A recent New York Times blog by Anahad O’Conner concluded that even a moderate amount of alcohol consumption may increase breast cancer risk. 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.

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.”