Green Tea
Green tea and green tea extract: what NIH says about cholesterol, weight and cancer research, and why extract supplements have been linked to liver injury and drug interactions.
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Drinking green tea and taking green tea extract capsules are different. NIH reports no safety concerns for green tea as a beverage in adults, but liver injury, although uncommon, has been reported mainly with extracts in tablet or capsule form. [1]
Overview
Green, black and oolong teas all come from the same plant and differ in preparation. For green tea, leaves are steamed, pan-fried and dried but not fermented. Green tea and its extracts are promoted as supplements for weight loss, cholesterol and preventing chronic diseases. The FDA has approved a prescription ointment containing a specific green tea extract for genital warts. [1]Names and parts
Camellia sinensis, leaf. [1][2]What the research shows (NIH summary)
NIH says definite conclusions cannot yet be reached for most of the purposes for which green tea is used. [1]| Use | What NIH says | Strength of evidence |
|---|---|---|
| Cancer risk | Overall results of studies are inconsistent. [1] | Inconsistent |
| Heart disease | Tea consumption has been linked to lower coronary heart disease risk in Asian populations but not in Western populations. [1] | Mixed |
| Body weight | Catechins and caffeine may have a modest effect, depending on the product and physical activity. [1] | Modest |
| Cholesterol | In randomized studies, mostly of extract supplements, green tea reduced total and LDL cholesterol to a small extent, without affecting HDL or triglycerides. [1] | Small effect |
| Genital warts | FDA-approved prescription ointment of a specific extract. [1] | Approved product |
Safety
- Green tea contains caffeine. [1]
- Extract supplements can cause nausea, constipation, abdominal discomfort and increased blood pressure. Liver injury has been reported, mainly with capsule or tablet extracts, and people with a specific immune-related gene variant (5 to 15 percent of Americans) appear especially susceptible. [1]
- Medicine interactions: high doses of green tea reduced blood levels of nadolol (a beta-blocker); extract can reduce blood levels of atorvastatin; an NIH-funded study showed an interaction with raloxifene. It may interact with other medicines. [1]
- In pregnancy, caffeine should not exceed moderate levels, and caffeine passes into breast milk. [1]
Frequently asked questions
Is green tea extract safe?
Liver injury, although uncommon, has been reported mainly with extract capsules and tablets. [1]
Does green tea help weight loss?
NIH says catechins and caffeine may have a modest effect on body weight. [1]
References
- National Center for Complementary and Integrative Health (NIH). Green Tea: Usefulness and Safety. Page last updated February 2025.
- GBIF Secretariat. GBIF Backbone Taxonomy. Names checked 2026-10-22 through the GBIF species match service.