Effect of Adding Medium-Chain Triglyceride (MCT) Oil to Rice on Postprandial Glucose Response in Healthy Adults: A Pragmatic Within-Subject Trial

Background and objectives: Postprandial hyperglycemia is a modifiable determinant of type 2 diabetes risk and vascular complications. Japonica rice produces pronounced postprandial glucose excursions. Medium-chain triglycerides (MCTs), absorbed via the portal vein, are rapidly oxidized in the liver and can stimulate glucagon-like peptide-1 (GLP-1) secretion and increase ketone body production, mechanisms that may attenuate postprandial glycemia. Methods and study design: This study aimed to determine whether mixing MCT oil into cooked rice reduces postprandial interstitial glucose responses in healthy adults under real-world consumption conditions. In a within-subject, two-condition meal test, 32 participants consumed on separate mornings either a rice-only meal (150 g packed Japonica rice plus 8 g fish miso paste) or the same meal with 12 g MCT oil mixed immediately before intake. Available carbohydrate was standardized at 56.8 g in both meals. Interstitial glucose was measured with Freestyle Libre (Abbott Laboratories, Abbott Park, IL, USA) at 15-minute intervals for 120 minutes. Results: The primary outcome was incremental area under the curve (iAUC₀-₁₂₀). Secondary outcomes included time-point glucose, subjective satiety (100-mm Visual Analog Scale (VAS)), and palatability (5-point Likert scale). Compared with the rice-only meal, the MCT meal significantly reduced interstitial glucose concentrations at 45, 60, and 75 minutes and lowered iAUC₀-₆₀, iAUC₀-₉₀, and iAUC₀-₁₂₀. Palatability ratings were lower for the MCT meal, whereas satiety did not differ between conditions. Conclusions: Adding 12 g of MCT oil to 150 g of cooked rice attenuated postprandial glycemia without diminishing satiety. This simple, low-burden strategy may have practical utility for dietary glycemic management in everyday settings.