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 is obtained from the plant Camellia sinensis. Black tea, green tea, and Oolong tea are all produced from varieties of the same plant. The different types of tea are created using different processing methods.

Green tea extract contains a variety of polyphenols that includes the most active polyphenol, epigallocatechin gallate. Green tea and Oolong tea have the highest levels of polyphenols, giving them the greatest health benefits. The fermentation and processing involved in creating black tea decreases the polyphenols by converting them to theaflavins and thearubigins. All of the teas contain catechins and tannins in varying amounts.

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

Tea is the second most popular beverage in the world and is consumed for its flavor and stimulant effect.

Demonstrated uses

Evidence from laboratory studies suggests that the polyphenols contained in tea, particularly green tea, may help reduce the risk or slow the growth of certain types of cancers. Studies done in humans have shown mixed results, however.

The theophylline (and to a lesser extent, theobromine) in tea act as a bronchodilator. Tea has classically been used to treat mild asthma and bronchitis. Although other potent anti-asthma medications are available with more therapeutic benefit, tea may be beneficial for mild respiratory problems and is safe, even for children.

Tea is used as a stimulant drink. The methylxanthines, specifically caffeine, increase alertness and produce mild stimulation.

Green tea has an anti-microbial effect against the bacteria that cause diarrhea, and therefore may help in treating simple diarrhea. Green tea also inhibits oral bacteria. Along with fluoride, tea may help prevent tooth decay.

Green tea extract ointment has been shown in clinical studies to clear external genital and perianal warts. The specific green tea extract is an FDA-approved prescription product.


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

Green tea is claimed to be a mild diuretic and effective in lowering cholesterol.

Suggested dosage

Different extract strengths are available in capsules. Follow package instructions.

Green tea infused from loose, dried leaves or from tea bags should be steeped in hot, but not scalding, water for a short period of time to preserve the important chemical substances present in the leaf.

Side effects

As with any caffeine-containing product, green tea can cause anxiety, tremors, irritability, and sleeping problems if taken in excessive doses or by individuals sensitive to caffeine. Side effects are less common with green tea than with other caffeine-containing beverages because the leaves are steeped for a relatively shorter time.

Although the fluoride content of green tea may help prevent tooth decay, tea also contains tannic acid, which can stain teeth.

Because it contains small amounts of vitamin K, green tea may decrease the effect of blood thinners.

There have been reports of liver problems  in people taking concentrated green tea extracts, so discontinue use and see a physician if you develop yellowing of the skin or eyes, nausea, or abdominal pain while using this product. 


Tea is used worldwide with no harmful effects, however, as a general rule women who are pregnant or breastfeeding should consult a physician before taking any herbal medicines.


There are no known significant food or drug interactions. However, since green tea acts as a mild stimulant, it is best to avoid using it with other stimulants.

Additional information

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