Vitamins: A B1 B2 B3 B5 B6 B7 B9 B12 C D E K
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Description and Use:
Vitamins are organic (containing carbon) compounds needed in minute amounts for normal health and growth. They, along with minerals and phytochemicals, are therefore referred to as micronutrients. Vitamins have many diverse roles which are described in more detail below but in general, they assist in many chemical reactions (vision, energy metabolism, blood clotting), the synthesis of new tissue (collagen, bone) and protection from free radicals (antioxidants), etc. There are 13 vitamins: A, 8 B's (collectively called B-Complex), C, D, E and K. Vitamins are generally divided into two groups, water soluble (B's and C) and fat soluble (A, D, E and K). In general, excess intake of the water soluble vitamins can be screened out by kidneys and excreted in the urine. This can be witnessed by the bright yellow color of urine associated with high levels of vitamin B intake. Water soluble vitamins are generally not stored in the body and need to be consumed in the diet on a regular basis. Fat soluble vitamins, as implied will need some dietary fat to aid in absorption and in general are stored in the body. Excess levels of some can therefore accumulate and become toxic.
Several vitamins, namely A (and its provitamin beta-carotene), C and E, act as antioxidants, protecting the body from the damaging effects of free radicals. Free radicals are unstable atoms lacking an electron in their outer shell. They then steal electrons from stable surrounding molecules, generating more unstable free radicals. This chain reaction can damage or destroy cells. This type of damage is linked to many diseases; cancer, heart disease, diabetes, arthritis, cataracts, Alzheimer, Parkinson etc. Aging is also considered to be a cumulative effect of free radical damage and reduced activity of antioxidant enzymes. Antioxidants protect against damage by donating an electron or hydrogen molecule to free radicals to stabilize them.
Free radicals are a normal result of energy metabolism and fighting infections but other external sources include smoke, environmental pollutants, overexposure to the sun, radiation etc. It is therefore important to get an adequate intake of antioxidant vitamins. Some speculate that increase levels of these antioxidants, above the RDA's, may provide extra insurance against chronic diseases such as heart disease and cancer. There have been numerous studies in this area but unfortunately the results are mixed. Overall, at this time, increase levels of antioxidant vitamins taken as supplements have not been shown to reduce heart disease and cancers. However, consuming significant amounts of fruits, vegetables and whole grains, which naturally contain these antioxidants, has been shown to decrease the incidence of heart disease and cancer. There is speculation that the phytochemicals and fiber found in whole foods play a significant role. Phytochemicals include the pigments in fruits and vegetables that give them their bright colors; red, yellow, blue, purple, green etc. and other substances. There are hundreds of phytochemicals and research in this area is fairly new.
Daily Reference Intakes:
DRIs, used in the U.S. are established by the Food and Nutrition Board, Institute of Medicine, National Academies. The DRIs for most nutrients include an RDA (Recommended Daily Allowance) or an AI (Adequate Intake) and a UL (Tolerable Upper Intake Limit). RDA is the intake level that meets the requirement of 98% of healthy individuals. AI is given if the RDA is unknown. UL is the highest intake level considered to be safe. Values are given for groups based on age, sex and pregnancy/lactation status. View DRI Tables Nutrition labels on foods and supplements state the vitamin content as a percent of daily value, DV, for the serving size indicated. The DVs used on labels are based on the RDA values established in 1968. They have been updated several times since then. The chart at the bottom of this page lists the current values as of 2012.
Interesting Historical Notes:
The discovery of many vitamins was the result of solving the cause of various diseases; beriberi, pellagra, scurvy, rickets etc. Fortification soon followed (B vitamins in refined flours/grains, D in milk, iodine in salt etc.) and now deficiency diseases are fairly rare in modern societies. Initially, the setting of RDAs was the amount to prevent deficiency diseases and symptoms. However, since then, there has been a shift in thinking. Some feel that 'optimum' health can be had by increasing levels beyond those that simply prevent disease. For example; the amount of vitamin C to prevent scurvy may be much less than the amount to provide adequate antioxidant protection. Of particular interest was the potential impact certain vitamins may have on preventing a number of widespread chronic diseases like heart disease, cancer, diabetes, osteoporosis etc. The RDAs have evolved since 1968. Some changes include; a decrease in A, and increases in folate, C, D, E and K.
