Editor’s Note: This is the first of four articles looking at how dietary supplements affect athletic performance.
Performance-enhancing dietary supplements are regularly used by competitive athletes and daily exercisers. Surveys indicate that 75 percent of college athletes and almost 100 percent of bodybuilders use at least one product that supposedly boosts performance.
Supplemental “ergogenic aids” is the general term for ingested substances that improve use of energy, increase energy production, or shorten recovery time. Growth in the ergogenic- supplement industry has been astounding, with new products entering the market weekly. But there is little evidence that the billions of dollars spent on performance-enhancers provide the advertised results.
Unlike medications that need to be approved by the U.S. Food and Drug Administration, dietary supplements can be sold without such preapproval. The FDA has used its limited authority to enhance product safety and to pressure manufacturers to label ingredients accurately. The FDA has also been more aggressive stopping promotions and advertisements claiming false benefits. But the agency has a daunting task because there are so many products, and it has to prove that the products are unsafe or that the promotions are untruthful.
Although special preparations of high-dose vitamin and mineral supplements are widely advertised as performance- enhancing, there’s no evidence that megadoses do more than a well-balanced diet. According to the American College of Sports Nutrition, an athlete regularly consuming a diet that provides sufficient protein and calories with plenty of fruits and vegetables should not need extra vitamins and minerals.
Increased demand is made on some of the B vitamins during exercise, including thiamin, niacin, riboflavin, pyridoxine and pantothenic acid. Enriched cereals and whole-grain carbohydrates combined with some lean meats will satisfy the needs of even the extreme athlete. Vegetarians and other competitors on restricted diets may need some supplementation. Women often need extra iron to replace monthly blood loss from menstruation. A daily generic multiple vitamin with iron is inexpensive and safe insurance if there is any concern that your diet is not providing all that you need.
In general, antioxidants do not enhance performance. The one exception may be vitamin E for high-altitude exercise. One study showed that athletes taking vitamin E at a dose of 400 units per day had more stamina at high elevations compared with those taking a placebo. Most other studies have not shown vitamin E to be superior to placebo at lower altitudes.
Some of the antioxidant vitamins may lessen muscle soreness after exercise by neutralizing free radicals that contribute to exercise-induced muscle damage. The evidence is not conclusive, and the proper doses of vitamins C and E and beta carotene have not been established. Supplemental doses up to 6 milligrams of beta carotene, up to 500 milligrams of vitamin C, and up to 200 units of vitamin E are probably reasonable for this purpose.
Next week: The effects of protein and amino-acid supplements on athletic performance.
Dr. Howard LeWine is a member of the Harvard Medical School faculty and practicing internist with Harvard Vanguard Medical Associates, and Brigham and Women’s Hospital, Boston, Mass. He serves as chief medical editor of Internet Publishing at Harvard Health Publications.
