Green Tea Extract

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 different types of the same plant. The teas are made using different processing methods.

Green tea extract contains polyphenols. These include the most active one, epigallocatechin gallate. Green tea and Oolong tea have the highest levels of polyphenols. This means they have the greatest health benefits. The fermentation and processing involved in making black tea decreases the polyphenols. It does this by converting them to theaflavins and thearubigins. All of the teas contain 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 beverage 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 of some cancers. Or it may slow the growth of certain types of cancers. Studies done in humans have shown mixed results.

The theophylline and theobromine in tea act as bronchodilators. Tea has been used to treat mild asthma and bronchitis. Tea may help mild respiratory problems. It’s even safe for children.

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

Green tea has an anti-microbial effect against the bacteria that cause diarrhea. This means it may help treat diarrhea. Green tea also stops oral bacteria. Along with fluoride, tea may help prevent tooth decay.

Green tea extract ointment has been shown to clear external genital and perianal warts. This product is approved by the U.S. Food and Drug Administration (FDA). It’s available by prescription.


Please note that this section reports on claims that have not yet been substantiated through studies.

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 infused from loose, dried leaves or from 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 caffeine-containing beverages. This is because the leaves are steeped for a shorter time.

The fluoride content of green tea may help prevent tooth decay. However, 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.


Tea is used worldwide without causing harmful effects. But women who are pregnant or breastfeeding should talk to their healthcare providers before taking any herbal medicines.


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.

Green tea may also keep the medicine nadolol from lowering your blood pressure as much as it should.

Online Medical Reviewer: Poulson, Brittany, RD, CDE

Online Medical Reviewer: Wilkins, Joanna, R.D., C.D.

Date Last Reviewed: 8/1/2016

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