There are a lot of myths about what these preservatives do and don't do.

By Marie Viljoen
September 18, 2019
Janelle Jones

There's a lot of confusion around sulfites. Many people have concerns about how they impact health or if they cause allergies or headaches, among other wellness issues. Furthermore, few people understand which foods and drinks they are added to and which they are naturally occurring in. We'll set the record straight: Sulfites have been used in the U.S. since the 1800s and are "generally regarded as safe" (GRAS) by the Food and Drug Administration. However, the FDA estimates that about one percent of the U.S. population is sensitive to sulfites. People affected by sulfites in food (as well as those in cosmetics and pharmaceuticals) may be those with an existing asthmatic condition; adverse reactions to sulfites in non-asthmatics are considered rare. Symptoms of an allergic-type response to sulfites include hives, swelling, and difficulty breathing.

Here, we take a closer look at what sulfites are, where they're most commonly found, and how to handle a sensitivity to them.

Related: What You Need to Know About Natural Wine

What Are Sulfites?

Sulfites are inorganic salts that have antioxidant and preservative properties. They occur in foods naturally or as deliberate additions. The term sulfite is a catch-all that encompasses sulfiting agents, which are other compounds that are capable of producing sulfite. These include sulfur dioxide, sodium sulfate, sodium and potassium bisulfites, and metabisulfites.

Sulfites in Food and Drink

It's not generally understood that sulfites occur naturally in some foods, but the simple fact is that they are a normal and unavoidable by-product of fermentation and are present in wine, beer, cider, black tea, and vinegar, as well as other fermented foods, like cheese and pickles. Added sulfites are used in food and drink to make products more attractive, to preserve their freshness, or to prevent them from spoiling. Perhaps the best-known use of sulfites is in wine-making. Because they are fermented, all wines contain natural sulfites. Sulfite-free wines do not exist, although the levels in organically-made or natural wines may be very low. Sulfites are often added to arrest fermentation and to prevent spoilage (especially in white and sweeter wines). In the U.S., wine is allowed to contain sulfites at less than 10 parts per million (ppm) without a warning label. But since 1987, if wine contains sulfites at levels between 10 ppm and 350 ppm, legislation dictates that the wine must be labeled as "contains sulfites." It is unlikely that a so-called "red wine headache" is due to sulfites; in fact, red wine contains lower levels of sulfites than white wine. A headache after drinking red wine may be a reaction to histamines.

Sulfite treatment levels vary widely. Dried fruits are often treated with sulfites, and can contain much higher levels than are permissible by law in wine. Residual levels may approach 1,000 ppm or more in certain fruit and vegetable products. Fruits treated with sulphur dioxide are light in color. Untreated fruit tends to be dark brown. It is worth noting that in California, under Proposition 65, sulphur dioxide—a sulfiting agent commonly used in dried fruit preservation has been named as a chemical known to cause reproductive toxicity.

Sulfites are routinely used on fresh and frozen shrimp, frozen lobster, and scallops. They prevent melanosis, a harmless but disconcerting brown spotting on the shellfish. Canned clams often contain sulfites. In 1986, the FDA prohibited the use of sulfites to preserve color and crispness of fresh fruits and vegetables in salad bars and in the fresh produce section of supermarkets. But FDA regulations do not require the managers of food service establishments to notify customers when sulfites are used in food preparation. A common use of sulfites is on peeled potatoes, like French fries (or any peeled, cut, or dehydrated potato), which prevents them from discoloration. In 1990, after a long legal fight, the potato lobby blocked a move by the FDA to require labelling for treated potatoes intended to be served to customers unpackaged and unlabelled.

Sulfites are also added to prepared doughs, flours, and food starches, where they act as bleaching agents. Currently, the addition of sulfites is prohibited and not GRAS for use in meat or in foods recognized as a major source of vitamin B1 (because sulfites scavenge thiamin). Nor are sulfites permitted for use in fresh produce intended to be served raw to consumers or to be sold to consumers as fresh.

Dealing with a Sulfite Sensitivity

Beyond their use in food and drink, sulfites are employed in pharmaceuticals, from eye drops to anaesthetics, to maintain the stability of some medications.

What to do if you have a sulfite sensitivity? Read the label when shopping. Avoid processed foods that contain sulfites. When you are buying food in bulk (like dried fruit from bins) or in portions (mostly chain restaurants), where labels are not evident, ask a manager what the bulk container labeling stipulated, or whether the potatoes were sourced already-peeled (if in doubt, order baked potatoes in their jackets). And when shopping for seafood, ask your fishmonger whether the shellfish were treated with sulfites.

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