Researchers in the United States say they may have discovered why some people get headaches after just a small glass of red wine, even though they have no problems when they consume other types of alcoholic beverages.
The team from the University of California says the reason is a compound present in red grapes that can interfere with the metabolism of alcohol.
That compound is an antioxidant or flavanol called quercetin.
Cabernet from sunny Napa Valley contains a high concentration of quercetin, experts say.
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High quality grapes
Red grapes make more quercetin when exposed to sunlight.
This means that more expensive, rather than cheaper, red wines would be worse for people prone to headaches, one of the researchers, Professor Andrew Waterhouse, told the BBC.
"Cheap grape varieties are grown on large vines with lots of leaves, so they don't get much sun," he said.
"On the other hand, high-quality grapes are obtained from a smaller yield with fewer leaves.
"Great attention is paid to the amount of sun the grapes receive in order to improve the quality of the wine".
Others, however, express doubt.
Professor Roger Corder, an expert in experimental therapeutics at Queen Mary University of London, told the BBC that based on consumer experience, cheaper wines cause worse headaches, so understanding certain additives used in lower-end consumer red wines could provide additional data.
A possible culprit
There are several theories to explain red wine-related headaches that can occur 30 minutes after consuming even a small amount.
Some believe that the cause could be sulfites - preservatives used to extend the shelf life and maintain the freshness of wine.
However, usually the concentration of sulfites is higher in sweet than in red wines.
And while some people may be allergic to sulfites and should avoid them, there is little evidence that they cause headaches.
Another possible culprit is histamine, which is more commonly found in red than white or rosé wines.
Histamine can cause blood vessels in the body to dilate, which can cause headaches. But there is no reliable evidence for this either.
A toxic compound
Experts know that more than one in three people of East Asian descent are intolerant to all types of alcohol - beer, wine and hard liquor - and that drinking alcohol causes flushing, headaches and nausea.
The reason for this is a gene that affects the work of an alcohol-metabolizing enzyme called aldehyde dehydrogenase ALDH2.
The breakdown of alcohol in the body takes place in two steps - alcohol is converted into a toxic compound called acetaldehyde, which is then converted by ALDH2 into harmless acetate, basically vinegar.
If this process cannot be done, harmful acetaldehyde builds up and causes symptoms.
According to the researchers, the same thing happens when a headache occurs due to the consumption of red wine.
In the laboratory, they showed that quercetin can indirectly block the work of ALDH2, through one of its own metabolites.
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'Stay tuned'
Quercetin is only problematic when mixed with alcohol, say researchers who crowdfunded their work and published their findings in the journal Scientific Reports (Scientific Reports).
Quercetin is also found in many other fruits and vegetables - and is even available as an anti-inflammatory supplement - and does not cause headaches on its own.
Researchers have yet to prove this theory in humans.
A simple trial could be conducted by giving volunteers prone to red wine headaches a quercetin supplement or a neutralizing pill, along with a regular glass of vodka.
Co-author, prof. Maurice Levine, a neurologist and director of the Headache Division at the University of California, San Francisco, said: "We are finally on the right track to explaining this millennium-old mystery. The next step is scientific testing on people who experience these headaches, so stay tuned."
They hope to start trials in a few months.
But prof. Korder, who studied the possible health benefits of wine, believes that other ingredients should be investigated as possible causes of headaches:
- Pectinases (a group of enzymes) enhance the extraction of anthocyanins, thus speeding up the process of obtaining the color of the wine, without the slow maceration that is applied in the traditional way of making wine, but they are hydrolases and the side product of their action is methanol.
- Dimethyl dicarbonate is used as a preservative in cheaper wines, especially those transported in large tankers to the UK for bottling, but it also breaks down to methanol on dissolution.
Consuming large amounts of alcohol, drinking quickly, or drinking to get drunk can have serious short- or long-term health consequences.
- Regular consumption of more than 14 units of alcohol per week - about six pints of medium-strength beer or 10 small glasses of light wine, regardless of the type of alcohol - can cause liver damage and other health problems, including strokes and heart disease.
- Alcohol causes seven different types of cancer - the risk increases with each drink.
About one in 10 cases of breast cancer is caused by alcohol consumption - about 4.400 per year in the United Kingdom.
You can also watch this video: Zrenjanin - a town without drinking water with a long tradition of brewing beer
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