Green Tea

Green tea (Camellia sinensis) is one of the world’s most consumed beverages and one of the most studied for health effects. Its primary active constituents are catechins , particularly epigallocatechin gallate (EGCG) , alongside a mild caffeine-theanine combination that promotes calm, focused alertness without the jitteriness of coffee.

Cognitive Protection {#cognitive-protection}

A 2025 meta-analysis pooling 18 observational studies with 58,929 participants found that regular green tea consumption was associated with a 37% reduction in cognitive impairment risk (OR 0.63, 95% CI: 0.54–0.73). Protective effects were observed across both dementia and mild cognitive impairment, and appeared strongest in adults aged 50–69. These neuroprotective effects are attributed to EGCG’s ability to reduce amyloid-beta aggregation, lower neuroinflammation, and improve cerebral blood flow.

Cardiovascular Health {#cardiovascular-health}

Green tea catechins influence lipid metabolism, vascular tone, and inflammation. A 2024 meta-analysis pooling 38 prospective cohort datasets with nearly 2 million participants found that drinking green tea 3 or more times per week was associated with a 22% lower risk of cardiovascular mortality (CVD mortality RR 0.86, 95% CI: 0.79–0.94). Meta-analyses of observational data also show modest reductions in LDL cholesterol and systolic blood pressure, with more consistent effects in individuals with elevated baseline markers. One meta-analysis of RCTs in people with metabolic syndrome found no improvement in cardiometabolic markers, suggesting that individual baseline status and dose form matter , brewed tea consumed consistently over the long term appears more beneficial than short supplemental courses.

Antioxidant Activity {#antioxidant-activity}

EGCG and other green tea polyphenols are potent scavengers of reactive oxygen species. Meta-analyses of RCTs confirm that green tea supplementation increases total antioxidant capacity and reduces markers of oxidative stress in adults. This broad antioxidant activity may partly explain its associations with reduced risk of multiple chronic diseases in long-term observational studies.

Metabolic Support {#metabolic-support}

There is modest evidence for green tea’s role in supporting glucose metabolism in people with type 2 diabetes or pre-diabetes, with some RCTs showing small reductions in fasting blood glucose. Effects on body weight are small and likely mediated through mild increases in thermogenesis and fat oxidation from the caffeine-EGCG combination, rather than any direct fat-burning mechanism.

Cancer Prevention {#cancer-prevention}

EGCG (epigallocatechin gallate) is the most studied anti-cancer compound in the diet. A comprehensive translational review (PMC7059963) documents that EGCG inhibits multiple stages of cancer development: it blocks tumor cell proliferation, suppresses angiogenesis (cutting off the blood supply that feeds tumors), induces apoptosis in malignant cells, and inhibits metastasis by reducing the expression of matrix metalloproteinases that cancer cells use to invade surrounding tissue. In lab models, EGCG has shown activity against colorectal, breast, prostate, lung, and pancreatic cancers. EGCG also modulates immune surveillance , helping the immune system identify and destroy rogue cells before they establish. While large-scale RCTs confirming cancer incidence reduction are limited, several observational studies in Japanese populations (where green tea intake is high) show associations with lower rates of certain cancers, particularly stomach and colorectal.

Practical Notes

Benefits in observational research are most consistently associated with 3–5 cups of brewed green tea per day. Supplements standardized to EGCG can deliver equivalent doses in capsule form, though the full matrix of polyphenols in brewed tea may provide synergistic effects not replicated by isolated extracts. Excess EGCG from concentrated supplements has been associated with rare cases of liver toxicity; brewed tea consumption at moderate levels has not.