We’ve all heard some version of “a glass of wine isn’t bad for you, it’s actually good.” Well, it’s not.

But — you may say — I’ve even read studies that reach this conclusion. If alcohol isn’t good for you, then why do some studies suggest it is? Tim Stockwell, from the University of Victoria asked himself the same question. Stockwell studies substance use and he was intrigued by the discrepancy between alcohol studies. Why is it that some studies find a negligible or even positive effect of low alcohol consumption, while others conclude it’s all bad?

The short answer is bad design. Studies that find benefits to alcohol focus on older adults and fail to account for people’s lifetime drinking habits.

A good hard look at alcohol

To get to the bottom of things, Stockwell and his colleagues carried out a meta-analysis — a study of studies. They looked at 107 published studies that followed people over time.

When they simply took all the data from these studies, it looked like moderate drinkers (those who drink between one drink per week and two per day) may live a little longer. At a shallow glance, that would be the end of it — but researchers weren’t taking a shallow glance.

They took a deeper dive and found that it was the “lower quality” studies that linked moderate drinking to greater longevity. By lower quality, the researchers mean that the studies made no distinction between people who were lifelong abstainers and those who were drinking and then quit. Another issue was the starting age of participants: oftentimes, they were older than 55 on average, which can lead to biased results.

In “higher quality” studies that had younger participants and made more careful distinctions, alcohol didn’t help at all.

“If you look at the weakest studies,” Stockwell said in a press release, “that’s where you see health benefits.”

No benefits to alcohol

The idea that small levels of alcohol are not dangerous (and may even be helpful) goes back decades. For consumers, this created confusion — a confusion that many also just choose to believe. The alcohol industry is also keen to take advantage of this and has promoted its own message, sometimes through misinformation.

“Studies with lifetime selection biases may create misleading positive health associations. These biases pervade the field of alcohol epidemiology and can confuse communications about health risks,” the researchers note in their study.

Drinking doesn’t seem to extend your lifespan or make you healthier, the researchers conclude, despite what some studies conclude. In this case, the science is more complex.

At the end of the day, the main takeaway is that there’s no level of alcohol that’s good for you.

Journal reference: Stockwell, T., et al. (2024). Why do only some cohort studies find health benefits from low volume alcohol use? A systematic review and meta-analysis of study characteristics that may bias mortality risk estimates. Journal of Studies on Alcohol and Drugs. doi.org/10.15288/jsad.23-00283.