More of a good thing is not always better! A number of vitamins can be toxic; A, niacin, B6, C and D. So, not only is it important to try to meet the RDAs but it is also important not to exceed the established ULs. Vitamins along with minerals and other nutrients participate in a complex symphony of bodily chemical processes. Increase levels of individual micronutrients can have unanticipated effects on other nutrients and bodily processes. Studies have repeatedly shown that diets high in healthy whole foods (fruits, vegetables, whole grains, legumes) are more effective at preventing long term chronic diseases than regimes with high levels of supplements. Foods contain many additional nutrients, (phytochemicals) that are still to be identified and studied.
Supplements:
Should you take a multivitamin for insurance? It's probably not a bad idea. Healthy individuals who eat a varied diet that includes lots of fruits and vegetables of different colors, whole grains and low-fat dairy (or fortified soy milk) generally won't need to take a vitamin pill. However, the U.S. Dietary Guidelines of 2010, identified seven "Nutrients of Concern" (page 40) which Americans in general do not get enough of; potassium, fiber, calcium, vitamin D, and for specific groups; iron (women), folic acid (women) and B12 (people 50+). Also, research indicates that B6, B12, folic acid and D are essential players in preventing heart disease, cancer, osteoporosis and other chronic diseases. These vitamins are commonly available in a multivitamin. Taking a multivitamin/mineral supplement with no more than 100% of the Daily Values as a safety net, is generally considered safe. Here are some general guidelines for vitamin supplements;
- The vitamin label should have USP (United States Pharmacopeia) symbol. It insures the multivitamin contains what the label says and that it disintegrates fast enough.
- Avoid mega doses. Look for 100% daily value levels.
- Avoid taking single-nutrient supplements unless advised by your healthcare practitioner.
- It is better to choose a formula geared to your age and gender. Men's and senior formulas may have less iron, women's formulas, more iron. Seniors may get more D and B12.
- Do not take on an empty stomach; take it preferably with a meal in the morning. If taken at night, it could affect your sleep.
- Be careful not to double up doses. Some fortified breakfast cereals like Total or Product 19, contain 100% DV of many nutrients including iron. If you eat these cereals, skip the multivitamin that day.
- Most multivitamins tested by Consumer Reports (Sept 2010) contained the levels of nutrients they claimed. The major criteria for choosing then is price. The best price found was Kirkland Daily Multi (Costco) then Equate Complete Multivitamin (Walmart version, copies Centrum). Centrum is good but more expensive. Most expensive was One A Day Maximum.
As mentioned above, supplements are optional for healthy people who eat an adequate and varied diet. The goal is always to try and meet nutritional needs with food first. However, in some cases, supplements may be recommended and beneficial. These are cases where diets are restrictive, not mix and varied, people with health conditions, poor absorption or people in different stages of life. Consult with a doctor or dietician before taking any supplements if you have any medical condition, are taking medications or are taking above the RDA. Here is a summary of people who may benefit from vitamin supplements;
- Women who may get pregnant - should have adequate folic acid to prevent neural tube birth defects.
- Women who are pregnant or nursing - doctors should prescribe a supplement.
- Menopausal women - may need calcium and vitamin D to prevent osteoporosis.
- People on restrictive diets, < 1600 calories.
- Vegetarians, particularly vegan - are at risk for B12 and D (also calcium, iron, zinc). If these are not obtained from fortified foods, a supplement is needed.
- People who avoid milk - are at risk for calcium and D. If these are not obtained from fortified foods, a supplement is recommended.
- People with digestive disorders and cannot absorb certain nutrients.
- People over 50 - may need extra B12 and D.
- People recovering from serious illness or surgery.
