  • Define the role of iron in our body.
  • Identify foods or substances that enhance or inhibit the absorption of iron.
  • Describe iron deficiency, symptoms, at-risk populations, and dietary measures to reduce the incidence of iron deficiency.
  • Describe iron toxicity and methods to prevent toxicity.
  • Explain the role of zinc in the body.
  • Identify food sources of zinc.
  • Describe the role of selenium in the body.
  • Identify food sources of selenium.
  • Examine the role of iodine in the body.
  • Identify food sources of iodine.
  • Examine the role of fluoride in the body.
  • Identify food sources of flouride.

 

Trace minerals are required in the diet in smaller amounts, specifically 100 milligrams or less per day. These include copper, zinc, selenium, iodine, chromium, fluoride, manganese, molybdenum, and others. Although trace minerals are needed in smaller amounts, a deficiency in a trace mineral can be just as detrimental to health as major mineral deficiencies.

 

Iodine deficiency is a major concern in countries such as Fiji. In the 1990s, almost 50% of the population had signs of iodine deficiency, also known as goiter. To combat this national issue, the government of Fiji banned non-iodized salt and allowed only fortified iodized salt into the country in hopes of increasing the consumption of iodine. With this law, and health promotion efforts encouraging seafood consumption, significant progress has been made in decreasing the prevalence of iodine deficiency in Fiji. Table 5.4.1 contains a summary of trace minerals.

Iron

Red blood cells contain the oxygen-carrying protein hemoglobin. It is composed of four globular peptides, each containing a heme complex. In the center of each heme, lies iron. Iron is needed to produce other iron-containing proteins such as myoglobin. Myoglobin is a protein found in muscle tissues that enhances the amount of available oxygen for muscle contraction. Iron is also a key component of hundreds of metabolic enzymes. Many of the proteins of the electron-transport chain contain iron-sulfur clusters involved in the transfer of high-energy electrons and, ultimately ATP synthesis. Iron is also involved in numerous metabolic reactions that take place mainly in the liver and detoxify harmful substances. Moreover, iron is required for DNA synthesis. The great majority of iron used in the body is recycled from the continuous breakdown of red blood cells.

 

The iron in hemoglobin binds to oxygen in the capillaries of the lungs and transports it to cells where the oxygen is released. If iron levels are low, hemoglobin is not synthesized enough, and the oxygen-carrying capacity of red blood cells is reduced, resulting in anemia. When iron levels are low in the diet, the small intestine becomes more efficient at absorbing iron to compensate for the low dietary intake, but this process cannot make up for the excessive loss of iron that occurs with chronic blood loss or low intake. When blood cells are decommissioned, the body recycles the iron back to the bone marrow where red blood cells are made. The body stores iron in the bone marrow, liver, spleen, and skeletal muscle. A relatively small amount of iron is excreted when cells lining the small intestine and skin cells die and in blood loss, such as during menstrual bleeding. The lost iron must be replaced with dietary sources.

 

The bioavailability of iron is highly dependent on dietary sources. In animal-based foods, about 60 percent of iron is bound to hemoglobin, and heme iron is more bioavailable than non-heme iron. The other 40 percent of iron in animal-based foods is non-heme, the only iron source in plant-based foods. Some plants contain chemicals (such as phytate, oxalates, tannins, and polyphenols) that inhibit iron absorption. Eating fruits and vegetables rich in Vitamin C at the same time as iron-containing foods markedly increases iron absorption. A review published in the American Journal of Clinical Nutrition reported that in developed countries iron bioavailability from mixed diets ranges between 14 and 18 percent and that from vegetarian diets ranges between 5 and 12 percent (CDC, 2018). Vegans are at higher risk for iron deficiency, but careful meal planning does prevent its development. Iron deficiency is the most common of all micronutrient deficiencies. Table 5.4.2 displays enhancers and inhibitors of iron absorption.

