Gut Environment and Dietary Habits in Healthy Japanese Adults and their Association with Bowel Movement.

Introduction: Constipation is a common symptom that impairs the quality of life (QOL). This study aimed to investigate the relationship between bowel movement and gut microbiota and dietary intake.

Methods: To investigate correlations among bowel movement, food intake, and gut environment, 60 healthy Japanese participants were recruited. Bowel movement was assessed using the Bristol stool form scale (BSFS) and constipation scoring system (CSS). Dietary habit was assessed with a self-administered questionnaire wherein the food intake frequency was classified into 8 categories for 72 food/food groups. Gut microbiota was analyzed using terminal restriction fragment length polymorphism analysis.

Results: The constipation rate was significantly higher in females than in males. The QOL was significantly impaired in the constipated group. The fecal count of Bacteroides was decreased and that of Clostridium cluster IV was increased in participants with constipation. The BSFS score was negatively associated with the fecal count of Clostridium cluster XI and positively associated with the fecal count of Clostridium cluster XVIII and consumption of green tea. The total CSS score was positively associated with the fecal Prevotella count and negatively associated with fecal acetate levels and consumption of vegetables. Discriminant analysis estimated that constipation could be predicted correctly in 83% (p < 0.001) of the participants based on fecal microbiota and fecal short-chain fatty acids.

Discussion/conclusion: Bowel movement was strongly affected by gut environment and food intake in Japanese participants. Improvement in dietary habits could promote bowel movement through the improvement of the environment in the gut, resulting in ameliorated QOL issues in healthy adults.