An explanation has been found for headaches after a couple of glasses of red wine

“We are well on our way to understanding this thousand-year-old mystery.”

The mystery of headaches caused by red wine seems to have been solved by scientists. Researchers believe phenolic flavonoids are responsible for the unpleasant sensations in the head that sometimes occur soon after one or two glasses of red wine.

For the Roman scientist Celsus, wine was a remedy for endless ailments, from fatigue and fever to coughs and constipation, writes The Guardian. But, despite its beneficial healing properties, the grapevine drink, according to its devoted admirers, can cause strange headaches.

Now researchers believe they have found the reason why wine – red wine in particular – causes headaches so quickly. “We think we’re finally on the right track to explaining this thousand-year-old mystery,” says Morris Levine, director of the Headache Center at the University of California, San Francisco. “The next step is to scientifically test this in people who develop similar headaches.”

Red wine headaches are different from the type of hangover that occurs the morning after the previous night, notes The Guardian. Instead of occurring after prolonged drinking of wine, they can begin 30 minutes after drinking nothing at all – just one or two small glasses.

Researchers have studied all sorts of compounds in red wine in search of the culprit of these unpleasant sensations. Tannins, sulfites, phenolic flavonoids and biogenic amines were suspected. But so far, none of these “suspects” have been identified as a clear trigger.

And in their scientific reports, the American researchers said they were focusing on phenolic flavonoids – compounds that come from grape seeds and skins and that give red wine its color and taste. The level of flavonoids in red wines can be 10 times higher than in white wines, making them prime candidates for immediate headaches.

When people drink wine, the alcohol is metabolized into acetate in two stages, The Guardian explains. The first step converts alcohol in the form of ethanol into acetaldehyde. The second converts acetaldehyde to acetate. Specific enzymes in the liver control each of these processes.

The researchers, including University of California viticulture expert Professor Andrew Waterhouse, carried out laboratory tests on more than a dozen compounds found in red wine. One that stood out from the general series was a flavanol called quercetin, found almost exclusively in red wine, which is processed by the body into various substances. One of them, quercetin glucuronide, has been shown to be particularly effective in blocking the enzyme that converts acetaldehyde to acetate.

This may serve as a clue to solving the mystery. Scientists believe that when a critical enzyme is suppressed, toxic acetaldehyde accumulates in the blood. At high concentrations, it causes headaches, nausea, facial flushing and sweating. In fact, a drug called disulfiram blocks the same enzyme and is used to treat alcoholics, giving them the same unpleasant symptoms if they drink.

When susceptible people drink red wine with even small amounts of quercetin, they may develop headaches, especially if they are prone to migraines, researchers say. It’s not clear why some are more affected than others – their enzymes may be easier to block, or they may simply be more susceptible to toxic acetaldehyde.

Now a team of scientists hopes to test this theory with a clinical study on the headache-inducing effects of red wines with different levels of quercetin. The findings could help people avoid red wine headaches in the future.

“This could potentially be very helpful for people who drink red wine to be able to choose wines that are less likely to cause headaches,” says Morris Levine. “In addition, winemakers can use our results to reduce the quercetin content in their wines.”