 

Table 5.4.2: Enhancers and Inhibitors of Iron Absorption

Enhancers

Inhibitors

Meat

Phosphate

Fish

Calcium

Poultry

Tea

Seafood

Coffee

Stomach Acid

Colas

 

Soy Protein

 

High Doses of Minerals

 

Bran or Fiber

 

Phytates

 

Oxalates

 

Polyphenols

 Iron Toxicity

The body excretes little iron, so the potential for accumulation in tissues and organs is considerable. Iron accumulation in tissues and organs can cause many health problems in children and adults, including extreme fatigue, arthritis, joint pain, and severe liver and heart toxicity. In children, death has occurred from ingesting as little as 200 mg of iron; therefore, it is critical to keep iron supplements out of children’s reach. The IOM has set tolerable upper intake levels of iron (Table 5.4.3). Hemochromatosis, a hereditary disease, leads to abnormal iron metabolism and an accumulation of iron in certain tissues such as the liver, pancreas, and heart. The signs and symptoms of hemochromatosis are similar to iron overload in tissues caused by high dietary intake of iron or other non-genetic metabolic abnormalities but are often increased in severity. Table 5.4.4 shows the iron content of various foods.

Dietary Reference Intakes for Iron

Table 5.4.3: Dietary Reference Intakes for Iron (mg/day) for adolescents and adults.

Age Group

RDA for Males and Females

UL

Adolescents (14-18 years)

Males: 11

45

Adolescents (14-18 years)

Females: 15

45

Adults (19-50 years)

Males: 8

45

Adults (19-50 years)

Females: 18

45

Adults (>50 years)

8

45

Dietary Sources of Iron

Table 5.4.4: Iron Content of Various Foods.

Food

Serving

Iron (milligrams)

Breakfast cereals, fortified

1 serving

18

Oysters

3 oz.

8

Dark chocolate

3 oz.

7

Beef liver

3 oz.

5

Lentils

½ c.

3

Spinach, boiled

½ c.

3

Tofu, firm

½ c.

3

Kidney beans

½ c.

2

Sardines

3 oz.

2

Key Takeaways

  • Red blood cells contain the oxygen-carrier protein hemoglobin.
  • Iron is needed to produce other iron-containing proteins, such as myoglobin.
  • Iron isa key component of hundreds of metabolic enzymes.
  • Iron is involved in numerous metabolic reactions that take place mainly in the liver and it works to detoxify harmful substances.
  • Iron is required for DNA synthesis.
  • Some foods enhance or inhibit the absorption of iron.
  • Iron deficiency anemia develops from insufficient iron levels in the body, resulting in fewer and smaller red blood cells containing lower amounts of hemoglobin.
  • Symptoms of iron-deficiency include fatigue, weakness, pale skin, shortness of breath, dizziness, swollen, sore tongue,and an abnormal heart rate.
  • Including iron-rich food sources in the diet is critical to avoiding deficiency. Vitamin C-rich foods eaten with sources of non-heme iron can increase the absorption of non-heme iron.
  • Iron supplements can resemble candy and as little as 200 mg can cause iron toxicity in a child.
  • Hemochromatosis is a genetic disorder that results in iron accumulation of iron in the body.

 

Contributors

University of Hawai’i at Mānoa Food Science and Human Nutrition Program: Allison Calabrese, Cheryl Gibby, Billy Meinke, Marie Kainoa Fialkowski Revilla, and Alan Titchenal

Zinc

Zinc is a cofactor for over two hundred enzymes in the human body and plays a direct role in RNA, DNA, and protein synthesis and energy metabolism. Due to its prominent roles in anabolic and energy metabolism, a zinc deficiency in infants and children blunts growth. The reliance of growth on adequate dietary zinc was discovered in the early 1960s in the Middle East, where adolescent nutritional dwarfism was linked to diets containing high amounts of phytate. Cereal grains and some vegetables contain chemicals, one being phytate, which blocks zinc absorption and other minerals in the gut. Half of the world’s population is estimated to have a zinc-deficient diet (Medes Garrido Abregu, et al., 2022). This is primarily due to the lack of red meat and seafood and reliance on cereal grains as the main dietary staple. In adults, severe zinc deficiency can cause hair loss, diarrhea, skin sores, increased wound healing time, loss of appetite, and weight loss. Zinc is a required cofactor for an enzyme that synthesizes the heme portion of hemoglobin, and severely deficient zinc diets can result in anemia. Table 5.3.15 provides the RDAs for zinc and Table 5.3.16 provides dietary sources of zinc. It has been estimated that 17.3% of the world has a zinc deficiency, with the highest area of concern being the middle to low-income countries (Mendes Garrido Abregu, et al., 2022). Severe deficiency is rare; moderate deficiencies are more commonly reported. Those at the highest risk for developing a zinc deficiency include children, breastfeeding women, and older adults (Medes Garrido Abregu, et al., 2022).