- People who consume a lot of alcohol - alcohol destroys vitamin B
Vitamin Table:
| Vitamin A Retinol Beta-carotene |
Function: Critical to maintain vision, cell differentiation, reproduction and normal bone growth. Helps the eye to adjust to changes in brightness of light and to see different colors. Promotes healthy surface linings (epithelial tissues) of the eyes, respiratory system, urinary and intestinal tracts. Helps the skin and mucus membranes function as a barrier to bacteria and viruses (immune system). Acts as an antioxidant. 90% of the A in the body is stored in the liver. The rest is in adipose tissue, kidneys and lungs. The active form of vitamin A is retinol which is found in animal foods like whole milk and eggs. Beta-carotene is a carotenoid found in plants and is easily converted to A. It is therefore called provitamin A. Beta-carotene is an antioxidant and protects the skin and eyes from sun exposure. Since it is not toxic, it is the recommended form to use in supplements. Vegetarians who do not consume eggs and dairy products need provitamin A carotenoids to meet their need for vitamin A. They should include a minimum of five servings of fruits and vegetables in their daily diet and regularly choose dark green leafy vegetables and orange and yellow fruits to consume recommended amounts of vitamin A. Only 20-40% of the carotenoids in foods we eat is absorbed. Cooking and some fat improves absorption. Vitamin A can be measured in IU (international units), mcg or RAE (retinol activity equivalents). 1 RAE = 1 mcg retinol = 12 mcg beta-carotene = 3.3 IU. More |
| Food Sources: For retinol, milk and eggs. For beta-carotene, orange and yellow colored fruits and vegetables; carrots, pumpkin, sweet potato, cantaloupe, apricot, butternut squash, tomato, green leafy vegetables; spinach, collards kale, lettuce etc. More |
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| Deficiency: Night blindness and color blindness. Hyperkeratosis where keratin clogs hair follicles making the skin rough and bumpy. Reduced mucus production by mucus membranes leading to an increase risk of infection. Deficiency is not common in developed nations but it is a severe public health concern in developing nations. The World Health Organization estimates 250,000-500,000 children go blind each year due to xerophthalmia, hardening of the cornea. | |
| Excess: Vitamin A (retinol) is highly toxic. Excess rarely results from food sources but supplements are known to have caused severe illness and even death. Excess while pregnant can cause birth defects and spontaneous abortion. Symptoms include fatigue, loss of appetite, blurred vision, hair loss, skin disorders, bone and joint pain, abdominal pain, nausea, diarrhea and damage to the liver and nervous system. Whew! The UL is set at 3,000 mcg/day just 3 times the RDA. Beta-carotene is not toxic. Excess can cause the skin to turn yellow or orange (carotenodermia). It is reversible and harmless. Supplements are generally not recommended since it is easy to get the RDA from fruits and vegetables. Synthetic beta-carotene supplements have been found to increase the risk of both colorectal and lung cancer in smokers, especially those who also drink alcohol. Top |
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| Vitamin B1 Thiamin |
Function: Coenzyme involved in the energy metabolism of carbohydrates and proteins. Also involved in the synthesis of DNA, RNA and neurotransmitters. More Effective for treatment of? |
| Food Sources: B1 is found naturally in the bran of whole grains and brown rice. However, since most the population consumes refined grains, the most common sources today are enriched grain products; white flour, breakfast cereals, white pasta, white rice and cornmeal. Other whole food sources include peas, soybeans and soybean products, legumes, and yeast flakes. More |
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| Deficiency: Berberi is caused by B1 deficiency. It is characterized by severe lethargy and fatigue, together with complications affecting the cardiovascular, nervous, muscular, and gastrointestinal systems. In severe cases, it can lead to heart failure and death. Prior to the 1900's it was common in areas of Asia where polished white rice was the main staple. Due to fortification of flour and grain products, this disease is very rare in modern societies. Alcohol destroys B1 and high intakes make alcoholics susceptible to Wernicke-Korakoff syndrome characterized by leg tremors, confusion, irritability, impairment of short-term memory and story telling to fill in memory gaps. |
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| Excess: No adverse effects from consuming high amounts of thiamin therefore a UL has not been established. Excess is excreted in the urine. Top | |
| Vitamin B2 Riboflavin |
Function: Coenzyme involved in the energy metabolism of carbohydrates, fats and proteins. At prescription level doses it may be helpful in reducing the frequency of migraine headaches. Light destroys B2. Milk is therefore stored either in cardboard or opaque containers. More Effective for treatment of? |
