Diurnal differences in glycemic responses, insulin responses and cognition after rice-based meals

Background and Objectives: The variation in glycemic responses to white rice caused by the circadian rhythm has been widely investigated but remain controversial. This study investigated diurnal differences in the effect of rice meals on glycemic responses, insulin responses, satiety, and acute cognitive function. Methods and Study Design: A total of 20 healthy participants in Group 1 and 14 in Group 2 were served identical servings of cooked white rice containing 50 g of available carbohydrates at 8:00 a.m. (rice at breakfast), 12:30 p.m. (rice at lunch), and 5:00 p.m. (rice at early supper) in a randomized order. Postprandial blood glucose, insulin, satiety, and cognitive performance tests were conducted for each test meal. Results: The rice at an early supper elicited significantly milder glycemic responses than did the rice at lunch and resulted in a lower insulin sensitivity than did rice at breakfast. No difference was observed among the test meals in terms of hunger and prospective food intake. Diurnal acute cognitive performance did not differ considerably among the meals. A correlation analysis indicated that low variability in glycemic responses was positively associated with superior cognitive performance. Conclusions: A high-glycemic index white rice supper at 5:00 p.m. may facilitate daily glycemic management.