Why green tea delivers the strongest health benefits

By Priyanjana Pramanik, MSc.Reviewed by Lauren HardakerDec 1 2025

A major scientific review uncovers how a simple cup of brewed tea can deliver real health gains, from heart protection to sharper cognition. However, it also warns consumers about the risks hiding in supplements and processed tea drinks.

Study: Beneficial health effects and possible health concerns of tea consumption: a review. Image credit: Pixel-Shot/Shutterstock.com

In a recent study published in Beverage Plant Research, researchers examined the health effects of tea consumption. They concluded that tea is broadly safe and beneficial, particularly when consumed as traditional brewed tea. Green tea exhibits the most consistent benefits, although black and other teas also offer advantages.

A globally popular beverage

Tea made from Camellia sinensis is among the most widely consumed beverages worldwide, with black and green teas accounting for the majority of production. Modern research has focused on identifying the active compounds that contribute to these effects, particularly tea polyphenols, mainly catechins in green tea and theaflavins and thearubigins in black tea.

Green tea is minimally fermented, preserving high levels of catechins, while black tea undergoes extensive oxidation that converts catechins into complex polyphenols. Caffeine and the amino acid theanine also contribute to tea’s physiological actions.

Large cohort studies have linked tea consumption to lower cardiovascular mortality, a reduced risk of certain cancers, and a decreased incidence of type 2 diabetes. Laboratory studies provide mechanisms related to antioxidant activity, improved lipid metabolism, and modulation of signaling pathways. However, translating findings from cell and animal studies to humans is challenging due to differences in bioavailability, dosage, and physiology.

Heart disease, cancer, and mortality

The strongest and most consistent evidence links tea consumption, particularly green tea, to a reduced risk of cardiovascular disease (CVD). Large cohort studies demonstrate that drinking around 1.5 to 3 cups per day lowers CVD and all-cause mortality, with cardiovascular benefits remaining significant even at higher intakes. However, diminishing returns are observed for overall mortality.

Benefits observed in Japan, China, and the UK suggest that both green and black tea contribute to improved vascular health. Mechanistic studies suggest that polyphenols reduce low-density lipoprotein (LDL) cholesterol, enhance endothelial function, lower blood pressure, and exhibit antioxidant and anti-inflammatory effects.

Evidence for cancer prevention is more mixed: while animal studies are robust, human findings vary by cancer type and population. Still, meta-analyses support risk reductions for oral, lung (in women), and colon cancers with regular green tea intake.

Weight management and type 2 diabetes

Green tea and catechin-rich preparations show modest but consistent effects on reducing body weight and fat mass, particularly in overweight individuals. Trials report reductions in LDL cholesterol and oxidative stress after several weeks of consumption.

Cohort studies generally indicate a lower risk of type 2 diabetes with higher tea intake. Yet, contradictory findings exist, most notably from the Shanghai Women’s and Men’s Health Studies, which reported an increased risk of diabetes.

Randomized trials in diabetic patients have not shown improvements in glucose or insulin measures, leaving uncertainty about tea’s role in glycemic control.

Neuroprotection and muscle health during aging

Epidemiological evidence from China and Japan suggests that habitual tea drinking is associated with reduced cognitive decline, improved cognitive performance, and lower biomarkers linked to Alzheimer’s disease. Meta-analyses also find a clear protective association, with the strongest effects observed in adults aged 50 to 69 years. Theanine, a unique component of tea, may contribute to stress-reduction and neurocalming effects, as well as its ability to cross the blood–brain barrier.

Research indicates that catechin-rich extracts can help maintain or increase muscle mass and strength, especially in older adults or individuals with sarcopenia. Human trials have shown improved grip strength and muscle function after supplementation, while animal studies have demonstrated protective effects against disuse-induced muscle loss.

Inflammation, immunity, and disease protection

Green tea consumption is linked to lower uric acid levels, with stronger associations observed in men. Small experimental studies have shown an enhanced excretion of uric acid following the intake of tea or catechins. Tea polyphenols also reduce inflammatory markers and improve markers of oxidative stress, including in individuals with hypertension or chronic kidney disease.

Tea catechins inhibit a wide range of bacteria and viruses. In the oral cavity, catechins can reduce the growth of cariogenic bacteria and improve oral health. Some demonstrate antiviral effects against hepatitis viruses, influenza, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and human papillomavirus (HPV), mainly by blocking viral entry processes. However, most antiviral studies are in vitro and cannot be directly extrapolated to humans.

Different types of tea and tea-based beverages

Although green tea carries the strongest evidence base, Oolong, white, dark, and yellow teas also show potential benefits. Animal studies comparing teas made from the same leaf batches suggest Oolong tea may outperform others in weight control, while white tea may be most effective for lipid reduction. Still, these findings cannot be reliably generalized to humans.

Bottled or bubble teas pose health concerns due to the addition of sugars, sweeteners, and preservatives, which may counteract their natural benefits. Processing and storage also reduce catechin content compared with traditional brewing.

Conclusions

The review highlights strong human evidence for cardiovascular and metabolic benefits of tea, with additional promising effects on cognition, muscle health, inflammation, and microbial activity. A major strength is its reliance on large cohort data supplemented by mechanistic insights.

However, inconsistent findings, especially for diabetes and cancer, and limited human research on non-green teas remain significant limitations. Results from animal and in vitro studies cannot be directly extrapolated to humans.

Despite these gaps, the overall conclusion is that tea is a safe, health-promoting beverage when consumed traditionally. However, high-dose supplements and low-quality commercial products present potential risks that consumers should be aware of. Further high-quality human research is needed across diverse tea types and health outcomes.

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