(CBS News) Research suggests women who have one drink each day are less likely to have a stroke and more likely to age healthily. But a new study of women shows just one drink a day might increase risk for breast cancer by 5 percent.
The risk goes up to 50 percent for women who drink heavily, defined as three or more drinks a day, the study found.
The study, published in the March 29 issue of Alcohol and Alcoholism, analyzed 113 previous studies on breast cancer and light drinking behavior of women in Germany, France and Italy. A drink was defined by 10 to 12 grams of ethanol, which is about one average strength glass of red wine or a pint of beer.
The study found that drinking alcohol daily causes about 5 percent of breast cancers in Northern Europe and North America and up to 10 percent in countries where society encourages women to drink, such as Italy and France.
According to the the non-profit organization BreastCancer.org, one out of eight women will develop invasive breast cancer. A woman's risk of breast cancer doubles if she has a first degree relative, such as a mother, sister or daughter, who has been diagnosed with breast cancer. However, about 85 percent of breast cancers happen to women who have no family history of breast cancer because of genetic mutations as a result of the aging process, not necessarily inherited mutations.
For women in the U.S., breast cancer is the second most common cancer in women, following non-melanoma skin cancer, the Center for Disease Control reported.
What explains this effect?
According to HealthDay, alcohol is thought to increase estrogen levels, which then ups the chance of a person getting breast cancer. Multiple studies show that estrogen receptor positive cancers have a strong link to alcohol.
When comparing those who drank a lot to those who drank nothing at all, the study also showed that alcohol consumption increased the risk of all estrogen receptor positive tumors by 27 percent and had a 14 percent higher risk for all estrogen receptor negative breast cancers.
"Since there is no threshold level of ethanol for breast cancer risk, the breast is one of the most sensitive organs for the carcinogenic action of alcohol. Healthy women should not exceed one drink a day," lead author Dr. Helmut Seitz, professor of medicine, gastroenterology and alcohol research at the University of Heidelberg in Germany, wrote in the paper.
"Women at an elevated risk for breast cancer such as those with a positive family history, or conditions associated with an increased breast cancer risk should avoid alcohol or consume alcohol only occasionally," he said.
Some studies however have found a daily drink might help women. A study earlier this month found women who drank a daily glass of alcohol were much less likely to suffer a stroke,