Is Green Tea Better Than Black Tea in Reducing Atherosclerosis?
To the Editor:
Chyu et al1 postulated another mechanism for green tea in reducing coronary atherosclerosis, but the authors did not mention black tea in their article.
According to Chinese legends, tea was discovered by the Emperor Shen Nong in about 2700 BC, when a gust of wind blew tea leaves into a kettle of boiling water.2 Since then, green tea has been a staple product and the main beverage in China.3 In China, tea has also been considered a crude medicine for more than 4000 years.3
Tea can be categorized into 3 types according to the different levels of fermentation: green (unfermented), oolong (partially fermented), and black (fermented). In general, green tea extracts showed stronger antioxidant activity than the semifermented and black tea extracts, mainly because of the higher content of (−)-epigallocatechin gallate.4 The processes used in the manufacture of black tea are known to decrease levels of the monomeric catechins to a much greater extent than the less severe conditions applied to other teas.4
Another hypothesis has been advanced recently to explain the beneficial effect of green tea in coronary artery disease. Green tea has preventive effects on chronic inflammatory diseases.5 Given the current interest in the inflammatory nature of coronary artery disease, the antiinflammatory property of green tea explains the recently reported paradox of why green tea did not protect against coronary artery disease in Japanese patients but did protect against myocardial infarction.5
Whereas green tea is consumed mainly in China, black tea is preferred in continental Europe and the United States. Therefore, it would be of interest to know if black tea is as good as green tea in reducing developing or established atherosclerosis.
Chyu K-Y, Babbidge SM, Zhao X, et al. Differential effects of green tea–derived catechin on developing versus established atherosclerosis in apolipoprotein E–null mice. Circulation. 2004; 109: 2448–2453.
Hoffmann F, Manning M. Herbal Medicine and Botanical Medical Fads. New York: Haworth Press; 2002: 202.
Cheng TO. Why did green tea not protect against coronary artery disease but protect against myocardial infarction? Am J Cardiol. 2003; 91: 1290–1291.
Dr Cheng is correct on the fact that green tea contains a higher amount of (−)-epigallocatechin gallate than that in black tea. However, it was not our intention to study whether green tea is better than black tea in reducing atherosclerosis. In our study, we used (−)-epigallocatechin gallate (EGCG) as a tool to answer the question of whether EGCG, as an antioxidant from tea, modulates evolving atherosclerotic plaques differently compared with established atherosclerotic plaques.1 We used EGCG to avoid the inconsistent and variable concentration of EGCG in brewed tea or tea extract. Our observation that EGCG reduced evolving atherosclerosis formation in the injured carotid artery but not the established plaques in the aortic sinus suggested that antiatherosclerotic therapy needed to be started early to reach its effect, in agreement with Dr Cheng’s viewpoint.2