Women dread a diagnosis of endometrial cancer, but those who drink at least two cups of caffeinated coffee a day may have a lower risk for this cancer of cells lining the uterus.

Coffee drinking seemed to particularly protect overweight and obese women, study co-author Dr. Emilie Friberg, at the Karolinska Intstituet in Stockholm, Sweden, told Reuters Health by email.

Friberg’s team twice surveyed 60,634 Swedish women about their coffee intake - when they enrolled in the Swedish Mammography Cohort study between 1987 and 1990, and again in 1997.

During the 17 years, on average, that the researchers followed patients, 677 women - about 1 percent - developed endometrial cancer. The average age at diagnosis was 67.

In the overall study group, those who daily drank 2 or more cups were significantly less likely to develop endometrial cancer, compared with those who drank fewer cups of coffee.

Each additional daily cup seemed tied to a 10 percent lower risk for endometrial cancer, after allowing for age and other factors potentially tied to endometrial cancer risk among all the women.

However, they observed the strongest effect among overweight and obese women, who, Friberg’s team notes, have “the highest risk for endometrial cancer.”

Each additional cup of coffee seemed to decrease endometrial cancer risk by 12 percent among overweight women and by 20 percent among obese women, Friberg and colleagues report in the International Journal of Cancer.

The investigators suggest that coffee may affect blood sugar, fat cells, and estrogen, all of which play a role in endometrial cancer. However, they write that the current findings should be confirmed in other populations.

In particular, “a study also including de-caffeinated coffee would make it possible to separate the effect of coffee and caffeine,” Friberg said.

SOURCE: International Journal of Cancer, November 15, 2009.