Bacillus coagulans Unique IS2 improves stool characteristics in healthy adults with infrequent bowel movements: a randomized, double-blind, placebo-controlled trial

Digestive health issues, including irregular bowel movements (BM) and gastrointestinal (GI) symptoms, affect millions of people in the United States and are associated with higher risks of various diseases. This randomized, double-blind, placebo-controlled study investigated the potential of Bacillus coagulans Unique IS2 to improve stool characteristics and reduce GI symptoms. Following a 2-week run-in, 144 healthy adults were randomized in a 1:1 ratio to either B. coagulans Unique IS2 (2 billion colony forming units/day) or placebo for 4 weeks. Participants were included if they had an average weekly complete spontaneous bowel movement (SBM) of ≥3.0 and <7.0 during the run-in. The primary outcome was the change in BM frequency after 4 weeks. Secondary outcomes included change in stool consistency (assessed by the Bristol Stool Form Scale), GI symptoms and quality of life, gut microbiota composition, and the proportion of complete SBM to total BM. Safety was assessed by vital signs and reports of adverse events. After 4 weeks of supplementation with Unique IS2, there was a significant increase in BM frequency ( P = 0.037). Stool consistency significantly improved after each week in the Unique IS2 group (all P < 0.05) and was significantly improved compared to a placebo after 4 weeks ( P = 0.018), driven by a significant improvement in the incidence of hard stool ( P = 0.001). There was no effect of Unique IS2 supplementation on GI symptoms and quality of life (Gastrointestinal Quality of Life Index), gut microbiota composition (analysis of stool samples by 16S rRNA), or proportion of complete SBM to total BM. Unique IS2 was safe and well tolerated over the 4 weeks of supplementation. Our results suggest that B. coagulans Unique IS2 is a promising strategy to improve stool characteristics of individuals with hard stools and poor stool quality. Clinicaltrials.gov registration: NCT05123664.