Herb library · Herb · Camellia sinensis
Green tea
Tea leaves dried without fermenting. As a drink it has no reported safety concerns beyond caffeine; concentrated extracts need more caution, and NCCIH says definite conclusions cannot yet be reached for most uses.
Traditional use
Tea was first cultivated in China thousands of years ago and used for health purposes for about 3,000 years. Today green tea and its extracts are promoted for weight loss, cholesterol, heart disease, and cancer risk.
What studies show
- Limited
Cholesterol: randomized studies, mostly of extract supplements rather than the drink, found green tea lowered total and LDL cholesterol a small amount, with no change in HDL or triglycerides.
- Limited
Body weight: the catechins and caffeine in green tea and its extracts may have a modest effect on weight, varying with the product and the person's physical activity.
- Limited
Heart disease: NCCIH describes a link between green tea drinking and lower coronary heart disease risk in Asian populations but not Western ones.
- Limited
Cancer: many studies have looked at green tea and cancer risk, with inconsistent overall results.
- Established
Genital warts: the FDA has approved a prescription ointment containing a specific green tea extract for external genital and perianal warts. That is a prescription drug; it says nothing about tea or extract supplements.
Be careful of
Cautions
- NoteNo safety concerns have been reported for green tea drunk as a beverage by adults, but it contains caffeine.
- AmountExtract supplements can cause nausea, constipation, abdominal discomfort, and increased blood pressure.
- ConditionLiver injury, though uncommon, has been reported with green tea products, mainly extracts in tablet or capsule form; people with a particular immune-gene variant, carried by an estimated 5 to 15 percent of Americans, appear especially susceptible.
- InteractionHigh doses reduce blood levels of the beta-blocker nadolol; the extract can reduce levels of atorvastatin; green tea interacts with raloxifene and may interact with other medicines.
- PregnancyKeep caffeine moderate in pregnancy; green tea is a source. Caffeine passes into breast milk, and high intakes can make an infant fussy and sleep poorly.
- Ask a clinicianTalk with a clinician or pharmacist before using this if you take prescription medicines, are pregnant or breastfeeding, or have a medical condition.
Sources
- Green Tea: Usefulness and Safety (opens in a new tab) · NCCIH · read September 15, 2026
Reviewed September 15, 2026.