"We can now say quite clearly that smoking has no effect, but drinking is associated with increased risk," says Gillian Reeves who conducts cancer research in the U.K.
Researchers analyzed 150,000 women around the world and found no difference in breast cancer risk between smokers and non-smokers. However, throwing alcohol into the daily mix significantly increased risk -- 6 percent for every drink after the first.
"I think it's very convincing that every ounce of alcohol makes a difference in risk. The more you drink the higher your risk," explains Dr. Paul Tartter, a breast cancer specialist at St. Luke's Roosevelt Medical Center.
The theory is that a lot of alcohol causes liver damage and since estrogen is normally metabolized in the liver, if the liver is damaged there are higher estrogen levels in the blood. High estrogen levels are one of the leading contributors to breast cancer risk.
The study may cause confusion among women who've heard for years that tobacco is deadly, and more recently, that moderate alcohol consumption may be good for you.
You basically have to balance the risk against the benefits.
Women with family histories of breast cancer will have different worries than those with heart disease in their genes for whom alcohol might be beneficial.
"Women who are particularly concerned about their breast cancer risk can take this information and if they so wish [and] change their drinking habits," Reeves tells Kaledin.
After all, when it comes to breast cancer risk so tied to genetics, there are few factors women can change. Finally, this may be one.