Lee Swanson Research Update

Probiotics May Reduce Cold and Flu Symptoms for Male Athletes

May 2011

Daily supplements of probiotic Lactobacillus fermentum may reduce the duration of symptoms of respiratory tract infections in male athletes. That’s what a new study out of Australia claims.

Competitive male cyclists receiving the daily probiotic supplement had a decrease in symptoms of upper respiratory tract infections (URTIs) 50% greater than a placebo group, according to results published in Nutrition Journal.

On the other hand, well-trained female athletes did not experience any benefits, and probiotic supplementation was actually associated with an increase in symptoms, report researchers led by Professor Allan Cripps from Griffith University.

"An increase in mild gastrointestinal symptoms most likely reflects an adaptive response of the gastrointestinal tract to alteration in the composition of the microflora," wrote Prof. Cripps and his co-workers. "The increased recovery of total Lactobacillus species in feces may have underpinned the clinical outcomes.

"Collectively these studies indicate that L. fermentum may be a useful nutritional adjunct for physically active males in both competitive and recreational settings."

Heavy exercise is a physical stressor that has been shown to reduce key immune system components such as natural killer cells, neutrophils, T and B cells. The potential of an immune-balancing ingredient for athletes is therefore evident.

For the new study, Prof. Cripps and his co-workers recruited 64 male and 35 female competitive cyclists with an average age of 35 and randomly assigned them to receive the probiotic supplement or placebo every day for 11 weeks.

At the end of the study, the researchers report that men displayed a 7.7-fold increase in numbers of Lactobacillus.

Men receiving the probiotic supplement reported a significant decrease in symptoms of respiratory illness, including duration and severity, but this was not repeated in women. The researchers said that the "effects on symptoms in females require further investigation."

"The explanation for the higher number and duration of self-reported symptoms of lower respiratory illness in females supplementing with the probiotic is unclear and difficult to reconcile with the reduced severity of symptoms," the researchers wrote.

"Clinical and immunological differences between the sexes are well recognized. It is possible that these divergent clinical findings were an artifact of sampling variation, given the large number of analyses reported in the study.

"However, taking the male and female results together, the findings with the symptoms are consistent with changes in cold and flu medication usage. Further work is required to clarify this apparent discrepancy between the sexes in physiological and clinical responses to probiotic supplementation."

"L. fermentum may be a useful nutritional adjunct for healthy exercising males," wrote the researchers. "However, uncertainty in the effects of supplementation on URTI and on illness symptoms in females needs to be resolved."

Nutrition Journal; Published online ahead of print.

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