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During the late 1980s, the Council for Responsible Nutrition (a supplement industry trade association) falsely suggested that average Americans were in danger of nutrient deficiency and should take supplements. This article was published in 1987 in response to a CRN pamphlet. For updated information about appropriate supplementation, see Dietary Supplements: Appropriate Use.
Vitamin deficiency diseases have not been encountered in the major health and nutrition surveys done recently in the United States. In fact, such diseases now occur so rarely in this country as to be medical curiosities. Nevertheless, large numbers of apparently healthy people take vitamin supplements. The reasons they give for this are a concern that they are not getting enough vitamins from their diets and the belief that they will be less healthy without supplements. These views are encouraged by nutrition supplement advertisers and others who suggest that dietary inadequacy is common and that many Americans have special nutrient needs for which supplementation is advisable.
One of the main points used to support recommendations for "insurance" with vitamin supplements is that health and nutrition surveys have found that intakes of some vitamins by some segments of the population are below the Recommended Dietary Allowances (RDA). [The abbreviation RDA is used for both the singular and plural of the term.] It is true that surveys have made such observations. But proper interpretation of these results requires understanding how the RDA are established and how dietary surveys are done.
The RDA are dietary standards: the levels of intake that the Committee on Dietary Allowances of the Food and Nutrition Board of the National Research Council/National Academy of Sciences considers "adequate to meet the nutritional needs of practically all healthy persons." But they were designed to provide food service personnel who prepare food for large groups of people with a set of values for desirable intakes of key essential nutrients and appropriate intakes of calories. The quantities of these essential nutrients in the food offered each day could then be compared with the RDA to determine whether the key nutrients were being provided in large enough amounts to prevent any nutritional inadequacy.
Because people differ in size and genetic makeup, their nutrient requirements differ; requirements of individuals for essential nutrients range from about 50% below to 50% above the population average. The RDA are therefore set high enough to ensure that, if the quantities of nutrients in the food being served meet this standard, they will meet the needs of individuals with the highest requirements. Thus the amounts of nutrients most people require will be below the RDA, and about half the population should require less than 75% of the RDA. It would require an elaborate probability analysis to determine how likely it is that people consuming less than the RDA have intakes that are not adequate. Using the RDA directly as standards for evaluating the adequacy of individual nutrient intakes is improper; it would be like setting the standard for height at seven feet and concluding that all those under seven feet have suffered growth retardation.
Even when the estimates of nutrient intakes obtained during dietary surveys are compared with the RDA, we find that only two vitamins -- A and C -- are identified consistently as "problem" nutrients. In interpreting these observations, we encounter two additional problems. The adult RDA for vitamin C is high enough to ensure that an adult who is consuming an amount of vitamin C equal to the RDA will have a store of the vitamin sufficient to prevent signs of deficiency even if no vitamin C is consumed for about two months. This standard, twice that of the World Health Organization, is much higher than necessary. Because of this, one would expect to find problems of "inadequate" intake where none exist -- and that is exactly what happens.
With vitamin A, a different problem is encountered. The main sources of vitamin A in the diet are carotenoids, precursors of the vitamin found in dark green and yellow to orange vegetables. These foods are not usually eaten every day. Sc when the results of dietary surveys are based on measurements of nutrient intakes for a single day -- as they frequently are -- many people have "low" intakes of vitamin A while others have unnecessarily high intakes. Since vitamin A is stored efficiently in the liver, a surplus consumed on one day will provide a reserve that is available on subsequent days. Intakes of vitamin A can probably be estimated accurately only by averaging daily intakes over at least a week.
Thus, because of the nature of the RDA and of dietary surveys, it is not possible to assess nutritional status by comparing estimates of nutrient intakes with the RDA. The only way that vitamin status can be determined reliably is from clinical observations and measurements of blood or tissue concentrations of vitamins or cofactors or the rates of metabolic reactions for which the vitamins are needed. When this has been done, a very small proportion of the population surveyed has been found to have values that are low, but still not low enough to be considered deficient. With such a high proportion of the population showing no evidence of inadequate vitamin intakes, the low values cannot be due to inadequacies of the food supply.
Estimates of the nutrient content of our food supply by the U.S. Department of Agriculture indicate that the amounts of most nutrients available to the consumer have increased during this century. Consumption of fruits, vegetables, cheese, skim milk, fish, poultry and pork -- all excellent sources of essential nutrients -- have increased during the past ten years more than enough to compensate for declines in the consumption of beef, whole milk, and eggs. Of low-income families studied by the Agriculture Department, 42% were consuming a diet that met the RDA for eleven nutrients. This is incontrovertible evidence that the food supply contains adequate amounts of essential nutrients. Families that were dependent on food stamp allotments were consuming less adequate diets, indicating that as income falls, food choices become more limited and intakes of some essential nutrients decrease. Inadequate intakes of food, and hence usually of nutrients also occur because of neglect, illness, alcoholism and ignorance. Dietary supplements are not an appropriate solution to these problems.