Dietary Reference Intakes for Zinc

Table 5.4.5: Dietary Reference Intakes for Zinc (mg/day) for adolescents and adults.

Age Group

RDA for Males and Females

UL

Adolescents (14-18 years)

Males: 11

34

Adolescents (14-18 years)

Females: 9

34

Adults (>19 years)

Males: 11

40

Adults (>19 years)

Females: 8

40

Dietary Sources of Zinc

Table 5.4.6: Zinc Content of Various Foods

Food

Serving

Zinc (milligram)

Oysters

3 oz.

74

Beef, chuck roast

3 oz.

7

Crab

3 oz.

6.5

Lobster

3 oz.

3.4

Pork loin

3 oz.

2.9

Baked beans

½ c.

2.9

Pumpkin Seeds

1 oz.

2.2

Yogurt, low fat

8 oz.

1.7

Oatmeal, instant

1 packet

1.1

Almonds

1 oz.

0.9

Contributors

University of Hawai’i at Mānoa Food Science and Human Nutrition Program: Allison Calabrese, Cheryl Gibby, Billy Meinke, Marie Kainoa Fialkowski Revilla, and Alan Titchenal

Selenium

Selenium has many roles in the body. It plays a role in reproduction, is a cofactor in thyroid metabolism, is involved with DNA synthesis, and acts as an antioxidant, protecting the body from Reactive Oxygen Species (ROS). Reactive oxygen species (ROS) are generated from mitochondrial metabolism and in response to bacterial invasion, among other things. Common ROS include superoxide and hydrogen peroxide. Left unchecked, ROS can cause oxidative damage to DNA, proteins and lipids in membranes. Glutathione peroxidase-1 is a selenium-containing intercellular enzyme that breaks down ROS hydrogen, protecting the body from oxidative damage.

Selenium and Cancer

As an antioxidant, it was thought that selenium may play a role in preventing cancer. A systematic review of selenium’s role in preventing cancer concluded that selenium had no effect in reducing the overall risk of cancer, including prostate cancer, and some trials showed an increased risk of high-grade prostate cancer, type 2 diabetes, and dermatological abnormalities (Vinceti et al., 2018; Benstoem et al., 2015).

Dietary Reference Intakes for Selenium

The IOM has set the RDAs for selenium based on the amount required to maximize the activity of glutathione peroxidases found in blood plasma. The RDAs for different age groups are listed in Table 5.4.7. Food sources of selenium are found in Table 5.4.8.

 

Table 5.4.7: Dietary Reference Intakes for Selenium (mcg/day) for adolescents and adults.

Age Group

RDA for Males and Females

UL

Adolescents (14-18 years)

55

400

Adults (>19  years)

55

400

Selenium at doses several thousand times the RDA can cause acute toxicity, and, when ingested in gram quantities can be fatal. Chronic exposure to foods grown in soils containing high levels of selenium (significantly above the UL) can cause brittle hair and nails, gastrointestinal discomfort, skin rashes, halitosis, fatigue, and irritability. The IOM has set the UL for selenium for adults at 400 micrograms per day.

 

Table 5.4.8: Selenium Content of Various Foods

Food

Serving

Selenium (micrograms)

Brazil nuts

1 oz.

544

Shrimp

3 oz.

34

Crabmeat

3 oz.

41

Ricotta cheese

1 c.

41

Salmon

3 oz.

40

Pork

3 oz.

35

Ground beef

3 oz.

18

Round steak

3 oz.

28.5

Beef liver

3 oz.

28

Chicken

3 oz.

13

Whole-wheat bread

2 slices

23

Couscous

1 c.

43

Barley, cooked

1 c.

13.5

Milk, low-fat

1 c.

8

Walnuts, black

1 oz.

5

Source: US Department of Agriculture, Agricultural Research Service. 2010. USDA National Nutrient Database for Standard Reference, Release 23.

