Common Names: green tea

Scientific Name: Camellia sinensis

Background

• Green, black, and oolong teas all originate from the same plant species, Camellia sinensis. The difference lies in how they are processed. Green tea leaves are steamed or pan-fried and dried without fermentation. In contrast, black tea is fully fermented, while oolong tea undergoes partial fermentation.

• The cultivation of the tea plant dates back thousands of years in China, with medicinal use suggested for at least 3,000 years.

• Today, green tea and its derivatives are often marketed as supplements for aiding weight control, lowering cholesterol, and supporting overall wellness. Some products designed for weight loss also include green tea alongside other compounds.

• A topical treatment containing a specialized green tea extract has been approved by the U.S. Food and Drug Administration (FDA) for managing external genital and anal warts.

How Much Do We Know?

• Numerous studies have explored the potential health benefits of green tea and its extracts. However, current research is not yet definitive in determining its effectiveness for most health claims.

What Have We Learned?

• A green tea extract-based ointment has received FDA approval as a prescription treatment for genital warts.

• Investigations into green tea’s impact on cancer risk have produced inconsistent findings across multiple studies.

• Some research has shown that green tea consumption is linked with a lowered risk of heart disease among Asian populations, a connection not observed in Western groups.

• The ingredients in green tea, notably caffeine and catechins, may provide slight support for weight loss. However, outcomes can differ depending on the product and an individual’s activity levels.

• Trials involving people randomly assigned to take green tea extracts or placebos have shown that green tea can slightly reduce total and LDL (bad) cholesterol. There was no noticeable change in HDL (good) cholesterol or triglycerides. Most studies used supplements rather than brewed tea.

What Do We Know About Safety?

• Drinking green tea in moderate amounts is considered safe for adults, though it does contain caffeine, which can affect some individuals.

• Supplements made from green tea extract can sometimes cause side effects such as nausea, constipation, stomach discomfort, and higher blood pressure.

• Rarely, green tea extracts—especially in capsules or tablets—have been associated with liver damage. People with a specific genetic trait affecting immune response may be more prone to this condition, and around 5 to 15 percent of Americans carry this trait.

• High doses of green tea can interfere with how the body absorbs certain medications. For example, it can lower the effectiveness of nadolol, a drug for high blood pressure, and reduce the blood level of atorvastatin, a medicine for lowering cholesterol. Research has also documented interactions with raloxifene, used in treating osteoporosis. It may interact with other medications as well. Speak to a healthcare provider before using green tea products if you take prescriptions, as combining herbs and medicines can be harmful.

• During pregnancy, it’s important to limit caffeine intake, and green tea is a caffeine source. Consult your doctor about appropriate levels. Caffeine can be passed to infants through breast milk. Large amounts may cause restlessness or disturbed sleep in babies, but moderate consumption is typically safe during breastfeeding.

Keep in Mind

• Take an active role in your health—have open discussions with your healthcare providers about any herbs or supplements you take. Together, you can make well-informed choices.

• Herbal products are regulated differently depending on their ingredients, intended uses, and method of administration. Many are sold as dietary supplements and are not held to the same approval standards as prescription drugs.

• Dietary supplements, unlike prescription medications, do not require FDA approval before reaching the market. However, if a product raises public health concerns, the FDA may take action. Manufacturers are responsible for assessing product safety and ensuring accurate labeling before distribution.

For More Information

• Guidance on the Safe Use of Dietary Supplements

• Understanding How Medicines and Supplements Might Interact

• Tips on Interpreting Scientific Research Articles

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Office of Dietary Supplements (ODS), NIH

The ODS promotes understanding of dietary supplements through research, education, and information sharing, offering facts and guidelines about various supplements like vitamin D and multivitamins.

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Key References

• American College of Obstetricians and Gynecologists. Moderate Caffeine Consumption During Pregnancy. ACOG Committee Opinion No. 462, 2010. Reaffirmed in 2020.

• Brody H. Tea. Nature. 2019;566(7742):S1.

• Clarke JD et al. Green tea and its effect on raloxifene levels. Clinical and Translational Science. 2023;16(10):1779–1790.

• Deka A, Vita JA. Tea and Cardiovascular Health. Pharmacological Research. 2011;64(2):136–145.

• Filippini T et al. Green Tea for Cancer Prevention. Cochrane Database of Systematic Reviews. 2020;(3):CD005004.

• Green tea. Drugs and Lactation Database (LactMed). NICHD. Updated May 15, 2024.

• Green tea. LiverTox: Clinical and Research Info on Drug-Induced Liver Injury. NIDDK. Updated November 20, 2020.

• Hoofnagle JH et al. Green Tea and Liver Injury Related to the HLA-B*35:01 Gene. Hepatology. 2021;73(6):2484–2493.

• Office of Dietary Supplements. Weight Management and Dietary Supplements: Fact Sheet. Accessed May 6, 2024.

• U.S. Department of Agriculture & U.S. Department of Health and Human Services. Dietary Guidelines for Americans 2020–2025. 9th Edition.

• Wang Z-M et al. Green Tea and Coronary Heart Disease Risk: Systematic Review. Nutrition, Metabolism & Cardiovascular Diseases. 2023;33(4):715–723.

• Xu R et al. Green Tea’s Effect on Blood Lipids: Meta-analysis. Nutrition Journal. 2020;19(1):48.

• Yang X et al. Tea Consumption and Coronary Artery Disease Prevention. Frontiers in Nutrition. 2022;9:1021405.

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