A Randomized Clinical Trial of Synbiotics in Irritable Bowel Syndrome: Dose-Dependent Effects on Gastrointestinal Symptoms and Fatigue

This double-blind, randomized controlled design study aimed to assess the dose-dependent effects of synbiotics on gastrointestinal symptoms of and fatigue in irritable bowel syndrome (IBS). Thirty subjects with IBS were randomly assigned into the following three groups and received 2 capsules a day for 8 weeks: (1) high-dose (2 capsules of synbiotics); (2) low-dose (1 capsule of synbiotics and 1 capsule of placebo); and (3) placebo (2 capsules of placebo). At baseline and 8 weeks, they completed the study questionnaires. Two subjects in the high-dose group were lost to follow-up, leaving a total of 28 patients for the analysis. After 8 weeks, abdominal discomfort, abdominal bloating, frequency of formed stool, fatigue Visual Analog Scale (VAS), and Multidimensional Fatigue Inventory were significantly different among the groups (P=0.002, 0.006, 0.007, 0.028, and 0.041, respectively, by Kruskal-Wallis test). However, only abdominal discomfort, abdominal bloating, frequency of formed stool, and fatigue VAS were significantly improved in the high-dose group compared with those in the placebo group (P=0.002, 0.003, 0.002, and 0.013, respectively) by Mann-Whitney test with Bonferroni correction. No adverse drug reactions were reported. High-dose synbiotics were superior to placebo in improving bowel symptoms and fatigue of IBS patients, suggesting that synbiotic dosage plays an important role in the treatment of IBS.