About half of Americans take some sort of dietary supplement. Collectively, we spend more than $23 billion per year on these products. The majority of supplements we consume are in the form of multivitamins and mineral supplements. We take these pills on a regular basis for a lot of reasons:
- We think they will make us feel better.
- We think we will have more energy.
- We think it can make up for our bad eating habits.
- We think vitamins can prevent the onset or recurrence of certain diseases.
- We think we will be healthier.
- We think we will live longer.
- Our parents told us to.
- Our doctors told us to.
- Our friend, or neighbors, or someone else we trust told us to.
- Media advertisements extol their benefits and we believe these claims.
That’s a lot of wishful thinking wrapped up in one little (or sometimes not so little) pill or, in some cases, many pills.
What does science tell us
What does the scientific community tell us about the benefits of taking dietary supplements? In order to answer that question, the National Institutes of Health convened a “State of the Science Conference on Multivitamin/Mineral Supplements and Chronic Disease Prevention” in May 2006. Experts in the field from across the country participated in the conference. The result is the NIH Conference statement on the topic published in the September 5, 2006 issue of the Annals of Internal Medicine.
The panel of experts only looked at a select list of supplements that had some scientifically proven evidence to support their benefit. The vitamin/minerals considered in this research review included vitamin A, vitamin E, vitamin B2 and niacin, vitamin B6, folic acid with or without vitamin B12, selenium, and the combination of calcium and vitamin D. The expert panel did not evaluate the usefulness of botanicals, hormones, or other supplements. They also did not address the treatment of known vitamin or mineral deficiencies (rare in this country), nor did they focus on the literature related to dietary supplements in pregnant women or children except as it related to safety of the supplement.
They were, instead, trying to determine if there is solid scientific evidence, primarily randomized controlled trials, to support a recommendation that generally healthy people should take vitamin and mineral supplements in order to improve health and/or prevent onset or recurrence of chronic disease.
The evaluation was complicated by the fact that so many foods available in the U.S. are now fortified with various vitamins and minerals. One industry report the experts cite estimates that 65% of Americans use such fortified foods or beverages. Multivitamin and mineral supplement users tend to have higher micronutrient intakes from their diets than nonusers. They may, in fact, be consuming these substances in amounts greater than the recommended upper limit. Another difficulty the panel encountered was that there was often uncertainty about exactly what and how much was in the supplements reported to have been taken by study participants as well as uncertainty about how frequently they were actually taken.
Because of these and other methodological difficulties, the panel’s strongest conclusion was that there is insufficient evidence to prove that use of multivitamin and mineral supplements by healthy individuals prevents (or fails to prevent) cancer and chronic disease.
The expert panel did, however, report of some notable benefits as well as hazards of multivitamin/mineral supplement use. Here are a few of their findings:
Single vitamin/mineral supplements
- Calcium and vitamin D in combination appears to have a beneficial effect on bone mineral density and risk of fractures in postmenopausal women.
- Use of folic acid by women of childbearing age is effective in preventing neural tube defects (serious congenital malformations) in their offspring.
- Based on single studies, selenium may reduce the risk for prostate, lung, and colorectal cancer; vitamin E may decrease cardiovascular deaths in women and prostate cancer incidence in male smokers; and vitamin A may decrease stomach cancer in rural Chinese.
- Supplementation with B-carotene was associated with an increase in lung cancer incidence and deaths in smokers and male asbestos workers.
- Trials of niacin, folate, and vitamins B2, B6, and B12 produced no positive effect on chronic disease occurrence in the general population.
Multivitamin and mineral supplements
- One study showed less progression of age-related macular degeneration (an important cause of visual impairment and blindness) in people who took a combination of vitamins C and E, B-carotene, and zinc.
- There may be a benefit of selenium, vitamin E, or both in cancer prevention, particularly in men, but some studies identified subsets of the population whose cancer risk might increase with these supplements.
- None of the studies showed any benefits or harm related to cardiovascular disease resulting from the use of multivitamin and mineral supplements.
The article goes on to point out that multivitamin and mineral supplements have not been subject to the same kinds of regulations and oversight as prescription drugs. For example, there is no requirement that adverse outcomes from taking supplements be reported to the FDA MedWatch adverse event reporting system. We know much less than we should about what happens when recommended upper limits are exceeded.
The bottom line
As Americans, we often believe that more is better in almost everything (with the notable exception of taxes)—multivitamin and mineral supplementation is no exception. The results of this expert panel, however, should make us more cautious. Although supplementation is probably safe in most circumstances, it could be hazardous for some, and it certainly can be a strain on the pocketbook for others. Before you plunk down large sums of money for the supplements discussed in this article, think about what you are trying to accomplish by taking those pills. Unless you fall into one of the categories discussed above that have proven benefit, you may decide that your money is better spent on a balanced diet of healthy vitamin and mineral rich foods as well as a good gym membership.