| Food Sources: Milk and milk products, eggs, legumes and green leafy vegetables. Enriched grain products; white flour, breakfast cereals, white pasta and cornmeal. More |
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| Deficiency: Sore throat, swelling of mucus membranes in mouth and throat, lips that are dry and scaly, cracks at the corners of the mouth, purple colored tongue, inflamed irritated patches on the skin. | |
| Excess: No adverse effects from consuming high amounts of riboflavin therefore a UL has not been established. Excess is excreted in the urine. Top | |
| Vitamin B3 Niacin |
Function: Coenzyme involved in the energy metabolism of carbohydrates, fats and proteins. Coenzyme for more than 200 enzymes. More Effective for treatment of? |
| Food Sources: Whole grains, brown rice, nuts (especially peanuts), sunflower seeds, mushrooms, legumes and enriched grain products; white flour, breakfast cereals, white pasta and cornmeal. More |
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| Deficiency: Pellagra is caused by niacin deficiency. It is characterized by the 3 D's": diarrhea, dermatitis and dementia. Untreated, sufferers can die in 4 to 5 years. In the early 1900s, pellagra reached epidemic proportions in the American South and parts of Europe where corn was a staple. Due to fortification of flour and grain products, this disease is very rare in modern societies. However, it still occurs in India, China and Africa. | |
| Excess: Excess will not occur from foods but only from supplements. Toxicity symptoms include flushing which causes the face, arms and chest to turn red accompanied by a burning, tingling and itching sensation. Large doses over time can result in elevated blood glucose levels, liver damage, blurred vision and edema of the eyes. The upper limit is set at 35 mg/day for adults. Doses below this should not cause flushing. Top | |
| Vitamin B5 Pantothenic Acid |
Function: Coenzyme involved in the energy metabolism of carbohydrates, fats and proteins. More Effective for treatment of? |
| Food Sources: B5 is widespread in many foods. It is high in whole grains, legumes, tomatoes, egg, mushrooms, avocado, yogurt and royal jelly. More |
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| Deficiency: Very rare. | |
| Excess: No adverse effects from consuming high amounts of B5 therefore a UL has not been established. Excess is excreted in the urine. Top | |
| Vitamin B6 Pyridoxine |
Function: Coenzyme for more than 100 enzymes involved in the metabolism of amino acids. Involved in gluconeogenesis (converting protein into glucose). Along with B12 and folate helps to clear the blood of homocysteine, an independent risk factor for cardiovascular disease. Assists in the synthesis of hemoglobin and antibodies. B6 was recommended by some for the relief of PMS symptoms. Some feel that doses of 50-100 mg/day may provide some improvement but in general there is insufficient evidence to support this claim. Caution is required since high doses (more than 100 mg/day) can be toxic. More Effective for treatment of? |
| Food Sources: Potatoes and other starchy vegetables, bananas, avocados, nuts and fortified breakfast cereals More |
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| Deficiency: Vitamin B6 deficiency is uncommon in the United States. People who don't get enough vitamin B6 can have a range of symptoms, including anemia, itchy rashes, scaly skin on the lips, cracks at the corners of the mouth, a swollen tongue, depression and confusion. | |
| Excess: Unlike other B vitamins, excess of B6 can be toxic. Excess is not possible through foods but only through supplements. Symptoms can include sensory neuropathy (pain and numbness of the extremities) and dermatological lesions. Taking high levels of vitamin B6 from supplements for a year or longer can cause severe nerve damage, leading people to lose control of their bodily movements (ability to walk). UL has been set at 100 mg/day. Top | |
| Vitamin B7 Biotin |
Function: Coenzyme involved in the energy metabolism of carbohydrates, fats and proteins. Also involved in lipogenesis (converting glucose, protein or alcohol into fat) and gluconeogenesis (converting protein or glycerol into glucose). More Effective for treatment of? |
| Food Sources: Because it is widespread, it is not listed in food composition tables. | |
| Deficiency: Does not normally occur because, in general, intestinal bacteria produce biotin in excess of the body's daily requirements. Deficiency has been created by consuming a large amount of raw egg whites which contain avidin. Avidin combines with biotin and renders it useless. Cooking destroys avidin. Symptoms of biotin deficiency include; thinning of hair, loss of hair color, red scaly rash around the eyes, nose and mouth, depression/confusion/panic. | |
