Wednesday, June 25, 2008
Posted by 醉茶生 at 10:08 PM | Comments (0) | Permalink
Categories: Tea Related

A wide number of health benefits have been claimed for tea, in particular, it is claimed that tea (particularly green tea) has beneficial effects on high blood pressure and on cancer. Of the many compounds present in tea, the one that has been singled out as being particularly beneficial is the catechin polyphenol known as epigallocatechin gallate (EGCG). It is this compound that is present in high amounts in green tea, and which is destroyed in the making of black tea.

In the laboratory, EGCG happily mops up free radicals (it is a powerful antioxidant), inhibits the growth of tumour cells and lowers blood pressure in mice. It also seems to ameliorate some of the harmful effect of an over-stimulated immune system. Yet, for all that, it is sensible to take all this enthusiasm with a pinch of salt, for there has never been an experimental trial in humans to show the that the benefits shown in the laboratory translate into a real benefit in humans. Consuming large amounts of green tea is not likely to cause you any harm (I do so on a regular basis, as does a large proportion of the populations of China and Japan), but many observational human studies (essentially just surveys asking people about their tea consumption and attempting to link this to disease) have reached mixed conclusions about the health benefits of tea. Some studies have shown a benefit, others have failed to show a difference, and a few seem to show the opposite effect.

It is right to be enthusiastic about the possible benefits of tea: if something as cheap and as pleasurable as tea can prevent cancer then who wouldn’t be enthusiastic? But until some hard research turns up that drinking tea will actually improve my health, I will continue to drink tea simply because I enjoy it.

Negishi H, Xu JW, Ikeda K, Njelekela M, Nara Y, Yamori Y. Black and green tea polyphenols attenuate blood pressure increases in stroke-prone spontaneously hypertensive rats. J Nutr 2004;134:38-42.
Yang CS, Wang ZY. Tea and cancer. J Natl Cancer Inst 1993;85:1038-049.

Epigallocatechin gallate is a catechin found in abundant amounts in green tea.

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