In the largest of three major studies to look at the causes of breast cancer in post menopausal women, researchers find that even moderate drinking in women increases the risk of developing breast cancer.
184,000 women were part of the investigation by the National Cancer Institute.
In it, women who had two small drinks a day faced a 32 percent increase in the risk of developing a hormone-sensitive tumor. Up that to three or more drinks and the risk rose by 51 percent.
"Regardless of the type of alcohol, the risk was evident," said Jasmine Lew, a researcher at NCI, presenting the findings here at a meeting of the American Association for Cancer Research.
Lab studies have shown that alcohol increases estrogen metabolites which can fuel hormone-sensitive breast cancer. The majority of tumors - 70 percent - are classified as positive for both estrogen and progesterone receptors, the reason that hormone replacement therapy (HRT) has been linked to breast cancer.
In this study, the authors reviewed data from the National Institutes of Health AARP Diet and Health study that began more than a decade ago. In the seven year period spanned, 70 percent of the women drank alcohol, the average being a little less than a drink a day. But even that had some increased risk of breast cancer.
Among those consuming less than one drink daily, the risk was seven percent. One to two drinks increased the risk to 32 percent and three or more drinks daily the increase in relative risk for the most common types of breast cancer was 51 percent.
The authors say more research is needed to pinpoint the effect of alcohol on other tumor types.
As far as recommendations- doctors are stopping short of recommending older women limit their drinking.
Other reports have linked a compound in grape skin, resveratrol, to improved heart health. Resveratrol has also been used as an anti-aging supplement that many swear by.
Resveratrol can also be consumed by eating grapes.
This year, breast cancer will kill a half million women and be diagnosed in 1.2 million worldwide. It is the leading cause of cancer in women, followed by lung cancer and colorectal cancer.
The mission of the American Association for Cancer Research is to prevent and cure cancer. Founded in 1907, AACR is the world's oldest and largest professional organization dedicated to advancing cancer research.