Vitamin and Mineral Supplements for Healthy People
Why take vitamin and mineral supplements? Supplements may help healthy people for a number of reasons. They can help prevent vitamin and mineral deficiencies when the diet is not adequate to provide all necessary nutrients. They can also provide amounts of nutrients larger than the diet can provide. Larger amounts of some nutrients may help to protect against future disease. Many of these nutrients will be briefly discussed here. However, for more information, refer to individual nutrient articles.
People may consume diets that are deficient in one or more nutrients for a variety of reasons. The typical Western diet often supplies less than adequate amounts of several essential vitamins and minerals.1 Recent nutrition surveys in the U.S. have found large numbers of people consume too little calcium, magnesium, iron, zinc, and, possibly, copper and manganese.2 3
Weight-loss, pure vegetarian, macrobiotic, and several other diets can also place some people at risk of deficiencies that vary with the type of diet. Certain groups of people are at especially high risk of dietary deficiencies. Studies have found that elderly people living in their own homes, often have dietary deficiencies of vitamin A and vitamin E, calcium, and zinc,4 and occasionally of vitamin D, vitamin B1, and vitamin B2.5 Premenopausal women have been found often to consume low amounts of calcium, iron, vitamin A, and vitamin C.6
What is the potential importance of taking vitamin A? Dietary deficiency of vitamin A is uncommon in healthy people except in older age groups.7 Although vitamin A is important for the function of the immune system, vitamin A supplementation did not help prevent infections in elderly people living in nursing homes, in one study.8 Due to concerns about birth defects9 and bone loss,10 people should not take over 10,000 IU of supplemental vitamin A in the form of retinol without consulting a doctor.
What is the potential importance of taking beta-carotene? Beta-carotene is a precursor to vitamin A, but may have a separate role in human health. Controlled research has shown that beta-carotene supplements can increase the numbers of some white blood cells and enhance cancer-fighting immune functions in healthy people who take 25,000–100,000 IU per day.11 12 However, some studies of smokers have reported that supplements of synthetic beta-carotene increased the risk of both heart disease13 14 and lung cancer.15 16 Other trials found no positive or negative effect of synthetic beta-carotene on the risk of many other diseases, including several types of cancer,17 18 19 20 21 22 23 2425 diabetes,26 age-related eye disease,27 28 or intermittent claudication.2930 No other studies have investigated whether natural beta-carotene could be more effective than synthetic in preventing other diseases, but the potential harm from taking synthetic beta-carotene suggests it should be avoided. angina pectoris, Natural beta-carotene, though very similar to synthetic, was found in one preliminary study to reverse pre-cancerous changes, while synthetic beta-carotene did not.
What is the potential importance of taking B-vitamins? Many of the B-vitamins, including thiamine (vitamin B1), riboflavin (vitamin B2), and niacin (vitamin B3), are in plentiful supply in the typical Western diet, because they are added to white flour products and other foods that have been depleted of those vitamins. Another vitamin, biotin, is produced by intestinal bacteria in amounts that, along with typical dietary biotin intake, provide enough of this vitamin to prevent deficiency in healthy people. Pantothenic acid (vitamin B5), on the other hand, appears to be in short supply in the typical diet. In one study, 49% of a group of male and female adolescents were consuming less-than-adequate amounts of pantothenic acid in their diet.31 No research has investigated whether supplements of these B-vitamins prevent disease.
Vitamin B6 (pyridoxine) deficiency, at least in a mild form, may exist in 10–25% of people living in Western societies,32 and may be most common in the elderly.33 34 35 The possible role of vitamin B6 in the prevention of heart disease by helping to regulate blood homocysteine levels is discussed below. No other research on preventive effects of vitamin B6 supplementation has been done.
What is the potential importance of taking folic acid? Folic acid deficiency has been considered somewhat common in the U.S. It affects about 11% of healthy people,3637 Recently, however, the U.S. Food and Drug Administration (FDA) mandated that some grain products provide supplemental folic acid. This appears to be causing a dramatic reduction in folic acid deficiency in the general population.38 Nonetheless, some authorities believe the recent increases in folic acid content of the food supply are not enough to optimally prevent diseases such as heart disease and birth defects (see discussions below).39 with a higher incidence among African-Americans and Mexican-Americans.
