February 21, 1998A cancerous side effect of alcohol
People who enjoy relaxing with a glass of wine, a beer, or a mixed drink at the end of the day have probably been taking solace for this indulgence from a host of studies indicating that these drinks can reduce the risk of heart disease. Further bolstering the beneficial image of wine, researchers have turned up several lines of evidence suggesting that heart-healthy constituents of this grape-derived libation may also fight the development of cancer.
The rub -- at least for women -- is that there appears to be a fine line between how much alcohol can be consumed safely and how much will foster breast cancer, the second leading cause of cancer deaths in U.S. women.
How fine a line? In the Feb. 18 Journal of the American Medical Association, an international panel of 16 scientists attempts to draw such a line. After reviewing data from six prospective studies -- each with at least 18,000 participants and 350 breast cancer cases -- the researchers found "a linear increase in breast cancer incidence in women" throughout the range of consumption indulged in by most women.
No surprise, but . . .
"It wasn’t surprising that we saw a positive association, because many other studies have previously shown such an association," observes Stephanie A. Smith-Warner, a research fellow in nutrition at the Harvard School of Public Health in Boston and a coauthor of the report. However, by being one of the largest such analyses, she notes, "we had more statistical power so that we could examine a wide range of alcohol consumption patterns and evaluate other risk factors -- such as a family history of the cancer or postmenopausal hormone use -- to see whether they modified the alcohol-breast cancer association."
The analysis showed a steadily increasing risk of breast cancer as the average daily consumption of alcohol increased. "There was a linear increase from zero," Smith-Warner told Science News Online. In general, she says, for each 10 grams of alcohol consumed daily -- an amount equivalent to about one drink a day -- the risk of developing breast cancer increased by about 9 percent.
The association was not restricted to any particular subset of the population -- postmenopausal women, for instance, or women with a family history of breast cancer.
At the upper end of consumption, more than 60 grams per day, risks appeared a bit lower than one would have predicted from the trend. However, Smith-Warner observes, "less than 1 percent of our study population was in this highest category, so the estimates here are imprecise. I don’t think we know what’s really happening here because we didn’t have enough people to strongly evaluate that."
Her team is more confident about risks for women in the moderate range of consumption. Compared to nondrinkers, women who consumed at least 30 grams of alcohol per day faced a 30 to 40 percent increased chance of developing breast cancer. This "is similar to or slightly stronger than associations observed for several reproductive factors [such as early menarche] and a positive family history," the scientists note.
There’s a big difference, though: Drinking behavior is potentially modifiable.
Indeed, Smith-Warner says, because alcohol’s hazard appears to piggyback on more well established breast cancer risks, "women may want to consult their personal physicians regarding their breast cancer and cardiovascular disease risk factors to determine whether modest alcohol consumption is advisable."
Wine’s no better
The link between drinking and cancer held regardless of the type of alcohol consumed. There was no indication that the host of potentially beneficial trace nutrients in wine compensated for the risks posed by alcohol.
Until a few months ago, there was some suspicion that they might.
For instance, a year ago, researchers at the University of Illinois at Chicago found that resveratrol, a compound present in grape skins and wine, functions as a moderate antioxidant and potent inflammation-fighting agent. More important, in cell studies and animal tests, it proved effective at halting the initiation, promotion, and progression of cancer.
Late last year, however, a team of scientists from Northwestern University showed that the same compound seems to mimic strongly the activity of natural estrogens. That’s important because the higher a woman’s lifetime exposure to estrogens, the greater her risk of developing breast cancer (SN: 4/25/92, p. 268).
Indeed, conclude J. Larry Jameson and his coworkers in the Dec. 9 Proceedings of the National Academy of Sciences, the new data "suggest that resveratrol could exert a growth-stimulating estrogenic effect on human breast [cancers]." With that finding, resveratrol joined the ranks of the notorious environmental "estrogens" -- dietary constituents and pollutants that may play a role in fostering disease by masquerading as hormones (SN: 7/3/93, p. 10).
Related Reading
Gehm, B.C., et al. 1997. Resveratrol, a polyphenolic compound found in grapes and wine, is an agonist for the estrogen receptor. Proceedings of the National Academy of Sciences 94(Dec. 9):14138.
Jang, M., et al. 1997. Cancer chemopreventive activity of resveratrol, a natural product derived from grapes. Science 275(Jan. 10):218.
Raloff, J. 1997. How peanuts resemble wine. Science News Online(Aug. 9).
_____. 1997. Grape juice: Better than aspirin? Science News Online (March 22).
_____. 1997. Versatile cancer weapon in grapes. Science News Online (Feb. 8).
_____. 1996. Have Danes solved the French paradox? Science News 149(March 30):197
_____. 1993. EcoCancers. Science News 144(July 3):10.
_____. 1992. Defining the women at high risk [of breast cancer]. Science News 141(Apr. 25):268.
Seachrist, L. 1995. Wine, beer, liquor benefit the heart. Science News 148(dec. 2):380.
Smith-Warner, S.A., et al. 1998. Alcohol and breast cancer in women: a pooled analysis of cohort studies. Journal of the American Medical Association 279(Feb. 18):535.
Sources
Stephanie A. Smith-Warner
Department of Nutrition
Harvard School of Public Health
665 Huntington Ave.
Boston, MA 02115J. Larry Jameson
Division of Endocrinology, Metabolism and Molecular Medicine
Northwestern University Medical School
303 E. Chicago Ave.
Chicago, IL 60611
This week's Food for Thought has been prepared by
Janet Raloff, senior editor of Science News.