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Green Tea: Might Americans Benefit? continued...

"This is association, not causation," Lichtenstein tells WebMD. "The Japanese are so different from us in terms of diet and lifestyle. The data -- at this point -- do not support the hypothesis that adding green tea to your diet will significantly reduce your risk of heart disease or stroke. But stay tuned."

Kuriyama points to a Dutch study that suggests Westerners may benefit from green tea. That's also the opinion of green tea researcher Tsung O. Cheng, MD, of George Washington University Medical Center.

"I would think that the effect of green tea is worldwide," Cheng tells WebMD. "There is no reason why it should be beneficial in the Eastern world and not in the West. I hope that Westerners will begin to drink more green tea, too. A person would drink two or more 8-ounce cups per day for maximum benefit."

More Benefits for Women?

Why do women seem to get more of a benefit from green tea than men do?

Kuriyama and colleagues note that the men in their study smoked more cigarettes than women did. And smokers, overall, got less of a benefit from green tea than nonsmokers.

But Cheng says it's related to estrogen. Green tea studies consistently show a greater effect for women than for men, he says. He suggests that green tea's active ingredients may interact with the female sex hormone estrogen to boost a heart-protective effect.

Green Tea: No Effect on Cancer

Kuriyama and colleagues found no evidence that green tea protects against cancer death.

Kuriyama says that was a surprise to him, as "abundant" evidence from animal and test-tube studies suggests that green tea ingredients fight cancer.

But he notes that the current findings are in line with other, smaller studies that find green tea has no effect on several specific kinds of cancer.

Green Tea Warnings

While it's yet to be proved that green tea really will protect you against early death, there's a lot of evidence that green tea is safe -- with two major exceptions.

Cheng warns that green tea contains vitamin K. Vitamin K affects blood clotting. People taking the blood-thinning drug Coumadin, he says, should not start drinking more green tea.

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