The requirement for folic acid doubles during pregnancy,40 and insufficient intake of folic acid has been linked with low birth weight and an increased incidence of neural tube defects in newborns. Supplementation with 400 mcg per day of folic acid prior to, and shortly after, conception, is effective in preventing neural tube defects.41
What is the potential importance of taking vitamin B12? Vitamin B12 deficiency is not common among healthy people,42 except for vegans (vegetarians who also avoid dairy and eggs)43 and in about 12–15% of the elderly in the U.S.44 45 Vitamin B12 deficiency may also occur in people who take acid-blocking drugs for long periods of time.46 Although vitamin B12 deficiency in the elderly is often due to age-related declines in absorption of vitamin B12 from food, vitamin B12 supplements can be absorbed sufficiently in members of this age group if they do not have pernicious anemia or other significant gastrointestinal disorders.47 Supplementation with 100 mcg per day of vitamin B12 was adequate to reverse vitamin B12 deficiency in healthy elderly people, according to one recent report.48
The B-vitamins folic acid, B12 and pyridoxine (vitamin B6) are important for the control of homocysteine levels in the blood.49 Elevated homocysteine levels are associated with several diseases, including heart disease,50 stroke,51 Alzheimer’s disease,52 and osteoporosis,53 though it is unknown whether homocysteine has a direct role in causing these diseases. Daily supplementation with these B-vitamins, typically at least 400 mcg of folic acid, 10 mg of vitamin B6, and 50 mcg of vitamin B12, lowers elevated homocysteine levels in most people.54 55 56 However, no research has investigated yet, whether lowering homocysteine levels with these supplements helps prevent any disease.
What is the potential importance of taking vitamin C? Severe vitamin C deficiency is uncommon in people who consume Western diets, but mild insufficiency is found in 6% of healthy adults57 and larger numbers of college students58 and smokers.59 On the basis of extensive analyses of published vitamin C studies, some authorities have suggested that optimal intake for disease prevention may be at least 90–100 mg per day.60 61 However, supplementation with over 200 mg per day of vitamin C by healthy people does not result in higher vitamin C concentrations in the body,62 and may be no more helpful for preventing disease than smaller amounts.
What is the potential importance of taking vitamin D? Vitamin D can be obtained either from the diet or from sunlight exposure, but these sources can be insufficient, especially in the older population63 and in vegans, during the winter months.64 Six to fourteen percent of healthy adult Western European populations have been reported to be vitamin D deficient,65 but good data are not available for the U.S. Vitamin D insufficiency is associated with bone loss and fractures in older people.66 67 Reduced bone loss from vitamin D supplements has been reported in some,68 69 though not all,70 studies. In one double-blind study, supplementation with 800 IU per day of vitamin D prevented bone loss more effectively than 200 IU per day in postmenopausal women.71 While vitamin D is known to be toxic in very high amounts, up to 2000 IU per day is considered safe.72
What is the potential importance of taking vitamin E? A nationwide study recently reported that 27% of the U.S. population had low blood levels of vitamin E.73 Supplementation with at least 100 IU per day of vitamin E is associated with lowered risk of heart disease,74 75 and a double-blind study found that 400–800 IU of vitamin E per day reduced the risk of nonfatal heart attacks, but not fatal ones.76 However, a recent double-blind trial found no benefit from 400 IU per day of vitamin E supplementation on the risk of non-fatal heart attacks,77 while another study found that 50 IU per day had no effect on heart attack risk.78 A reduced risk of prostate cancer in smokers was reported in a double-blind trial with 50 IU per day of vitamin E.79 However, similar studies have not found vitamin E supplements to protect against other cancers.80 81 82 83
What is the potential importance of taking vitamin K? Vitamin K deficiency severe enough to cause bleeding problems is rare in healthy people. However, low vitamin K in the blood84 85 and in the diet86 has been associated with osteoporosis. Preliminary research has suggested that supplements of at least 1 mg per day of vitamin K reduce indicators of bone loss in some women.87 88 89 90
What is the potential importance of taking calcium? Compared to recent calcium intake recommendations, most people have calcium deficient diets, and less than 10% of women in the U.S. have adequate dietary intakes.91 Good calcium nutrition throughout life is essential for achieving peak bone mass and preventing deficiency-related bone loss.92 Calcium supplements are effective in increasing bone mass in children93 94 95 and slowing bone loss in adults according to most,96 97 98 99 100 101 though not all,102 double-blind studies. Calcium supplements have also been shown to reduce the risk of bone fractures in some elderly adults.103 104 105 106 The protective effect of calcium on bone is one of very few health claims permitted by the FDA. In order to achieve the 1,500 mg per day calcium intake deemed optimal by many researchers for postmenopausal women, 800–1,000 mg of supplemental calcium are generally added to diets that commonly contain between 500–700 mg calcium per day.
What is the potential importance of taking phosphorus? Phosphorus is a necessary nutrient, but diets are almost always adequate in this mineral.107 Some authorities have suggested that excess intake of phosphorus is hazardous to normal calcium and bone metabolism.108 However, this idea has been challanged.109 In any case, there does not seem to be a need for phosphorus supplementation. For this reason, many multivitamin-mineral supplements do not contain phosphorus.