Contributors

University of Hawai’i at Mānoa Food Science and Human Nutrition Program: Allison Calabrese, Cheryl Gibby, Billy Meinke, Marie Kainoa Fialkowski Revilla, and Alan Titchenal

Iodine

Recall the discovery of iodine and its use to prevent goiter, a gross enlargement of the thyroid gland in the neck. Iodine is essential for the synthesis of thyroid hormone, which regulates basal metabolism, growth, and development. Low iodine levels and consequently hypothyroidism has many signs and symptoms including fatigue, sensitivity to cold, constipation, weight gain, depression, paleness, and dry, itchy skin. The development of goiter may often be the most visible sign of chronic iodine deficiency. The consequences of low levels of thyroid hormone can be severe during infancy, childhood, and adolescence, as it affects all stages of growth and development. Thyroid hormones play a significant role in brain development and growth.  Fetuses and infants with severe iodine deficiency develop a condition known as cretinism, in which physical and neurological impairment can be severe. The World Health Organization (WHO) estimates insufficient iodine intake affects over two billion people worldwide, and it is the number one cause of preventable brain damage worldwide (WHO, 2019).

Dietary Intake References for Iodine

The mineral content of foods is determined by the soil in which it grew. For instance, iodine comes from seawater. The greater the distance from the sea, the lower the iodine content in the soil. Table 5.4.9 shows the RDAs for iodine and Table 5.4.10 shows the iodine content of some foods.

 

Table 5.4.9: Dietary Refernce Intakes for Iodine (mcg/day) for adolescents and adults.

Age Group

RDA for Males and Females

UL

Adolescents (14-18 years)

150

900

Adults (>19 years)

150

1100

Table 5.4.10: Iodine Content of Various Foods.

Food

Serving

Iodine (micrograms)

Seaweed

1 g.

16 to 2,984

Codfish

3 oz.

99

Yogurt, low fat

8 oz.

75

Iodized salt

1.5 g.

71

Milk, reduced fat

8 oz.

56

Ice cream, chocolate

½ c.

30

Egg

1 large

24

Tuna, canned

3 oz.

17

Prunes, dried

5 prunes

13

Banana

1 medium

3

Contributors

University of Hawai’i at Mānoa Food Science and Human Nutrition Program: Allison Calabrese, Cheryl Gibby, Billy Meinke, Marie Kainoa Fialkowski Revilla, and Alan Titchenal

Chromium

The function of chromium in the body is less understood than other minerals. It enhances the actions of insulin, so it plays a role in carbohydrate, fat, and protein metabolism. Currently, the results of scientific studies evaluating the usefulness of chromium supplementation in preventing and treating Type 2 diabetes are largely inconclusive.1 More research is needed to better determine if chromium is helpful in treating certain chronic diseases and, if so, at what doses. Dietary sources of chromium include nuts, whole grains, and yeast. There is insufficient evidence to establish a UL for chromium. Table 5.4.11 Show the RDA for Chromium.

 

Table 5.4.11: Dietary Reference Intakes for Chromium (mcg/day) for adolescents and adults.

Age Group

RDA for Males and Females

Adolescents (14-18 years)

Males: 25

Adolescents (14-18 years)

Females: 21

Adults (19-50 years)

Males: 35

Adults (19-50 years)

Females: 25

Adults (>50 years)

Males: 30

Adults (>50 years)

Females: 20

Source: The National Academies Press (2006). Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. The National Academies of Sciences Engineering Medicine. 296.

Contributors

University of Hawai’i at Mānoa Food Science and Human Nutrition Program: Allison Calabrese, Cheryl Gibby, Billy Meinke, Marie Kainoa Fialkowski Revilla, and Alan Titchenal

Fluoride

Fluoride’s Functional Role

Fluoride is known chiefly as the mineral that combats tooth decay. It assists in tooth and bone development and maintenance. Fluoride combats tooth decay via three mechanisms:

  • Blocking acid formation by bacteria
  • Preventing demineralization of teeth
  • Enhancing remineralization of destroyed enamel

The optimal fluoride concentration in water to prevent tooth decay ranges between 0.7–1.2 milligrams per liter. Exposure to fluoride at three to five times this concentration before the growth of permanent teeth can cause fluorosis, which is the mottling and discoloring of the teeth.

Dietary Reference Intake

The IOM has given Adequate Intakes (AI) for fluoride but has not yet developed RDAs. The AIs are based on the doses of fluoride shown to reduce the incidence of cavities, but not cause dental fluorosis. From infancy to adolescence, the AIs for fluoride increase from 0.01 milligrams per day for ages less than six months to 2 milligrams per day for those between the ages of fourteen and eighteen. In adulthood, the AI for males is 4 milligrams per day and for females is 3 milligrams per day. The UL for young children is set at 1.3 and 2.2 milligrams per day for girls and boys, respectively. For adults, the UL is set at 10 milligrams per day. Table 5.4.12 contains the AIs for flouride.

