Jennifer Chaussee of WIRED notes that a couple years ago, a researcher named Curtis Ellison took the podium in a crowded lecture hall at Boston University’s School of Public Health to tackle a question that had divided the university’s public health community: whether moderate drinking of alcohol should be recommended as part of a healthy lifestyle. Ellison’s take? “I mean, it’s so obviously ‘yes,’ ” he told the crowd.

But Ellison wasn’t going unchallenged. Watching from the other side of the stage was Tim Naimi, a public health professor at BU who studies binge drinking in the same building as Ellison. He was there to argue the less attractive position: Drinking is distinctly unhealthy. And not in the typical ways you might associate with alcoholism, but in the sense of increased cancer risk — even for moderate drinkers.

For folks within the realm of public health, that’s no surprise. The World Health Organization has recognized alcoholic beverages as a Group 1 carcinogen since 2012, meaning evidence supports a link between alcohol and increased cancer risk. This past March, Jennie Connor, a preventative and social medicine researcher from New Zealand’s University of Otago, published a review of studies looking at the correlation between drinking and cancer, concluding that “there is strong evidence that alcohol causes cancer at seven sites in the body and probably others.” Her analysis credits alcohol with nearly 6 percent of all cancer deaths worldwide.

Ellison doesn’t deny that there is a link between alcohol and cancer — he just thinks it’s only relevant for heavy drinkers. But that starts a whole new debate: What exactly constitutes moderate drinking, and how do you study moderate vs. heavy drinking in study participants with vastly different body sizes, metabolisms, and socioeconomic backgrounds?

Still, the less-than-perfect current evidence suggests that about 15 percent of breast cancer deaths are alcohol-related, says Naimi. Nearly 20,000 cancer deaths are attributable to alcohol every year in the United States, he says, and we’re not even the world’s biggest drinkers.