| Excess: No adverse effects from consuming high amounts of biotin therefore a UL has not been established. Excess is excreted in the urine. Top | |
| Vitamin B9 Folate or Folic acid |
Function: Helps produce and maintain new cells. This is especially important during periods of rapid cell division and growth such as infancy and pregnancy. Folate is needed to make DNA and RNA, the building blocks of cells. Needed to make normal red blood cells and prevent anemia. Folate along with B6 and B12 is essential for the metabolism of homocysteine, and helps maintain normal levels of this amino acid. Folic acid is the form of folate used in supplements. 85% to 100% of consumed folic acid is absorbed. However, only about 50% of food folate is absorbed. To account for this, the content in food is expressed in DFE, Dietary Folate Equivalents. DFE takes into account the form of folate and adjusts accordingly to bioavailability. Folate is extremely important for health and to prevent birth defects. In an effort to address the birth defect issue, in 1998 the USDA required the fortification of flour, rice, pasta, corn meal etc. to include folic acid as well (in addition to B1, B2 and Niacin). Data from US birth certificates indicate a 19% decline in the birth prevalence of NTDs and a 23% decline in spina bifida prevalence among births conceived after mandatory folic acid fortification. More Effective for treatment of? |
| Food Sources: Leafy green vegetables (like spinach and turnip greens), fruits (like citrus fruits and juices), dried beans and peas are all natural sources of folate. Fortified grain products are a source of folic acid. More |
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| Deficiency: Anemia (inability to make red blood cells), elevated levels of homocysteine (a risk factor for heart disease) and for pregnant women, deficiency can cause spina bifida and other neural tube defects in the fetus. | |
| Excess: Excess of folate cannot be derived from foods but only from supplements. No toxic symptoms reported from high levels of folate however, since high levels can mask a B12 deficiency a UL is set at 1000 mcg/day. Top | |
| Vitamin B12 Cobalamin |
Function: Needed for the production of red blood cells. Needed for the maintenance of the central nervous system. Helps make DNA. Prevents a type of anemia called megaloblastic anemia that makes people tired and weak. Two steps are required for the body to absorb vitamin B12 from food. First, stomach acid separates vitamin B12 from the protein to which vitamin B12 is attached in food. After this, vitamin B12 combines with a protein made by the stomach called intrinsic factor and is absorbed by the body. Only about 50% of B12 in foods is absorbed. Pernicious anemia is a condition where the body cannot make intrinsic factor. As a result, there is trouble absorbing vitamin B12 from any foods or supplements. It is estimated that 10-30% of people over the age of 50 may have a decreased ability to absorb B12 due to lower levels of stomach acid. It is recommended that they eat fortified foods or take supplements. More |
| Food Sources: B12 is only found in animal foods (original source is synthesized by bacteria) and therefore is a concern for vegetarians. Milk and milk products, eggs and nutritional yeast are food sources. If these are excluded from the diet, either fortified foods or supplements are required. Fortified foods include soy milk and breakfast cereals. More |
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| Deficiency: Anemia, pale skin, diminished energy, fatigue, shortness of breath. Neurological symptoms include tingling and numbness in extremities, abnormal gait, memory loss, dementia, insomnia and impaired bladder and bowel control. Deficiency can cause permanent damage to the nervous system even in people who don't have anemia, so it is important to treat a deficiency as soon as possible. | |
| Excess: No adverse effects from consuming high amounts of B12 therefore a UL has not been established. Unlike other B vitamins where excess is excreted in the urine, excess B12 is stored in the liver. It is needed in such small amounts that liver stores (about 2-3 mg) can last for from a few months up to a couple of years. Top | |
| Vitamin C Ascorbic acid |
Function: Acts as an antioxidant helping to protect cells from the damage caused by free radicals. Regenerates vitamin E after it has been oxidized. Assists in the synthesis of collagen, a protein used in connective tissues (tendons, ligaments, bones, teeth, skin, blood vessels) and wound healing (scar tissue). It also assists in the synthesis of DNA, bile, neurotransmitters (serotonin) and carnitine. Improves the absorption of iron from plant-based foods. Helps the immune system. Because of the free radicals in smoke, smokers are recommended to get an additional 35 mg/day of C. Injury, surgery, burns etc. may increase ones needs for vitamin C. Vitamin C does not prevent or cure the common cold. It may lessen the symptoms and shorten the duration of the cold by 1 to 1.5 days. The body becomes saturated with doses of 120-200 mg. Amounts above that are excreted. If taken as a supplement, it may be better to take small doses (100 mg) a couple of times a day. The UL for adults is set at 2000 mg. Heat and oxygen destroy vitamin C. So, the best sources are fresh raw foods. Cooking vegetables using steam, microwave or stir-fry methods will preserve more vitamin C than the boil and drain method. More |
