Sulfites are natural substances that are used as preservatives in food and wine. They prevent oxidation and the growth of bacteria. Because wine is easily oxidized to vinegar, sulfites are especially important in preserving wine. Sulfites are also used in nuts to prevent them from turning brown from oxidation. Sulfites are naturally produced by the yeast that makes wine, and they are also added by the winemaker. Wine needs sulfite in a dosage of about 35 mg / L to preserve wine, but the law in the US allows wine to have up to 350 mg / L. The human body produces sulfites from protein, so that the average human has more sulfites than an average bottle of wine. Therefore, a small amount of sulfite seems unlikely to cause asthma. However, there are some people who have had asthma attacks from drinking wine.
A study conducted in Australia evaluated 24 people who had had asthma attacks after drinking wine. Only four had asthma attacks when exposed to sulfite, and they only had attacks after consuming high doses of sulfite, close to the legal limit and higher than those found in most wines. This suggests that sulfite is not the main problem, although it can contribute to asthma. So what is the problem?
We do not know for sure. One suggestion is that the bees in the wine are the problem. Another suggestion is that salicylates, which are similar to aspirin, can cause asthma. Oxidized wine contains some acetic acid (vinegar) and acetaldehyde. Also, the liver converts alcohol into acetaldehyde. One study showed that acetaldehyde causes airway constriction and an allergic response in mice. The same study tested in humans an important gene for the breakdown of acetaldehyde in the body. People who have lower levels of this acetaldehyde dehydrogenase, which metabolizes acetaldehyde, have higher levels of acetaldehyde in their body after drinking alcohol. They are also more likely to have asthma attacks after drinking wine. This suggests that, ironically, sulfite might protect some asthmatics from having a bad reaction to wine. Sulfites reduce the oxidation of wine.
Interestingly, some drugs can mimic genetically low levels of acetaldehyde dehydrogenase, and these drugs are used to treat alcoholism. Alcoholics who take these drugs have a bad reaction to alcohol. Some antibiotics and antifungal drugs also inhibit acetaldehyde dehydrogenase and therefore can cause an allergic reaction to alcohol.
