Some women who drink to their health may want to reconsider. A new study shows that women who routinely have even small amounts of alcohol, as few as three drinks a week, have an elevated risk of breast cancer.
The research, which looked at the habits of more than 100,000 women over 30 years, adds to a long line of studies linking alcohol consumption of any kind — whether beer, wine or spirits — to an increased risk of breast cancer. But until now the bulk of the research largely focused on higher levels of alcohol intake. The latest study is among the first to assess the effect of relatively small amounts of alcohol over long periods of time, drawing on a large population of women to provide new detail about the breast cancer risks associated with different patterns of drinking.
The rise in cancer risk from three to six drinks a week, though, was modest, and for many women may not be enough to outweigh the heart-healthy benefits of drinking in moderation.
Among the factors women will have to consider, experts say, are family history of heart disease and cancer, as well as their use of hormone therapies like estrogen. Alcohol may increase the risk of breast cancer in part by raising a woman’s levels of estrogen, the authors said.
“We’re not recommending that women stop drinking altogether,” said Dr. Wendy Y. Chen, an assistant professor at Harvard Medical School and the lead author of the study. “For an individual woman to make the best decision it would depend on what her own breast cancer risk factors are, as well as her cardiovascular risk factors. “
Dr. Chen and her colleagues looked at 105,986 women enrolled in the Nurses’ Health Study, which has followed the habits, health and lifestyles of nurses in the United States for several decades. The study, published in the latest issue of The Journal of the American Medical Association, examined the quantity, frequency and age at which women consumed alcohol from 1980 to 2008.
During that period, roughly 7,700 of the women enrolled developed invasive breast cancer. The researchers found that having 5 to 10 grams of alcohol a day, the equivalent of roughly three to six glasses of wine a week, raised a woman’s risk of breast cancer by 15 percent. The effects were cumulative; with each 10-gram increase in alcohol consumption per day, the risk climbed 10 percent.
While such an increase may sound alarming, experts caution that it translates into only a very small risk for the average woman. A typical 50-year-old woman, for example, has a five-year breast cancer risk of about 3 percent, so a 15-percent increase would increase that risk only to 3.45 percent.
The type of alcohol the women drank did not alter the risk: Red wine raised it just as much as beer. The researchers also asked the nurses about drinking patterns early in adulthood and found strong associations with increased risk regardless of age.
But like much of the previous research on alcohol’s risk and benefits, the new study was observational and lacked a control group, and it drew from self-reports, which can be unreliable. Nor was it able to determine whether changing one’s drinking habits over time – drinking a lot early on, for example, and then stopping at age 50 – made any difference.
In an accompanying editorial, Dr. Steven Narod of the Women’s College Research Institute in Toronto pointed out that based on the findings, women who consumed two or more drinks a day would see their 10-year risk of breast cancer climb to 4.1 percent from 2.8 percent. And for women who had one drink a day, it would rise to only 3.5 percent from 2.8 percent.
Dr. Susan Love, a clinical professor of surgery at the David Geffen School of Medicine at the University of California, Los Angeles, said the question for many women remained whether the effect on breast cancer risk of cutting back on alcohol is worth losing out on the reduction in heart disease that comes with moderate drinking.
“If you do drink, you have to weigh the risks and benefits,” she said. “But obviously if you don’t drink and you’re worried about breast cancer, don’t start.”
NEW YORK TIMES