Many studies touting the healthful effects of moderate alcohol consumption made a black-and-white comparison between people who drink and people who don't. But by lumping ex-drinkers into the latter group, those studies may have exaggerated the protective effect of alcohol, say researchers involved in a new study of 25,000 Japanese men.
People who quit drinking have a much higher risk of dying than those who never touched a drop, and by factoring that into their study, the researchers in Japan found that moderate drinkers did not have a decreased mortality rate.
But before you put the cork back in the bottle, remember that disease patterns in Japan are different than they are in the West, says a researcher involved in one of the studies that said moderate drinking can help people survive heart attacks. Dr. Kenneth Mukamal of Harvard University says while the Japanese study makes a good point, its finding does not negate the protective effect moderate drinking can have on coronary heart disease.
Dr. Yoshitaka Tsubono, lead author of the Japanese study, says, "The main endpoint of this study is all-cause mortality rather than coronary heart disease." Tsubono, a research associate with the Tohoku University Graduate School of Medicine in Sendai, Japan, says in an e-mail interview: "Our findings should caution researchers and the public to reconsider the existing evidence and the popular notion that moderate drinking is good for general health."
The notion of a protective effect from moderate alcohol consumption -- defined as three to 15 drinks a week -- arose as researchers struggled to understand the so-called French paradox -- why the French can eat all the butter, foie gras and cheese they want and yet have much lower rates of obesity and heart disease than Americans. Initially focused on red wine, researchers in the late 1980s and through the 1990s showed that moderate consumption of alcohol seemed to decrease deaths from coronary heart disease.
The researchers found that alcohol increases levels of HDL, the so-called good cholesterol, making blood less likely to clot. And they said moderate drinking lowers blood pressure, though heavy drinking increases blood pressure. In addition, animal studies showed that alcohol dulls the effects of hormones that may trigger events that lead to heart failure.
Tsubono says, "Many but not all of these studies showing the decreased risk of total morality associated with moderate drinking have a methodological problem in that they do not separate never-drinkers and ex-drinkers. Ex-drinkers might have quit drinking due to ill health and had higher mortality than never-drinkers."
Tsubono and his colleagues studied more than 25,000 men, ages 40 to 64, from 14 cities and towns in Japan. After ascertaining their drinking habits in 1990, they looked at disease and death statistics in 1997.
Of the 818 deaths in those eight years, 380 were from cancer, 64 were from heart disease, and the rest were from stroke and other causes, the study shows. "We found that 1) moderate drinkers did not actually have a decreased mortality when compared with never-drinkers; 2) ex-drinkers had a much higher risk than never-drinkers; 3) thus moderate drinkers spuriously showed a decreased risk when compared with 'nondrinkers,' which erroneously included both ex-drinkers and never drinkers," says Tsubono's e-mail.
His findings appear as a research letter in the Sept. 12 issue of the Journal of the American Medical Association.
Mukamal, an instructor in medicine at Harvard Medical School, says while the study makes an important point, "it does not invalidate the really large body of research out there that shows moderate drinking's protecting effect." Mukamal's study, published last spring, says people who drank moderately before a heart attack lived longer, while people who rarely drank or who abstained had the shortest survival rate after a heart attack.
"There's some relatively unusual characteristics of the population that was studied," Mukamal says. "In particular, the authors note that only 8 percent of the cohort died from coronary heart disease whereas in most populations around the world, that figure is closer to 30 to 50 percent. And about half the deaths in their cohort were due to cancer, and that's a smaller figure than other populations."
These differences may prevent the findings from being generalized, Mukamal says. "While it's true that some studies have lumped ex-drinkers and nondrinkers together, certainly not all of them have. There are clearly studies that have separated long-term drinker from non-drinkers and still found that moderate drinkers have lower rates of coronary heart disease."
What To Do: For more on the effects of alcohol and its effects on health, see the American Heart Association or the National Clearinghouse of Alcohol and Drug Information.