Sulfites or sulfur dioxide is a fruit preservative widely used in dried fruits as well as wine. It is also produced by the human body at the level of about 1000 mg (milligrams) per day. Consumption of food preserved with sulfites is generally not a problem except for a few people who are deficient in the natural enzyme to break it down. For these people, the additional sulfites from food can be a problem. There are reports of severe and life threatening reactions when sulfites were added at erroneously and enormously high levels (100 times what was supposed to be used!) on salad bar vegetables. I have found two reviews of the medical effects of sulfites-unfortunately I could find neither on-line as they appear to be too old. They should be available at medical school libraries.
AF Gunnison and DW Jacobsen, Sulfite hypersensitivity. A critical review. CRC Critical Review in Toxicology, 17: 185-214 (1987). CRC Journals
R.K. Bush, S.L. Taylor and W. Busse, A critical evaluation of clinical trials in reactions to sulfites, J. Allergy Clin. Immunol. 78:191-202 (1986). J. Allergy Clin Immunol
The levels in wine average 80 mg/liter, or about 10 mg in a typical glass of wine, with slightly higher amounts in white versus red. A number of studies show reactions by sensitive patients to drinking wine with sulfites, but it appears that their reactions are also caused by other components. For details on this issue see this review: A.T. Bakalinsky, Sulfites, Wine and Health, in Wine in Context: Nutrition, Physiology, Policy, A.L. Waterhouse and R.M. Rantz, Eds. American Society for Enology and Viticulture, Davis, 1996. (Publication List)
The medical literature has virtually no reports on sulfites inducing headache. There are many studies of sulfites and asthmatic responses, and a few of these address sulfites in wine. A few studies from Australia shows that even with extremely sensitive people, there is only an asthmatic response in a small number of sensitive subjects (4 out of 24) for a single drink (150 ml) at extremely high sulfite levels-300 mg/liter or 45 mg. No effects were seen at lower levels, such as 150 mg/liter, or with several increasing doses up to 750 mg/liter! See H Valley and PJ Thompson, Role of sulfite additives in wine induced asthma: single dose and cumulative dose studies, Thorax 56:763-769 (2001). Link
There are many erroneous ideas about sulfites, so to put the record straight:
- All wines contain sulfites. Yeast naturally produce sulfites during fermentation so there is only a rare wine which contains none.
- The US requires a "sulfite" warning label and Australia requires a label indicating "preservative 220," but nearly all winemakers add sulfites, including those in France, Italy, Spain, Australia, Chile, etc etc. So, the wine you drink in foreign countries contains sulfites, but you just are not being warned about it when purchased abroad. Survey studies show that European wines contain an average of 80 mg/L sulfites just as in the US.
- There are a few (very few) winemakers who make wines without adding sulfites. In the US, organic wine must be made without added sulfites. These are unusual because the wine is very perishable and often have unusual aromas from the aldehydes that are normally bound and rended aroma-less by the sulftes. Look for these wines at natural food stores.
- There is no medical research data showing that sulfites cause headaches! There is something in red wine that causes headaches, but the cause has not yet been discovered. Refer to the Bakalinsky article above. To avoid these common headaches, try drinking less wine, and drink with food. If you think sulfites are causing your headache, try eating some orange-colored dried apricots, and let me know if that induces a headache. If not, sulftes are not the likely culprit. These bright colored dried fruits typically have 2000 mg/kg sulfites, so a two ounce serving (56 gm) should contain about 112 mg sulfites. It is certainly possible that sulfites cause headaches, but as noted above, there is no data available. Feel free to send a memo to the NIH suggesting this be the target of future research so the question can be addressed.
So, if you feel that you are so afflicted and you are willing to go on a verified list of potential subjects of a scientific study, please send me a note that includes your postal address, daytime phone, and a statement of your willingness to be a participant in a future study to email@example.com. Anonymous letters of complaint will be promptly deleted. This personal information will NOT be posted in the internet. I will keep this in a list for medical researchers interested in such a study. Just so you know, your note will NOT be a legal document and any future study on human subjects will include many more documents explaining the nature of any study in which you may participate as well as the risks, etc., and you will have ample opportunity to back out if you have concerns about the study.
- In the US, the law states that
- Wines cannot contain more than 350 mg/liter sulfites
- Wines with more than 10 mg/liter must have a "Contains Sulfites" warning label
- Producers must show levels below 10 mg/liter by analysis to omit the label
- Wines must have less than 1 mg/liter to have a label that says "No Sulfites"
- This level must be shown by analysis
- All wines must carry the label whether made in the US or abroad
- Still want to get rid of sulfites? In theory, you can remove sulfites by adding hydrogen peroxide to your wine. I don't recommend it but I mention it only because I keep getting asked how to do this. The correct amount to add will depend on the sulfite level in the wine, an amount you cannot deduce except by chemical analysis. However, for the typical wine at 80 mg/L sulfites, 1 milliliter of 3% hydrogen peroxide, the form sold in pharmacies, will remove the sulfites in one bottle of wine. If you want to learn more, there is a study of the reaction between sulfite and hydrogen peroxide in simple water solutions: M.R. Hoffman and J.R. Edwards, Kinetics of the Oxidation of Sulfite by Hydrogen Peroxide in Acidic Solution, J. Phys. Chem. 79: 2096 (1975) Link Hydrogen peroxide has been used to remove sulfites from cucumbers and dried fruit. Ozkan, M; Cemeroglu, B. 2002. Desulfiting dried apricots by hydrogen peroxide. JOURNAL OF FOOD SCIENCE 67 (5): 1631-1635. McFeeters, RF. 1998. Use and removal of sulfite by conversion to sulfate in the preservation of salt-free cucumbers. JOURNAL OF FOOD PROTECTION 61 (7): 885-890.
- Every 5 years or so a M.D. asks me if I want to collaborate on wine headaches, but there is no funding for such research. So, if anyone wants to support a Master's student research project on the topic of wine headaches ($50K) we can start to investigate.
- Not sure if I know what I am talking about. A story in the WSJ by Lettie Teague.