| Within minutes of drinking a glass of pinot, I can feel my cheeks flushing. It’s not long before the dreaded red wine headache sets in. I’ve always wondered why red wine seems to affect me more than other types of alcohol — and I’m not the only one. I’ve heard tons of theories over the years: Perhaps preservatives like sulfites are to blame? Or maybe it’s histamines, naturally occurring compounds that are found in some food and beverages? Could it be tannins, the plant chemicals responsible for giving red wine its flavor? More recently, signs have pointed to another culprit: a chemical called quercetin that’s produced by red grapes as they’re exposed to sunlight. “It’s sunscreen for grapes,” says Andy Waterhouse, a wine chemist at UC Davis. White wine also contains quercetin, but usually at much lower levels. It can be difficult for wine buyers to easily find levels of quercetin in both red and white wines, because they’re not regularly tested for it. Waterhouse said it’s not uniform or consistent even among wine varietals, since its dependent on sun exposure. Waterhouse and his collaborators have found that the quercetin in red wine inhibits the body’s ability to fully break down alcohol. That leads to a buildup of acetaldehyde, the toxic byproduct of alcohol that’s also through to be one of the main drivers of headaches and other hangover symptoms. Acetaldehyde is metabolized in the liver and the gut, and small amounts typically aren’t harmful. But when it’s allowed to accumulate, it can be toxic. Some people actually lack the enzyme responsible for quickly breaking down acetaldehyde, which can lead to symptoms of alcohol intolerance. People of East Asian descent, for example, are more likely to have a genetic mutation that limits this enzyme’s ability to rid the body of acetaldehyde, which can make them more sensitive to alcohol’s effects. More research is needed to determine whether quercetin really is responsible for the dreaded red wine headache. Waterhouse says he hopes to run a study in people who are prone to these headaches, testing their reactions to wines that are higher or lower in quercetin. It’s well known, he says, that some wines have higher amounts of the chemical. In fact, Waterhouse’s research has also found that the amount of quercetin in wine tends to increase with price. More than two decades ago, he conducted a study on the 20 best selling cabernets in California. The most expensive cabs on the list had about four times as much quercetin than the average ones. That’s because higher-quality wines tend to be made from grapes with carefully controlled sun exposure. Lower-quality wines, on the other hand, are usually made from large vines that have more shade for the grapes, Waterhouse said. So, the good news for people who suffer from red wine headaches: Cheaper wine may actually be a better choice. — Madison Muller | 