 

Table 5.4.12: Dietary Reference Intakes for Fluoride (mg/day) for adolescents and adults.

Age Group

RDA for Males and Females

UL

Adolescents (14-18 years)

3.00

10.0

Adults (>19  years)

Males: 4.00

10.0

Adults (>19  years)

Females: 3.00

10.0

Dietary Sources of Fluoride

In communities where water is fluoridated, more than 70 percent of a person’s fluoride comes from drinking fluoridated water. Other beverages with high amounts of fluoride include teas and grape juice. Solid foods do not contain a large amount of fluoride. Fluoride content in foods depends on whether it was grown in soils or cooked in water that contained fluoride. Canned meats and fish that contain bones do contain some fluoride. Table 5.4.13 contains the fluoride content of some foods.

 

Table 5.4.13: Fluoride Content of Various Foods

Food

Serving

Fluoride (milligrams)

Fruit Juice

3.5 fl oz.

0.02-2.1

Crab, canned

3.5 oz.

0.21

Rice, cooked

3.5 oz.

0.04

Fish, cooked

3.5 oz.

0.02

Chicken

3.5 oz.

0.015

Current AI used to determine Percent Daily Value Micronutrient Information Center: Fluoride. Oregon State University, Linus Pauling Institute.

Contributors

University of Hawai’i at Mānoa Food Science and Human Nutrition Program: Allison Calabrese, Cheryl Gibby, Billy Meinke, Marie Kainoa Fialkowski Revilla, and Alan Titchenal

 

Table 5.3.11: Summary of Trace Minerals

 

Micronutrient Sources Recommended Intakes for Older Adults Major Functions Deficiency Diseases and Symptoms Groups at Risk for Deficiency Toxicity UL
Iron Red meat, egg yolks, dark leafy vegetables, dried fruit, iron-fortified foods Males:

6-8 mg/day

Females:

5-8 mg/day

Assists in energy production, DNA synthesis required for red blood cell function Anemia: fatigue, paleness, faster heart rate Infants and preschool children, adolescents, women, pregnant women, athletes, vegetarians Liver damage, increased risk of diabetes and cancer 45 mg/day
Copper Nuts, seeds, whole grains, seafood 700-900 ug/day Assists in energy production, iron metabolism Anemia: fatigue, paleness, faster heart rate Those who consume excessive zinc supplements Vomiting, abdominal pain, diarrhea, liver damage 10,000 ug/day
Zinc oysters, wheat germ, pumpkin seeds, squash, beans, sesame seeds, tahini, beef, lamb Males: 9.4-11 mg/day

Females:

6.8-8 mg/day

Assists in energy production, protein, RNA and DNA synthesis; required for hemoglobin synthesis Growth retardation in children, hair loss, diarrhea, skin sores, loss of appetite, weight loss Vegetarians, older adults Depressed immune function 40 mg/day
Selenium Meat, seafood, eggs, nuts 45-55 ug/day Essential for thyroid hormone activity Fatigue, muscle pain, weakness, Keshan disease Populations where the soil is low in selenium Nausea, diarrhea, vomiting, fatigue 400 mcg/day
Iodine Iodized salt, seaweed, dairy products 95-150 mcg/day Making thyroid hormone, metabolism, growth and development Goiter, cretinism, other signs and symptoms include fatigue, depression, weight gain, itchy skin, low heart rate Populations where the soil is low in iodine, and iodized salt is not used Enlarged thyroid 1110 mcg/day
Chromium Not Determined Males:

30 ug/day

Females:

20 ug/day

Assists insulin in carbohydrate, lipid and protein metabolism abnormal glucose metabolism Malnourished children None ND
Fluoride Fluoridated water, foods prepared in fluoridated water, seafood Males:

4 mg/day

Females:

3 mg/day

Component of mineralized bone, provides structure and microarchitecture, stimulates new bone growth Increased risk of dental caries Populations with non fluoridated water Fluorosismottled teeth, kidney damage 10 mg/day
Manganese Legumes, nuts, leafy green vegetables Males: 2.3 mg/day