Another reason given for the use of vitamin supplements is deteriorating or haphazard eating habits. America's eating habits have changed, but whether this represents deterioration is certainly debatable. A pattern of eating three or more substantial meals a day is common in agricultural communities and others in which human energy expenditure is high. This was accepted as the most desirable pattern when our population was largely rural and when mechanization was much less in both the home and the workplace than it is today. One might well ask whether, in a society in which energy expenditure is low, it may not be preferable to eat several small meals throughout the day and to eat when hungry rather than when the clock says it is mealtime. There is much speculation but little evidence that "irregular" eating patterns result in consumption of inadequate amounts of essential nutrients except when total food intake is low.
Even the claim that many people, especially women, have low caloric intakes, and therefore low intakes of essential nutrients, deserves careful scrutiny. The basis for the RDA for energy (calories) is different from that for essential nutrients. The RDA for energy represent average requirements. Half of the population should thus require less than the RDA. Also, with as much as 20% of the population (especially women) on weight reduction regimens at any one time, the proportion found to have caloric intakes below the RDA in any dietary survey would be expected to exceed 50%. Despite this, underweight is a problem for very few people in this country; hence, the number of dieters who stay on low-calorie diets for very long cannot be high.
Furthermore, dietary surveys usually find that protein intakes meet or exceed the RDA. Since protein tends to make up a relatively constant proportion of calories in most diets, this suggests that caloric intake has been underestimated. Persons with calorie intakes above the RDA are reported to have intakes of most essential nutrients that are well above the RDA. Thus, underestimation of caloric intakes probably accounts for some of the low estimates of micronutrient intakes.
Since there is little evidence that will stand up to scrutiny to suggest that any substantial proportion of the U.S. population is consuming a nutritionally inadequate diet for any length of time, there is little reason to assume that vitamin supplements will benefit a substantial portion of the population. Foods contain important nutrients that are not provided in vitamin supplements; they also contain many constituents whose significance for health is unknown. Learning how to select foods properly to meet nutritional needs, regardless of changing eating patterns or changes in the food supply, is the only reliable way to ensure lifelong nutritional health. Encouraging the use of vitamin supplements as a corrective for poor eating habits defeats the entire purpose of nutrition education, i.e., to learn the nutritional principles needed to select a healthful diet instead of accepting nutritional advice on faith.
In recent years it has been suggested that above-RDA amounts of vitamins are needed to counteract the effects of various environmental stresses. However, since the human subjects used in experiments which provided the information on which RDA are based were not protected from usual environmental stresses or infections, it is doubtful that vitamin supplements are needed in these conditions. During illness, recovery from illness, and periods of drug therapy, food intake may be so low that it becomes difficult or even impossible to meet nutritional needs from foods. Nutritional supplements can be useful under such conditions, but as part of a comprehensive program of treatment under the guidance of a physician.
Various observations have led to suggestions that certain vitamins -- particularly A, E and C -- may have some unique value in preventing or reducing adverse effects from environmental hazards. (Hoffmann-La Roche has even designated these three as "Protector Vitamins" in an extensive advertising campaign.) Some of these observations are tantalizing, e.g., that these vitamins may act in some way to protect against certain cancer-inducing agents; and, that vitamins E and C, as antioxidants, may protect against ill effects from certain chemical contaminants. Some studies indicate that vitamin deficiencies can increase susceptibility to toxic agents, but it does not follow from this that extra vitamins provide extra protection. This concept is the subject of much current research, but unless direct evidence is found, it seems unwise to recommend supplementation on this basis.
Advocates of vitamin supplements have suggested that many people belong to population groups that have special vitamin needs. Probably the most elaborate presentation of this concept is contained in "Personal Health Circumstances Benefited by Nutritional Supplementation," a six-page flyer published recently by the Council for Responsible Nutrition (CRN), a coalition of major food supplement manufacturers and distributors.
According to the flyer: "CRN believes that the analysis of personal nutrition need categories strongly suggests that large groups of people are at risk for a variety of reasons and that their nutritional status, overall quality of health, and consequent mortality and morbidity are affected. Thus it makes good sense to help guide those in these special need categories to take some action that will protect or improve their nutrition status. Nutrition is a dynamic, rapidly evolving science. CRN believes it is foolish for some old-fashioned health, medical and nutrition personnel to automatically exclude supplements as one worthwhile choice. Instead, it is rational for the millions of people in self-identifiable circumstances to investigate and choose from among all appropriate alternatives of proven benefit." In line with these thoughts, the flyer designates 18 "groups with proven nutrient needs" for which "scientific evidence available today suggests that a nutritional supplement as part of total intake will be beneficial."
