No effect of resveratrol supplementation after 6 months on insulin sensitivity in overweight adults: a randomized trial

Randomized, double-blind, placebo-controlled trial in overweight to obese adults, including middle-aged and older men and postmenopausal women. For the resveratrol group, 20 participants were randomized; body mass index was 30 ± 0.5 kg/m2 and the inclusion range was 27 to 35 kg/m2.

Oral trans-resveratrol (resVida, 99.9%) at 150 mg/day, given as two 75 mg supplements daily with lunch and dinner for 6 months. The active regimen was compared with placebo in a 1:1 randomized trial.

Resveratrol did not improve insulin sensitivity after 6 months. The primary outcome, Matsuda index, was not different from placebo postintervention (5.18 ± 0.35 vs 5.50 ± 0.34; P = 0.549). HbA1c was lower with resveratrol (35.8 ± 0.43 mmol/mol vs 37.6 ± 0.44; P = 0.007), but intrahepatic lipid content was not significantly changed (F(1, 34) = 2.510, P = 0.122) and other glucose/insulin measures were comparable between arms. No adverse events were reported.

Small active group size (n = 20) limits precision and generalizability. The trial lasted 6 months and tested a single dose, so it cannot address whether longer treatment or higher dosing would produce different metabolic effects. Many secondary outcomes were assessed, making the isolated HbA1c finding less certain in the context of a null primary outcome.