Six months of resveratrol supplementation has no measurable effect in type 2 diabetic patients. A randomized, double blind, placebo-controlled trial

The polyphenol resveratrol is considered to exert many beneficial actions, such as antioxidant, anti-inflammatory, insulin-sensitizer and anticancer effects. Its benefits in patients with type 2 diabetes mellitus (T2DM) are controversial. Our aims were to determine whether resveratrol supplementation at two different dosages (500 and 40mg/day) for 6 months i) reduced the concentrations of C-reactive-protein (CRP) and ii) ameliorated the metabolic pattern of T2DM patients. In the present double-blind, randomized, placebo-controlled trial, 192 T2DM patients were randomized to receive resveratrol 500mg/day (Resv500arm), resveratrol 40mg/day (Resv40arm) or placebo for 6-months. At baseline and at the trial end, CRP values, anthropometric, metabolic and liver parameters were determined. No serious adverse event occurred. A dose-dependent, though not significant, CRP decrease of 5.6% (Resv40arm) and 15.9% (Resv500arm) was observed vs placebo. We failed to detect significant differences in weight, BMI, waist circumference, and values of arterial blood pressure, fasting glucose, glycated hemoglobin, insulin, C-peptide, free fatty acids, liver transaminases, uric acid, adiponectin, interleukin-6, in both the Resv500 and Resv40 arms vs placebo. Total cholesterol and triglycerides slightly increased in the Resv500arm. Subgroup analyses revealed that lower diabetes duration (in both Resv500 and Resv40arms), and, in the Resv500arm, younger age, aspirin use and being a smoker were associated with a significantly higher CRP reduction vs placebo. The supplementations with 40mg/day or 500mg/day resveratrol did neither reduce CRP concentrations, nor improve the metabolic pattern of T2DM patients.