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The Chemistry of a Hangover

You know how it works. You're celebrating a friend's birthday and the alcohol is flowing. One drink turns into two, then three, and before you know it…. you wake up feeling less than wonderful the following day. What to do? Does the science say anything about how to cure a hangover?

First off, let’s examine why you may feel so gross the morning after a night of drinks. The culprits are acetaldehyde and formaldehyde.

Acetaldehyde, a metabolite of ethanol (ie alcohol) is eventually excreted from the body as acetic acid. But before its conversion to acetic acid, acetaldehyde contributes to the symptoms of a hangover. We know that genetic factors play a role in the breakdown of alcohol, which is why hangover symptoms vary from person to person. Many people of Asiatic origin, for example, are severely affected by facial flushing because nature has dealt them a very slow acting version of aldehyde dehydrogenase, the enzyme that normally degrades acetaldehyde. Indeed, the same concept lies behind a prescription drug known as disulfiram (Antabuse) which is given to alcoholics. The idea being that the drug inactivates aldehyde dehydrogenase, forcing acetaldehyde into blood circulation causing the drinker to get sick enough to give up the booze. Unfortunately, often the drug will be abandoned instead of the alcohol.

There is more to the hangover, however, than just acetaldehyde. Dehydration plays an important role, as does hypoglycemia, which can happen due to alcohol causing sugar to be lost in the urine. But in all likelihood, the greatest contributor to the hangover is methanol, another fermentation product found in alcoholic beverages, luckily in small amounts because methanol is highly toxic. Like its ethanol partner, methanol is metabolized by the same enzymes as ethanol. The only difference is the that this time formaldehyde is formed instead of acetaldehyde. But it too can produce the hangover symptoms.

Why does this usually happen the morning after?

Because the enzymes prefer to work on ethanol instead of methanol. Only when all the ethanol has been metabolized, do they switch to methanol. This explains why some people will actually try to combat their hangover with more alcohol the following morning, since this drink would then supply ethanol for the enzymes to act upon, thereby leaving methanol alone. As unappetizing as a cocktail may sound to someone with a hangover, it actually works. Because while the enzymes are busily metabolizing the ethanol, methanol is excreted in the urine without being converted to formaldehyde. A Bloody Mary may be the best choice here because vodka contains very little methanol, hence its popularity as a “boozy brunch” cocktail. Confirmation about the critical role of methanol in hangovers comes from a study showing that treatment with 4-methylpyrazole, a drug that blocks the breakdown of methanol, can eliminate the symptoms.

Now while all of this may provide some reprieve to what may follow a night of holiday socializing, alcohol can be an extremely destructive beverage. Just this past September, data from the Canadian Institute for Health Information (CIHI) showed that 10 Canadians die in hospital every day from harm caused by substance use, and 75% of these deaths are related to alcohol.

That’s also not to say that one should stop drinking entirely. Just use your brain. And don’t let the alcohol get to it first.


@JoeSchwarcz

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