Even after adjusting for other factors including diet and exercise, they found that women who drank three or more cups of coffee a day had half the risk of developing colon cancer, compared with those who drank no coffee at all.
The researchers, whose findings have been published in the International Journal of Cancer, did not find any link between consumption of green tea and colon cancer.
The mechanism by which coffee may prevent cancer is unknown, Inoue said. The caffeine it contains could stimulate the working of the colon, or the effect could be due to coffee's antioxidant properties, she said.
"Some people cannot tolerate caffeine, so they should not force themselves to drink coffee. But for people who like it, there is no reason to give it up," Inoue said.
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