For the ancient philosopher Celsus, the wine it was the answer to endless ailments, from fatigue and fever to cough and constipation. But despite its healing powers, the grape, he admitted to his loyal readers, could occasionally cause headache.
From the time of Celsus, as stated by Guardianresearchers have looked at all sorts of compounds in red wine in an attempt to find out which ones cause these headaches, which can even strike 30 minutes after drinking one or two small glasses. Tannins, sulfites, phenolic flavonoids, and biogenic amines have been suspected but not yet proven to be responsible.
Writing to Scientific Reportsthe American researchers said they focused on phenolic flavonoids, compounds that come from the seeds and skin of grapes and contribute to the color, flavor and mouthfeel of red wine. Flavonoid levels can be 10 times higher in red wines than in whitesmaking them prime candidates for causing immediate headaches.
When people drink wine, alcohol is metabolized to acetate in two stages. The first converts alcohol in the form of ethanol into acetaldehyde. The second converts acetaldehyde into acetate. Special enzymes in liver they orchestrate each of these processes.
The guilty substance
The researchers, including Professor Andrew Waterhouse, a viticulturist at the University of California, Davis, conducted laboratory tests on more than twelve compounds of red wine. One of them stood out. A flavanol called quercetin, which is found almost exclusively in red wine, is dissolved by the body into various substances. One of them, cquercetin lycuronideproved particularly effective in blocking the enzyme that converts acetaldehyde to acetate.
This could be the key to solving the mystery. By suppressing the critical enzyme, as scientists believe, toxic acetaldehyde builds up in the bloodstream. At high levels, this causes headaches, nausea, facial flushing and sweating. In fact, there is a drug called disulfiram and is used for treatment of alcoholicswhich does exactly the same thing: it blocks the same enzyme, causing the same unpleasant symptoms when one drinks.
According to the researchers, when people prone to migraines or other sensitivities drink red wine with even moderate amounts of quercetin, they may experience a headache. Why some are more affected than others is unclear: their enzymes may be more easily blocked, or they may simply be more sensitive to toxic acetaldehyde.
The team now hopes to test the theory with a clinical trial on headaches caused by red wines with different levels of quercetin. The results could help people avoid red wine headaches in the future. The grapes produce quercetin in response to sunlightso grapes grown in exposed areas, such as cabernets in Napa Valley in California, they can have five times more quercetin than other red wines. Skin contact during fermentation and aging also affect quercetin levels.
The researchers believe that this way people who drink red wine will be able to choose wines that are less likely to cause headaches, while winemakers they will be able to use the findings for to reduce quercetin in their wines.