April 11/Aukland, New Zealand/Nutrition Journal 2011 -- Probiotics purportedly reduce symptoms of gastrointestinal and upper respiratory-tract illness by modulating commensal microflora. Preventing and reducing symptoms of respiratory and gastrointestinal illness are the primary reason that dietary supplementation with probiotics are becoming increasingly popular with healthy active individuals.

There is a paucity of data regarding the effectiveness of probiotics in this cohort; however, a recent study sought to evaluate the effectiveness of a probiotic on fecal microbiology, self-reported illness symptoms and immunity in healthy well trained individuals.

Competitive cyclists (64 males and 35 females; age 35 +/- 9 and 36 +/- 9 y, VO2max 56 +/- 6 and 52 +/- 6 ml.kg-1.min-1, mean +/- SD) were randomised to either probiotic (minimum 1109 Lactobacillus fermentum (PCC(R)) per day) or placebo treatment for 11 weeks in a double-blind, randomized, controlled trial.

The outcome measures were fecal L. fermentum counts, self-reported symptoms of illness, serum cytokines.

Lactobacillus numbers increased 7.7-fold (90% confidence limits 2.1- to 28-fold) more in males on the probiotic, while there was an unclear 2.2-fold (0.2- to 18-fold) increase in females taking the probiotic.

Frequency and duration of mild gastrointestinal symptoms were ~2-fold greater in the probiotic group. However, there was a 0.7 (0.2-1.2) of a scale step reduction in the severity of gastrointestinal illness at the mean training load in males, which became more pronounced as training load increased.

The load (durationseverity) of lower respiratory illness symptoms was less by a factor of 0.31 (99%CI; 0.07 to 0.96) in males taking the probiotic compared with placebo but increased by a factor of 2.2 (0.41 to 27) in females. Differences in use of cold and flu medication mirrored these symptoms.

The effects of the probiotic on upper respiratory symptoms were unclear. There were clear reductions in the magnitude of acute exercise-induced changes in some cytokines.

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

The trial was registered in the Australia and New Zealand Clinical Trials Registry (registration number ACTRN12611000006943)

From the April 11, 2011, Prepared Foods' Daily News