Tea (Camellia sinensis) is known to have health benefits. However, evidence for the role of tea in the prevention of cancer is weak, possibly due to the usual dosage being too low. Tea has been shown to be anti-bacterial, anti-viral, anti-oxidant and offers some protective from atherosclerosis. The protective chemicals are polyphenols*, catechins, polysaccharides, caffeine and theabrownins. (Catechins, especially EGCG, are the main polyphenols in tea.)
The fermentation of tea may alter the ability of the tea to cause apoptosis** and block the abnormal cell cycles of stomach cancer cells. Of importance, green tea is largely unfermented, so oxidation is avoided, and polyphenol and catechin levels are among the highest in green teas.
Black tea is fermented and pu-erh is a post-fermented tea. The processing of tea promotes the natural oxidation of polyphenols by enzymes in the leaves. Polyphenols are decreased by fermentation, and polysaccharides are increased, but the amount of caffeine is not altered. In black tea and pu-erh, oxidation is promoted, producing theaflavins and theabrownins. Black tea and pu-erh tea had the highest caffeine levels in this study.
All three of the above tea extracts cause apoptosis in specific lines of gastric cancer cells, with higher doses increasing the rate of apoptosis in 48 hours. Green tea had the strongest effects. The authors speculate that catechins in tea may be responsible for more apoptosis than theabrownins and caffeine. Pu-erh has the weakest apoptosis effect. Normal cells are not altered by tea extracts.
CONCLUSION: This study leads to the conclusion that the fermentation process of tea may alter the ability of tea to cause cancer cell apoptosis and inhibit cancer cell division and growth. All tea extracts showed the ability to alter stomach cancer growth without changing normal cells, however unfermented green tea was strongest in countering cancer growth.
NOTE: *Polyphenols are a large group of chemicals found in fruits and vegetables. Products sold under the title of bioflavonoids come under this classification, and they have many health benefits. Matcha green tea powder has the highest levels of polyphenols.
**Apoptosis is a natural form of cell suicide whereby abnormal cells, such as cancer cells or autoimmune cells, destroy themselves.
NOTE: Read about the heart effects of catechins from green tea.
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