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
What this study found
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.
- Study & population
- Systematic review and dose-response meta-analysis of 38 randomized controlled trials involving 1985 adults.
- Intervention
- 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.
- Key limitation
- The evidence base was highly heterogeneous in supplement form, dose, and participant health status, which limits direct comparability across trials.
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Open PDFOriginal abstract
Green tea, a plant rich in bioactive compounds, has been highlighted for its beneficial effects. In the present systematic review and meta-analysis of randomised controlled trials (RCTs), the impact of green tea on inflammatory and oxidative markers is investigated. Using pre-defined keywords, online databases (PubMed, Scopus, Web of Science Core Collection, and Google Scholar) were searched for relevant articles, published from inception up to February 2024. The outcomes included C-reactive protein (CRP), tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1 beta (IL-1β), total antioxidant capacity (TAC), malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GPX). Analyses of subgroups, linear, and non-linear associations were also carried out. Out of 1264 records initially retrieved, 38 RCTs were included. Supplementation with green tea improved the following indicators: IL-1β (weighted mean difference (WMD): -0.10 pg/mL; 95% CI: -0.15, -0.06), MDA (WMD: -0.40 mcmol/L; 95 % CI: -0.63, -0.18), TAC (WMD: 0.09 mmol/L; 95% CI: 0.05, 0.13), SOD (WMD: 17.21 u/L; 95% CI: 3.24, 31.19), and GPX (WMD: 3.90 u/L; 95% CI: 1.85, 5.95); but failed to improve others, including CRP (WMD: 0.01 mg/L; 95% CI: -0.14, 0.15), IL-6 (WMD: -0.34 pg/mL; 95% CI:-0.94, 0.26), and TNF-α (WMD: -0.07 pg/mL; 95% CI: -0.42, 0.28). Supplementation with green tea can improve the body's oxidative status. However, the results showed no significant effect of green tea on inflammatory markers, except for IL-1β. Further studies are needed to determine the effectiveness of green tea, particularly on inflammatory status.