Tea may protect against endometrial cancer, but researchers caution that more research is needed to establish if there is a real benefit.

Endometrial cancer forms in the lining of the uterus and is the fourth most common cancer in American women, with 42,000 new cases and nearly 7,800 deaths reported annually.

Researchers from the National Shanghai Center for New Drug Safety Evaluation and Research in China analyzed several published studies and examined the role of green and black tea in the prevention of endometrial cancer.

They found that while existing research indicates that drinking tea - particularly green tea - may offer some protection against endometrial cancer, the limited number of comprehensive studies is inconclusive.

Analysis of seven studies appeared in the American Journal of Obstetrics and Gynecology.

After accounting for the different ways the studies measured tea drinking, researchers reported that increasing tea intake of green tea by two cups a day appears to be associated with a 25% reduced risk of developing endometrial cancer. Increasing black tea consumption appeared to have less significant results. The protective effect was more evident in Chinese and Japanese studies but not the American studies, suggesting other dietary, genetic, emotional or environmental influences may also be involved.

Endometrial cancer is associated with late menopause or infertility, and the caffeine in tea can affect hormone levels, the researchers said, adding that the antioxidants and phytoestrogens contained in tea may affect cancer development.