Preventive Medicine: Alcohol and cancer risk

Dr. David Katz

Dr. David Katz

Perhaps no subject in nutrition is a source of more concentrated ambiguity than alcohol consumption and health. Consider the irony and intrinsic contradictions of the widespread practice, across many cultures and languages, and, candidly, my own family table — of toasting to one another’s health with a product that the American Society of Clinical Oncology just told us constitutes a significant cancer risk.

The position statement just released, rightly receiving high-profile media attention, does not represent new research. Rather, the Cancer Prevention Committee of ASCO apparently judged that the aggregated evidence available was sufficient to make a statement, and that a reality check on the topic was timely.

Their basic conclusion is that even moderate and light alcohol intake contribute meaningfully to cancer risk. Moderate alcohol intake is defined as up to one drink (1.5oz of distilled spirits; 5oz of wine; or 12oz of beer) daily for women, up to two for men. The difference is based in science, not sexism, of course; even when body size is comparable, men have higher levels of the key, metabolizing enzyme, alcohol dehydrogenase, than women. Less than that threshold is light drinking; more is heavy. Achieving that “average” by having six or seven drinks on both Friday and Saturday night is binge drinking.

The ASCO report tells us that roughly 3.5 percent of all cancer deaths in the United States are attributable to drinking alcohol. Moderate alcohol consumption roughly doubles the risks of oral and esophageal cancer, and contributes meaningfully but less to the risk of colorectal and laryngeal cancer. Light to moderate alcohol intake increases the risk of breast cancer in women between about 5 percent and 20 percent.

The immediate temptation is to call these “sobering” statistics, and allow that characterization to have two meanings. But these risks, while real and worthy of attention, require context. The lifetime risk of esophageal cancer in the U.S., for instance, is less than 1 percent in men, and less than 0.25 percent in women. A doubling of such risk is certainly not trivial, but the product is still a small number.

Another important consideration is the lifestyle pattern in which alcohol intake figures. Drinking might be accompanied by smoking, or even just routine exposure to second-hand tobacco smoke. That smoke is the far more carcinogenic of the two exposures, and the harms of alcohol are much compounded by the pairing. Drinking might accompany a poor diet, lack of exercise, or obesity — each of which contributes to cancer risk. Obesity on its own has been associated with increased risk for almost every cancer, and is thought to account for some 14 percent of cancer deaths in men, 20 percent of those in women in the U.S.

Or, to the contrary, moderate alcohol intake might take place in the context of a generally healthful lifestyle and healthy weight. This, apparently, is the pattern in the Blue Zone populations where wine intake is customary, notably Ikaria, Greece. The Ikarians have low rates of all chronic disease, cancer included, and like all Blue Zone populations, live to 100 and die peacefully in their sleep far more often than the rest of us.

Does this mean that Ikarians are somehow selectively immune to any harmful effects of alcohol? Certainly not. Rather, it means that, within reason, the overall impact of lifestyle is greater than a component in isolation. Cancer risk is reduced if obesity is rare, if smoking is rare, if other chronic disease is rare, and perhaps even if stress is at low levels. If alcohol increases cancer risk from its baseline, a lower baseline means lower absolute risk with drinking. Perhaps the Ikarians would have even less cancer if they gave up that wine.

But would they have better overall health? That remains the most contentious point of debate, and the most challenging matter of data. Light to moderate drinking is associated with reduced heart disease and overall mortality compared to no drinking at all. This might be because alcohol actually confers health benefit as well as harm, and when the dose is right, reduces heart disease risk by more than it increases cancer risk. There are established mechanisms for this, from elevations of HDL, to elevations of a clot-dissolving substance called endogenous TPA, to the concentrated antioxidants like resveratrol in red wine. Light to moderate alcohol intake may confer net benefit, along with harm.

Drinking alcohol for the sake of health, per se, seems misguided to me; there are far more reliable ways to get there from here. But I confess I consider a fine Bordeaux with a great meal one of life’s signature pleasures, and pleasure is good for health. Perhaps more importantly, pleasure and overall quality of life is why health matters in the first place. Other things being equal, healthy people have more fun, or health would be less important than it is. Dose matters. Tradeoffs are likely. Uncertainty is inescapable. Pleasure and health both matter, and interact. To that constellation, I raise a toast.