Antioxidants for greyhounds? Not a good bet. (Nutrition).

The heavy breathing associated with strenuous exercise draws huge amounts of oxygen into the lungs. Knowing that this can spawn free radicals, which are reactive molecular fragments that can damage tissue, many athletes down daily megadoses of vitamins C and E. These potent antioxidants quell free radicals. Lately, people who race greyhounds have been giving their dogs megadoses in hopes they'll enhance performance.

In fact, the practice impairs speed, new studies show.

Race after race, seasoned greyhounds turn in remarkably consistent times, notes Richard C. Hill of the University of Florida College of Veterinary Medicine Gainesville. To test any benefit of antioxidants, his team randomly cycled five experienced sprinters through a trio of 4-week-long diets. They gave the dogs normal kibble during one session. In the other two, the researchers supplemented this diet with an extra daily gram of vitamin C--either an hour before or shortly after race time.

In the June Journal of Nutrition, Hill's group reports that the only major impact of both the pre- and postrace supplements was that they made the dogs slower--an average of 0.2 seconds slower over 500-meter sprints. That may not sound like much, but it equates to trailing by 3 meters at the finish "and may represent the difference between winning and losing," the scientists say. Especially curious, Hill says, is that the postrace feeding regimen impaired the next day's performance. Long before that next race, the feed's water-soluble vitamin C should have been used up or eliminated from the animals' systems, he notes.

Hill told Science News that experiments with vitamin E-enriched diets yielded similar performance results. Together, these findings could have a bearing on dog racing, says Hill. The dogs, because of the consistency of their performance, may also make a good model for evaluating possible impacts of antioxidants in human athletes, Hill adds.--J.R.