One study led by Susan E. McCann of the Roswell Park Cancer Center Institute in Buffalo, New York surveyed 1100 women.  In this study it was found that the chance of developing uterine cancer was

-50% less with 4 cups of coffee and tea a day
-44% less with 2 cups of tea a day
-29% less with 2 cups of coffee a day
-no different with decaffeinated coffee

In the other study, done by Japan’s National Cancer Center, 53,724 women aged 40 to 69 were divided into 4 groups by the amount of coffee consumed.

In the Japanese study it was found that those women who consumed at least 3 cups of coffee a day were 60% less likely to develop endometrial cancer than those who drank coffee less than twice a week.  Green tea was observed to have no effect.

The exact mechanism by which coffee and tea reduce the odds of developing cancer are not known, but both are known to contain flavonoids, catechins, and isoflavenoids.  These substances may reduce the levels of insulin and estrogen in the body.  Increased levels of estrogen appear to play a role in the development of endometrial cancer.

Additionally, caffeine induces enzymes that work to neutralize potential cancer causing substances.

If you are a woman concerned about developing uterine cancer and love your coffee and tea, drink up!