What is the potential importance of taking magnesium? Dietary magnesium deficiency may occur in up to 25% of adult women in the U.S. and in even higher numbers of elderly people of both sexes.110 Magnesium supplements of at least 250 mg per day may help prevent bone loss.111 112
What is the potential importance of taking potassium? While potassium is lower in modern diets compared to so-called primitive diets, true deficiencies are rare.113 Some,114 though not all,115 research suggests that raising potassium intake may help prevent high blood pressure. Other research suggests higher potassium intake may help prevent stroke.116 However, the maximum amount of supplemental potassium allowed in one pill (99 mg) is far below the recommended amounts (at least 2,400 mg per day). Multiple potassium pills should not be taken in an attempt to get a higher amount, since they can irritate the stomach. The best way to get extra potassium is to eat several servings per day of fruits, vegetables, or their juices.
What is the potential importance of taking iron? Iron deficiency is not uncommon among some groups of healthy people, including some vegetarians,117 menstruating girls and women,118 pregnant women,119 and female and adolescent athletes.120 Nonetheless, many people in these groups are not iron deficient 121 and excessive iron intake has been associated in some studies with heart disease,122 some cancers,123 diabetes,124 increased risk of infection,125 and exacerbation of rheumatoid arthritis.126 While none of these links has yet been proven, people should avoid iron supplements unless they have been diagnosed with having, or being at high risk of, iron deficiency.
What is the potential importance of taking iodine? Although iodine deficiency is a concern in many developing countries,127 until recently it was considered abundant in Western diets, due to the introduction of iodized salt and the presence of added iodine in many foods.128 However, iodine intake has decreased considerably in recent years and may be low in as many as 12% of the total U.S. population, and 15% of women of childbearing age.129 These numbers may be greater in countries where iodized salt is not available. Still, most people have adequate iodine intake unless they avoid iodized salt, seafood and sea vegetables. People with thyroid diseases should check with their doctor before using iodine supplements.
What is the potential importance of taking zinc? Zinc deficiency is not common in Western countries, except in people with low incomes.130 131 Zinc supplements (10 mg per day) have prevented growth impairment in deficient American and Canadian children.132 Supplementation with 25–150 mg of zinc per day has been shown to increase immune function in healthy people.133 134 135 136 However, too much zinc has been reported to impair immune function137 and some healthcare practitioners recommend no more than 30–50 mg per day. It is unknown whether these immune system changes are sufficient to cause or prevent infections or other diseases in people taking zinc supplements. Regular supplementation with zinc should be accompanied by copper supplements to prevent zinc-induced copper deficiency.
What is the potential importance of taking copper? The average dietary copper intake in the U.S. has been found to be below accepted standards.138 Although the significance of this is unclear, since symptomatic copper deficiency is quite rare.139 Supplementation with 3 mg per day of copper may help prevent bone loss.140 Since zinc can interfere with copper absorption, copper should be taken whenever zinc supplementation occurs for more than a few weeks.141
What is the potential importance of taking manganese? Dietary intake of manganese is adequate for most people, according to recent studies in the U.S.142 However, manganese, along with other trace minerals, is often low in refined and processed foods.143 144 People whose diets consist primarily of these types of foods may have low manganese intake. Manganese deficiency has been associated with osteoporosis in an unpublished study.145 A double-blind trial found that a combination of mineral supplements including manganese prevented bone loss in postmenopausal women.146 No other studies have investigated the health effects of manganese supplementation. Manganese may be especially important to include when iron is supplemented, since iron can reduce manganese absorption and cause lower body levels of manganese.147
What is the potential importance of taking chromium? Chromium nutrition has been difficult to study because of technical problems in analyzing foods and human body fluids for chromium content. Partly for this reason, there is disagreement about the extent of chromium deficiency in Western societies. Many studies have found sub-optimal levels of chromium in the diet, compared to published recommendations.148 149 150 However, some authorities question the validity of the recommended minimum requirements.151 Chromium deficiency has been associated with blood sugar and cholesterol abnormalities.152 Also, chromium levels in the body decline as people get older, which is when these problems often appear.153 Therefore, while chromium supplements have not been tested for their ability to prevent diabetes or heart disease, many healthcare practitioners recommend chromium supplements as a reasonable precaution. A few single case reports have described possible serious side effects in people taking large amounts of chromium, from 600–2400 mcg per day.154 155 156 Although it is not clear whether chromium was responsible for these reactions.
What is the potential importance of taking selenium? Dietary intake of selenium appears to be adequate in most people. This is according to recent studies in the U.S. based on the Recommended Dietary Allowance of 70 mcg per day of selenium.157 However, a recent double-blind study found that people given a supplement of 200 mcg of yeast-based selenium per day for 4.5 years, had a 50% drop in the cancer death rate over seven years compared with the placebo group.158 Higher amounts of selenium than are available in the diet may be necessary for this protective effect. The upper end of safe long-term selenium intake has been estimated to be 350–400 mcg per day.159
What is the potential importance of taking molybdenum? Molybdenum is an essential trace element with low potential for toxicity.160 Since little is known about human needs and deficiencies are quite rare, estimated requirements are based on what people typically receive in their diets.161 Cancer and cardiovascular disease prevention studies in China found no benefit from a supplement containing molybdenum and vitamin C.162 163 No other research has investigated disease prevention with molybdenum supplements.