Why take vitamin and mineral supplements?

For healthy people, supplements may help prevent vitamin and mineral deficiencies when the diet does not provide all necessary nutrients. They can also supply 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 D, vitamin A, vitamin E, calcium, and zinc,⁴ and occasionally of 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 B-vitamins?

Some of the B-vitamins, including thiamine (vitamin B1), riboflavin (vitamin B2), and niacin (vitamin B3), may be adequately supplied by 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 to 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 vitamin B12?

Vitamin B12 deficiency is not common among healthy young people,⁴² except for vegans (vegetarians who also avoid dairy and eggs).⁴³ However, about 12 to 15% of the elderly in the U.S. have been found deficient in this vitamin.^{44 45} Vitamin B12 deficiency may also occur in people who take acid-blocking drugs or antacids 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 and some, though not all, research suggests that 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} Some studies have shown that supplementing with one or more of these vitamins helps prevent or reverse hardening of the arteries (atherosclerosis) and may also reduce the risk of bone fractures.^{57 58}

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RESEARCH UPDATES

High-Dose Vitamin D Protective Against Colorectal Cancer
SAN DIEGO-- ¬Contrary to earlier reports that low-dose vitamin D supplementation did not lower colon cancer risk, a recent review of five studies suggests higher serum levels of the vitamin could decrease risk of colorectal cancer by as much as 50 percent. The meta-analysis (Am J Prev Med. 32, 3:210-16, 2007) was a collaboration between University of California, San Diego; Harvard School of Public Health, Boston; Strang Cancer Prevention Center, New York; State University of New Jersey and Cancer Institute, New Brunswick; Boston University School of Medicine; and Sunlight, Nutrition and Health Research Center, San Francisco. Reviewers looked at five studies involving serum 25-(OH)-D (D3) levels and colorectal cancer using standard methods for pooled analysis. The trials measured serum D3 in healthy volunteers who were then followed for periods ranging from two years to 25 years. There were 535 cases in the pooled analysis and 913 controls, or 1,448 total participants. Researchers divided the results in quintiles of serum vitamin D levels¬6, 16, 22, 27 and 37 ng/mL. The lowest serum level group became the reference group, and reviewers assessed odds ratios using Peto’s Assumption-Free Method. Odds ratios, from lowest to highest quintile, were 1.00, 0.82, 0.66, 0.59 and 0.46 (ptrend<0.0001) for colorectal cancer. After analyzing the results, the reviewers found a 50-percent decreased risk of colorectal cancer in those with serum D3 levels of at least 33 ng/mL, compared to those with 12 ng/mL D3 or less. They concluded the evidence to date suggests daily intake of 1,000 to 2,000 IU of vitamin D3 could reduce the incidence of colorectal cancer with minimal risk.  Reviewed by Lester Packer, PhD, Chairman of the Dietary Supplement Information Bureau Scientific Advisory Board

Higher intakes of vitamin A, retinol and provitamin A carotenoids may reduce gastric cancer risk
STOCKHOLM, Sweden-- ¬Higher intakes of vitamin A, retinol and provitamin A carotenoids may reduce the risk of gastric cancer, according to a prospective cohort study in more than 82,000 Swedish adults (Am J Clin Nutr, 85, 2:497-503, 2007). Swedish researchers, coordinated through the Karolinska Institute, examined the association between intakes of vitamin A, retinol and specific cartenoids and the risk of gastric cancer in adults aged 45 to 83. During a mean seven-year follow-up, 139 incident cases of gastric cancer were diagnosed. High intakes of vitamin A and retinol from foods only (dietary intake), from foods and supplements combined (total intake), and from dietary alpha-carotene and beta-carotene (provitamin A carotenoids) were associated with a lower risk of gastric cancer. Compared with adults in the lowest quartile of intake of specific compounds, those with the highest intake of total vitamin A had a 47-percent reduced risk; total retinol dropped the risk by 44 percent, beta-carotene by 45 percent, alpha-carotene by half. Previous research has suggested vitamin A may influence gastric carcinogenesis through its role in controlling cell proliferation and
differentiation. Reviewed by Lester Packer, PhD, Chairman of the Dietary Supplement Information Bureau Scientific Advisory Board

Vitamin D, Calcium Aid in Weight Loss
STE-FOY, Quebec-- Researchers from Laval University observed the effects of vitamin D and calcium supplementation on weight loss in 63 women randomly assigned 600 mg elemental calcium and 200 IU vitamin D tablets or placebo daily. All subjects participated in a 15-week weight loss intervention program. At the conclusion of the intervention, significantly greater decreases in total, low-density lipoprotein (LDL) and the LDL-to-high-density lipoprotein (HDL) cholesterol ratio were observed in the calcium/ vitamin D group compared to the placebo group. These metabolic variables were independent of changes in fat mass and in waist circumference. Researchers concluded vitamin D and calcium benefit the lipid and lipoprotein profile in dieting overweight or obese women with usual low daily calcium intake. The study was published in the American Journal of Clinical Nutrition (85, 1, 54-59 2007).