A glass of wine in the evening, maybe a beer with friends: According to a new study, alcohol consumption, which is often classified as low to moderate, is associated with changes in the brain. The research, which draws on data from more than 36,000 adults, shows that people who consume two units of alcohol per day – roughly one glass of wine – have reduced brain capacity compared to people who consume no more than one unit of alcohol per day take day. The differences are comparable to an aging of two years.
It is widely accepted that alcohol is not good for the brain. The question is, however, at what level of alcohol consumption is to be classified as problematic and up to what level it is considered tolerable from a health point of view. International standards call “low-risk consumption” about one standard glass a day for women and twice as much for men. A standard glass corresponds – with slight deviations between countries – about eight to twelve grams of pure alcohol or about 300 milliliters of beer or 100 milliliters of wine.
Recommended “safe” levels too high
A new study now suggests that even these supposedly low-risk amounts have noticeable effects on the brain. A team led by Remi Daviet from the University of Wisconsin-Madison analyzed data from more than 36,000 adults who answered questions about their health and lifestyle for the UK Biobank, provided genetic data and had MRI brain scans. “The fact that we have such a large sample allows us to find subtle patterns even between drinking the equivalent of half a beer and a beer a day,” says co-author Gideon Nave of the University of Pennsylvania.
While previous, smaller studies have found no negative health consequences for small amounts of alcohol, the large data set used by Daviet and his colleagues shows a clear correlation: people who reported drinking more alcohol had a smaller brain size than people who reported less consumed alcohol. The researchers controlled for factors such as age, height, handedness, gender, smoking status, socioeconomic status, genetic ancestry and place of residence. “These results are contrary to scientific and government guidelines on safe drinking levels,” says Nave’s colleague Henry Kranzler. “The officially recommended limits are above the amounts that were associated with reduced brain volume in the study.”
Brain ages by years
The higher the alcohol consumption, the clearer the effects observed in the study. The difference between people who lived abstinent and those who consumed a maximum of one alcohol unit a day was smaller than that between people who consumed two instead of a standard glass a day. “It’s not linear,” says Daviet. “It gets worse the more you drink.” The reductions in brain volume affected almost all regions of the brain, including the frontal cortex, the insula and the brainstem. The researchers also observed changes in the structure of the white matter.
To illustrate the changes, the researchers compared them to changes caused by aging processes. According to this, the brain of a 50-year-old who consumes two standard glasses of alcohol a day is two years “older” than that of a peer who consumes no more than one standard glass a day. Each additional alcohol unit per day led to a stronger aging effect in the brain. An increase from two to three standard glasses a day corresponded to an aging of three and a half years, the difference between zero and four glasses a day was more than ten years aging.
Skip the last glass
The evaluated data show a correlation between alcohol and brain volume, but do not allow any conclusions about causal relationships. The researchers want to clarify this with future studies in which they track the alcohol consumption and brain volume of test subjects over several years. In addition, they want to clarify further details on the type of consumption and the respective effects on the brain. “Our study looked at average consumption, but we’re curious if drinking one beer a day is better than none during the week and seven on the weekend,” says Nave. “There is some evidence that excessive alcohol consumption is worse for the brain, but we haven’t looked at that further.”
However, the researchers believe that the current study also gives reason to recommend reducing one’s own alcohol consumption. “There is some evidence that the effects of alcohol consumption on the brain are exponential,” says Daviet. “So one extra drink per day could have a greater impact than all previous drinks that day. This means that cutting back on the last drink of the evening could have major implications for brain aging.”
Source: University of Pennsylvania, Remi Daviet (University of Wisconsin-Madison, USA) et al., Nature Communications, doi: 10.1038/s41467-022-28735-5