Cancer Research Lab

A new study suggests that drinking a single alcoholic beverage daily may increase a woman’s risk of developing invasive breast cancer by 9 percent.

Drinking just over two drinks daily may increase their breast cancer risk by 32 percent, Dr. Shumin M. Zhang of Harvard Medical School in Boston and colleagues found.

“Moderate alcohol consumption increases your risk of breast cancer,” Zhang said “If you drink alcohol, you should think about the risks and benefits, there is a risk definitely.”

Beer, liquor, and white wine all conferred increased risk, but not red wine. Zhang said it’s possible chemicals in red wine such as resveratrol and other polyphenols could counteract the harmful effects of alcohol. But, she added, the findings don’t prove red wine is safe.

A number of studies have linked moderate alcohol consumption to an increased risk of breast cancer, Zhang and colleagues point out in a report in the American Journal of Epidemiology. They set out to determine if the type of tumor might influence this relationship. Most breast cancer tumors contain receptors for both estrogen and progesterone, while some have receptors for just one of the hormones or for neither.

The researchers followed 39,876 women participating in the Women’s Health Study. During the 10-year follow up period, 1,190 developed invasive breast cancer and 294 were diagnosed with early-stage disease.

Women who consumed 10 grams of alcohol a day — between three-quarters of a drink and one drink — were at 7 percent greater risk of developing breast cancer, and at 9 percent greater risk of developing more advanced disease. Among those who drank 30 grams of alcohol daily, overall risk of breast cancer rose 32 percent, and 43 percent for invasive disease.

The increased risk was most substantial for women who had tumors carrying both estrogen and progesterone receptors, who represented about two-thirds of all breast cancer cases.

Alcohol is thought to affect breast cancer risk by influencing estrogen levels, and the finding that the link was strongest among women with estrogen- and progesterone-receptor positive tumors backs up this hypothesis, Zhang notes.

Women who were taking postmenopausal hormones also showed a greater risk; those who drank 10 grams of alcohol daily and were on hormone therapy were 84 percent more likely to develop breast cancer than those who didn’t drink and weren’t taking hormones.