Safety evaluation of the excessive intake of Bacillus subtilis C-3102 in healthy Japanese adults: A randomized, placebo-controlled, double-blind, parallel-group, comparison trial

Objective: Continuous intake of Bacillus subtilis C-3102 (B. subtilis C-3102) has been reported to modulate the gut microbiota and increase the bone mineral density of the femur in healthy adults. This study aimed to evaluate the safety of excessive B. subtilis C-3102 intake through a randomized, placebo-controlled, double-blind, parallel-group study. Method: A total of 69 individuals provided an informed consent, and 44 subjects who met the inclusion criteria were allocated to either the B. subtilis C-3102 (C-3102 group, n = 22) or the placebo group (P group, n = 22). All subjects took 18 tablets containing either containing B. subtilis C-3102 or placebo per day for 4 weeks with water and without chewing. Subjects in the C-3102 group consumed 4.8 × 1010 colony forming units (cfu) per day. Physical examination, urinalysis, blood analysis, records of subjective symptoms, and a medical questionnaire administered by a clinical trial physician were performed to determine the safety of test tablets. Furthermore, bone mineral density was measured. Results: The final analysis included data from 22 subjects (9 men, 13 women; age, 46.1 ± 13.8 years) in the C-3102 group and 22 subjects (9 men, 13 women; age, 46.1 ± 13.5 years) in the P group. The results revealed no medical-related problems in both C-3102 and P groups. Conclusion: This study proved the safety of 4-week continuous consumption of an excessive amount of B. subtilis C-3102 tablets.