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A recently published letter in the Archives of Internal Medicine summarizes some of the beneficial effects of tea, particularly green tea, on the heart, cardiovascular system and other areas as well.
Dr. Tsung O. Cheng, of Washington, DC states that:
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A previous report in the same journal showed that tea flavonoids may protect against aortic atherosclerosis (1).
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Another recent report studied the association of caffeinated coffee, decaffeinated coffee, and teas, and found that only tea was associated with a lower risk of heart attack (2).
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In China, tea has been considered a crude medicine for 4000 years (3). Different kinds of pharmacologic effects have been reported such as (4):
Protection of blood vessels
Reduction of serum cholesterol level
Prevention of atherosclerosis
- Green tea's antioxidant effects help to retard atherosclerosis (3).
Other Chinese teas also possess antioxidant activities. One study looked at 12 tea products (6 green teas, 4 semifermented (oolong) teas, and 2 black teas) all obtained from China (5). They found that, in general, green tea extracts showed stronger antioxidant activity than the semifermented and black tea extracts, mainly owing to the higher content of specific catechins.
One recent study compared Chinese and white adults in Australia, and found that older Chinese subjects are less susceptible to impaired endothelial function, which researchers suggest may be due to the fact that the Chinese consume a great deal of green tea (6)
Not only is green tea good for the heart, but may help to prevent cancer as well. Researchers have found that breast and prostate cancers in animal experiments are reduced by green, but not black, tea (7)
Another study found reduced amounts of catechins in decaffeinated black tea, and catechins were undetectable in herbal tea (8). Therefore, Dr. Cheng maintains that "there is no question that all teas are not created equal."
Archives of Internal Medicine August 14/28, 2000; 160.
References:
1. Geleijnse JM, Launer LJ, Hofman A, Pols HAP, Witteman JCM. Tea flavonoids may protect against atherosclerosis: The Rotterdam Study. Arch Intern Med. 1999;159:2170-2174.
2. Sesso HD, Gaziano JM, Buring JE, Hennekens CH. Coffee and tea intake and the risk of myocardial infarction. Am J Epidemiol. 1999;149:162-167.
3. Cheng TO. Antioxidants in Chinese green tea [letter]. J Am Coll Cardiol. 1998;31:1214.
4. Cheng S, Wang Z, Ho CT. Current Medicine in China. Beijing, China: The People's Medical Publishing House; 1988:165-172.
5. Ho C-T, Chen QY, Shi H, Zhang K-Q, Rosen RT. Antioxidant effect of polyphenol extract prepared from various Chinese teas. Prev Med. 1992;21:520-525.
6. Woo KS, McCrohon JA, Chook P, et al. Chinese adults are less susceptible than whites to age-related endothlial dysfunction. J Am Coll Cardiol. 1997;30:113-118.
7. Jankun J, Selman SH, Swiercz R, Skrzypczak-Jankun E. Why drinking green tea could prevent cancer. Nature. 1997;387:561.
8. Wehrwein P. More evidence that tea is good for the heart. Lancet. 1999;353:384.
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