The Surprising Latest Study on Alcohol and Your Brain

The Surprising Latest Study on Alcohol and Your Brain

A glass a day may not be so harmless after all.

You might drink a glass of wine each night for your heart and you wouldn’t be alone—many doctors would probably join you. For years, studies have suggested moderate alcohol intake may be better for your health than heavy drinking or abstaining.

But in 2016, the UK changed its national guidelines on safe intake to include no more than 14 units, about a bottle and a half of wine, per week. They suspected the benefits of moderate drinking might not outweigh the risks, after all. At that point, studies had already linked the practice 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 from The BMJ. (Moderate drinking was defined by researchers as seven to less than 14 units a week for women, seven to less than 21 units per week for men.) Researchers followed 550 people over 30 years, tracking their:

  • Weekly alcohol intake
  • Cognitive, or thinking abilities, periodically
  • MRI brain scans, once (at the end of the study)

The more people drank, the more atrophy, or shrinking they experienced in their brain’s hippocampal region, an area involved in memory. Even moderate drinkers were three times more likely to have atrophy than people who abstained.

Light drinkers, who had 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 had over 30 units (more than about 15 glasses of wine) per week.

“The next question is, do those changes mean anything?” asks Keith Roach, MD, Chief Medical Officer of Sharecare. “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, including routine lexical fluency tests (how many words with the same first letter they could name in one minute).

People who had more than seven units of alcohol were more likely to have a reduction in cognitive function [lexical fluency], says Dr. Roach. But the differences between groups were pretty small, he adds, 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 over time to see how specific factors like 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 a picture. And it’s often difficult to sort out whether alcohol is causing the effects, or if people who drink moderately are just healthier in other ways, explains Dr. 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.

“But you can immediately see the problem with a randomized controlled trial,” he continues. “There's no such thing as ‘placebo alcohol.’ You’d say ‘here drink this wine,’ and people would spit it out and say, ‘that's not wine!’ And there goes the end of your study.”

The approach taken by these researchers 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
These 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 Dr. 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 the study in the first place.

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 US,” says Dr. Roach. “That's someone who's drinking one drink a day, and maybe two drinks a day on the weekend, so a moderate alcohol user would have a higher risk of hippocampal atrophy, according to this study.”

This contradicts popular knowledge, previous studies and the national recommendations on safe alcohol consumption. The study’s authors conclude that it “calls into question the current US guidelines.”

But do the heart benefits outweigh the risks of drinking? “There's no definitive evidence from anywhere that alcohol causes a true benefit to your heart,” says Dr. 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.

Medically reviewed in May 2018.

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