Green Tea and EGCG

1. What Is Green Tea and EGCG?

Green tea is an infusion from the leaves of the tea plant Camellia sinensis. After harvest, the leaves are briefly heated or steamed and dried so that they hardly oxidize (that is, hardly react with oxygen and discolor). EGCG (epigallocatechin gallate) is the quantitatively most important plant substance of this kind in green tea and counts among the polyphenols (a group of plant substances). In East Asia, green tea is traditionally drunk as an everyday beverage. In studies, both the beverage and extracts made from it (concentrated extracts) are investigated.

2. Where Is It Found, and What Is It Made From?

Green tea is in the cup as an infusion from the leaves of the tea plant Camellia sinensis. Extracts are obtained from the same leaves and offered in capsules, tablets or powders. There is also decaffeinated green tea, extract with particularly much EGCG and ground leaf powder for stirring. The plant grows mainly in East Asia and other subtropical regions. Black tea and oolong tea do not belong to it, because their leaf is oxidized more strongly.

3. What Does Green Tea and EGCG Do? What Research Shows

Body Weight and Metabolism

There are many studies on body weight and metabolism. In review papers, green tea extract slightly lowered weight, BMI and body fat 423. Beverages with added tea catechins reduced abdominal fat more strongly than the same beverages without this addition (placebo) 1236. Together with training, however, green tea brought only little additional weight loss 24. A review paper found no difference in weight outside Japan; the authors consider the small advantages in studies from Japan to be hardly significant 31.

Heart and Circulation

There are also many studies on the heart and circulation. Review papers found somewhat lower total and LDL cholesterol with green tea and its catechins than in the control groups 592630. Blood pressure fell slightly 81930.

Teeth and Oral Cavity

There are several studies on teeth and the oral cavity. Mouth rinses, dental floss and chewing gum with green tea extract reduced dental plaque compared with placebo or usual care 39424346. Gum bleeding also decreased in two controlled studies (with a comparison group) 4246. In gum inflammation, however, a review paper saw no confirmed benefit for green tea mouth rinses 13. After tooth extraction, soaked swabs lowered pain and painkiller consumption 4750.

Skin

For skin and hair, the picture is mixed. A review found that ingested green tea catechins mitigated skin redness after UV irradiation more strongly than placebo 17. Green tea catechins with vitamin C showed no difference in sunburn and skin inflammation 45. A combination preparation of green tea extract, bamboo extract and selenium improved hair density in acute hair loss; which component acted is open 41. A face cream with green tea extract in tiny spheres of chitosan (a substance from the shells of crustaceans) improved skin elasticity and wrinkles more strongly than a placebo cream 51.

Cancer

In cancer diseases, the picture is still unclear. The controlled studies predominantly found no difference 3444. With green tea extract, new intestinal adenomas (benign growths) did not occur less often than with placebo 34. In prostate cancer precursors, just as many cancer cases occurred with green tea catechins as with placebo 44. A review saw recurrence less often with EGCG after removal of intestinal polyps 10. In observational studies, green tea drinking was associated with less frequent ovarian and uterine cancer 32. Such data, however, do not show whether the tea is the cause.

Liver

For the liver, the picture is inconsistent. With high-dose extract, a liver value (ALT) increased, particularly strongly with a certain gene variant 33. A decaffeinated extract confection did not change liver values compared with placebo 48. In a small open-label study, no participant showed signs of liver damage 49. Still open is which amount of extract burdens the liver.

Other Investigations

In further investigations, a mixed picture emerged. Green tea extract lowered an inflammation value in the blood in two studies 4052. Other works found no difference in inflammation values 2238. Review papers found a higher antioxidant capacity in the blood and mostly less malondialdehyde, a marker of oxidative stress 41522. In painful diabetic nerve damage, green tea extract relieved pain more strongly than placebo 35. In sleep quality and mood, two matcha studies showed only tendencies 3759.

4. How Was Green Tea and EGCG Taken in the Studies?

Investigated were the infusion from the leaves, green tea extract in capsules or tablets, decaffeinated extract, EGCG-enriched extract and ground leaf powder. For teeth and the oral cavity, mouth rinses, gels, chewing gum, dental floss and soaked pads were additionally used. Some of the studies tested mixed preparations, for instance with vitamin C, selenium or hyaluronic acid, or green tea together with training. Such mixed preparations say nothing about the tea alone.

5. Is Green Tea and EGCG Safe? Side Effects in the Studies

In a large placebo-controlled study, green tea extract was well tolerated 34. High-dose green tea extract can, however, burden the liver; in a large study, liver values increased with it, markedly more strongly with a certain gene variant 33. A review paper advises caution with concentrated extracts and, if necessary, monitoring of liver values 11. In small studies, green tea and green tea extract also led to markedly lower blood levels of several medications, which could thereby act more weakly: nadolol, lisinopril, atorvastatin, rosuvastatin, fexofenadine and nintedanib 535455565758.

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