Monday, March 2, 2009

Cancer and Women Who Drink: A Flawed Study?

Taking a second look at the numbers.

Last week’s front page Washington Post story on the increased risk of cancer among women who drink shed more heat than light on the underlying conundrum: Are a few drinks good for you, or aren’t they?

A British study involving almost one and a quarter million women—a huge survey by any standards—found that just one drink of alcohol per day increased the statistical risk of contracting cancer. According to the Post story by Rob Stein, as little as 10 grams of alcohol a day elevated women’s risk for cancer of the breast, liver, and rectum in particular. “Based on the findings, the researchers estimated that about 5 percent of all cancers diagnosed in women each year in the United States are the result of low to moderate alcohol consumption,” the Post reported. “Most are breast cancers, with drinking accounting for 11 percent of cases—about 20,000 extra cases each year—the researchers estimated.”

But wait a minute. Wasn’t it just yesterday that researchers were confirming and reconfirming that a couple of drinks a day was good for your heart? Presumably, this included women’s hearts as well. What’s going on?

For starters, the conclusions of the study itself, published in the Journal of the National Cancer Institute, have some problems. In an article entitled, “Women: How Bad is a Regular Nip?” Janet Raloff writes in the Web edition of Science News that female participants were queried only about weekly alcohol consumption. To arrive at figures for daily intake, the researchers divided by seven. “However,” writes Raloff, “if someone averages seven drinks a week, those beverages might have been downed on weekends only—leading to consumption of three or more drinks at a sitting. That would be bad even for the heart. Also, in the long haul, for anyone’s liver.” Unless we know about daily drinking, the study “only offers fodder for speculation.”

There are other problems. As it turns out, nondrinkers have an elevated risk for certain kinds of cancers. Study author Naomi Allen and coworkers at the University of Oxford write that alcohol apparently confers some sort of protective effect when it comes to cancers of the pharynx, esophagus, stomach, cervix, and other sites.

In addition, Raloff, points out, “There’s the impact of smoking.” Some of the alcohol-linked cases of cancer in women—esophagus, liver, and larynx, for example—increased only among those women in the study who also smoked.

Specifically, Raloff recommends that women with a genetic predisposition for breast cancer might decide that “no alcohol is the best policy.” And for people at low risk for heart disease, it’s difficult to justify drinking because it’s good for your heart. However, “study after study has offered quantitative evidence that middle-age and older adults who take a regular nip—like that proverbial glass of sherry after dinner or at bedtime—suffer less heart disease and diabetes than teetotalers or people who consume more than two drinks a day.”

And that, at present, is where the matter still stands. As Raloff sensibly concludes, “Let’s not scare people with incomplete data. There will be plenty of time to hammer home a call for temperance if and when stronger data emerge.”

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