Effects of medium chain triglycerides supplementation on insulin sensitivity and beta cell function: A feasibility study.

Objective: Medium chain triglycerides (MCT) have unique metabolic properties which may improve insulin sensitivity (Si) and beta cell function but data in humans are limited. We conducted a 6-week clinical trial of MCT oil supplementation.

Methods: 22 subjects without diabetes (8 males, 14 females, mean ± standard error age 39±2.9 years, baseline BMI 27.0±1.4 kg/m2) were counseled to maintain their body weight and physical activity (PA) during the trial. Dietary intake, PA data, body composition, and resting energy expenditure (REE) were obtained through dietary recall, international PA questionnaire, dual x-ray absorptiometry, and indirect calorimetry, respectively. MCT prescriptions were given based on REE and PA to replace part of dietary fat with 30 grams of MCT per 2000 kcal daily. Insulin-modified frequently sampled intravenous glucose tolerance tests were performed before and after MCT to measure changes in Si, acute insulin response (AIR), disposition index (DI), and glucose effectiveness (Sg).

Results: MCT were well tolerated and weight remained stable (mean change 0.3 kg, p = 0.39). Fasting REE, respiratory quotient, and body composition were stable during the intervention. There were no significant changes in mean fasting glucose, insulin, insulin resistance, fasting total ketones, Si, AIR, DI, Sg, leptin, fructosamine, and proinsulin. The mean change in Si was 0.5 10-4 min-1 per mU/L (95% CI: -1.4, 2.4), corresponding to a 12% increase from baseline, and the range was -4.7 to 12.9 10-4 min-1 per mU/L. Mean total adiponectin decreased significantly from 22925 ng/mL at baseline to 17598 ng/mL at final visit (p = 0.02). The baseline clinical and laboratory parameters were not significantly associated with the change in Si.

Discussion: There were a wide range of changes in the minimal model parameters of glucose and insulin metabolism in subjects following 6 weeks of MCT as an isocaloric substitution for part of usual dietary fat intake. Since this was a single-arm non-randomized study without a control group, it cannot be certain whether these changes were due to MCT so further randomized controlled trials are warranted.