The reason for 'red wine headaches' is revealed

Researchers in the United States say they may have cracked why some people get a headache after just one small glass of red wine, even though they are fine drinking other types of alcohol. It’s all down to a natural “sunscreen” molecule made by red grapes called “quercetin”. Professor Andrew Waterhouse is from the University of California Davis.

Andrew - So I was talking to a winemaker in Napa Valley and he was having trouble with wine headaches and I said, 'you know, I think one possibility is there's a compound in wine that causes vasorelaxation and that's known to cause some headaches.' And he said, 'oh, that doesn't cause real serious headaches. It's an inflammatory response that gives serious headaches.' That was a bit deflating, but after thinking about how we get inflammation when people drink wine, I thought of this situation where some people, mostly East Asians, when they drink they get a flushing reaction and that's inflammatory. Their skin turns red. And so I started looking into whether those folks get headaches? And it turns out they do. Then I looked into how this happened? How do these people get this inflammatory response and this flushing? And it turns out they have an enzyme used to clear acid aldehyde, which is a normal metabolite of alcohol. So when you consume alcohol, it's broken down in two steps. First is acetaldehyde, which is somewhat toxic. And then we have a second enzyme that quickly clears it. Problem is for those folks who get flushing, the second enzyme does not work well. So is it possible that something in wine could be blocking that second enzyme?

Chris - Does that mean then that something in the wine can inhibit the removal of the acetaldehyde, which is the first thing that alcohol gets broken down to in the body, so that that builds up to a level that would be higher than normal. And that's what gives people a bright red face and a tendency or preponderance to get a headache in the aftermath with some red wine?

Andrew - Exactly. The approach I took was to say, okay, since I've worked on wine chemistry for 30 years, I have, in the back of my head, a pretty good inventory of what's in red wine that's different from white wine. So I started looking through that list of compounds to see if any of them have been reported to inhibit the enzyme. And that's when I stumbled upon quercetin. Quercetin is much higher in red wine than in white wine. Levels are tenfold or greater.

Chris - It's in the skin, isn't it?

Andrew - Yes, the grapes produce it in response to sunlight. It's like sunscreen for grapes. It just happens to block the metabolic process and lead to accumulation of acetaldehyde. So what we did actually for our experiment was we simply got this enzyme and tested a series of wine phenolics to see if they would inhibit the enzyme. And it turns out a specific metabolite of quercetin inhibits it very well.

Chris - Does that mean then you drink this stuff, it gets metabolised in your body into the thing that inhibits the enzyme? Or does it just do it without any further metabolism in the body? Is it a direct inhibitor there from the get-go?

Andrew - There's a little bit of a nuance here. When you consume quercetin into your body, your body converts most of it to quercetin glucuronide. It's a metabolite form that helps your body clear it from your system.

Chris - And in the process of trying to clear it, you actually effectively activate or enhance the inhibitory effects. So you need a little while to metabolise your red wine. And then it starts to become more potent as a way of making you have a headache. So does that mean then that the more red wine I drink, the more likely I am to get a headache, but not just because I'm boozing, but because I'm building up this metabolite and any alcohol I've then consumed is gonna contribute to this mix?

Andrew - Well I don't recommend drinking a lot, but the occurrence of a headache, everyone doesn't experience that. So some people get a headache as soon as they start drinking red wine and some never do. So we're not sure how to explain that. I mean we presume that there's obviously a difference in their metabolic systems, but the details of course are going to take more research

Chris - Given that you've identified and you can point the finger at at least one causative molecule that does this. I'm staring at a cheeky little French Côtes du Rhône. Is that as bad as say one of your Napa Valley wines or are all red wines made equal? How are you going to take this forward?

Andrew - Well, it turns out that because the grapes produce this in response to sunlight, winemakers can actually modify the levels by adjusting the amount of sun the grapes experience. One of the problems with reducing sun exposure is that a certain amount in fact enhances the quality of red wine. And if you look in famous vineyards, you'll see that the vines are relatively small and often, or most of the time, you can see the grapes. And since you can see the grapes, the sun can see the grapes and the grapes get exposed directly to some sunlight. On the other hand, very inexpensive wine generally comes from very large vines, which have a lot of shade over the fruit. They need all that, all those leaves, to produce enough sugar to ripen the fruit because they usually have a large crop. So the only advice I can give you today is that less expensive wines are most likely going to have less of the quercetin in its various forms.

Chris - So can you share with us your favourite tipple as a wine chemist? You must have one that you are prepared to put your name behind, either extremely worth the headache or one that definitely doesn't go headache positive.

Andrew - Oh boy. In California there's a wine company that makes some very nice Zinfandels. And I like Zinfandel because it's sort of the iconic California grape. And there's a company called Ridge that has been making very good Zinfandels for about 50 years. And so if I was going to recommend one wine, I would say a California Zinfandel and I believe you might even be able to find that brand in UK wine shops.