▎ WuXi AppTec content team editor
When it comes to the health hazards of alcohol, I believe you will be able to list three or two. Alcohol consumption can not only lead to cirrhosis, psychological problems, obesity and cardiovascular disease, but is also closely related to a variety of cancers. A study in the journal The Lancet tells us that alcohol intake simply doesn't have a so-called "safe dose": as long as you drink alcohol, the risk of cancer increases.
In addition to these health risks, alcohol can also cause permanent damage to the brain. In existing studies, the relationship between alcoholism and brain damage is becoming increasingly clear: excessive alcohol intake is enough to alter the structure of the brain, causing a decrease in gray and white matter throughout the brain, which in turn may cause cognitive impairment. However, the effects of relatively small amounts of alcohol consumption on the brain are not clear.
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Seeing this, if you think that "moderate" drinking (such as drinking a few bottles of beer or a bottle of liquor a week) is harmless to the brain, you are very wrong. In a study published in Nature Communications, a team of researchers led by the University of Pennsylvania told us through a large-scale study that mild to moderate alcohol intake is also associated with the attenuation of brain volume. The health hazards of alcohol to the brain may be more serious and common than we expected.
Research on this topic often has a problem: the lack of a sufficiently large database. For the study, the authors used data from the Uk's Biobank. The dataset contains genetic and medical information for 500,000 middle- to older adults. The study used some of this information, particularly the results of the magnetic resonance imaging of the brains of more than 36,000 people , from which the volume of gray matter and white matter in different brain regions can be extrapolated.
"The sheer size of the sample we have allows us to spot subtle trends, even the health risks associated with half a bottle of beer and a bottle of beer a day," said co-corresponding author Professor Gideon Nave of the University of Pennsylvania. ”
The key to revealing the potential association between alcohol consumption and the brain is to control the myriad of variables and avoid making the relationships more mixed. To do this, they controlled for variables such as age, height, sexual behavior, smoking status, socioeconomic status, genetic ancestry, and more. In addition, they standardized brain volume data based on the age of the participants.
The 36,000 participants in Biobank answered their own alcohol intake in the survey, ranging from no alcohol drops to 4 alcohol units per day (1 alcohol unit refers to 10 ml of alcohol, which is equivalent to about half a bottle of beer). When the researchers grouped participants based on how much they drank, they observed a trend that was clear enough: as the amount of alcohol consumed increased, the gray and white matter volumes of the brain decreased, and the change was not linear: the more they drank, the worse it became.
▲The trend of standardized gray matter and white matter volume with average alcohol intake (Image source: Reference[1])
The team noticed that the changes in the size of the brains of these people were not concentrated in a single brain area, but were ubiquitous throughout the brain, similar to the changes caused by aging. Therefore, the authors compared alcohol consumption to the brain volume reduction caused by aging.
Specifically, for people in their 50s, if they switch from drinking alcohol to an average daily intake of one unit of alcohol, their brain is equivalent to aging by 0.5 years; from an average daily intake of one unit of alcohol to two units, the brain is equivalent to aging by 2 years. With the increase in intake, the brain also shows a trend of accelerated aging: from 2 units to 3 units, which is equivalent to 3.5 years of brain aging. In more extreme cases, from not drinking alcohol to ingesting 4 units per day, it is equivalent to the brain aging by more than 10 years.
▲The relationship between different degrees of alcohol intake and gray matter and white matter volume (Image source: Reference[1])
"These findings contradict previous recommendations for safe intake of alcohol that people have received," said Professor Henry Kranzler, another corresponding author of the paper, "for example, the previous recommendations for women at the U.S. Institute for the Prevention of Alcohol Abuse and Alcoholism were no more than one unit per day; for men was two units." In this study, this value has been able to cause the brain to shrink. ”
With the help of large-scale databases, this study reveals for us the close relationship between drinking alcohol and the brain. For the researchers, they also plan to build on the study and further study the relationship between the two. For example, advance conclusions from correlation to causality, and reveal the effects of a single heavy dose of alcohol on the brain.
"The study focused on average alcohol intake, but we also wanted to know how differently drinking seven cups a day would make a difference to the brain compared to drinking one glass a day, not drinking seven cups in a short period of time on the weekend." Studies have shown that the latter is more harmful to the brain, but we have not studied this in detail. Professor Nave said.