CRN is correct that individuals in these groups have "proven nutrient needs." In fact, it is a truism that all subgroups of the population have proven nutrient needs. But these needs are taken into account by the scientists who determine the RDA! Here is my analysis of each of the groups listed in CRN's flyer:
People taking prescription drug(s): 125 million. Although certain drugs are known to increase the requirements for specific vitamins, it is improper to assume that drugs automatically increase nutrient requirements. Problems are most often associated with consumption of marginal diets -- and with prolonged use of drugs that cause malabsorption or metabolic impairment. It is important to identify drug-nutrient interactions that can create clinical problems, Individuals taking such drugs need a recommendation from a physician for the appropriate extra amount of any specific nutrient that is needed. General supplementation is not a rational approach because only the nutrient(s) that will correct the problem will be of any value.
Dieters: 95.4 million. Certainly dieters who are consuming less than 1,200 calories per day should consider whether the total amount of food they consume will provide adequate amounts of all of the essential nutrients they require. Many dieters do not consume such low amounts of calories and, if they do, they usually do so for only a short period of time. If caloric intakes are reduced below 1,000 calories a day for longer than one week, it is probably wise to take a standard one-a-day vitamin-mineral supplement. However, such low-calorie dieting should be done under supervision of a physician with the appropriate supplement being provided as part of the overall diet plan.
Premenopausal women of childbearing age: 55 million. Premenopausal women of childbearing age are part of the population of normal healthy individuals. The RDA for healthy adult women are based on their needs. Many of these women need education about appropriate food use, but if they are eating wisely they should not need supplements except during pregnancy when they may not eat enough total food to build up adequate iron stores. A standard iron supplement is commonly recommended during pregnancy, as are additional milk and milk products to ensure that the RDA for calcium will be met.
Smokers: 54 million. There has been much emphasis on the fact that vitamin C levels in the blood of smokers are lower than those of nonsmokers. However, the suggestion that smokers need high doses of vitamin C seems incongruous when one considers that most of the subjects used in the major experiments that served as the basis for present RDA for vitamin C allowances were reported to be smokers. It would seem much more appropriate to suggest that nonsmokers need less than the RDA. Moreover, smoking is so devastating to health that even if vitamin C did offer slight protection against its ravages, it would be senseless to encourage smokers to believe that they can avoid the consequences of smoking through nutritional measures!
People with specific gastrointestinal disorders: 40 million. Most gastrointestinal disorders last only a few days and require no special nutrient supplements. For chronic or prolonged gastrointestinal disorders, management by a physician is essential and emphasis should be placed on identifying the cause and curing the condition. Supplements may be desirable while nutrient loss is occurring but should be done under medical supervision. In malabsorptive diseases -- where absorption of specific vitamins is impaired -- specific supplementation is advisable until the condition can be brought under control.
Postmenopausal women: 39 million. The major change in nutrient needs of healthy postmenopausal women is reduced energy requirement. From age 50 on, caloric needs decline steadily while the need for essential nutrients remains the same. The best way to obtain these nutrients while eating less is to select a large proportion of foods that are rich in essential nutrients. It is also wise for postmenopausal women to maintain and possibly increase their physical activity. This will also help prevent loss of calcium from their bones and will decrease their chances of becoming overweight.
The elderly: 28 million. The active elderly who are healthy have no special needs beyond those covered by the RDA. (Of course, the above comments about declining energy needs and the desirability of increased physical activity apply to the elderly generally.) The elderly who are ill, and a substantial proportion are, need medical advice and not a general recommendation for a nutrient supplement. The older elderly may have unusually low caloric requirements because of low activity as well as low metabolic rate. Here again, attention should be given to maintaining an adequate intake of foods that are highly nutritious. In some circumstances, food intake may be so low that a supplement becomes appropriate.
Women taking postmenopausal estrogen: 2.3 million. Women taking postmenopausal estrogens should be no different from the normal healthy elderly. They should maintain calcium intake in the RDA range because the beneficial effect from estrogens on osteoporosis has been shown most clearly when calcium intake is in that range or somewhat higher.
People with osteoporosis: 20 million. There is no evidence that individuals with osteoporosis have any general need for nutrient supplements. Even the evidence of benefits from high intakes of calcium is inconsistent and controversial. For normal bone maintenance, a calcium intake that meets the RDA is needed throughout adult life. This can be obtained from foods, especially dairy products, but dietary surveys show that many elderly women have low total food and calcium intakes. Increased physical activity will enable them to eat more without gaining weight, and tends to reduce bone mineral loss. It is unclear whether calcium supplements alone are helpful in treating osteoporosis. Combined calcium and estrogen therapy is reportedly beneficial, but of course should be done under medical guidance.
