By JESSICA YARBER, M.D.

Should women stop drinking alcohol altogether? Not quite, but maybe they should stop after that first drink.

A new study by the National Cancer Institute of 1,900 post-menopausal women found that consuming seven to 14 alcoholic drinks per week - in other words, one or two a day - carries a 30 percent to 60 percent increase in breast cancer risk. Most interesting, it was found that these women developed the most common type of breast cancer called "estrogen and progesterone hormone receptor positive" cancer. In comparison to other types of breast cancer, fewer women die from this type.

"[These cancers] behave better, are less aggressive," says Dr. Claudine Isaacs, professor of oncology at the Georgetown University Lombardi Comprehensive Cancer Center and one of the study's authors.

This study provides additional support to a larger study published November 2011 in the Journal of the American Medical Association that looked at more than 100,000 women and found that consumption of three to six alcoholic drinks per week carried a 15 percent increased risk of breast cancer. But whereas previous studies demonstrated overall increased risk of breast cancer with alcohol consumption, this new study focuses on the type of breast cancer that would be affected by alcohol.

"The findings from this study are significant because there are relatively few breast cancer risk factors that someone can actually modify or do something about," Isaacs says, "and alcohol intake is one of them."

In light of the new research, some women might wonder what constitutes a safe amount of alcohol to drink. According to Isaacs, "no more than one drink a day is safe."