Do supplements boost athletic performance?

First of four parts.

Performance-enhancing dietary supplements are regularly used by athletes and daily exercisers. Surveys indicate that 75 percent of college athletes and almost 100 percent of body builders use at least one product that allegedly boosts performance.

Supplemental ergogenic aids is the general term for ingested substances that improve efficient use of energy, increase energy production or shorten recovery time. Growth in the ergogenic supplement industry has been astounding. There is little evidence, however, 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 accurately label ingredients. The FDA also has been more aggressive stopping promotions and advertisements claiming false benefits.

Although special preparations of high-dose vitamin and mineral supplements are widely advertised as performance enhancing, there's no evidence that mega doses 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 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 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 to 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.

Today's Medicine Cabinet was written by Howard LeWine, M.D., a member of the Harvard Medical School faculty and practicing internist with Harvard Vanguard Medical Associates and Brigham and Women's Hospital, Boston, Mass. For additional consumer health information, visit health.harvard.edu.