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Green Tea Extract

Botanical name(s):

Camellia sinensis. Family: Theaceae

Other name(s):

green tea, Chinese tea, green sencha tea, Japanese tea, Yame tea

General description

Green tea comes from the plant Camellia sinensis. Black tea, green tea, and oolong tea are all made from the same plant but are prepared using different processing methods.

Green tea extract contains polyphenols. These include the most active type, epigallocatechin gallate. Green tea and oolong tea have the highest levels of polyphenols. This means they have the most health benefits. The fermentation and processing to make black tea decrease the polyphenols. It does this by converting them to theaflavins and thearubigins. All of the teas have catechins and tannins in different amounts.

Other significant parts of tea include caffeine, theobromine, and theophylline. The polyphenols of green tea are strong antioxidants.

Tea is the second-most popular drink in the world. People drink it for its flavor and stimulant effect.

Demonstrated uses

Studies suggest that the polyphenols in tea, especially green tea, may help reduce the risk for some cancers. Or it may slow the growth of certain types of cancers. Studies done in humans have shown mixed results.

Tea is used as a stimulant drink. The methylxanthines, specifically caffeine, increase alertness. It’s also a mild stimulant.

Green tea extract ointment has been shown to cure external genital and perianal warts. This product is approved by the FDA. It’s available by prescription.


There may be benefits that have not yet been proven through research.

Green tea may be a mild diuretic. It may help lower cholesterol.

Suggested dosage

Green tea extract comes in oral capsules. It’s available in different strengths. Follow the instructions on the package for the correct dose.

Green tea as loose, dried leaves or in tea bags should be steeped in hot water for a short time. Make sure the water isn’t scalding. This is done to preserve important chemicals in the leaf.

Side effects

Green tea can cause side effects due to caffeine. These can include anxiety, tremors, irritability, and sleeping problems. This is more likely if you’re sensitive to caffeine or take large doses. Side effects are less common with green tea than with other drinks that have caffeine. This is because the leaves are steeped for a shorter time.

The fluoride content of green tea may help prevent tooth decay. But the tea also contains tannic acid. This can stain teeth.

Green tea extracts may cause liver problems. Symptoms can include yellowing of your skin or the whites of your eyes, nausea, and stomach pain. If you have these symptoms, stop using green tea and see your healthcare provider right away. The negative effects of green tea extract on the liver may depend on how much green tea extract you consume each day.


Green tea may change the effects of medicines such as nadolol, a beta-blocker used for high blood pressure and heart problems. It may keep nadolol from lowering your blood pressure as much as it should. Green tea contains small amounts of vitamin K. This means it may decrease how well blood thinner medicines work. Since green tea acts as a mild stimulant, you shouldn’t use it with other stimulants. It may change the effects of other medicines.

Talk with your healthcare provider about the use of green tea. Women who are pregnant or breastfeeding should talk to their healthcare providers before taking any herbal medicines.

Online Medical Reviewer: Brittany Poulson MDA RDN CD CDE
Online Medical Reviewer: Heather M Trevino BSN RNC
Date Last Reviewed: 8/1/2023