Resveratrol fails to shift liver enzymes in pooled trials

Resveratrol, the polyphenol famously found in red wine and grapes, has been promoted for everything from longevity to metabolic health, and the liver is one organ where benefits are often claimed. Yet the trial evidence on whether it actually improves liver function has been inconsistent, with individual studies pointing in different directions. Liver enzymes such as ALT and AST are the standard blood markers used to gauge liver stress. This meta-analysis pooled the randomised evidence to ask whether resveratrol supplementation moves those markers at all in adults.

The authors systematically searched PubMed, Scopus, Web of Science and the Cochrane Library up to February 2020 for randomised controlled trials of resveratrol supplements in adults. Fifteen trials with a combined 714 participants met the inclusion criteria. Results were pooled in a random-effects meta-analysis, with the overall effect expressed as the weighted mean difference between resveratrol and comparison groups for each liver marker: ALT, AST, GGT, alkaline phosphatase and bilirubin.

Across the pooled trials, resveratrol changed nothing significantly. ALT showed a weighted mean difference of exactly 0 IU/L; AST fell a non-significant 2.40 IU/L; GGT changed by -1.26 IU/L, alkaline phosphatase by 3.80 IU/L and bilirubin by 0.13 — none of these reached statistical significance. Heterogeneity was substantial for some markers, reaching 82.9% for AST and 74.2% for ALT. The authors note that subgroup analysis suggested results may be influenced by resveratrol dose, study duration and population status, but the headline pooled result was firmly null.

This null adds clarity to a mixed literature in which single trials had reported both benefits and no effects on liver markers. Pooling raises confidence that, on average, resveratrol supplementation does not shift standard liver enzymes in adults. The high heterogeneity, however, means the door stays open for effects in specific groups or at specific doses and durations — questions the authors say only future high-quality trials can settle. It also says nothing about resveratrol's other claimed benefits, which were not examined here.

If resveratrol features in your supplement thinking partly on the promise of liver support, this pooled analysis of 15 trials is a reason to temper that expectation: none of the standard liver blood markers improved significantly. Equally, the analysis found no significant worsening of those markers either. The possibility that dose, duration or health status changes the picture remains unproven for now. The fairest current reading is that resveratrol's average effect on liver enzymes in adults is no effect at all.