Females: 1.8 mg/day

Glucose synthesis, amino-acid catabolism Impaired growth, skeletal abnormalities, abnormal glucose metabolism None Nerve damage 11 mg/day
Molybdenum Milk, grains, legumes 34-45 ug/day Cofactor for a number of enzymes Unknown None Arthritis, joint inflammation 2000 ug/day

 

Contributors

University of Hawai’i at Mānoa Food Science and Human Nutrition Program: Allison Calabrese, Cheryl Gibby, Billy Meinke, Marie Kainoa Fialkowski Revilla, and Alan Titchenal

 

References

Benstoem C, Goetzenich A, Kraemer S, et al. Selenium and its supplementation in cardiovascular disease–what do we know?. Nutrients. 2015;7(5):3094–3118. DOI:10.3390/nu7053094. Accessed May 30, 2019.

Birkett NJ. Comments on a Meta-Analysis of the Relation between Dietary Calcium Intake and Blood Pressure. Am J Epidemiol. 1998;148(3), 223–28. http://aje.oxfordjournals.org/content/148/3/223.long. Accessed June 30, 2019.

Bolland, MJ, Grey, A, and Avenell, A. Effects of vitamin D supplementation on musculoskeletal health: a systematic review, meta-analysis, and trial sequential analysis. Lancet Diabetes & Endocrinology.2018; 6 (11), 847-858. Accessed June 30, 2019.

Carr. A,C. Vitamin C and Immune Function. Nutrients 2017, 9(11), 1211; https://doi.org/10.3390/nu9111211

Carr.  A,C. Factors Affecting Vitamin C Status and Prevalence of Deficiency: A Global Perspective. Nutrients 2020, 12(7), 1963; https://doi.org/10.3390/nu12071963

Centers for Disease Control and Prevention. “Iron” Updated December 3, 2018. Accessed June 30, 2019.

Costello RB, Dwyer JT, Bailey RL. Chromium supplements for glycemic control in type 2 diabetes: limited evidence of effectiveness. Nutr Rev. 2016;74(7):455–468. DOI:10.1093/nutrit/nuw011. Accessed May 30, 2019.

Dietary Reference Intakes. Government of Canada. https://www.canada.ca/en/health-canada/services/food-nutrition/healthy-eating/dietary-reference-intakes/tables/reference-values-vitamins-dietary-reference-intakes-tables-2005.html

Dietary Supplement Fact Sheet: Vitamin A. National Institutes of Health, Office of Dietary Supplements. Updated October 5, 2018. Accessed June 30, 2019.

Dietary Supplement Fact Sheet: Vitamin E.National Institutes of Health, Office of Dietary Supplements. Updated August 17, 2018. Accessed June 30, 2019.

Dietitians of Canada (2019). Food sources of vitamin B12. Practice Based Evidence in Nutrition. https://www.pennutritioncom.libproxy.stfx.ca/viewhandout.aspx?Portal=UbY=&id=J83vWA0=&PreviewHandout=bA==

Goodman M, Bostlick RM, Kucuk O, Jones DP. Clinical trials of antioxidants as cancer prevention agents: past, present, and future. Free Radic Biol Med. 2011; 51(5), 1068–84. https://www.ncbi.nlm.nih.gov/pubmed/21683786. Accessed June 30, 2019.

Goodman GE, et al. The Beta-Carotene and Retinol Efficacy Trial: Incidence of Lung Cancer and Cardiovascular Disease Mortality During 6-year Follow-up after Stopping Beta-Carotene and Retinol Supplements. J Natl Cancer Inst. 2004; 96(23), 1743–50. http://jnci.oxfordjournals.org/content/96/23/1743.long. Accessed June 30, 2019.

Institute of Medicine. Dietary reference intakes for vitamin A, vitamin K, arsenic, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium, and zinc. Washington, DC: National Academy Press; 2001.

Iron deficiency anemia. (2022, January 04). Retrieved February 3, 2023, from https://www.mayoclinic.org/diseases-conditions/iron-deficiency-anemia/symptoms-causes/syc-20355034

Lee IM, et al. Vitamin E in the Primary Prevention of Cardiovascular Disease and Cancer: The Women’s Health Study. JAMA.2005; 294, 56–65. http://jama.ama-assn.org/content/294/1/56.long. Accessed June 30, 2019.

