By David Jammalo - July 22, 2023
The use of sulfites has been a contentious subject for some people. However many facts are misunderstood.
What are sulfites and why are they in wine?
What are the facts about the health effects?
Do European wines have sulfites?
First, as a disclaimer, I am a winemaker and not a qualified physician. This information does not constitute health advice. I am qualified as an educated winemaker and not an expert in chemistry or health. So take it as just a way of expanding knowledge about the industry. But I give factual references so the information is scientifically verified.
What are sulfites and why are they in wine?
I’ll start with the first question. Sulfites (or Sulphites) are actually various forms of sulfur dioxide (SO2). When wine yeasts (s. cerevisiae) ferment grapes into wine, they expel tiny amounts of SO2 as part of their metabolism(1). So young wines almost always have SO2 with levels typically from less than 10 parts per million (ppm) to more than 100, but typically it is less than 30 ppm.
How much is a ppm? To visualize 1 part-per-million, it is about 1 inch in 16 miles, 1 minute in 2 years, or 2.5 liters in an Olympic swimming pool.
Wine yeast have evolved through the millennia to out-compete and dominate the other native microbes by excreting alcohol and SO2. SO2 acts as an antimicrobial agent, however the yeast are not inhibited by these small amounts they generate.
Two Benefits of Sulfites in Winemaking
As an antimicrobial, SO2 can be added in the winemaking process to inhibit spoilage microbes and encourage the beneficial microbes: those that make our delicious wines. Many wineries have modern practices that minimize the need for excessive SO2 additions. These additions can range from none (in some organic wine), or up to the legal limit of 350 ppm in the United States(2). But most industry members only need to add 25-35 ppm SO2 in order to maintain the quality.
One tool winemakers use to reduce the use of SO2 is to maintain a lower pH so the wine becomes self-preserving without excess SO2. SO2 becomes exponentially more effective in higher acid wines like Sauvignon Blanc or Riesling (wines with a low pH)(3). Another tool is filtration at the time of bottling so that the vast majority of microbes are removed before it is sold.
SO2 is also an antioxidant. It sequesters compounds that prematurely age wines in a negative way. Small amounts of SO2 added at bottling, even about 10 ppm, can add years to a wine's aging potential.
European Wines Don’t Have Sulfites: Myth
First of all I want to dispel a common myth that European wines have no sulfites. “Many” European wineries do add sulfites. Not all, but many do. It is a common misinterpretation of the labels from Europe. There is simply no European regulation that requires them to state “contains sulfites” on the label. I am speaking of wines that are only sold IN Europe, not imported into the U.S.
I’ve personally heard people tell me they don’t get headaches from Italian wine because they don’t add sulfites. There is a lot of confusion on this topic.
Why do most domestic wine labels have the statement “CONTAINS SULFITES”, whereas wines in Europe do not? (Imported wines sold in the U.S. do indeed have the statement on the label). This statement is a Federal TTB regulation for consumer protection. But there is a historical reason for it in the U.S.: The Salad Bar incident.
Fast food restaurants back in the 1980’s were adding extremely high amounts of SO2 to keep the fresh vegetables from browning, estimated to be about 10,000 ppm. That is like taking 200 aspirin tablets per dose. It was done by inexperienced staff without proper training or instruction. Over time 13 people died from excessive SO2 in these cases (see “Sulfites in the Salad Bar”(4)).
Laws were passed to stop the practice altogether in restaurants, but remained as a warning statement on wine bottles, even though the wine legal limits are exponentially less. The United States is the only country in the world that requires this warning statement.
Organic Wines: Wineries that choose to add no SO2, like organic wine, can claim statements like “No Sulfites Detected” on the label among a few others(3).
Health Effects & Allergies
A true sulfite allergy is also commonly misunderstood. When some wine drinkers complain of sulfite headaches, they most probably have a sensitivity to higher concentrations of SO2, or other compounds naturally occurring in grape wine, like histamines(5).
Let's discuss allergies first. There are very few people that have allergies to sulfites. Those who do lack the digestive enzyme sulfite oxidase and therefore cannot metabolize sulfites. Our own bodies produce about 1000 ppm of SO2 every day as a part of metabolism. Many people born with a true sulfite allergy have chronic issues or never even survive beyond the first year of life, because our own bodies produce much higher quantities than what is legally allowed in wine(5).
That brings us to sensitivity. Some people are much more sensitive to white wines than reds, and some are vice versa. So what is going on? People that are sensitive to sulfites include people who suffer from asthma. This is a very real and valid concern for those who consume wine containing higher levels of SO2. It can actually be dangerous for those asthmatics in rare cases.
For the majority of wine drinkers and wines, SO2 is barely or completely undetectable. But is this really true? It depends on the wine and the winemaker.
In general red wines have and use less SO2 for long term stability when the tannins are higher (think Napa Valley Cabernet). Tannin from the seeds and skins provide natural protection against oxidation (and aging). White wines don’t have tannin, so sometimes winemakers add a bit more SO2 for protection against aging (think antioxidant). But then again, some bright acidic white wines need a lot less SO2 for the same protection. So it depends on many factors.
Final Thoughts on Sulfites
Sulfites in wine are a natural byproduct from fermentation. It generally exists in minute quantities and, according to the FDA, is generally regarded as safe(6). It has been used since the Roman Empire as a preservative that allowed wines to last and age while avoiding spoilage.
The natural end state of grape wine is vinegar, unless humans intervene and provide methods of protection. For thousands of years and with modern winemaking techniques, SO2 is still the best compound of choice that helps winemakers keep oxidation away from wine, and judicious use of minute quantities helps preserve the quality. Some winemakers claim it enhances freshness and fruitiness.
A final tip: sulfites are volatile. If your wine is younger than about 5 years, open it and pour it while you splash. Swirl it - not just to look fancy - there’s a purpose for the swirl. Decant it and let it breathe a bit by exposing it to the air. All these actions help dissipate the sulfites and aeration improves the aromas.
When we put these myths and facts in perspective when discussing sulfites as it relates to wine, we become better informed about the beverage we love.
(1) Rankine, B.C. and K.F. Pocock. 1969. Influence of yeast strain on binding of SO2 in wine and on its formation during fermentation. J. Sci. Food and Agric. 20. pp. 104-109. Eschenbruch, R. 1974. Sulfite and sulfide formation during winemaking - a review. Am. J. Enol. and Vitic. 25:3, pp. 157-161.
(2) TTB Federal Code of Regulations: Title 27 CFR 4.22(b)(1)
(3) TTB Federal Code of Regulations
(4) The Washington Post
(5) The Regents of the University of California 2007,Lesson 7: Fermentation & Aging: Sulfur Dioxide (SO2) Topic 7.2: Health and SO2 Sensitivity
(6) Select Committee on GRAS Substances (SCOGS) Opinion: Potassium metabisulfite, sodium bisulfite, sodium metabisulfite, sodium sulfite, sulfur dioxide