Intense training is known to suppress immune function in athletes, making upper respiratory infections more common during heavy training periods. Research published in the International Journal of Sport Nutrition and Exercise Metabolism (February 2011; 21(1): 55–64) examined the effects of probiotic supplementation on immune function in athletes. The study included 58 athletes who were randomly assigned to receive either a probiotic supplement containing Lactobacillus casei Shirota (LcS) or a placebo for 16 weeks.
During the study period, the placebo group experienced a 36% higher incidence of upper respiratory tract infections (URTI) compared to the probiotic group. According to the authors, “Regular ingestion of LcS appears to be beneficial in reducing the frequency of URTI in an athletic cohort, which may be related to better maintenance of salivary IgA levels during a winter period of training and competition.”