Lonn, E. et al. HOPE and HOPE-TOO Trial Investigators. Effects of Long-Term Vitamin E Supplementation on Cardiovascular Events and Cancer. JAMA. 2005; 293, 1338–47. http://jama.ama-assn.org/content/293/11/1338.long., Accessed June 30, 2019.

Mahmood, L. (2014). The metabolic processes of folic acid and vitamin B12 deficiency. Journal of Health Research and Reviews. 10.4103/2394-2010.143318

McGinley C, Shafat A. Donnelly AE. Does antioxidant vitamin supplementation protect against muscle damage? Sports Med. 2009; 39(12), 1011–32. https://www.ncbi.nlm.nih.gov/pubmed/19902983. Accessed June 30, 2019.

Mendes Garrido Abregú, F., Caniffi, C., Arranz, C. T., & Tomat, A. L. (2022). Impact of Zinc Deficiency During Prenatal and/or Postnatal Life on Cardiovascular and Metabolic Diseases: Experimental and Clinical Evidence. Advances in Nutrition, 13(3), 833–845. https://doi.org/10.1093/advances/nmac012

Nakamura, H., Sekiguchi, A., Ogawa, Y., Kawamura, T., Akai, R., Iwawaki, T., Makiguchi, T., Yokoo, S., Ishikawa, O., & Motegi, S. (2019). Zinc deficiency exacerbates pressure ulcers by increasing oxidative stress and ATP in the skin. Journal of Dermatological Science, 95(2), 62–69. https://doi.org/10.1016/j.jdermsci.2019.07.004

Pobocik RS, Trager A, Monson LM. Dietary Patterns and Food Choices of a Population Sample of Adults on Guam. Asia Pacific Journal of Clinical Nutrition. 2008; 17(1), 94-100. http://apjcn.nhri.org.tw/server/APJCN/17/1/94.pdf. Accessed June 30, 2019.

Prasad, Ananda. “Zinc deficiency.” BMJ 2003 February 22; 326(7386): 409–410. DOI: 10.1136/bmj.326.7386.409. Accessed July 5, 2019.

Ross EA, Szabo NJ, Tebbett IR. Lead Content of Calcium Supplements. JAMA. 2000; 284, 1425–33.Accessed June 30, 2019.

Schulte, R et al. Rise in late-onset vitamin K deficiency bleeding in young infants because of omission or refusal of prophylaxis at birth. Pediatr Neurol. 2014; 50(6):564-8. DOI: 10.1016/j.pediatrneurol.2014.02.013. Accessed June 30, 2019.

Sommer A. Vitamin A Deficiency and Clinical Disease: An Historical Overview. J Nutr. 2008; 138, 1835–39. http://jn.nutrition.org/content/138/10/1835.long. Accessed June 30, 2019.

Stover, P. J. (2010). Vitamin B12 and older adults. Current opinion in clinical nutrition and metabolic care, 13 (1), 24. 10.1097/MCO.0b013e328333d157

Tan, V. (2022, August 25). How to increase the absorption of iron from foods. Retrieved February 1, 2023, from https://www.healthline.com/nutrition/increase-iron-absorption#enhancing-iron-absorption

Tucker KL, Hannan MT, et al. Potassium, Magnesium, and Fruit and Vegetable Intakes Are Associated with Greater Bone Mineral Density in Elderly Men and Women. Am J Clin Nutr. 1999; 69(4), 727–36. Accessed June 30, 2019.

Vinceti M. et al. Selenium for Preventing Cancer. Cochrane Database of Systematic Reviews. Updated January 29, 2018. Accessed June 30, 2019.

Waters DD, et al. Effects of Hormone Replacement Therapy and Antioxidant Vitamin Supplements on Coronary Atherosclerosis in Postmenopausal Women: A Randomized Controlled Trial. JAMA. 2002; 288(19), 2432–40. https://jamanetwork.com/journals/jama/fullarticle/195531. Accessed June 30, 2019.

World Health Organization. “Iodine Status Worldwide.” Accessed June 30, 2019.

 

Media Attributions

  • fig_9.2.1

About the Authors

License

Icon for the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License

Chapter 5: Nutritional Requirements - General Information Copyright © 2023 by Tracy Everitt; Brittany Yantha; and Megan Davies is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

Share This Book