What Are Sulfites and Why are They Used?
Sulfites, or sulfiting agents, are a group of sulfur-based compounds that release sulfur dioxide ($SO_2$). For centuries, they have been added to many foods and drinks to perform several functions, including:
- Preservation: They inhibit bacterial growth and spoilage, extending a product's shelf life.
- Antioxidation: They prevent discoloration and browning in certain foods, such as dried fruit and potatoes.
- Bleaching: They are used to lighten the color of some food starches.
Common sulfites used as food additives include sodium sulfite (E221), sodium bisulfite (E222), sodium metabisulfite (E223), potassium metabisulfite (E224), and sulfur dioxide (E220).
The Health Risks of Sulfite Sensitivity
While most people can consume sulfites without issue, a small percentage of the population is sensitive, and adverse reactions can occur. The most significant risks are to those with asthma and those with a specific sulfite oxidase deficiency.
Respiratory Reactions
For sulfite-sensitive asthmatics, consuming or inhaling sulfites is a well-documented trigger for asthma attacks. The sulfur dioxide gas released by sulfites can irritate the airways and cause them to narrow, leading to symptoms such as:
- Wheezing
- Chest tightness
- Coughing
- Shortness of breath
Allergic-like and Other Symptoms
Beyond respiratory issues, a wide range of other symptoms can manifest in sensitive individuals. These are often described as allergic-like because they can resemble allergic reactions but do not typically involve the immune system in the same way. Symptoms can include:
- Skin reactions: Hives, rashes, flushing, and swelling (especially around the face, lips, or tongue).
- Gastrointestinal issues: Abdominal pain, cramps, diarrhea, and nausea.
- Neurological symptoms: Headaches, migraines, dizziness, and a feeling of anxiety.
Anaphylaxis Risk
Although very rare, severe reactions like anaphylaxis are possible, particularly in highly sensitive individuals. Anaphylaxis is a life-threatening allergic reaction that requires immediate medical attention.
Sulfite Sensitivity vs. True Allergy
It is important to distinguish between a sulfite sensitivity or intolerance and a true IgE-mediated food allergy. Sulfites can cause allergy-like symptoms, but they usually do not trigger the same immune pathway as a true allergy.
| Feature | Sulfite Sensitivity/Intolerance | True IgE-Mediated Allergy |
|---|---|---|
| Immune Response | Not typically an IgE immune system response | The immune system releases IgE antibodies in response to an allergen |
| Symptoms | Respiratory (asthma), skin (hives), GI distress; can be mild or severe | Wide range of symptoms, including skin, respiratory, GI, and severe anaphylaxis |
| Onset of Reaction | Often occurs within minutes to hours after exposure | Can be immediate, within minutes of exposure |
| Diagnosis | Primarily clinical, based on patient history; provocation tests may be used | Standard allergy tests (skin prick, blood tests) are used for diagnosis |
Who is Most at Risk for Sulfite Reactions?
People with asthma are particularly susceptible to sulfite sensitivity, with an estimated 5-10% of asthmatics experiencing adverse reactions. Women tend to be more sensitive than men. Individuals with a deficiency of the sulfite oxidase enzyme, which helps break down sulfites, are also at increased risk. It is also possible to develop sulfite sensitivity at any point during your life, so a past tolerance does not guarantee future safety.
Common Foods and Drinks Containing Sulfites
Sulfites can appear in a wide array of products, both naturally and as an additive. The US FDA requires that sulfites present at 10 parts per million (ppm) or more be labeled on food products.
Common sources include:
- Dried fruits: Especially apricots, raisins, and prunes.
- Wine and beer: Sulfites occur naturally but are also added as preservatives.
- Processed potatoes: Dehydrated, frozen, or pre-cut potatoes, like frozen fries.
- Canned and jarred goods: Pickled vegetables (onions, peppers), sauerkraut, fruit juices, and syrups.
- Condiments and sauces: Some salad dressings, gravies, and wine vinegars.
- Processed meats: Deli meats, sausages, and hot dogs.
- Seafood: Shrimp and other crustaceans may be treated with sulfites.
- Baked goods: Pie crusts, pizza dough, crackers, and biscuits.
How to Avoid Sulfites in Your Diet
Reading Ingredient Labels
Since food manufacturers are required to label added sulfites, careful label reading is the most effective way to avoid them. Look for specific terms like:
- Sulfur dioxide
- Sodium bisulfite
- Sodium metabisulfite
- Potassium metabisulfite
- Potassium bisulfite
- The European food additive codes E220-E228.
Choosing Fresh Over Processed
Whenever possible, opt for fresh, unprocessed foods. Fresh fruits, vegetables, meat, and fish do not contain added sulfites, unless they have been pre-cut, pre-peeled, or otherwise preserved.
Dining Out Precautions
When eating at restaurants, always inform the staff of your sulfite sensitivity. Sulfites may be used in food preparation for things like preserving salad bar items or in sauces and dressings.
The Complexity Behind Sulfite-Induced Headaches
While some people report headaches after consuming sulfites, especially from wine, the mechanism is not fully understood. Some research points to other compounds in wine, like biogenic amines or histamine, as potential culprits. It's also known that red wine often contains fewer sulfites than white wine, yet is more frequently blamed for headaches. This suggests that for many, sulfites alone are not the cause of wine headaches, but they can be a contributing factor.
Conclusion
Sulfites serve a valuable purpose in the food industry, but their use is not without risks, particularly for sensitive populations. For most people, consuming sulfites poses no significant health threat. However, for the small percentage of individuals with sulfite sensitivity—especially those with asthma—the consequences can be serious. Managing sulfite sensitivity is a matter of vigilance, requiring careful attention to product labels and ingredients. By understanding why are sulfites bad in food for certain individuals and learning how to avoid them, those affected can take control of their health and minimize adverse reactions.
For more detailed information on regulations, you can review the official FDA Regulations on Sulfites.
