Updated on November 27, 2023.
Are you still drinking a glass of wine each evening for the heart benefits? If so, you wouldn’t be alone. For years, studies have suggested that moderate alcohol intake may be better for your health than either heavy drinking or abstaining.
But in 2016, the United Kingdom changed its national guidelines on safe alcohol intake to include no more than 14 units per week. That equates to roughly a bottle and a half of wine. Experts there suspected that the benefits of moderate drinking might not, after all, outweigh the risks. The reasoning was that studies had already been fidning links between drinking alcohol—in any amounts, but particularly at higher intake levels—to a higher risk of breast, throat, and other cancers.
Moderate intake may damage the brain over time as well, according to a 2017 study published in BMJ. (Moderate drinking was defined by researchers as between seven and 14 units of alcohol per week for women, seven to less than 21 units per week for men.) Researchers followed 550 people over 30 years, tracking several measures, including:
- Weekly alcohol intake
- Cognitive (or thinking) abilities, periodically
- MRI brain scans (taken at the end of the study)
The more people drank, the more atrophy, or shrinking, they experienced in their brain’s hippocampal region. This is an area of the brain involved with memory. Even moderate drinkers were three times more likely to have atrophy than people who abstained.
Light drinkers, who consumed less than seven units per week (about three and a half glasses of wine) didn’t have significant brain changes. But they didn’t experience any health benefits, either. The most severe damage was found among heavy drinkers, or people who consumed more than 30 units (more than about 15 glasses of wine) per week.
“The question is, do those changes mean anything?” asks Keith Roach, MD, associate professor in clinical medicine in the division of general medicine at Weill Cornell Medical College and New York Presbyterian Hospital. “Everyone develops some brain atrophy as they age and most people continue to function pretty well, even though they've got fewer brain cells than they used to.”
To find out, researchers had people repeat 10 memory tests at different points in the study. These included routine lexical fluency tests, which measure how many words beginning with the same letter people could name in one minute.
People who drank more than seven units of alcohol per week were more likely to have a reduction in cognitive function (measured by lexical fluency), says Dr. Roach. That said, the differences between groups were pretty small, he notes, so it’s possible other factors could have affected their scores.
What type of study was it?
This was a prospective cohort study, meaning researchers followed one large group of people over time to see how specific factors such as alcohol intake—as well as stress, income level, and others—would affect their health.
Previous studies linking health benefits to moderate drinking may not have provided as complete of a picture. And in those studies, it’s often difficult to sort out whether alcohol is causing the beneficial effects or if people who drink moderately are just healthier in other ways, explains Roach.
“The only way to really know alcohol’s long-term effects would be to do a randomized controlled trial,” he says. “You'd have to put half of the group on alcohol and the other half on placebo, or fake alcohol.” Why? If someone knows they’re drinking the real thing, it can influence their thoughts and behaviors related to health, which may affect the results.
“But you can immediately see the problem with a randomized controlled trial,” Roach says. “There's no such thing as ‘placebo alcohol.’ You’d say ‘Here, drink this wine,’ and people would say, ‘That's not wine!’ And there goes the end of your study.”
The approach taken by the researchers publishing in BMJ may be the next best thing because it follows many people over many years, and involves evidence of physical brain changes as well as cognitive changes. But certain factors may still have interfered with the results.
Some limitations of the research
Several factors could have influenced the study’s outcomes:
- More men than women participated, which matters because alcohol affects women differently. Also, the men who signed up were typically middle class and middle aged with above average IQs, so results might not apply to everyone.
- This was a self-reported study, says Roach. “People could have lied about their alcohol intake. It was also done at the workplace, so people may have wanted to minimize the amount they drank,” he adds.
Then, there’s the possibility that healthier people might have been attracted to participate in the study in the first place, further skewing the results.
What does it mean for you?
“The effects of alcohol reached significance once people drank 14 units per week, which is about eight standard drinks in the United States,” says Roach. “That's someone who's drinking one drink a day, and maybe two drinks a day on the weekend. So according to this study, a moderate alcohol user would have a higher risk of hippocampal atrophy.”
What about the supposed heart benefits of drinking alcohol that have persisted over time. Do those possible upsides outweigh the risks of drinking?
“There's no definitive evidence from anywhere that alcohol causes a true benefit to your heart,” says Roach. “There's just good evidence that people who drink moderately have less risk of heart disease and less risk of overall death. There's absolutely perfect evidence that once you exceed moderate drinking, alcohol is harmful for you.”
The bottom line: If you’re going to drink, limit yourself to one serving daily or less. In the U.S. that means no more than one drink a day for women and no more than two drinks a day for men.
