Weekend Reads | Why Do Some People Get Red Wine Headaches?

by Kevin Schofield

This weekend's read is a new scientific report in the journal Nature on a question that plagues many of us, especially during the holiday season: Why do some people get headaches from drinking red wine? It may surprise you to know that science currently doesn't have a definitive answer to that question.

While I try to pick "reads" for this column that are generally, well, readable, I will admit upfront that this one is on the more difficult end of the spectrum, with a fair amount of chemistry and biology terminology. Nevertheless, it's very interesting, in part because it attempts to finally provide an explanation for red wine headaches, but also for several other points it makes along the way.

Science does understand how our bodies deal with alcohol intake, and it involves two enzymes in the liver: one named ADH that converts the alcohol into the chemical acetaldehyde, and another called ALDH that then converts that acetaldehyde into acetate — which our body gets rid of through its regular waste processes. The first part of this two-step process, converting alcohol into acetaldehyde, runs fast and can scale up quickly, so if you pound back a few, it can generate a lot of acetaldehyde in your body. The second part — converting it into acetate — is where this story gets interesting. It's very important for this part of the process to run well, because when it doesn't, the acetaldehyde accumulates in our bodies and can lead to nausea, face blushing, irregular heartbeat, and — you guessed it — headaches.

It turns out there are a few different variations of the ALDH enzyme, though the one that does the bulk of the conversion work is known as ALDH2. We each carry in our DNA two copies of the gene that knows how to manufacture ALDH2, one inherited from each of our parents. However, about 40% of people of East Asian descent carry a gene that makes a "dysfunctional" version of ALDH2. If we get two good genes, then our bodies can fully convert acetaldehyde; if we have two bad ones, we can't convert it at all; and if we get one of each, then we can convert it, but at a much slower pace. Research has shown that people carrying two copies of the "dysfunctional ALDH2" gene have high levels of acetaldehyde in their blood after consuming alcohol.

And this isn't necessarily a bad thing; some have attributed this inability to convert acetaldehyde, its accumulation in the blood, and the resultant ill effects as contributing to the relatively low alcoholism rate among Asians with the "dysfunctional ALDH2" gene. In fact, a drug (called disulfiram) that blocks ALDH2 from working is sometimes used as a treatment for alcoholism, because if you are taking it and try to consume alcohol, the acetaldehyde will build up in your body and make you sick — a strong negative reinforcement.

And that brings us back to red wine. Here's a little-known fact: The juice from red wine grapes is clear. All the pigment is in the skin, and winemakers create red wine by grinding up some of the skin and mixing it in with the juice (as opposed to white wine, where the skin is discarded). But it turns out the skin also includes a number of other chemicals, including "phenols" and "flavonoids." The never-ending debate about whether drinking wine has health benefits largely revolves around the properties of these other chemicals.

But one of the phenols, called quercetin, has been shown to interfere with ALDH2's ability to convert acetaldehyde. The skin of red wine grapes contains a large quantity of quercetin, so when we drink red wine, we take in both alcohol and a chemical that interferes with our body's ability to process it. Some other types of alcohol contain quercetin, but not nearly as much as red wine. And thus the researchers' hypothesis for what causes "red wine headaches": the quercetin in the wine.

It also turns out that not all red wine grapes have the same amount of quercetin. One of the most significant factors is how much sun the grapes receive while growing on the vine: the more sun, the more quercetin, and the more the wine made with the grapes is likely to cause headaches. The researchers point out that vineyard-management practices have a significant effect on sun exposure for the grapes. The grapevines for higher-end, more expensive wines tend to get pruned back more extensively, which increases sun exposure; and the vines for cheaper, bulk wines tend to grow bulkier and create more shade for the grapes hanging lower on the vine. As a result, more expensive red wines often have more quercetin — which leads to the very strange recommendation that if you are susceptible to red wine headaches, buy cheaper wine.

Wine grapes are not the only produce that contains quercetin; it turns out that onions also contain a significant dose. Onions don't contain alcohol, so eating them alone won't give you a "red wine headache." But if the researchers are right that quercetin is the culprit, eating onions while drinking white wine would leave your head pounding too.

The researchers haven't actually run the experiments that would directly tie the quercetin in red wine with headaches, but at this point, they are proposing it as the most credible hypothesis. The good news is that it's not hard at all to design and run the tests that would confirm it.

One final amusing side note: While there is a neurologist on the research team, the two lead authors are from the Department of Viticulture and Enology at the University of California, Davis, one of the leading academic departments in the world on grape growing and winemaking and the one that gives guidance to California's wine industry. It's notable that the infamous "red wine headache" isn't seen just as a medical issue: Winemakers also want to know why their product sometimes makes their customers sick.

Inhibition of ALDH2 by quercetin glucuronide suggests a new hypothesis to explain red wine headaches

Featured image via Prostock-studio/Shutterstock.com.