Athletes who train in any populated area are probably inhaling ozone, a common pollutant and dangerous oxygen derivative. Ozone compromises breathing ability and limits aerobic capacity.
Vitamins C and E, the best-known antioxidants, might protect against the ozone effect, says Linda Grievink of Wageningen Agricultural University in the Netherlands in the American Journal of Epidemiology.
Grievink compared the lung function of 20 cyclists given 500 mg vitamin C and 100 IU vitamin E daily for 15 weeks with 18 cyclists given placebo. To measure lung function, Grievink used two measures of lung volume: forced expiratory volume, which is the amount of air someone can expel in one second; and forced vital capacity, the total amount of air that can be expelled. Baseline forced expiratory volume was about 4.65 liters and forced vital capacity was about 5.8 liters. All cyclists were studied on several occasions, either after a training session or a race, and their lung function was compared with ambient ozone levels.
The average ozone concentration was 77 g/M3 and ranged from 14 to 186. In this range, ozone did not diminish lung function in supplemented cyclists, but it did decrease lung function among those receiving placebo. Grievink didn't speculate whether the increased aerobic capacity correlated to better athletic performance, but this study certainly suggests that vitamins C and E may help athletes maximize their aerobic potential.
Recommendation: If exercising outdoors in an area of high pollution, make sure to add antioxidants to your pre-exercise supplement program.