GradedHealth

Green Tea

Last reviewed October 2026 · Based on 13 studies

Bottom line

Small drops in weight and blood pressure in trials, with a small extra weight loss when combined with exercise. Links to lower death rates are observational, and concentrated extracts can raise liver enzymes at high doses.

What it helps with

  • Helps with weight loss — Benefit, evidence grade B (Moderate). Umbrella review of 13 meta-analyses (about 0.9 kg); downgraded once for indirectness: extracts and teas at varied doses.
  • Adds weight loss to exercise — Benefit, evidence grade B (Moderate). Meta-analysis of 10 randomised trials; downgraded once for indirectness (extracts versus tea, varied doses). The authors call the added effect minimal.
  • Lowers blood pressure — Benefit, evidence grade C (Limited). Umbrella review (starts at A); downgraded once for surrogate marker (blood pressure, not heart events) and once for indirectness (mixed teas and extracts).
  • Lowers cholesterol — Mixed results, evidence grade C (Limited). Umbrella review shows pooled falls, but a camellia and herbal tea meta-analysis found no total cholesterol effect (inconsistency); cholesterol is a surrogate marker.
  • Linked to lower risk of death — Mixed results, evidence grade C (Limited). Observational cohorts only, so they cannot show cause; the all-cause result is significant in one cohort and not in the other, and differs by sex.
  • Can raise liver enzymes at high doses — Harm, evidence grade C (Limited). Secondary analysis of one trial (surrogate marker: liver enzymes) plus case reports; indirect (concentrated extracts, high doses); no placebo comparison in the abstract and no injury rates reported.
  • Tea with meals can reduce iron absorption — Harm, evidence grade C (Limited). One small trial of black tea in 20 young women; no green tea trial found; indirect.

What it is

Green tea's main catechin is EGCG [1]. Trials used concentrated extracts: about 857 mg of EGCG a day in one [2], and 500 mg of extract a day in another [3].

What the research says

An umbrella review of 13 meta-analyses found green tea lowered weight by about 0.9 kg and waist size by about 1 cm [4]. Blood pressure fell by about 1 mmHg in the same review [4]. In a 2024 meta-analysis of 10 randomised trials, green tea added to exercise gave a small extra weight loss and no extra cholesterol benefit [5]. A 2022 meta-analysis of camellia and herbal tea trials in type 2 diabetes found no effect on total cholesterol [6]. Two Shanghai cohorts linked green tea to lower cardiovascular death (hazard ratio 0.86) but not to lower all-cause death (hazard ratio 0.95, not significant) [7]. A Vietnamese cohort of 42,146 people found lower all-cause death with more green tea, in men but not women [8].

Safety and interactions

Common side effects: the 102-woman trial reported no side effects or adverse events over 12 weeks at about 857 mg of EGCG a day [2]. Upper limits: we found no official upper limit for green tea or EGCG. Case reports link liver injury to EGCG intakes from 140 mg to about 1,000 mg a day [9]. In one trial, ALT, a liver enzyme, rose more in postmenopausal women with one gene variant who took 843 mg of EGCG a day for 12 months [1]. Green tea contains caffeine; up to 400 mg of caffeine a day in healthy adults is generally not linked to overt adverse effects [10]. Tea with meals can reduce iron absorption: black tea with a rice meal cut it by 49% to 67% in a small study, and no green tea iron study was found [11]. Medicines: a clinical drug study showed a small rise in levels only for CYP3A4-cleared drugs, judged clinically irrelevant [12]. Pregnancy: no green tea study in pregnancy was found; up to 300 mg a day of caffeine is generally not linked to adverse reproductive effects in pregnant women [10]. Kidney disease and breastfeeding: we found no studies of green tea in either.

Caveats and open questions

The trials we read used extracts, not brewed tea or matcha, and ran 8 and 12 weeks [3][2]. Cholesterol results conflict between reviews [4][6]. The cohort results are observational [7][8]. The liver finding comes from a secondary analysis of one trial and from case reports [1][9]. The iron finding comes from black tea, not green tea [11].

References

  1. Hepatotoxicity with High-Dose Green Tea Extract: Effect of Catechol-O-Methyltransferase and Uridine 5'-Diphospho-glucuronosyltransferase 1A4 Genotypes.. J Diet Suppl, 2023.
  2. Therapeutic effect of high-dose green tea extract on weight reduction: A randomized, double-blind, placebo-controlled clinical trial.. Clin Nutr, 2016.
  3. Does green tea extract enhance the anti-inflammatory effects of exercise on fat loss?. Br J Clin Pharmacol, 2020.
  4. A comprehensive overview on the effects of green tea on anthropometric measures, blood pressure, glycemic and lipidemic status: An umbrella review and meta meta-analysis study.. Nutr Metab Cardiovasc Dis, 2022.
  5. Does green tea catechin enhance weight-loss effect of exercise training in overweight and obese individuals? a systematic review and meta-analysis of randomized trials.. J Int Soc Sports Nutr, 2024.
  6. Effects of Camellia tea and herbal tea on cardiometabolic risk in patients with type 2 diabetes mellitus: A systematic review and meta-analysis of randomized controlled trials.. Phytother Res, 2022.
  7. Green tea consumption and cause-specific mortality: Results from two prospective cohort studies in China.. J Epidemiol, 2017.
  8. Green Tea Consumption and Risk of All-Cause Mortality: Findings from a Prospective Cohort Study.. Nutrients, 2026.
  9. United States Pharmacopeia (USP) comprehensive review of the hepatotoxicity of green tea extracts.. Toxicol Rep, 2020.
  10. Systematic review of the potential adverse effects of caffeine consumption in healthy adults, pregnant women, adolescents, and children.. Food Chem Toxicol, 2017.
  11. Iron absorption in young Indian women: the interaction of iron status with the influence of tea and ascorbic acid.. Am J Clin Nutr, 2008.
  12. Green tea extract and the risk of drug-induced liver injury.. Expert Opin Drug Metab Toxicol, 2014.