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Vitamin-Mineral Supplements and Their Usage by Adults

by Judy A. Driskell, Ph.D., R.D., Extension Foods and Nutrition Specialist

"Should I take vitamins, vitamins plus iron, or vitamin-mineral supplements?"

This is a question that people in all socioeconomic groups ask. People without a high school education as well as those with doctoral degrees including M.D.s ask this question. The answer to this question is not a simple "yes" or "no". Several health organizations including the American Medical Association have responded to the question.

Let's first consider the POTENCY of the supplement. Vitamins, vitamins plus iron, and vitamin-mineral supplements available for nonprescription purchase have different potencies. The potency of the supplement is the amounts of the vitamins and/or minerals present in a daily dosage. The label may give these amounts as weights of the different nutrients or, more commonly, as percentages of the US Recommended Daily Allowances, or U.S. RDAs. The U.S. RDAs are based on the 7th edition of the Recommended Dietary Allowances (RDAs), published in 1968.

The RDAs "are levels of intake of essential nutrients that, on the basis of scientific knowledge, are judged by the Food and Nutrition Board to be adequate to meet the known nutrient needs of practically all healthy persons".

The U.S. RDA is used by the Food and Drug Administration (FDA) as a standard for nutritional labeling. The amounts of the nutrients that constitute 100 percent of the U.S. RDA for adults and children 4 or more years of age are given in Table 1. The forms of the nutrients which are most commonly used in supplements are also listed in Table 1.

The FDA has proposed making changes in this labeling and the amounts of nutrients that are to be used as legal standards concerning recommended daily nutrient consumption levels. So, the "recommended" levels will change in the next couple of years but the principles remain the same.

Health Organization Recommendations

Various health organizations have published statements on the usage of supplements. The following statements are direct quotes.

The American Medical Association

"Healthy adult men and healthy adult nonpregnant, nonlactating women consuming a usual, varied diet do not need vitamin supplements. Infants may need dietary supplements at given times, as may pregnant and lactating women. Occasionally, vitamin supplements may be useful for people with unusual lifestyles or modified diets, including certain weight reduction regimens and strict vegetarian diets.

"Vitamins in therapeutic amounts may be indicated for the treatment of deficiency states, for pathologic conditions in which absorption and utilization of vitamins are reduced or requirements increased, and for certain nonnutritional disease processes.

"The decision to employ vitamin preparations in therapeutic amounts clearly rests with the physician. The importance of medical supervision when such amounts are administered is emphasized. Therapeutic vitamin mixtures should be so labeled and should not be used as dietary supplements."

The American Medical Association reviewed the statement which follows. They stated that this statement was consistent with their statement.

The American Institute of Nutrition, The American Society for Clinical Nutrition, The American Dietetic Association, and The National Council Against Health Fraud

"Healthy children and adults should obtain adequate nutrient intakes from dietary sources. Meeting nutrient needs by choosing a variety of foods in moderation, rather than by supplementation, reduces the potential risk of both nutrient deficiencies and nutrient excesses. Individual recommendations regarding supplements and diets should come from physicians and registered dietitians.

Supplement usage may be indicated in some circumstances including the following:

Women with excessive menstrual bleeding may need to take iron supplements.

Women who are pregnant or breastfeeding need more of certain nutrients, especially iron, folic acid and calcium.

People with very low calorie intakes frequently consume diets that do not meet their needs for all nutrients.

Some vegetarians may not be receiving adequate calcium, iron, zinc and vitamin B-12.

Newborns are given, under the direction of a physician, a single dose of vitamin K to prevent abnormal bleeding.

Certain disorders or diseases and some medications may interfere with nutrient intake, digestion, absorption, metabolism or excretion and thus change requirements.

Nutrients are potentially toxic when ingested in sufficiently large amounts. Safe intake levels vary widely from nutrient to nutrient and may vary with the age and health of the individual. In addition, high dosage vitamin and mineral supplements can interfere with the normal metabolism of other nutrients and with the therapeutic effects of certain drugs. The Recommended Dietary Allowances represent the best currently available assessment of safe and adequate intakes, and serve as the basis for the U.S. Recommended Daily Allowances shown on many product labels. There are no demonstrated benefits of self supplementation beyond these allowances."

The American Heart Institute, the National Institute on Aging, the Department of Agriculture, and the Department of Health and Human Services have stated agreement with the above statement. Hence, the recommendations of these nine health organizations are similar.

The National Academy of Sciences' Food and Nutrition Board issues statements/publications regarding nutrition and the maintenance of good health. Committees/Subcommittees of this Board have recently published statements concerning supplements.

