Scientists from the University of California believe they may have finally uncovered the mystery behind why some people experience an intense headache shortly after drinking even a single glass of red wine – despite handling other types of alcohol without issue.
The culprit, according to their findings, isn’t how much you drink, but what’s inside the wine itself – specifically, a natural compound found in red grapes known as quercetin.
Blame the sunshine, not the bottle
Quercetin is a flavanol – an antioxidant compound found in many fruits and vegetables – but in red wine, its concentration increases depending on how much sun the grapes are exposed to. Grapes from sunnier regions like California’s Napa Valley tend to develop higher levels of quercetin, especially those used for premium wines.
Professor Andrew Waterhouse, one of the study’s authors, explains that expensive wines are often made from grapes grown in conditions designed to enhance flavor – which also intensifies quercetin levels. “Cheaper grapes are typically shaded by large canopies, reducing sun exposure,” he says. “Meanwhile, high-end vineyards carefully manage sunshine for maximum quality – and, as a side effect, higher quercetin.”
The paradox of high-end headaches
This leads to an unexpected twist: people who suffer from red wine headaches may actually react worse to more expensive bottles. Though this seems counterintuitive, the connection makes sense once you understand the chemistry.
Once in the body, quercetin itself isn’t harmful. In fact, it’s even sold as a health supplement for its anti-inflammatory properties. But when combined with alcohol, it transforms. The researchers found that one of quercetin’s byproducts interferes with a crucial enzyme called ALDH2 – aldehyde dehydrogenase – which helps the body process alcohol safely.
How alcohol gets toxic
Normally, alcohol is broken down in two steps. First, the liver converts it into a toxic compound called acetaldehyde. Then ALDH2 converts acetaldehyde into harmless acetate – basically, vinegar. But if ALDH2 is blocked or impaired, acetaldehyde builds up in the bloodstream, causing symptoms like headaches, flushing and nausea.
This reaction is similar to what happens in people of East Asian descent who lack a functional version of the ALDH2 gene and are highly intolerant to alcohol in any form.
A centuries-old mystery in focus
Red wine headaches have puzzled scientists for generations. Previously, other potential causes had been considered:
- Sulphites – preservatives in wine, often blamed for adverse reactions. But sulphite levels are generally higher in white wines and are more likely to affect those with allergies rather than cause headaches.
- Histamines – present in greater quantities in red wines than in whites. These compounds dilate blood vessels and can theoretically trigger headaches, although strong scientific proof is lacking.
Now, the focus is shifting to how red wine’s unique chemical mix might disrupt alcohol metabolism itself – particularly through quercetin’s effect on ALDH2.
What comes next?
The California team published their results in *Scientific Reports* after crowdsourcing funding for their research. But so far, the study has only been conducted in the lab. The next step is to test the theory on actual people.
One proposed experiment would involve giving red-wine-sensitive volunteers either a quercetin supplement or a placebo, followed by a standard dose of alcohol like vodka, to see whether headaches develop. Professor Morris Levin, a neurologist and co-author of the study, says they’re preparing for human trials in the near future. “We’re finally making progress on a mystery that’s puzzled people for ages,” he says. “Now we need to prove it in the real world – so stay tuned.”
Still some doubts
Not everyone is convinced quercetin is the only villain. Professor Roger Corder, a wine and therapeutics expert at Queen Mary University of London, believes other components used in wine production – particularly in mass-market reds – deserve scrutiny.
He points to the use of additives like:
- Pectinases – enzymes that release color from grape skins but also produce methanol, a potential headache trigger.
- Dimethyl dicarbonate – a preservative commonly used in bulk wines, which also breaks down into methanol during bottling.
With so many variables in winemaking, isolating one universal cause of headaches is tricky. But the latest research opens new avenues that could finally provide relief for those who love red wine – but dread the consequences of a single glass.
