Effects of green tea supplementation on antioxidant status and inflammatory markers in adults: a grade-assessed systematic review and dose-response meta-analysis of randomised controlled trials

Systematic review and dose-response meta-analysis of 38 randomized controlled trials involving 1985 adults. Participants included healthy adults and people with obesity, type 2 diabetes, metabolic syndrome, NAFLD, cardiovascular disease, PCOS, colorectal adenoma history, and other chronic or athletic populations across multiple countries.

Green tea supplementation was delivered in multiple forms across the included randomized trials, including brewed green tea, green tea extract, EGCG, green tea polyphenols, green tea catechins, matcha green tea, and decaffeinated green tea extract. Doses varied widely across studies, from 300 to 2000 mg/day for many standardized preparations and 5 to 10 g/day for brewed green tea.

Green tea supplementation showed benefits for oxidative stress markers, with improvements in TAC, MDA, SOD, and GPX, and it also lowered IL-1β. It did not show consistent beneficial effects on major inflammatory markers such as CRP, IL-6, or TNF-α. Evidence quality was moderate for IL-1β, low for TAC and TNF-α, and very low for CRP, IL-6, MDA, GPX, and SOD. Overall, green tea may help reduce oxidative stress, but there is no solid evidence that it meaningfully modulates inflammatory status long term.

The evidence base was highly heterogeneous in supplement form, dose, and participant health status, which limits direct comparability across trials. Certainty was low to very low for most outcomes, and the inflammatory findings were inconsistent despite pooled analyses. Long-term clinical relevance remains uncertain because the review did not show robust effects on key inflammatory markers.