| Food Sources: Citrus fruits (oranges, lemons, limes, grapefruit), red and green peppers, broccoli, strawberries, papaya, sweet potato, potato, mango, cantaloupe, tomatoes, cabbage, dark greens (kale, collards, spinach). Fortified drinks and cereals are also a major source. More |
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| Deficiency: Deficiencies of C are rare in modern societies but in times of old, scurvy was the disease caused by vitamin C deficiency. It develops about one month after a lack of C. It was once common to sailors/pirates on long voyages after their supply of fruits and vegetables ran out. They then relied on salted meats and dried grains. Between 1500 and 1800, it has been estimated that scurvy killed at least two million sailors. Today more milder symptoms are related to the inability to synthesize collagen which results in bruising (black and blue marks) and bleeding. | |
| Excess: Taking too much vitamin C can cause diarrhea, nausea, stomach cramps and nosebleeds. Large amounts of vitamin C can increase the chance of getting kidney stones. The UL for adults is 2000 mg/day. Top | |
| Vitamin D | Function: Maintains strong bones. Needed for the calcification of bone. Regulates blood calcium levels. Aids in the absorption of calcium and phosphorus. There is ongoing research to determine if it may help prevent cancer, diabetes and MS (multiple sclerosis). The body can synthesize vitamin D from exposure to sunlight. Cholesterol in the skin is converted to provitamin D (cholecalciferol) which in the liver is converted to and stored as calcidiol. When needed, it sent to the kidneys where it is converted to calcitriol, the active form of vitamin D in the body. If your exposure is adequate, you do not need to consume vitamin D. It only takes about 15-20 minutes (calculate 1/3 the time to get sunburned) two or three times a week to synthesize enough D. However, a number of factors can limit the ability to make D; protective clothing, sunscreen, darker skin, living in northern climates in winter, etc. In these cases, D should be consumed in the diet. There is no RDA for D so an AI has been established for adults at 15 mcg or 600 IU/day. D is measured either in micrograms, mcg, or international units, IU. 1 mcg of D equals 40 IU. There are two active forms of vitamin D; D2 (egocalciferol) is the form found in plants and D3 (cholecaliciferol) the form found in animal foods. More |
| Food Sources: Plants contain very little vitamin D. The major source in the American diet for vegetarians is fortified milk (10 mcg/quart), egg and fortified breakfast cereals. Vegans who avoid milk, should get adequate amounts from either sun exposure or fortified foods. Soy milk which is designed as a substitute for milk is normally fortified with calcium and vitamin D. Some bottled orange juices are fortified with D. More |
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| Deficiency: Due to the fortification of milk, deficiency is uncommon in the U.S. When D is inadequate, the intestines can only absorb 10-15% of the calcium consumed. This can result in loss of bone mass. In children, deficiency causes rickets; bones do not form properly and result in the characteristic bowed legs. In adults, deficiency causes osteomalacia; soft bones. Osteoporosis (brittle bones) can also result. | |
| Excess: Since the body regulates how much D is made from sun exposure, excess is only possible through supplements. Consuming 5-10 times the AI can result in hypercalcemia, high blood calcium. This can cause calcium deposits in soft tissues (kidney, liver, heart) and bone loss. The UL for adults is set at 4000 IU/day. Top | |
| Vitamin E Alpha-tocopherol |
Function: Acts as an antioxidant protecting against the oxidation of PUFA (polyunsaturated fatty acids), LDL and other fatty components of our cells and cell membranes. Protects red and white blood cells and enhances immune function. Helps to widen blood vessels and keep blood from clotting within them. 90% of the vitamin E in the body is stored in adipose tissue. The rest is in cell membranes. Active forms of vitamin E are alpha, beta, gamma and delta tocopherol. The most potent form found in food and supplements is alpha-tocopherol. At present, the vitamin E content of foods and dietary supplements is listed on labels in international units (IUs), a measure of biological activity rather than quantity. Naturally sourced vitamin E is called d-alpha-tocopherol; the synthetically produced form is dl-alpha-tocopherol. Conversion rules are as follows: To convert from mg to IU: 1 mg of alpha-tocopherol is equivalent to 1.49 IU of the natural form or 2.22 IU of the synthetic form. To convert from IU to mg: 1 IU of alpha-tocopherol is equivalent to 0.67 mg of the natural form or 0.45 mg of the synthetic form Vitamin E is destroyed by light, heat and exposure to air. Raw nuts and seeds contain more vitamin E than roasted versions. More |