Poor people: 33.1 million. The poor need a support system; they need food programs that provide them with adequate quantities of essential nutrients and energy sources. In other words, they need proper food. Supplements of essential nutrients cannot substitute for basic needs for energy sources and protein, and are expensive in relation to the income of this group of people.
People with chronic or infectious disease(s) or under chronic physical stress: unknown millions. Chronic and infectious diseases generally cannot be assumed to increase nutrient needs. This is an irrational grouping in relation to nutritional requirements. Infectious diseases are individual problems and should be dealt with by appropriate medical care, not by general recommendations for increased intakes of nutrients. If a chronic or degenerative disease results in severely depressed food intake and weight loss, it may be appropriate to provide a supplement with the food during the period of debilitation.
Teenagers: 25.9 million. Teenagers represent an active part of the total healthy population. Students up to college age are usually physically active and often have caloric intakes that are quite high. They need mainly to learn how to achieve dietary balance by choosing nutritious foods and moderating intake of foods that contain small quantities of essential nutrients. They need nutrition advice, not supplements which tend to distract them from learning about sound food choices.
Alcoholics: 25 million. Supplements are not a solution for alcoholism. Alcoholics need food instead of alcohol and guidance to learn how to control the problem of addiction. If food intake of an alcoholic is extremely low, severe vitamin deficiencies can develop. These need prompt clinical attention and a program of rehabilitation. Inappropriate vitamin supplements may delay the appearance of certain deficiency signs and result in medical treatment being put off until serious deterioration of vital organs has occurred.
Women taking estrogen for birth control: 8.8 million. There have been reports of changes in the metabolism or blood levels of certain essential nutrients in women using birth control pills. However, claims that these provide evidence of nutritional inadequacy have not stood up to rigorous testing. Again the most important dietary advice for women using contraceptive estrogens is to maintain an adequate intake of all nutrients through appropriately balanced diets that meet the recommended allowances.
Strict vegetarians: 8.5 million. I do not believe there are 8.5 million strict vegetarians in the United States. Moreover, vegetarians are often more knowledgeable about nutrition than the average person because they have organizations that offer valid nutrition advice. Most vegetarians consume eggs and dairy products and obtain adequate quantities of all nutrients including vitamin B12, although some may not. For those who are strict vegetarians, a source of vitamin B12 is required. It is also particularly important for vegetarians to select a wide variety of different types of fruits and vegetables and cereal grains because serious malnutrition has been found to occur in individuals who have restricted their intake to a narrow range of foods from plant sources. Supplements are not a substitute for sound diet planning.
Pregnant women: 3.6 million. There are modest increases in needs for essential nutrients during pregnancy. Food consumption usually increases during gestation so the pregnant woman will be eating increased quantities of all nutrients. If food intake declines, a supplement providing about half the RDA for the vitamins most likely to be in short supply, together with iron, would not be inappropriate.
Lactating women: 2.16 million. During lactation, energy needs of women increase substantially. Their increased food intake will normally compensate for the increased quantities of essential nutrients needed for production of milk. For women who are reducing weight during lactation or who have low food intake, a standard vitamin-mineral supplement may be appropriate, but otherwise essential nutrient needs are readily met by diet.
Premature infants: 0.36 million. Premature infants require medical care; their needs should be determined carefully by the physician to ensure that the essential nutrient supply is adequate. Essential nutrients are usually provided as part of the formula, not as a special supplement.
The most appropriate use of vitamin supplements is in conditions in which caloric intake is below 1,200 calories per day and particularly if, at the same time, requirements are increased, perhaps as the result of illness. A correctly balanced multivitamin supplement may also be appropriate for pregnant women. Supplements of vitamins A and D of appropriate potency can be justified for young infants as insurance against nutritional inadequacy. And supplementary fluoride is vital to help strengthen the teeth of children growing up in nonfluoridated communities -- a need that CRN does not address. I see no evidence in the scientific literature that Americans generally require vitamin supplements. Rather, they need accurate nutrition information about food and health to counter the nutrition misinformation to which we are constantly exposed.
This article was published in the May/June 1987 issue of Nutrition Forum Newsletter when Dr. Harper was Professor of Biochemistry and Nutritional Sciences at the University of Wisconsin. He was chairman of the Food and Nutrition Board of the National Research Council/National Academy of Sciences from 1978 to 1982 and has served on other NRC/NAS committees involved in determining the RDA.