Researchers have found that a natural flavonol compound in red wines can interfere with the metabolism of alcohol which leads to a headache.
The University of California team in Davis say it's all about quercetin, which is naturally present in many fruits and vegetables, including grapes. It's a healthy antioxidant that is even available in supplement form—but when mixed with alcohol, it can be problematic.
"When it gets in your bloodstream, your body converts it to a different form called quercetin glucuronide," said Professor Andrew Waterhouse. "In that form, it blocks the metabolism of alcohol."