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: 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/ctr_view.cgi?recptno=R000060455; identifier UMIN000052997.