Experts could now make a red that doesn’t hurt the head
By Joe Pinkstone SCIENCE CORRESPONDENT
SCIENTISTS believe they have identified the chemical that is to blame for red wine headaches and flushes. Quercetin, which is part of a group called flavonoids that are found in high quantities in grapes, is responsible for many of the touted health benefits of wine but has now also been shown to inhibit an enzyme called ALDH2, which the body uses to break down alcohol. As a result, it allows toxic chemicals to build up. In other drinks, such as beer or cider, there is no quercetin so the body can break down the ethanol easily. However, when red wine is processed the quercetin blocks this enzyme from working. As a result, acetaldehyde, a toxic chemical that is made when processing alcohol, is left to accumulate rather than be flushed out quickly. Symptoms of high levels of acetaldehyde include flushes, headaches and nausea. Laboratory studies reveal that a 150ml glass of wine is enough to inhibit ALDH2 activity by about 37 per cent. “When quercetin gets in your bloodstream, your body converts it to a different form called quercetin glucuronide,” said Andrew Waterhouse, professor emeritus at the University of California, Davis. “In that form, it blocks the metabolism of alcohol.” Other foods, including onions, have higher concentrations of quercetin. However, in these instances there is no alcohol involved and no acetaldehyde to cause discomfort. “When susceptible people consume wine with even modest amounts of quercetin, they develop headaches, particularly if they have a pre-existing migraine,” said Prof Morris Levin, the study co-author. “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 academics are now planning a Phase 3 clinical trial to test the theory on volunteers. Researchers said there are still many unknowns about the causes of red wine headaches and add why some people are more prone to them than others. It is possible that some people’s enzymatic function is more easily inhibited than others or that some have a higher tolerance for acetaldehyde. “If our hypothesis pans out, then we will have the tools to start addressing these important questions,” Prof Waterhouse said. One potential experiment touted in the journal Scientific Reports is to give people wines with different chemical compositions to see if there is a pattern in who gets headaches. “Another, simpler, experiment would be to provide red wine headache subjects with a quercetin supplement or placebo and a standard drink of vodka, to see if headaches result,” the scientists said. It is hoped that if the theory proves true it could be possible to create specific red wines that have no, or little risk, of headaches. For example, the quercetin levels are up to eight times higher in some wines than others, with variables such as sunlight exposure and the processing method of the grapes having an impact. One study found that high-end wines have four times as many flavonoids as cheap, mass produced wines, probably because of trellised vines, crop thinning and leaf removal, all of which increase the sunlight reaching the grapes and lead quercetin production to soar. “But, the variations in levels arise not just from differences in grape composition induced by sun exposure but also from wine-making techniques, including skin contact during fermentation, stabilisation/fining procedures, and ageing methods,” the authors said.