Effects of low-dose medium-chain triglycerides on bowel habit outcomes in Japanese adults prone to constipation: a randomized, double-blind, LCT-controlled crossover trial

Background In Japan, many individuals experience symptoms of constipation. Medium-chain triglycerides (MCTs), composed solely of medium-chain fatty acids, have been suggested to improve bowel movements in athletes. However, most prior studies have assumed high-dose intake for ergogenic purposes, and evidence on the effects of low-dose interventions in generally healthy Japanese adults with a tendency toward constipation remains limited. In this study, we investigated the effects of consuming a small amount of MCTs on bowel movements, subjective abdominal condition, and health-related quality of life (HRQOL) in Japanese adults prone to constipation. Methods This randomized, double-blind, long-chain triglyceride (LCT) -controlled, crossover trial with a 2-week washout enrolled 88 healthy Japanese adults aged 20–64 years with three to five bowel movements per week. Participants ingested 2 g/day of MCTs and 2 g/day of LCTs for 2 weeks each. Bowel movement indicators, subjective abdominal condition, and HRQOL were measured. Results Using a statistical model for within-participant comparisons, significant diet effects were observed for the number of days with bowel movements, bowel movement frequency, and stool volume. A post-hoc analysis further confirmed that the change from baseline in the number of days with bowel movements at week 2 was significantly greater during the MCT intake period than during the LCT intake period. By contrast, although multiple questionnaire-based endpoints showed significant pre–post changes within intervention periods, the corresponding between-diet differences were not clearly demonstrated. Conclusion Daily intake of even a small amount of MCTs, compared with LCTs, may be helpful in improving bowel movements in Japanese adults prone to constipation. Clinical trial registration https: //center6. umin. ac. jp/cgi-open-bin/ctr/ctrᵥiew. cgi? recptno=R000060455 ; identifier UMIN000052997.