Effects of the regular intake of the probiotic Lactobacillus reuteri (DSM 17938) on respiratory and gastrointestinal infections in a workplace setting: a double-blind randomized placebo-controlled trial

BACKGROUND: The regular intake of probiotics is alleged to help prevent or shorten the duration of common colds and gastrointestinal diseases. Previous clinical trials have shown protective effects in young children, while effects in adults have not yet been sufficiently investigated. METHODS: This study examines the effect of the regular intake of the probiotic Lactobacillus reuteri (DSM 17938) on the number of days of sick leave caused by respiratory and gastrointestinal diseases among male steelworkers. For this RCT, 242 male employees of ArcelorMittal Bremen were randomized. One hundred and twenty-one participants were assigned to take one chewable tablet containing at least 5 × 108 colony-forming units of L. reuteri per day over a period of 90 days. The 121 control participants were assigned to take a placebo. All participants were asked to keep a diary reporting days of sick leave and respiratory and gastrointestinal symptoms. Data of 159 participants were available for intention-to-treat analysis. RESULTS: Participants in the intervention group reported sick due to respiratory and gastrointestinal symptoms at an average of 2.24 of the 90 days under observation. In the control group, the average number of sick days was 2.02 (p = 0.53). Prevention of diarrhea was the only protective effect detected for the probiotic. Participants in the intervention group reported this symptom at an average of 0.60, participants in the control group at 1.33 days (p = 0.01). CONCLUSIONS: Our study could not show an effect of the intake of L. reuteri on the number of days of sick leave or on any of the symptoms of respiratory and gastrointestinal diseases with the exception of diarrhea