“Wine is synonymous with pleasure, yet it’s a source of pain for many frustrated drinkers. Allergic reactions, including headaches, skin rashes and runny noses, affect as many as 8 per cent of wine drinkers, according to some estimates.
Now, recent news out of Denmark could spell hope for many sufferers. Scientists have isolated molecules in wine that may be the source of a large number of these allergies. And here’s the twist. They are substances unrelated to such usual – and often falsely accused – suspects as sulphites, tannins and pesticides. The discovery could lead to new winemaking techniques that would reduce or remove the culprit molecules, ushering in an era of headache-free merlots and pinot grigios for those with sensitivities.
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Giuseppe Palmisano and his colleagues report in the Journal of Proteome Research that substances called glycoproteins – proteins coated with sugars – could be at the root of many wine allergies. Similar molecules in latex, ragweed pollen and olives have been shown to provoke nasty bodily reactions, but Dr. Palmisano believes that he is the first to identify potentially allergenic glycoproteins specific to wine.
“This discovery has a real clinical outlook,” he told me over the phone from Denmark. However, he stressed that that clinical trials, which are beyond his current scope, could be a long way off.
The son of a winemaker in southern Italy, Dr. Palmisano chose a chardonnay from his native region of Puglia for the study. After isolating 28 glycoproteins in the white wine, he compared them against a database of known allergens. Bingo: Several proteins were bonded to their sugars at roughly the same site in the amino-acid sequence as known allergens. (Proteins are chains of amino acids, and the location of the sugar bond in glycoproteins largely determines their cellular function.)
Alas, it won’t help allergy sufferers simply to steer clear of chardonnay. Dr. Palmisano has now turned his attention to other grapes, both red and white from various regions. He suspects that he will find much the same result. That hunch is based in part on the fact that certain glycoproteins, such as those identified in the study, are considered weapons in a plant’s defensive mechanism – irritating substances designed to fight off pathogens. Grapevines can’t run from or physically overpower invaders, so they must wage a biological war. It stands to reason, then, that all vine varieties possess a substantial glycoprotein arsenal.
The discovery not only offers hope for allergy sufferers, but also may help to demystify common misconceptions about adverse wine reactions. I regularly get letters from distressed sufferers asking about organic brands. They’re convinced that pesticides or sulphites are to blame for their headaches and sniffles.
The threat from those substances is highly exaggerated. In quality wines, pesticides and herbicides are used sparingly, and most are cleansed during fermentation. For example, 99.8 per cent of wines sold through the Liquor Control Board of Ontario, which screens every product, contain no detectable pesticide and herbicide residues, says George Soleas, the LCBO’s senior vice-president for logistics and quality assurance. The tiny remainder has levels thatare far below federal limits. That said, organic farming is friendlier to the environment, ensuring a healthier vineyard ecosystem that can, in some cases, yield better-tasting wines.
As for sulphur, found naturally in wine but also commonly used in the form of sulphur dioxide as an antiseptic and an oxygen barrier during production, its risk to health is overblown too. Those ominous wine-label warnings – “contains sulphites” – are intended mainly for a minority of asthmatics. About 5 per cent of asthmatics are severely sensitive. Keep in mind that a serving of dried fruit, such as apricots, generally contains far more sulphur than a glass of chardonnay.
Tannins, the antioxidants found in skins, seeds and stems of grapes as well as wood barrels, can indeed be problematic for certain headache sufferers. But tannins also are found in tea and walnuts, and few people complain of migraines after a cup of Red Rose or serving of Waldorf salad. If you suffer after a glass of white wine but not red, sulphur, not tannins, should be your more likely suspect because white wine is generally not fermented on its skins and seeds and contains far less tannin.
And there are probably many people who simply can’t tolerate alcohol. The test is simple. If you react badly after vodka or beer as well as wine, you can rule out just about everything else.
As far as the Denmark discovery goes, there are, alas, no extrapolations that can be made yet about which grapes or styles may be more benign than others, if any. But Dr. Palmisano, whose main work involves studying how glycoproteins change in breast-cancer progression, is optimistic about the prospect of allergen-reduced wines. He has begun working with a producer in his hometown of Turi to determine in principle whether his suspected glycoproteins can be removed from wine without significantly altering flavour. “If we know the culprit, we should be able to treat it or remove it,” he said. “We want to improve the quality of wine and the quality of life of allergic people.”