Subcommittee on the Tenth Edition of the RDA's
National Academy of Sciences
National Research Council
Recommended Dietary Allowances

"The recommended allowances for nutrients are amounts intended to be consumed as part of a normal diet. If the RDAs are met through diets composed of a variety of foods derived from diverse food groups rather than by supplementation or fortification, such diets will likely be adequate in all other nutrients for which RDAs cannot currently be established."

Committee on Diet and Health

National Academy of Sciences

National Research Council

"A large percentage of people in the United States take dietary supplements, but not necessarily because of nutrient needs. The adverse effects of large doses of certain nutrients (e.g., vitamin A) are well documented. There are no documented reports that daily multiple vitamin-mineral supplements equaling no more than the RDA for a particular nutrient, are either beneficial or harmful for the general population. The potential risks or benefits of the long-term use of small doses of supplements have not been systematically examined."

Many Adults Take Supplements

Many adults in the United States take supplements. USDA surveys showed that 45 percent of men and 58 percent of women, nonpregnant and nonlactating, 19 to 50 years of age, reported using supplements regularly or occasionally in 1985. A 1980 FDA survey showed that 36 percent of men and 44 percent of women, nonpregnant and nonlactating, consumed supplements daily. The FDA survey indicated that supplement use was greatest among Caucasians with relatively high incomes and at least a high school education.

The most common supplements taken by adults are multiple vitamins with or without iron and vitamin C. Researchers at land-grant universities in the western U.S. did this research. The supplement user was most likely to be a young female with some college education who "believes that the nutritional quality of food has decreased in the last 10 years and in the efficacy of supplements for disease prevention or cure, and primarily receives information concerning food and nutrition from books and health food stores."

The two most frequently given reasons for using supplements were "to prevent colds and other illnesses" and "to make up for what is not in food."

Research has shown that generally the nutritional status of individuals who take supplements is similar to that of individuals who do not take supplements. Also, the dietary nutrient intakes of individuals who take supplements are generally similar to individuals who do not take supplements.

Possible Nutrient Toxicities

Numerous adverse health effects are associated with consumption of excessive amounts of vitamins and/or minerals. Practically all vitamin toxicities have been a result of consumption of supplements, not of foods, containing the vitamins. Most mineral toxicities have been a result of inhalation.

Numerous reports on toxicities of single vitamins and minerals exist in which laboratory animals were used. Most of the data on adverse health effects from large intakes of a vitamin or mineral by humans pertain to acute rather than chronic use. The consumption of excessive amounts of one nutrient may cause a deficiency of another. Nutrients work together in the body.

Surveys show that some individuals take supplements in potentially harmful amounts. However, currently there is no evidence that low levels of supplements adversely affect the health of typical individuals.

Recommendation

The author of this NebFact recommends that if a typical adult wants to take a supplement, that supplement should be a multivitamin-multimineral one that contains vitamins and minerals at U.S. RDA levels. Many multivitamin-multimineral supplements containing 100 percent U.S. RDA levels are on the market. The consumption of this level of supplement will not be harmful to health and may or may not be helpful.

The best advice is to obtain vitamins and minerals by eating a wide variety of foods. If an individual chooses to take a multivitamin-multimineral supplement, a balanced diet also should be consumed. This is because knowledge is inadequate as to all of the essential nutrients needed by adults -- all required nutrients may not be present in the supplement.

Table 1. U.S. Recommended Daily Allowances, U.S. RDAs, for Adults and Children 4 or more Years of Age

Selected References

Diet and Health: Implications for Reducing Chronic Disease Risk. Washington, DC: National Academy Press, 1989.

Food and Drug Administration. Food labeling. Federal Register 38, No. 13, Pt. 111, January 19, 1973.

Food supplement usage in seven Western states. American Journal of Clinical Nutrition 1982;36:897-901.

Recommendations concerning supplement usage: ADA statement. Journal of The American Dietetic Association 1987;87:1342-3.

Recommended Dietary Allowances, 10th edition. Washington, DC: National Academy Press, 1989.

Statement on Vitamin and Mineral Supplements. Journal of Nutrition 1987;117:1649.

USDA, CSFII: Nationwide Food Consumption Survey -- Continuing Survey of Food Intakes by Individuals. Hyattsville, MD: USDA, HNIS, 1986.

Vitamin Preparations as Dietary Supplements and as Therapeutic Agents. Journal of The American Medical Association 1982;257:1929-36.

University of Nebraska Cooperative Extension

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