Women who drink a lot of coffee daily lower risk of Endometrail cancer, a Harvard study suggest.

Endometrial cancer originates in the uterine lining, and is the most common gynecologic cancer in the U.S., according to HealthDay. In addition to weight management, researchers suspected dietary habits may play a role in preventing it. To find out, they analyzed data from the Nurses' Health Study, launched in 1976 and involving 67,500 women between 30 and 55 from 11 different states.The women filled out dietary surveys every four years between 1980 and 2002.

The team found 672 cases of endometrial cancer.

Correcting for factors such as body mass index, alcohol and tobacco use, they found drinking at least four or more cups of caffeinated coffee per day led to a 25 percent drop in endometrial cancer risk. But drinking less than four cups had no effect, nor did drinking tea. Decaf, on the other hand, was linked to a 22 percent drop in endometrial cancer risk.

Study author Dr. Edward Giovannucci, professor of nutrition and epidemiology at Harvard's School of Public Health, told HealthDay that "this study does not prove cause and effect. But this observation has been suggested previously, and there's strong reason now to believe that this association is real."

Among other explanations, "One is that women with higher levels of estrogen and insulin are at a higher risk for endometrial cancer, and coffee seems to reduce levels of both," he told the site. "Also women with diabetes also face a much higher risk, and coffee has been associated with a lower risk for diabetes. So there are several factors that could be involved.

He also pointed out the effect is not necessarily related to caffeine, since coffee has thousands of compounds, many of which are known antioxidants.