The effects of resveratrol supplementation in patients with type 2 diabetes, metabolic syndrome, and nonalcoholic fatty liver disease: an umbrella review of meta-analyses of randomized controlled trials

Zeraattalab-Motlagh S, Jayedi A, Shab-Bidar S · The American Journal of Clinical Nutrition

The most rigorous synthesis available, and the verdict is deflating in a specific way: some outcomes improved, but for almost all of them the effect was trivial in magnitude, the GRADE certainty was very low to low, or too few trials existed. The single exception was HbA1c in the short term (under 12 weeks), where the mean difference was -1.05% (95% CI -2.09 to -0.02) with moderate certainty.

Population

38 meta-analyses covering 79 outcomes in 2,474 patients with type 2 diabetes, metabolic syndrome or non-alcoholic fatty liver disease

Intervention

Oral resveratrol

Comparator

Placebo or control

Limitations

Inherits the quality of the underlying meta-analyses, which pool small, often single-centre trials. The HbA1c exception rests on six studies with short follow-up and small samples.