Effect of multispecies probiotics on irritable bowel syndrome: A randomized, double‐blind, placebo‐controlled trial

Abstract Background and Aim The efficacy of treatment with multispecies probiotics on irritable bowel syndrome ( IBS ) symptoms and the alterations of gut microbiota in patients who have taken probiotics were investigated. Methods This randomized, double‐blind, placebo‐controlled trial involved 49 IBS patients (probiotics: 25, placebo: 24) diagnosed according to the R ome III criteria. Patients were randomly assigned to two groups: either to receive multispecies probiotics (a mixture of B ifidobacterium longum , B . bifidum , B . lactis , L actobacillus acidophilus , L . rhamnosus , and S treptococcus thermophilus ) twice a day for 4 weeks or to receive a placebo twice a day for 4 weeks. The primary efficacy end‐point was the proportion of participants whose IBS symptoms were substantially relieved at week 4. Secondary end‐points were the intensity of abdominal pain/discomfort, bloating, stool frequency/consistency, alterations in fecal microflora over the 4 weeks. Fecal microflora were analyzed in 34 patients (probiotics: 17, placebo: 17) by quantitative real‐time polymerase chain reaction assays. Results The proportion of patients whose IBS symptoms were substantially relieved at week 4 was significantly higher in the probiotics group than in the placebo group: 68.0% (17/25) versus 37.5% (9/24) ( P < 0.05). Secondary end‐points such as improvement in abdominal pain/discomfort and bloating occurred in the probiotics group but not in the placebo group. Fecal analysis revealed that B . lactis , L . rhamnosus , and S . thermophilus had increased significantly in the probiotics group after 4 weeks and that B . lactis had increased in the placebo group. Conclusions Multispecies probiotics are effective in IBS patients and induce the alterations in the composition of intestinal microbiota.