Alcoholism: when the gut microbiota and the brain drink too much
Alcoholism could turn your brain into a sieve. But a tiny bacterium called Faecalibacterium prausnitzii could be the savior and protect your memory.
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About this article
We know that alcohol can damage the brain. But did you know that it could also weaken the barrier that protects the brain from “intruders” coming from the blood? This protection, called the blood-brain barrier, is a bit like a safety net for our gray matter. And surprise: our gut seems to be playing a role in this scenario.
A microbiota not so innocent
Chronic alcoholics not only have problems with memory and concentration, but also with anxiety, depression and sleep disorders. Their gut microbiota is also suffering: Faecalibacterium, an anti-inflammatory bacterium, is less present, while Streptococcus, an inflammatory bacterium, is taking advantage of the situation to set up shop. And that’s not all: the blood plasma of alcoholic men is very different from that of men who are not addicted to drinking, with more than 600 molecules in excess and just as many in deficit. In short, an alcohol use disorder disrupts the gut microbiota, the composition of the blood and the functioning of the brain.
When the brain leaks... literally
To better understand the underlying mechanisms, mice were given alcohol for several weeks. The result: chronic alcohol consumption makes the barrier protecting their noggin permeable; leaks appear in key areas, and proteins essential to the integrity of the blood-brain barrier are down.
More surprisingly, transferring the intestinal microbiota of alcoholic patients to germ-free mice that do not drink alcohol is enough to induce the same type of brain leaks. Thus, the alteration of the intestinal microbiota caused by alcoholism is responsible for the disruption of the blood-brain barrier.
- Excessive alcohol consumption is defined, particularly in Anglo-Saxon countries, as more than 3 drinks per day or 7 per week for women, and more than 4 drinks per day or 14 per week for men 1.
- In 2019, an estimated 400 million people, or 7% of the world population aged 15 years and older, had alcohol use disorders. Of these, 209 million people (or 3.7% of the world adult population) were dependent on alcohol 2.
Faecalibacterium prausnitzii, the savior?
Since the friendly bacterium Faecalibacterium is missing in alcoholics, the researchers tested whether it could protect mice. Bingo! A few doses of Faecalibacterium prausnitzii allow mice to regain better cognitive abilities and their brain leaks less. How can a gut bacterium protect the barrier that surrounds the brain? Probably through the small anti-inflammatory fatty acids it produces in our digestive system, which slip into the bloodstream and thus reach the brain. Could F. prausnitzii protect against the damage caused by alcoholism? Maybe, although many other studies are still needed, this study 3 having been conducted only in men (not women) and mice. In any case, alcohol remains a substance to be consumed in moderation.
