Aims: Resveratrol has been reported to lower glycaemia in rodents with type 2 diabetes, associated at least in part with stimulation of GLP-1, which slows gastric emptying, stimulates insulin secretion and suppresses glucagon secretion and energy intake. The aim of this study was to evaluate the effects of five weeks of resveratrol supplementation on GLP-1 secretion, gastric emptying, and glycaemic control in patients with type 2 diabetes.

Methods: 14 non-obese patients with type 2 diabetes controlled by diet alone (10 males and 4 females; age 67.5±1.6yrs; BMI 27.7±1.4kg/m²; HbA1c 6.4±0.2% (46.4±2.2mmol/mol) received resveratrol (500mg twice daily) or placebo over two intervention periods (5 weeks each) with a 5-week washout in between, in a double-blind, randomized, crossover design. Before and after each treatment period (week 0 and week 5), patients were evaluated with a standardized mashed potato meal labelled with 100mg ¹³C-octanoic acid after an overnight fast. Blood glucose, plasma total GLP-1 and gastric emptying (breath test) were evaluated for 240 min. Body weight and HbA1c on each study day were also measured. Daily energy intake was estimated from a 3-day food diary during the week before, and the last week of, each intervention period.

Results: Fasting and postprandial blood glucose and plasma total GLP-1, as well as gastric emptying, were unchanged with 5 weeks of either resveratrol or placebo treatment, without significant differences between the two interventions. Similarly, HbA1c, body weight, and average daily energy intake did not change after 5 weeks resveratrol or placebo.

Conclusions: In patients with diet-controlled type 2 diabetes, five weeks of resveratrol supplementation has no effect on GLP-1 secretion, gastric emptying, glycemic control, body weight, or energy intake. Our observations do not support the use of resveratrol for improving glycemic control in such patients.