A study published in ‘Science Advances’ has shed light on why some people cannot drink red wine, even in small quantities, because it gives them a headache.

A team from the University of California at Davis (USA) has accused a flavanol, a compound found naturally in red wines, of interfering with the proper metabolism of alcohol and causing headaches. The flavanol in question is quercetin, which is naturally present in all types of fruits and vegetables, including grapes. It is considered a healthy antioxidant and is consumed as a supplement, but when metabolized with alcohol, it can be problematic.

When quercetin reaches the bloodstream, the body converts it into a different form called quercetin glucuronide. This blocks the metabolism of alcohol and causes the buildup of acetaldehyde toxin, which leads to redness, headache, and nausea. The lead author Apramita Devi explains that acetaldehyde is a toxin that causes facial redness and inflammation. High levels of acetaldehyde can also cause migraines and other primary headache conditions.

The medicine disulfiram works by preventing this buildup of acetaldehyde in the body when normally an enzyme would break it down. About 40% of East Asians have an enzyme that doesn’t work very well allowing acetaldehyde to build up in your system. Morris Levin, professor of neurology and director of Headache Center at the University of California-San Francisco says that susceptible people who consume wine with even modest amounts of quercetin may develop headaches if they have preexisting migraine or other primary headache condition.

It’s important to note that levels of quercetin can vary dramatically in red wine. Quercetin is produced by grapes in response to sunlight, but its levels can differ depending on how the wine is made including skin contact during fermentation, fining processes and aging