American Institute for Cancer Research
  For decades, alcohol has been linked to breast cancer risk. Yet many women wonder just how big a risk alcohol actually represents. Recently, a major review in the British Journal of Cancer examined 53 studies and provided an answer: as daily consumption of alcohol rises, a woman’s risk of breast cancer does indeed steadily increase.

That doesn’t mean, however, that an occasional drink is enough to “push your luck.” According to the review, a woman who consumes no alcohol at all has an 8.8 percent chance of developing breast cancer before she reaches 80. A woman who drinks one alcoholic drink daily faces a 9.4 percent chance of doing so. Two drinks a day raise the odds to 10.1 percent, and four drinks a day raise her chances to 11.6 percent.

These figures are a bit deceptive because alcohol does not pose equal risks for all women. Its effects may vary with the quality of a woman’s diet. For example, several studies show that women who don’t get enough folate – a B vitamin found in dark, leafy greens and other plant foods that is essential for repair of damaged DNA – are at greater risk. This makes sense, because one of the ways alcohol is believed to increase cancer risk is by damaging our DNA.

Genetic changes can also affect a woman’s susceptibility to damage from alcohol. All of us, for example, possess a gene for producing a specific enzyme that detoxifies potential carcinogens before they can damage our DNA. But some of us have an abnormal form of this gene that doesn’t produce the enzyme; women with this abnormal gene experience nearly double the risk of post-menopausal breast cancer. And if women possessing this genetic variation drink fairly regularly – say, an average of 13 alcoholic drinks per week for 25 years or more – their risk increases seven-fold.

Another kind of mutation in this gene doesn’t raise breast cancer risk – at least, not by itself. But if women with that trait drink any amount of alcohol, their risk of breast cancer becomes more than twice that of women with the same trait who don’t drink at all. Alcohol also increases the risk of breast cancer much more in women who possess still another kind of genetic variation that affects enzymes that metabolize alcohol.

Unfortunately, women don’t know which form of these various genes they have. That’s why it’s best to exercise caution. A drink now and then, or even daily, is not enough to double or triple a woman’s risk of breast cancer. Nevertheless, the risk does increase – especially in amounts beyond one drink a day.

It is also important to note that alcohol may have a greater impact when consumed at younger ages. Between puberty and a woman’s first pregnancy, breast cells are more susceptible to damage from cancer-causing agents.

And keep in mind that limiting or avoiding alcohol is just one way a woman can reduce her breast cancer risk. Eating more vegetables, fruits, whole grains and beans is another. Diets too low in these foods, according to a major report from the American Institute for Cancer Research, are responsible for at least as many breast cancers as alcohol. Being overweight after menopause raises risk as much as drinking three to four drinks a day, and being obese represents an even greater risk. One new study demonstrates that as little as two hours a week of brisk walking can actually protect as much as alcohol damages.