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Alcohol May Increase Breast Cancer Risk
Fat Hormone Leptin Could Explain Alcohol, Breast Cancer Link

By
Salynn Boyles

Reviewed By Michael Smith, MD
on Tuesday, November 18, 2003
WebMD Medical News






Nov. 18, 2003 - Drinking alcohol, even in moderation, may increase a woman's breast cancer risk. Now a carefully controlled government study may help explain why.

Consuming one or two alcoholic drinks per day was found to increase blood levels of the fat hormone leptin in postmenopausal women taking part in the National Cancer Institute study. Early research shows that elevated leptin levels may be associated with an increased breast cancer risk, as well as colorectal and prostate cancers.

"This study provides insight into how this hormone could potentially impact the health of women," researcher Mark J. Roth, MD, tells WebMD. "In addition to cancer, there is also evidence that leptin is associated with infectious diseases and autoimmune disorders."

Risks vs. Benefits

For women especially, the health implications of moderate drinking are a subject of continuing confusion. An international review of nearly 50 studies published late last year, showed that the more women drank, the higher their breast cancer risk. But researchers concluded that the beneficial effects of moderate drinking on the heart and circulation probably outweigh this risk.

In another study published just last month, moderate drinking was linked to a reduced risk of developing type 2 diabetes, but diabetes risk tripled among women consuming three or more drinks per day.

Many say that alcohol influences breast cancer risk and other diseases by elevating hormone levels in the blood. The current study was designed to test this theory.

Youngest Women Had Biggest Increase

Roth and NCI colleagues studied 53 healthy, nonsmoking, postmenopausal women. Each woman rotated through three eight-week observation periods in which they drank either no alcohol, one drink per day, or two drinks per day. The women were not told how much alcohol they were consuming during any given eight-week period, and their food intake was also carefully controlled.

After adjusting for the influence of body weight on leptin levels, the researchers found that women who drank the equivalent of one or two drinks per day had blood leptin levels that were 7% and 9% higher, respectively, than women who did not drink alcohol.

Once age was taken into account, the association between alcohol consumption and leptin was significant only among women between the ages of 49 and 54 -- with a 24% jump in leptin levels.

The findings are reported in the Nov. 19 issue of the Journal of the National Cancer Institute.

Modifying Breast Cancer Risk

If elevated leptin does explain the link between drinking alcohol and breast cancer risk, it could also help explain the increase in risk among women who are obese. Being overweight is also associated with elevated leptin levels.

American Cancer Society epidemiologist Marji McCullough, ScD, says it is clear that both drinking alcohol and obesity increases a woman's breast cancer risk.

"The good news is that both of these are modifiable risk factors," she tells WebMD. "There are a lot of risk factors for breast cancer that cannot be modified, but maintaining an ideal weight and limiting alcohol consumption are two things that women can do to reduce their risk."

According to ACS guidelines, men should consume no more than two alcoholic drinks per day and women should drink no more than one. McCullough says women should discuss their individual breast cancer risk profile with their physician.

SOURCES: Roth, M. Journal of the National Cancer Institute, Nov. 19, 2003; vol. 95: pp. 1722-1725. Mark J. Roth, MD, staff physician, cancer prevention studies branch, National Cancer Institute. Marji McCullough, ScD, senior epidemiologist, American Cancer Society. "International Collaborative Group on Hormonal Factors in Breast Cancer," Nature, Nov. 13, 2002. Diabetes Care, October 2003