Across 3 studies, all reported beneficial effects on gastrointestinal symptoms, but effect sizes were mixed (two small and one moderate). None of the studies reported statistically significant findings. Evidence is limited to a small number of reviews and a systematic review, with no data on specific doses or forms. The most studied population is athletes, but general adult humans also appear.
Caveats: Available evidence is overwhelmingly positive — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed). Evidence base is small (only 3 studies) — conclusions should be considered preliminary. Many of the included studies did not reach statistical significance — effect may be smaller than the predominant direction suggests. Two of the three studies are reviews with low evidence scores (1), and no dosing or form information is available, making it difficult to generalize.
Only slight evidence was found for a positive effect of probiotics on GI symptoms in athletes during training, exercise, and competition
probiotics have a beneficial effect on mental health, cognitive functions, sleep, gastrointestinal, and upper respiratory symptoms in adult humans.
studies that demonstrated the probiotic potential of enterococcal consumption (e.g., gastrointestinal and respiratory disease, hyperlipidemia alleviation, as well as infection prevention)