Is There an Alcohol/Cancer Connection?
New research can complicate women's decision about whether to drink or not. Does alcohol increase the risk of breast cancer? Yes, even light to moderate drinking, according to a new analysis from the well-known Nurses' Health Study, which followed 106,000 women for more than 25 years.
The study found that women who routinely consumed 3 to 6 drinks per week were 15 percent more likely to develop breast cancer than nondrinkers, regardless of the type of alcoholic beverage they drank. For women averaging 6 to 19 drinks per week, the increased risk was 20 percent. Among those consuming more than 19 drinks per week, the risk jumped by 50 percent.
Alcohol, in moderation, has gotten a bit of a healthy reputation because it may help prevent heart attacks (and possibly diabetes, dementia, osteoporosis and other disorders), so you may be surprised to hear that it can boost cancer risk. In the past 15 years, accumulating evidence has strongly linked alcohol to a number of cancers, notably of the esophagus, mouth and throat, but also of the liver, colon and breast.
It may contribute to breast cancer by raising blood levels of estrogen. The studies on alcohol and breast cancer have mostly blamed heavy drinking; many have not found significantly higher risk among light drinkers. The new study, in the Journal of the American Medical Association, got lots of attention not only because it was large and comprehensive, but because it found that light or moderate drinkers also face increased risk. In addition, it concluded that lifetime alcohol consumption (starting in early adulthood), rather than current levels, was the best measure of risk.
Difficult to Prove the Link between Alcohol and Cancer Risk
All studies of alcohol and cancer are observational; it would be very difficult to do clinical trials in which subjects are randomly assigned long-term alcohol consumption or abstinence. In the new study, researchers observed how many cases of cancer occurred in the women over the decades, and matched these up with how much alcohol they consumed (based on self reports, which can be unreliable). They took into account factors such as age, weight, smoking, family history and hormone use. This type of research cannot prove cause and effect or precisely indicate where the risk thresholds lie, but it can be strongly suggestive.
Alcohol and Breast Cancer Risk in Perspective
Any additional cancer risk is bad, of course, but a 15 percent increased risk (found for 3 to 6 drinks a week in this study) is not as threatening as it may sound. At age 50, for instance, the average woman has a 2.4 percent chance (1 in 42) of developing breast cancer in the next 10 years. An increase of 15 percent would raise the risk to about 2.8 percent (1 in 37).
Stated another way, among 1,000 women age 50, light drinking may cause an extra 3 or 4 cases of breast cancer during the next decade - which would presumably be more than offset by a reduction in heart attacks. Keep in mind, these are only averages. For women with a family history of breast cancer, for example, the estimated risks will be higher. For others, the risks may be lower.
Advice for Women
If you're a woman and drink, should you quit to reduce your risk of breast cancer? Or should you continue to drink to help protect your heart, particularly if you’re at high risk for heart disease? Here are some pointers:
- If you drink, keep your intake light to moderate. For a woman, that means no more than a drink a day (for men, it’s two drinks). A standard drink is 4 to 5 ounces of wine, 12 ounces of beer or 1.5 ounces of 80-proof liquor, which all contain about 14 grams of pure alcohol (ethanol). That’s all you need for heart health. And that limits the increase in cancer risk.
- If you know you are at high risk for breast cancer, or if you have had breast cancer, it may make sense to quit drinking or drink only occasionally. Discuss your risk factors for both breast cancer and heart disease with your doctor.
- If you are a light or moderate drinker at average risk for breast cancer, you may reduce the risk somewhat by giving up drinking - but nobody knows for sure.
Alcohol has many known harms as well as many known or potential benefits. An increased risk of breast cancer is only one factor to consider. Age is another. Women are far more likely to die from cardiovascular disease than breast cancer, especially later in life. So for older women, the benefits of light or moderate drinking are more likely to outweigh the risks.
Benefits of Folate
Woman who drink should be sure to consume enough folate, one of the B vitamins. Studies suggest that an adequate folate intake reduces the increased risk of breast cancer associated with alcohol. Alcohol impairs folate absorption in the body and increases its excretion, and folate deficiency is linked to an increased risk of certain cancers, including breast cancer. Thus, female drinkers with low folate intake, in particular, may be at increased risk for breast cancer.
The recommended dietary allowance (RDA) for folate is 400 micrograms a day. Leafy greens and citrus fruit are good sources; many grain products are fortified with folic acid (the form of folate used for fortification and in supplements). A basic ultivitamin provides the RDA. Higher-dose supplements are not necessary or recommended. The exception is women who may become pregnant. They should take 400 to 800 micrograms of folic acid a day to help prevent birth defects.
Adapted from The University of California, Berkeley Wellness Letter (March 2012)