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Appalling drunk? Can't drink at all? It's your genes, not the amount, says professor

TOKYO -- House of Representatives member Hodaka Maruyama made headlines with his suggestion that war might be appropriate to solve Japan and Russia's territorial dispute over the Northern Territories. The lawmaker, who had been drinking, made a commotion during the night and tried to head out on a late excursion; but the next morning he apologized.

But why do people get inebriated to the point of ending up a bad drunk who does and says things that defy common behavior? The Mainichi Shimbun asked the author of "People who become bad drunks and those who don't," Toshihiro Masaki, professor of neurology at Teikyo University, to find out more.

But what is bad drunkenness? Professor Masaki defines it this way, "It's the state when someone's cerebral cortex is paralyzed by ethanol, the primary ingredient in alcohol, leading them to do or say things that are somewhat misaligned with a normal societal response. Or, in the case of a bad drunk, it's someone who descends into that drunken state often."

Around one to two hours after ingesting ethanol, it's absorbed from organs like the stomach and small intestine, where it then paralyzes the brain's neocortex, which controls our reasoning functions.

Professor Toshihiro Masaki of Teikyo University is seen there on May 29, 2019, in Adachi Ward, Tokyo. (Mainichi/Hiroyuki Wada)

But the explanation as to why some of us get drunk at faster and stronger rates than others isn't down to the amount we consume. It's actually caused by sudden increases in the blood's alcohol concentration. What kind of person experiences quick onset high concentrations of alcohol and what kind doesn't is thought to be answered by our individual genetic makeup, with no connection to the amount we drink. Professor Masaki has examined a number of his fellow doctors' genes, and in doing so landed on the following hypothesis.

Ethanol absorbed by the body gets broken down by alcohol dehydrogenase (ADH) into a toxic compound called acetaldehyde. Enzymes called aldehyde dehydrogenases (ALDH) then reduce the compound into harmless acetic acid. There are two types of genes in ALDH -- one that breaks down acetaldehyde quickly and one that does so slowly. One of the genes is passed down from each parent, making three permutations possible: having two slow genes, two fast ones or one of each.

Masaki calls the slower genes "lightweight genes." Someone with two slow ones can't drink a drop. People who have just one that's slow are likely to get red in the face easily, and aren't able to have too much alcohol. "If you have just one lightweight gene, it's thought that you can't turn into a bad drunk. This state applies to about 50% of people in Japan."

There are also two types of genes in ADH -- one that can break down ethanol quickly and one that can do so slowly. The fast ones are called "heavyweight drinker's genes" and the sluggish ones are "bad drunk's genes." In the same way that genes affecting the speed at which alcohol concentrates in our bodies can be split into three basic categories, so too can the genes governing the speed at which we break down the harmful by-products of drinking.

If those who have no lightweight genes at all carry two heavyweight genes, concentration in the blood doesn't increase rapidly, enabling them to calmly carry on consuming with a strong tolerance for alcohol's effects.

However, those with two of the bad drunk genes and no lightweight genes are most likely to act out when under the influence due to their slow rate of alcohol decomposition. Those with one bad drunk but no lightweight gene have a tendency to alternate between strong and bad drinkers -- the type who can hold their drink but also the type who can lose control. In Japan, the proportion of people estimated to carry one or more bad drunk genes is under 20%, meaning around one in every five or six people is liable to lose some control during a drinking session.

There are simple ways to discern which types of the genes you have. One is by using an alcohol patch test, which measures your body's ability to handle alcohol. If your skin goes red after applying the patch, you're carrying one or more lightweight genes. If you have many experiences of blacking out and losing your memories when drinking, it's likely you're carrying at least one bad drunk gene.

But the prognosis for those with all heavyweight genes isn't cause for relief. Sustained consumption of ethanol can lead to dangers such as alcohol dependency and addiction.

"The truth is, I'm a bad drinker type," revealed professor Masaki. "Those with a tendency to behave badly when drunk have some ability to predict that they could get out of hand when they consume alcohol. There's no excuse for taking actions that don't consider where you are and the position of those around you," he added.

His advice to those with such tendencies is to drink slowly, avoid exceeding a limit that past experience has taught you will lead to blacking out, and to eat snacks in accompaniment to the beverages.

(Japanese original by Hiroyuki Wada, Integrated Digital News Center)

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