The aim of this study was to evaluate the effect of probiotics Lactobacillus rhamnosus IMC 501 and Lactobacillus paracasei IMC 502 on oxidative stress in athletes during a four-week period of intense physical activity. Participants included two groups of 12 subjects; the first group consumed a daily dose of a mixture of the two probiotic strains and the second group (control) did not consume any supplements during the 4 weeks. The results demonstrated that intense physical activity induced oxidative stress and that probiotic supplementation increased plasma antioxidant levels, thus neutralizing reactive oxygen species. The two strains, L. rhamnosus and L. paracasei, exerted strong antioxidant activity. The authors conclude "Athletes and all those exposed to oxidative stress may benefit from the ability of these probiotics to increase antioxidant levels and neutralize the effects of reactive oxygen species".
Martarelli D, Verdenelli MC, Scuri S, Cocchioni M, Silvi S, Cecchini C, Pompei P. Effect of a probiotic intake on oxidant and antioxidant parameters in plasma of athletes during intense exercise training. Curr Microbiol. 2011 Jun;62(6):1689-96.