Green tea, black coffee

Coffee or tea? There’s a growing body of research to suggest that both are probably good for you.

We’ve heard a lot about the health benefits of tea, especially green tea. It is high in polyphenols–compounds with strong antioxidant activity that in test-tube and animal models show anticancer and heart-protective effects. Good clinical studies are few, however, and although I and other physicians tell our patients to drink green tea, there hasn’t been any definitive proof of the value of that advice.

That’s why I was so interested in a report last week in the Journal of the American Medical Association. A team of Japanese researchers was able to link green-tea consumption with decreased mortality from all causes–including cardiovascular disease. The researchers tracked 40,530 healthy adults ages 40 to 79 in a region of northeastern Japan where most people drink green tea, following them for up to 11 years. Those who drank five or more cups of green tea a day had significantly lower mortality rates than those who drank less than one cup a day. There were also fewer deaths from cardiovascular disease.

But no such association was seen with deaths from cancer. Nor was consumption of oolong or black tea correlated with any decrease in mortality. Those teas are more oxidized in processing, which not only darkens the color of the leaves and changes their flavor but also reduces their polyphenol content.

Japanese people have access to better-quality green tea than do most North Americans. If you want the good stuff (like gyokuro or matcha, the powdered tea used in Japanese tea ceremonies), go to the nearest specialty-tea shop, Asian grocery store or the Internet.

Coffee is more complicated. It has received both gold stars and black marks in the medical literature. It too contains antioxidants, although they are less well studied than tea polyphenols. Evidence for the health benefits of coffee is growing, however. In the August issue of the European Journal of Clinical Nutrition, for example, a group of investigators from Finland, Italy and the Netherlands report that coffee seems to protect against age-related cognitive decline. The scientists studied 676 healthy men born from 1900 to 1920 and followed them for 10 years, using standardized measures of cognitive function. Their conclusion: the men who consumed coffee had significantly less cognitive impairment than those who didn’t. Three cups a day seemed to provide maximum protection.

Population studies like those help us form hypotheses about relationships between dietary habits and long-term health. We still have to test our suppositions in controlled conditions and measure the effects of coffee and tea on various systems of the body.

In the meantime, enjoy your tea and coffee, get the best quality you can, and know that they are probably doing you more good than harm.

(By Andrew Weil, M.D., Sept 2006, Time Inc)
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