Significant changes in gut microbiota was noted after the high-volume bowel preparation with PEG before colonoscopy. The dynamic changes were found to be short-term. However, the perturbation pattern of gut microbiota found after bowel preparation may link to metabolic syndrome and obesity. No study had investigated the supplementation of probiotic in this dynamic situation before. Here we proposed this study to fulfill the knowledge gap and also inquiry on the potential therapeutic strategy.1.To test the hypothesis of probiotic supplementation after bowel preparation alters the composition of gut microbiota in a short-term and long-term manner.2.To test the hypothesis of GI tract associated symptoms affected by probiotic supplementation after bowel preparation. 3. To test the hypothesis of clinical events, especially parameters of metabolic syndrome affected by probiotic supplementation after bowel preparation.

Objectives: Colonoscopy is widely used for identification and treatment of colon polyps and intestinal symptoms. High-volume polyethylene glycol (PEG) bowel preparation prior to colonoscopy causes significant dysbiosis of gut microbiota. Currently dysbiosis of gut microbiota is associated with metabolic syndrome and obesity. However, inconclusive conclusions were drawn from clinical trials studying supplementary probiotics and beneficial clinical effects on metabolic parameters. However, no study has addressed the effects of probiotic supplementation on the labile and dynamic intestinal environment following bowel preparation. Aims: Our study aims at studying the short-term and long-term changes on gut microbiota following the probiotic supplementation after bowel preparation. We also aim at studying the changes in abdominal symptoms and parameters of metabolic syndrome. Methods: This study is a prospective, multicentered, randomized double blind three-armed placebo-controlled trial. Targeted population will be those undergoing PEG bowel preparation before colonoscopy. Each individual will be randomly assigned to one of the active probiotic or placebo supplementation. General health parameters and anthropometric measurements, stool, serum lab data, abdominal sonography, oral carnitine/choline challenge tests will be analyzed. The follow-up timepoints are pre- and post-bowel preparation, receiving probiotics/placebo for 8 weeks, 3 months and 6 months thereafter.Outcome measurement: Primary end point: Evaluate the chronological change of gut microbiota post-bowel preparation between probiotic group and placebo group. Secondary end points:To compare incidence of GI associated symptoms after taking probiotics between two groups. Also evaluate the effects of probiotic supplementation on parameters of metabolic syndrome, evaluate the effects on fatty liver and the interaction between SNP variation and the benefit of probiotic supplementation.

Inclusion Criteria:

1. Adults age >20
2. Undergoing colonofibroscopy (CFS) with PEG bowel preparation

Exclusion Criteria:

1. Inadequate bowel preparation
2. Subjects with active cancer or IBD (inflammatory bowel disease)
3. Subjects with history of abdominal surgery (including stomach, gallbladder, pancreas, small bowel, large bowel)
4. Subjects who take medication related to gastrointestinal motility within 1 months
5. Subjects who take antibiotics or probiotics within 1 months
6. Subjects under pregnancy
7. Allergic or intolerance to the study medication
8. Refused to randomization