If there was ever a research area to inspire confusion in the public, itâ€™s the alcohol-and-health debate. Some studies suggest that alcohol may be good for us in certain ways, while others find that itâ€™s decidedly bad.
Much of the discrepancy may have to do with the quantity of alcohol consumed, and the other lifestyle habits that go, or donâ€™t go, along with it. Now, a new paperÂ in the journal Addiction suggests that alcohol is not only linked to, but may actually cause, seven different types of cancer. But as always, the dose makes the poison.
The reviewÂ looked at a number of long-term studies including the World Cancer Research Fund/American Institute for Cancer Research, the International Agency for Research on Cancer, and the Global Burden of Disease Alcohol Group. Lead researcher Jennie ConnorÂ of the University of Otago in New Zealand found that drinking alcohol was routinely linked to cancer of the oropharynx, larynx, esophagus, liver, colon, rectum and, in women, the breast.
â€œThere is strong evidence that alcohol causes cancer at seven sites, and probably others,â€ says Connor. Itâ€™s important to point out that the study doesnâ€™t actually â€œproveâ€ that alcohol causes cancer, but Connor argues that the whole body of literature taken together gets about as close to showing causation as one can, without randomly assigning people to drink alcohol or abstain over the course of their lifetimes.
The biological mechanisms behind the connection arenâ€™t completely mapped out, but there are some good bets. One mechanism, at least for cancers of mouth, pharynx, larynx, esophagus and liver, may be due to DNA damage from acetaldehyde, a metabolite of alcohol and a carcinogen. In other cases, compounds in alcohol may also facilitate entry of other types of carcinogens, like thoseÂ from tobacco, intoÂ the mucosal cells that line the upper digestive tract. And for breast cancer, alcohol is known to increase levels of reproductive hormones, like estrogen, which can increase cell division and increase cancer risk.
Itâ€™s hard to know what to do when some studies have suggestedÂ that a little alcohol is healthy, and some experts have even recommended that abstinent people have a drink at dinner to reap these benefits. Others, though, have done the opposite, recommending that we limit alcohol pretty drastically. Just last month a study found that even light levels of drinking increased the risk of breast cancer. And itâ€™s studies like these that have prompted Britain (not the U.S. so far) to reduce its recommendations for an upper limit of alcohol consumption. And though the research outlined here will certainly lend weight to that argument, the matter is far from settled.
â€œOngoing research will elucidate mechanisms more clearly and increase confidence in the epidemiology,â€ says Connor. â€œAt the same time there will be orchestrated attempts to discredit the science and the researchers, and to confuse the public. The stakes are high for alcohol industries when there is no argument, on current evidence, for a safe level of drinking with respect to cancer.â€
While science and industry are duking it out, it may be wise to cut back a bit, depending on your usual intake. It used to be that drinking moderately seemed likeÂ theÂ safe betâ€“but in recent years, the research suggests, we may have to go a little lower. Drinking lightly, or even sparingly, may be the new normal, at least if we look at the science. But theÂ beverage industry may not be readyÂ to hear that.