A new study said that drinking alcohol may aid the development of the most common kind of breast cancer.

Researchers from the University of Chicago found that one or two drinks a day increased the risk of tumors that can grow from either estrogen or progesterone, the type of tumors seen in 70 percent of cases, according to a news releas.

The more a woman drank, the higher the risk, said author Jasmine Q. Lew, a fourth-year medical student who led the study.

For the study, Lew looked at more than 184,000 postmenopausal women in a previous study. About 3 percent of the women developed breast cancer during an average period of seven years.

Women who had one drink a day were 7 percent more likely to get the common type of breast cancer than those who did not drink alcohol. One or two drinks a day raised the risk 32 percent and three or more drinks a day raised it 51 percent.

"Our study at this point provides evidence for the notion that alcohol affects estrogen metabolism, which increases risk of hormone-sensitive breast cancer," Lew said. "Still, more study is needed to clarify the effect of alcohol on other tumor types."