| Food Sources: Since vitamin E protects against oxidation of PUFA, in nature's way, these then happen to be the common sources of vitamin E. Sunflower, safflower, canola, peanut and soy oil, dressings and mayonnaise made from them, nuts, seeds, wheat germ, canned tomato products, spinach and other greens, sweet potatoes, soybeans and fortified breakfast cereals are other sources. Since heat, light and air can damage vitamin E, it is best to store unused PUFA oils in the refrigerator and use them as cold oils (mayonnaise and dressing). MUFA oils are better suited for cooking. More |
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| Deficiency: Is uncommon but being fat soluble, E depends on fat for absorption. Diseases which cause malabsorption of fats or fat-free diets can result in vitamin E deficiency. Symptoms can include anemia, loss of muscle coordination and reflexes, leading to impairments of vision, speech and movement. | |
| Excess: Toxicity is uncommon but vitamin E can interact negatively with anticoagulants (aspirin, Coumadin, etc.) causing excessive bleeding. The UL for adults is set at 1000 mg/day. Some studies have shown that doses of 400 IU or more daily over prolonged periods (5+ yrs) may increase the risk of prostate cancer or death (hemorrhagic stroke). Because of the questions raised, E has somewhat fallen into disfavor from its days of boom in the 1990's. Top | |
| Vitamin K | Function: Coenzyme that assists in blood coagulation and bone metabolism. Most of vitamin K is stored in the liver; small amounts are stored in adipose tissue and bone. It is found in all circulating lipoproteins. There are two natural forms, K1, phylloquinone which is found in plants and K2, menaquinone which is produced by bacteria in the large intestine. K3 is a synthetic form. We obtain a good portion of our K from bacteria in the intestine. Absorption of K from plant sources can inefficient, between 10-80%. More |
| Food Sources: Vitamin K is found in dark, leafy greens; kale, collards, spinach, Swiss chard, mustard greens, beet greens, Brussels sprouts, lettuce etc. Broccoli, peas, okra, cabbage and green beans are other vegetables high in K. The bioavailability of K is greater in cooked foods. More |
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| Deficiency: Deficiency is rare and may reduce the ability to form blood clots, resulting in excessive bleeding and easy bruising. Deficiency could develop due to other diseases that cause malabsorption of fats. Also, prolonged use of antibiotics can kill bacteria in the large intestine. Newborns are given an injection of K at birth since they lack the intestinal bacteria to produce it. | |
| Excess: No adverse effects from consuming high amounts of K therefore a UL has not been established. People using blood thinning drugs (such as anticoagulant, antiplatelet drugs), may need to limit vitamin K foods. Top |
Vitamin RDA Chart:
For a quick reference, the chart below is a high level summary showing values for an adult male, age 19-50 years. The RDA from 1968 is used for determining the daily value, DV, percent on nutrition labels. The RDA values from 2001 are the most current. ND means Not Determinable. For reference, the vitamin portion of the Kirkland Daily Multi (Costco) and Centrum Adult Under 50 formulas (as of Apr 2012) are listed. To see all values for each age/gender visit the DRI Tables or to find values just for your specific age/gender, try using the DRI Tool.
| VITAMIN | NAME | RDA 1968 | RDA 2001 | UL | Kirkland | Centrum |
| A | Retinol/Carotene | 1500 mcg (5000 IU) |
900 mcg (3000 IU) |
3000 mcg (10,000 IU) |
3500 IU | 3500 IU |
| B1 | Thiamin | 1.5 mg | 1.2 mg | ND | 1.5 mg | 1.5 mg |
| B2 | Riboflavin | 1.7 mg | 1.3 mg | ND | 1.7 mg | 1.7 mg |
| B3 | Niacin | 20 mg | 16 mg | 35 mg | 20 mg | 20 mg |
| B5 | Pantothenic Acid | 10 mg | 5 mg | ND | 10 mg | 10 mg |
| B6 | Pyridoxine | 2 mg | 1.3 mg | 100 mg | 2 mg | 2 mg |
| B7 | Biotin | 300 mcg | 30 mcg | ND | 30 mcg | 30 mcg |
| B9 | Folic Acid | 400 mcg | 400 mcg | 1000 mcg | 500 mcg | 400 mcg |
| B12 | Cobalamin | 6 mcg | 2.4 mcg | ND | 6 mcg | 6 mcg |
| C | Ascorbic acid | 60 mg | 90 mg | 2000 mg | 90 mg | 60 mg |
| D | D2 egocalciferol or D3 cholecaliciferol |
10 mcg (400 IU) |
15 mcg (600 IU) |
100 mcg (4000 IU) |
400 IU | 400 IU |
| E | Alpha-tocopherol | 20 mg (30 IU) |
15 mg (22 IU) |
1000 mg (1500 IU) |
30 IU | 30 IU |
| K | 80 mcg | 120 mcg | ND | 25 mcg | 25 mcg |
Myths:
Lastly, a few myths about vitamins;
- We need supplements because our produce is grown on soil depleted of nutrients.
