Even a small amount of red wine can give some people a headache. Scientists have now identified the culprit. In new research published in Scientific Reports, Researchers have shown that a molecule that is naturally found in red wine called quercetin can disrupt the metabolism of alcohol, and cause a headache.
Quercetin is a type of flavanol and is a natural chemical found in grapes and many other fruits and vegetables. It's thought to be a health boosting molecule with antioxidant powers, and some people even take it as a dietary supplement. However, when it's consumed along with alcohol, problems can arise.
“When it gets in your bloodstream, your body converts it to a different form called quercetin glucuronide,” said wine chemist and corresponding study author Andrew Waterhouse, a professor emeritus at the University of California (UC) Davis. “In that form, it blocks the metabolism of alcohol.”
This can lead to the buildup of acetaldehyde, a known toxin that has been linked to flushing, headache, and nausea.
“Acetaldehyde is a well-known toxin, irritant and inflammatory substance,” said lead study author Apramita Devi, a postdoctoral researcher with the UC Davis Department of Viticulture and Enology. “Researchers know that high levels of acetaldehyde can cause facial flushing, headache and nausea.”
A drug called disulfiram that has been developed to prevent alcoholics from consuming alcohol causes the same effect; the drug also causes acetaldehyde to accumulate in the body when an enzyme would normally degrade the substance. This enzyme also does not work properly in many people of East Asian descent, which has the same acetaldehyde-accumulating effect.
The study authors hypothsize that if certain susceptible people drink even a little bit of wine that contains quercetin, they get headaches, especially if they have a susceptibility to headaches or migraines, said study co-author Morris Levin, a professor of neurology and director of the Headache Center at UC San Francisco (SF). “We think we are finally on the right track toward explaining this millennia-old mystery. The next step is to test it scientifically on people who develop these headaches, so stay tuned.”
The levels of quercitin can also vary significantly from one red wine to another, added Waterhouse. The molecule is generated in grapes when exposed to sunlight, so when clusters are exposed, there are higher levels of quercetin. The grapes grown in Napa Valley that are used to produce cabernets are one example; they have quercetin levels that are four or five times higher than other red wines.
Different aspects of wine production, like fermentation or aging, can also produce varying amounts of quercetin.
In future research, the scientists want to assess the effects of red wines with very little quercetin compared to those with a lot, to see if this theory accurately reflects what people experience. A planned trial will be funded by the Wine Spectator Scholarship Foundation and led by UCSF.
Scientists still do not know why some people are more prone to headaches after red wine consumption than others, however. It could be that some individuals may have enzymes that are more likely to be impaired by quercetin, or some may be more affected by acetaldehyde buildups.
“If our hypothesis pans out, then we will have the tools to start addressing these important questions,” Waterhouse said.