RESUMEN
BACKGROUND: A number of clinical trials have successfully been performed using whey and/or soy proteins in the treatment of many diseases. They both have antioxidant properties, which appears to be a factor in aerobic physical performance as well. In addition, these are the most often used supplements that sportsmen take to increase their performance. AIM OF THE STUDY: To investigate the effect of whey and soy protein supplementation on redox parameters in the muscle, on body weight, and body composition in swimming-trained and non-trained animals. METHODS: The effect of whey and soy protein-isolate supplementation on muscle redox parameters, body weight, and body composition in trained and non-trained mice was investigated after a single exhaustive bout of exercise. Steady state free radical concentration measured using electron spin resonance (ESR) spectroscopy, reduced and oxidized glutathione ratio, thiobarbituric acid-reactive substances (TBARS), and protein carbonyl levels of the red leg muscle were measured. RESULTS: Free radical concentrations and glutathione composition of the tissue indicated that whey protein supplementation of the regular diet was able to prevent oxidative stress regardless of training. Soy protein supplementation decreased TBARS only in the muscle of untrained animals, while training per se lowered protein damage in all investigated groups. A mixture of soy and whey protein supplementation resulted in leaner animals after training, but had no synergistic effect on either of the measured redox parameters. CONCLUSIONS: Athletes consuming these supplements could train with higher exercise intensity. The antioxidant effect of the two proteins is based on different mechanisms of action.