Fact: If the soil can grow crops, the food produced is nutritious. If the soil lacks minerals, plants don't grow properly. - Vitamins help you deal with stress.
Fact: Emotional stress does not increase nutrient needs. - Vitamins can help build muscles and improve athletic performance.
Fact: An athlete's nutritional needs are the same as most people except for more energy (calories) which can be obtained from eating more carbs. Eating more will also increase vitamin intake. Protein needs may be more. - If supplements don't help, at least they won't hurt.
Fact: High doses of A, niacin, B6 and C can be harmful. Minerals are discussed in the next section. - Vitamin C can prevent or cure colds.
Fact: Vitamin C does not prevent or cure the common cold. It may lessen the symptoms and shorten the duration of the cold by 1 to 1.5 days. - Sources of B12 include; spirulina, algae, sea vegetables, fermented foods (miso, tempeh, tamari, sauerkraut) or raw foods.
Fact: None of the above should be depended on as reliable sources of B12.
Summary:
- There are 13 vitamins: A, 8 B's (collectively called B-Complex), C, D, E and K. Vitamins are generally divided into two groups, water soluble (B's and C) and fat soluble (A, D, E and K).
- Vitamin A (and its provitamin beta-carotene), C and E, act as antioxidants, protecting the body from the damaging effects of free radicals.
- Study after study of isolated, high doses of vitamins has found they failed to prevent cancer, dementia, heart disease, or type 2 diabetes. However, people who ate foods rich in those vitamins had lower rates of those diseases.
- In general, it's better to get your nutrients from food. The whole food package contains a combination of nutrients that work together. Fruits, vegetables, whole grains and legumes are rich sources of phytochemicals and fiber.
- People who may need a multivitamin include; women who are pregnant, breast feeding or trying to conceive; people on restrictive diets; people with conditions that deplete nutrients (cancer, diabetes, gastrointestinal problems); people over 50 whose ability to absorb D (from sunlight) and B12 may be diminished.
- A multivitamin can be good for insurance. Avoid mega doses and single nutrient formulas. Look for a multivitamin with 100% daily value levels. Specific formulas for your age and gender are better.
- A number of vitamins can be toxic; A, niacin, B6, C and D. It is important not to exceed the established ULs.
- Vegans are at risk for B12 and D (also calcium, iron, zinc) deficiency. If these are not obtained from fortified foods (breakfast cereals, nutritional yeast, soy milk, meat analogs, etc.), a supplement is needed.
- Food sources that come up repeatedly for many of the vitamins include; fortified milk (or fortified soy milk as a substitute), whole grains (with germ and bran), dark leafy greens (all types), nuts, legumes, brightly colored fruits and vegetables. These should be a regular part of the daily diet.
Disclaimer:
The contents of this Web site are not intended to offer personal medical advice. You should seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this Web site.
References:
- Thompson, Janice L., Melinda M. Manore and Linda A. Vaughn. "Nutrients Involved in Energy Metabolism", "Nutrients Involved in Antioxidant Function", "Nutrients Involved in Bone Health", "Nutrients Involved in Blood Health and Immunity" The Science of Nutrition San Francisco, CA : Pearson Benjamin Cummings 2008
- Duyff, Roberta L. "Vitamins, Minerals and Phytonutrients", "Supplements: Use an Abuse" American Dietetic Association Complete Food and Nutrition Guide Hoboken, NJ : Wiley 2006
- Weil, Andrew. "The Micronutrients" Eating Well for Optimum Health New York : Quill 2001
- Willet, Walter C. "Take a Multivitamin for Insurance" Eat Drink and Be Healthy New York : Free Press 2001
- Melina, Vesanto, and Brenda Davis. "Fine-Tuning the Vegetarian Diet: Vitamin B12" Becoming Vegetarian Summertown, TN : BPC 2003
- Craig, Winston J. "Supplements: Their Use and Abuse", "Vitamin B12 Status of Vegetarians" Nutrition and Wellness Berrien Springs, MI : Golden Harvest Books 2008
- Messina, Virginia, and Mark Messina. "Vitamins in Vegetarian Diets" The Vegetarian Way New York : Three Rivers Press 1996
- "Multiplex" Nutrition Action Healthletter, September 2011 issue, Washington, DC: CSPI 2011
- "Multivitamins", Consumer Reports, September 2010 issue, Yonkers, NY : Consumers Union
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