The meeting, like much of Ellison’s work, was partly financed by industry grants. And the summary was written by him and Marjana Martinic, a senior vice president for the International Center for Alcohol Policies, a group supported by the industry.

Two central questions, meanwhile, remain unresolved: whether abstainers and moderate drinkers are fundamentally different and, if so, whether it is those differences that make them live longer, rather than their alcohol consumption.

Dr Naimi of the CDC, who did a study looking at the characteristics of moderate drinkers and abstainers, says moderate drinkers are healthier, wealthier and more educated, and they get better healthcare, even though they are more likely to smoke. They are even more likely to have all of their teeth, a marker of well-being.

“Moderate drinkers tend to be socially advantaged in ways that have nothing to do with their drinking,” Naimi said. And simply advising the non-drinkers to drink won’t change that, he said.

Some scientists say the time has come to do a large, long-term randomised controlled clinical trial, like the ones for new drugs. But experts who believe in the health benefits of alcohol say this is an implausible idea. Large randomised trials are expensive and they might lack credibility. And there are practical and ethical problems in giving alcohol to abstainers without making them aware of it and without contributing to accidents.

“The last thing we want to do is expose people to something that might harm them,” said Sei Lee of the University of California, San Francisco, who recently proposed a large trial on alcohol and health.