Resveratrol dents inflammation, but only on some markers

Resveratrol, a polyphenol best known from red grapes, is one of the most heavily marketed supplements for inflammation and healthy ageing. In people with metabolic syndrome, chronic low-grade inflammation and oxidative stress are thought to sit near the heart of the problem, so a compound that dials them down would be genuinely useful. Individual trials of resveratrol have reached conflicting conclusions, which is exactly the situation where pooling all of them can reveal whether there is a consistent effect underneath the noise.

Two reviewers independently searched MEDLINE, EMBASE, the Cochrane Library and Web of Science up to May 2018 for randomised controlled trials of resveratrol supplementation in patients with metabolic syndrome and related disorders. From 317 potential citations, 24 trials met the inclusion criteria. The quality of each trial was assessed with the Cochrane risk of bias tool, results were combined using a random-effects model, and the reviewers formally tested how much the trials disagreed with one another.

Resveratrol supplementation significantly lowered C-reactive protein, with a standardised difference of 0.55, and tumour necrosis factor alpha, at 0.68. The other two markers told a different story: IL-6 showed essentially no change, and superoxide dismutase, an antioxidant enzyme, did not move either. Disagreement between the individual trials was substantial across all four outcomes, which widens the uncertainty around every one of these pooled figures.

This analysis lands between the enthusiasts and the sceptics: resveratrol does appear biologically active on some inflammatory markers in metabolically unwell people, but the effect is selective rather than across the board. The high level of disagreement between trials suggests dose, duration and patient characteristics matter in ways not yet mapped. The authors themselves call for further studies using higher doses and longer supplementation before firmer conclusions can be drawn, and nothing here speaks to hard outcomes like heart attacks or diabetes.

If resveratrol is in your supplement stack for its anti-inflammatory reputation, this is a reason to hold a measured view: two markers moved, two did not, and everyone in these trials had metabolic syndrome or a related condition. It is not evidence of benefit in healthy people, and lower blood markers are not the same as fewer disease events. The honest reading is a promising, partial effect in a specific group, still waiting on longer and larger trials.