A new study from scientists at the University of California-Davis says that a naturally-occurring plant compound found in red wine called quercetin, which is a flavanol, could be the culprit.
Researchers found quercetin interferes with an enzyme that helps break down alcohol, which can lead to a headache.
What is quercetin?
As mentioned, quercetin is a flavanol that exists naturally in fruits and vegetables, including grapes – the fundamental ingredient in wine.
Quercetin levels vary dramatically in red wine, study authors noted, depending on how the grapes are grown and how the wine is made.
"Quercetin is produced by the grapes in response to sunlight," said wine chemist and corresponding author Andrew Waterhouse, professor emeritus with the UC Davis Department of Viticulture and Enology.
"If you grow grapes with the clusters exposed, such as they do in the Napa Valley for their cabernets, you get much higher levels of quercetin. In some cases, it can be four to five times higher."
Grape skin contact during fermentation, fining processes and aging plays a role in the levels as well.
Quercetin is considered a healthy antioxidant, researchers said, but can turn problematic when it’s metabolized with alcohol.
File image of people drinking red wine. Getty Images
Red wine headaches
"When (quercetin) gets in your bloodstream, your body converts it to a different form called quercetin glucuronide," Waterhouse explained in a press release. "In that form, it blocks the metabolism of alcohol."
When alcohol isn’t metabolized, it can lead to a buildup of acetaldehyde, a toxin, which causes facial flushing, headache and nausea.
Some medications prescribed to those with an alcohol dependency cause the same build-up, and about 40% of the East Asian population also has an enzyme that doesn’t work very well, allowing acetaldehyde to build up in their system.
"We postulate that when susceptible people consume wine with even modest amounts of quercetin, they develop headaches, particularly if they have a preexisting migraine or another primary headache condition," said co-author Morris Levin, professor of neurology and director of the Headache Center at the University of California, San Francisco.
Testing the theory
Scientists will test their findings next on people who are more prone to developing headaches, as well as by comparing wines with high levels of quercetin with those that have lower levels.
Researchers hope to learn if the enzymes of people who get red wine headaches are more easily inhibited by quercetin, or if this population is just more easily affected by the buildup of the toxin acetaldehyde.
The study was published in the journal Scientific Reports.
This story was reported from Detroit.