What causes the “red wine headache”? Is it sulfites? A histamine reaction? Andrew Waterhouse, Professor Emeritus of Enology in the Department of Viticulture and Enology at UC Davis and Apramita Devi, Postdoctoral Scholar in the Department of Viticulture and Enology at UC Davis have identified a flavanol that can interfere with the metabolism of alcohol. That flavanol is quercetin, a natural product made in grape skins in response to sunlight. It is a natural sunscreen produced to protect the fruit from ultraviolet light.

This conversation covers why quercetin may be more prevalent in high end wines, how skin contact during wine production impacts quercetin levels, and why sulfites may play a role in “red wine headache”.

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Transcript

[00:00:00] Beth Vukmanic: What causes. The red wine headache? Is it sulfites or a histamine reaction?

[00:00:10] Welcome to sustainable wine growing with the vineyard team. Where we bring you the latest in science and research for the wine industry. I'm Beth Vukmanic executive director. I've been your team. Since 1994, we've brought you the latest science-based practices, experts growers and wine industry tools through both infield and online education. So that you can grow your business. Please raise a glass. With us as we cheers to 30 years.

[00:00:37] In today's podcast, Craig Macmillan, critical resource. Manager at Niner wine estates with long time sip certified. Vineyard and the first ever sip certified winery. Speaks with two university of California Davis researchers. Andrew Waterhouse. Professor emeritus of enology and the department. of, viticulture and enology. And. Oprah meta Debbie. Post-doctoral scholar and the department of viticulture and enology.

[00:01:04] They have identified a flavonol that can interfere. With the metabolism of alcohol. And that flavonol is called quercetin. A natural product made in the grape skins in response. To sunlight. It's a natural sunscreen produced to protect. The fruit from ultraviolet light. This conversation covers. Why quercetin may be more prevalent in high end wines. How. Skin contact during wine production impacts quercetin levels. And why sulfites may still play a role in that red wine headache.

[00:01:36] Want to be more connected with the viticulture industry. But don't know where to start become a vineyard team member. Get access. to the latest science-based practices, experts, growers, and wine industry. The tools. Through both infield and online education so that you. You can grow your business. Visit vineyard team.org. And choose grower or business to join the community today.

[00:01:57] Now let's listen. in.

[00:02:01] Craig Macmillan: Our guests today are Andrew Waterhouse, Professor Emeritus in Enology in the Department of Viticulture Davis, and also Aparmita Devi. She is a postdoctoral scholar, also in the Department of Viticulture & Enology Davis. Thank you both for being here.

[00:02:17] Andrew Waterhouse: Oh, we're glad to be here.

[00:02:19] Craig Macmillan: Today we're going to talk about a really interesting topic. It's the role of quercetin , in wine headaches. The two of you recently co authored a paper on this one particular mechanism that might cause some people to get a headache after drinking even a small amount of red wine. But before we get into that, I want to ask you, how did you get interested in this topic?

[00:02:37] Andrew Waterhouse: Well I've been talking to Steve Mathiasson. He's a Napa winemaker for actually quite a while, some years back. He suffers from headaches when he drinks certain wines. And we were chatting about possible mechanisms, and we even did a study many years ago with another postdoc in my lab to investigate a question we had or a theory we had, and that didn't pan out. But more recently we were chatting again, and I got interested in the topic again, and that's what got me interested, you know, just somebody knowledgeable who was suffering from headaches and. for listening. It was, it makes it more real and it's like, well, maybe we can figure something out. So that's what got us started.

[00:03:17] Craig Macmillan: Apramita , how same for you.

[00:03:19] Apramita Devi: Yeah. Same. Like I've been in touch with Andy and we have been talking about this project many years. So I was always interested because I come from biological science and metabolism and stuff I got interested after talking to Andy.

[00:03:33] Craig Macmillan: Well, let's start with some basics. What is quercetin?

[00:03:38] Andrew Waterhouse: Well, basically, it's a natural product made by grapes, but it's a very specific one. It's in the class of polyphenolic compounds, and it's in the class of flavonoids called flavonols. And what makes it interesting, I think, is that it is made By grapes, in the skin of the grape, and only in the skin of the grape, in response to sunlight. It's sometimes referred to as sunscreen for grapes. And it specifically absorbs UV light that would cause damage to, say, DNA and other macromolecules. So it's very clear that the grapes are producing this in order to protect themselves from ultraviolet light.

[00:04:22] Craig Macmillan: Right.

[00:04:22] Andrew Waterhouse: So the amount that's present in wine is highly dependent on the amount of sunlight the grapes experience. Not the vine, but the grapes themselves, And a friend of mine, Steve Price, was the first to note this. In a study way back in the 90s on Pinot Noir, he noted that there was more quercetin in sun exposed Pinot Noir grapes. And that observation has been confirmed many times now in different studies. where sun exposure is correlated with quercetin levels.

[00:04:58] Craig Macmillan: and this is true just for red grapes as opposed to white grapes.

[00:05:02] Andrew Waterhouse: Oh, no, no, there's more in white grapes. But when you make white wine, you throw away the skins. So there's no opportunity to get those materials into the wine. Now, an exception might be orange wine. But I don't know of any data on orange wine.

[00:05:21] Craig Macmillan: Apramita , maybe you can talk about the metabolism part, the biology part. So when people consume alcohol, it's metabolized down certain pathways. Quercetin is also metabolized by the body into other forms?

[00:05:33] Apramita Devi: Yeah, so the pathway for alcohol and quercetin are a bit different, but the location is liver, where it goes. So when people consume alcohol, it goes to the liver and then there are two enzymes which work on the alcohol. So the first enzyme is alcohol dehydrogenase, which convert it into alcohol into acetaldehyde. The acetaldehyde is the like the toxic metabolite in the body and it can have many side effects. That's why body has to get rid of it out of the liver system. So it has a second enzyme which is called the acetaldehyde dehydrogenase. So that convert acetaldehyde dehydrogenase into a non toxic component, which is acetate or acetic system.

[00:06:24] So it comes out of ...

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