A team of U.S. scientists believe they have found a piece of advice that breast cancer-stricken mothers can give their daughters to help them stave off the disease: stay clear of alcohol.
The team found that among teen girls with breast cancer in the family, those who had a drink a day on average were more than twice as likely as nondrinkers to develop benign breast disease.
That's not really a disease, but a catch-all for lumpy breast tissue that isn't dangerous in itself. A few of those lumps may turn into cancer down the road, though, so the new study uses them as a stand-in for breast cancer risk.
To researcher Catherine Berkey, of Brigham and Women's Hospital in Boston, that means adolescent girls and young women from breast cancer-stricken families "should be aware that drinking alcohol may increase their own risk for (benign breast disease) and for breast cancer later on."
Berkey told Reuters Health in an email that she believes that in adults "alcohol is the primary preventable dietary risk factor for breast cancer."
But an independent expert said the advice to give up alcohol, while well-intentioned, is unlikely to make a significant dent in breast cancer risk.
"It is mostly an interesting observation, but it is going to have a very limited public health impact," said Dr. Steven Narod, who heads the Familial Breast Cancer Research Unit at Women's College Hospital Research Institute in Toronto.
Berkey and her colleagues, whose work is published in the journal Cancer, tracked nearly 7,000 girls from 1996, when they were between nine and 15 years old, until 2007.
Seventeen percent had either a mother, an aunt or a grandmother with breast cancer, and slightly more had a mother with benign breast disease.
Among the heaviest drinkers (at age 22, that amounted to about a drink a day) 3.1 percent had benign breast disease. For abstainers, the number was 1.3 percent, Berkey said.
Because the study is based on observations, and not a real experiment, there is no proof that alcohol caused the extra breast lumps, however. And most lumps never become cancer, Narod pointed out.
"I would be very, very reluctant to say that a 24-year-old woman with benign breast disease is at increased risk of breast cancer," he told Reuters Health.
"Even if it were true that family history and alcohol together increase the risk of benign breast disease, and benign breast disease increases the risk of breast cancer, I think the maximum number of breast cancers you could prevent would be much less than one percent," Narod added. "Is there any hope for this approach? No."
It's not the first time alcohol has been linked to breast cancer.
Earlier this month, for instance, a report in the Journal of the American Medical Association (JAMA) estimated that 2.8 percent of teetotalers would develop the disease over 10 years, compared to 3.5 percent of women who downed up to 13 drinks a week.
But since alcohol has also been tied to fewer heart attacks, it's difficult to know what to do with this information, said Narod, who wrote an editorial about the JAMA findings.
"It's not even clear that stopping drinking would prevent breast cancer," he told Reuters Health.
There are several risk factors for breast cancer, such as having the disease in the family, having dense breasts, being older or drinking alcohol.
"The fact that they are risk factors is a scientific truth," said Narod. "But it certainly does not lead to the conclusion that one can eliminate breast cancer by eliminating all risk factors." Often the risk factors are too rare to have a big impact, or their link to the disease is too weak, or they can't be changed.
"I think we should keep our eyes on the prize: finding the cause of breast cancer," said Narod.