Source of red wine headaches could be chemical

Medical accounts of red wine headaches date back to Roman times, but the experience is probably as old as winemaking – around 10,000 years.

As chemists specializing in oenology, we wanted to try to understand the origin of these headaches.

Many components of red wine have been blamed for these woes: sulphites, biogenic amines and tannins are the most popular. Our research suggests that the most likely culprit is one you may not have considered.

Common suspects

Sulphites have become a popular scapegoat for all kinds of illnesses since it became mandatory in the 1990s to label them on wines in the United States.

However, little evidence directly links sulfites to headaches, and other foods contain levels comparable to wine without the same effects. White wines also contain the same amount of sulfites as red wines.

Your body also produces about 700 milligrams of sulfites per day when you metabolize proteins in your food and excrete them as sulfate. It does this by containing compounds called sulfite oxidases that create sulfate from sulfite—the 20 milligrams in a glass of wine are unlikely to overwhelm your sulfite oxidases.

Some people point the finger at biogenic amines for red wine headaches. These are nitrogenous substances found in many fermented or spoiled foods and can cause headaches, but their amount in wine is far too small to be a problem.

Tannins are a good guess, since white wines contain only small amounts of them, while red wines contain substantial amounts. Tannin is a type of phenolic compound: it is found in all plants and generally plays a role in preventing disease, resisting predation, or promoting seed dispersal by animals.

But there are many other phenolic compounds in the skin and seeds of grapes, in addition to tannins, which are part of the composition of red wines from the winemaking process and which are not present in white, so any of them could be a potential culprit.

Tannin is also found in many other common products, such as tea and chocolate, which generally do not cause headaches. And phenolic compounds are good antioxidants: they are unlikely to trigger the inflammation that would cause a headache.

A hunt for red wine

Some people experience red, flushed skin when they drink alcohol, and this redness is accompanied by headaches. This headache is caused by a metabolic delay when the body breaks down alcohol.

Alcohol metabolism occurs in two stages. First, ethanol is converted to acetaldehyde. Next, the ALDH enzyme converts acetaldehyde into acetate, a common and harmless substance.

This second step is slower for people who have reddened skin, because their ALDH is not very effective. They accumulate acetaldehyde, a somewhat toxic compound also linked to hangovers.

So if something unique in red wine could inhibit ALDH, slowing down this second metabolic step, would it lead to higher acetaldehyde levels and headaches? To try to answer this question, we went through the list of phenolic compounds abundant in red wine.

We found an article showing that quercetin is a good inhibitor of ALDH. Quercetin is a phenolic compound found in the skin of grapes. It is therefore much more abundant in red wines than in white wines, because the skins of red grapes remain in place longer during the fermentation process than the skins of white grapes.

Putting enzymes to the test

Testing ALDH was the next step. We set up an inhibition test in test tubes. In the test, we measured the rate at which the ALDH enzyme breaks down acetaldehyde. Then we added the suspected inhibitors – quercetin, as well as other phenolic compounds we wanted to test – to see if they slowed the process.

These tests confirmed that quercetin was a good inhibitor. Some other phenolic compounds had varying effects, but quercetin glucuronide was the winner. When your body absorbs quercetin from food or wine, most of it is converted to a glucuronide by the liver to quickly eliminate it from the body.

Our enzymatic tests suggest that quercetin glucuronide disrupts the metabolism of alcohol in your body. This disruption leads to additional circulation of acetaldehyde, causing inflammation and headaches. This discovery highlights what is called a secondary or synergistic effect.

These side effects are much more difficult to identify because two factors must both be at play for the outcome to occur. In this case, other foods containing quercetin are not associated with headaches. So you may not initially consider quercetin as the cause of the red wine problem.

The next step might be to give human subjects two high-quercetin and low-quercetin red wines and ask them if either wine causes headaches. If quercetin-rich wine causes more headaches, we’d know we’re on the right track.

So, if quercetin causes headaches, are there red wines without it? Unfortunately, the data available on specific wines is far too limited to provide useful guidance.

However, grapes exposed to sunlight produce more quercetin, and many inexpensive red wines are made from grapes that receive less sunlight.

If you’re willing to take a chance, look for an inexpensive, lighter red wine.

Andrew Waterhouse, professor of enology, University of California, Davis and Apramita Devi, postdoctoral researcher in food science and technology, University of California, Davis

This article is republished from The Conversation under a Creative Commons license. Read the original article.