|Ever since the discovery of these nutritional cofactors, vitamins have attracted enormous public interest. This is understandable given the power of these small molecules. It has been well documented that diets deficient in these vital micronutrients will result in disease, disability and/or death. What is less well understood is whether vitamin supplementation, in the absence of any defined deficiency, will improve health or lessen the risk of disease. This article will review some of the recent information regarding vitamin supplementation. (Minerals, such as iron and calcium, will be covered in another article.)
It is estimated that 30% of the US population takes vitamin supplements, but it is unlikely that all of these individuals benefit from this practice. On the flip side of the coin, there are undoubtedly members of the other 70% -- the "non-vitamin" group who would benefit from vitamin supplementation. The practical question that this raises is how does one know whether taking a supplement will be helpful?
There are many ways that vitamin supplementation may be evaluated. The results of these investigations depend upon study design, dosage of vitamin used, population studied, length of time, presence of other risk factors or diseases, and specific vitamin "effect" that is being investigated. Returning to the question at hand, one approach to the answer is to break down the general population into certain groups and evaluate the specific effect(s) of a vitamin supplement. This methodology allows one to investigate individuals who may have increased needs due to special demands on their bodies (e.g., pregnancy), or due to disease states (e.g., heart disease).
A number of studies have identified groups that show "definite" or "probable" benefit from supplementation. These positive studies help to raise public and practitioner awareness to target the "at risk" groups. The best example is the conclusive evidence for folate supplementation in pregnant women (prevention of certain birth defects). There are other examples, which will be discussed below.
There are, of course, negative studies as well. These may be divided into "no effect" or "possibly harmful". An example of the latter is an investigation into the potential cancer reducing effects of high dose beta-carotene supplementation in male smokers. Compared to the placebo group, the supplemented group had a slightly higher rate (not statistically significant) of lung cancer. The take home message from this is, quit smoking! A final note on the downside of supplementation is the potential for harm with high doses of some vitamins.
Up to this point this discussion has focused on the role of vitamins in general health and disease, but what about athletics? Could supplementation help athletes perform better? Unfortunately, the research into this area is less extensive and generally limited in nature. This is because there is obviously much greater interest and funding for disease treatment and prevention, than for chopping a minute off of your 10 k time. For most healthy athletes extra vitamin supplementation will not improve performance. However there are some circumstances, just like the questions regarding general health, in which supplementation might be beneficial. A good example is vitamin E, which may aid in recovery from intense exercise. The best advice is that athletes should be aware of the general health "at risk" groups and supplement with the appropriate vitamin if they fall into one of these categories. For example, a vegan athlete should take vitamin B12 because he or she has a self-imposed dietary deficiency. A final bit of advice is that it is probably a good idea for all athletes to take a daily multivitamin (e.g., Centrum).
There is an extensive amount of information available on vitamin supplements, and it is being churned out at a torrid pace. Advertising adds to the confusion. Trying to make sense of it all, and determining its specific applicability to you, can be a daunting task. One practical tip is to pick a few reliable resources -- and periodically go back to them to update your knowledge base. Let your team of experts decipher and decode the vast array of supplement information. A few useful websites for this are, Intellihealth (www.intellihealth.com), The Family Doctor (www.familydoctor.org), and Dr. Koop.com (www.drkoop.com). Stay well away from websites and other sources that are selling a product. Similarly, personal testimonials dont tell you anything useful.
Reference: The New England Journal of Medicine. Dec. 20, 2001. Vol. 345 (25) pp1819 1824
Examples and additional information.
Dosage range: 400 800 micrograms per day. Well documented benefit for women who are pregnant. Reduces the incidence of certain birth defects (neural-tube defects). All women who are pregnant or trying to get pregnant should take a folic acid supplement.
Despite the popularity there is very little evidence that vitamin C supplementation, above that provided in the diet, provides any benefit. The RDA (recommended daily allowance) is 90 mg for men and 75 mg for women (add 35 mg if you smoke). These amounts are easily met in the diet. For both general health and a variety of diseases (e.g., colds, hypertension) extra vitamin C has no demonstrable benefit. Similarly, there is no evidence that it helps treat or prevent overuse injuries.
Evidence is accumulating that supplemental vitamin E may reduce the risk of cardiovascular disease (e.g., heart attacks). Cardiovascular disease is a leading killer in the U.S. Thus, there is considerable interest in the potential benefit of vitamin E supplementation. Furthermore, this vitamin has shown promise in aiding recovery from high intensity, or high volume, exercise. A commonly recommended regimen is 400 IU per day and this dosage appears safe. A typical multivitamin (Centrum) contains 30 IU, which is RDA. If you had to pick one single vitamin to "supplement" a multivitamin the best choice would be vitamin E.
There are a bewildering array of multivitamins, so how does one choose the right one? As a rule a multivitamin should cover a broad range of established vitamins and minerals, and should not exceed 100% RDA, or percentage daily value. To reiterate, a multivitamin that boasts 800% RDA of several different vitamins is not better than one that provides100%. Stick with the well known names (e.g., Centrum), or generics, that provide 100% RDA or less. You achieve the best results possible and are less likely to get into trouble.
COPYRIGHT© 2002 SportsMed Web Mark Jenkins, MD
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