What Exactly Are Sulphites?
Sulphites, often identified on food labels by various names such as sulphur dioxide (E220) and sodium metabisulphite (E223), are sulphur-based compounds used for their preservative and antioxidant properties. They prevent microbial spoilage, inhibit enzymatic and oxidative browning, and help maintain the color and freshness of many food products. Sulphites can be naturally present in some foods, such as wine, which produces them during fermentation. However, they are most commonly added during processing to extend shelf life.
Who Needs to Avoid Sulphites?
For the vast majority of the population, sulphites are considered safe to consume in normal amounts and do not pose a health risk. However, certain groups of people need to be mindful of their sulphite intake and may need to avoid them entirely.
- Individuals with Asthma: People with asthma are at a significantly higher risk for sulphite sensitivity, with studies suggesting that 5-10% of people with asthma may react to them. Sulphite exposure can trigger wheezing, chest tightness, and coughing.
- Sulphite-Sensitive Individuals: This is not a true allergy, but a sensitivity that causes adverse, allergy-like symptoms. Reactions can be mild to severe and include hives, flushing, dizziness, stomach pain, and diarrhea.
- Individuals with Sulphite Oxidase Deficiency: In rare cases, a genetic condition can lead to a deficiency of the enzyme sulphite oxidase, which is needed to break down sulphites in the body. Low levels of this enzyme can lead to a buildup of sulphites and neurological issues.
- Individuals with IBD or SIBO: Emerging research suggests that a high intake of sulphur-containing compounds may exacerbate symptoms in people with inflammatory bowel disease (IBD) and small intestinal bacterial overgrowth (SIBO).
Sulphite Sensitivity vs. Sulfa Drug Allergy: A Critical Distinction
It is vital to understand that sulphite sensitivity is different from a sulfa drug allergy. A sulfa drug allergy is an immune system reaction to medications containing sulfonamides, while sulphite sensitivity involves a reaction to the preservative compounds found in foods. People with a sulfa drug allergy do not need to avoid sulphites in their diet.
Common Food Sources of Sulphites
Sulphites are ubiquitous in the food supply, and label reading is crucial for those who need to avoid them. Sulphites must be declared on a food label when concentrations are at 10 mg/kg or more.
Foods high in sulphites include:
- Dried fruits: Apricots, raisins, and dried mango are often treated with sulphites to prevent browning and preserve color.
- Wine and Beer: Sulphites are added to these beverages to prevent spoilage and oxidation. Levels are generally higher in white wine and boxed wine than in red wine.
- Processed potatoes: Pre-cut, peeled, or frozen potatoes, such as fries, often contain sulphites.
- