Effect of combined consumption of Lactobacillus brevis KB290 and β-carotene on minor diarrhoea-predominant irritable bowel syndrome-like symptoms in healthy subjects: a randomised, double-blind, placebo-controlled, parallel-group trial.

People with non-pathological diarrhoea-predominant irritable bowel syndrome (IBS-D)-like symptoms are present at a significant level even in healthy populations, but established prophylaxis is lacking. Previously, we have found that co-administration of Lactobacillus brevis KB290 (KB290) and β-carotene (βC) attenuated murine colitis (potential cause of IBS-D-like symptoms) significantly. Here, we investigated the effect of KB290 and βC on minor IBS-D-like symptoms in healthy volunteers. After a 4-week run-in period, subjects received a KB290 + βC or placebo capsule for 12 weeks, followed by a 4-week washout period. The KB290 + βC group showed a significant improvement in intensity of abdominal pain and stool frequency compared with the placebo group. The KB290 + βC group showed a significantly higher serum concentration of anti-inflammatory cytokine, interleukin-10, compared with the placebo group. In conclusion, we demonstrated that consumption of KB290 + βC improves minor IBS-D-like symptoms and inflammatory status in healthy volunteers. (UMIN000018002).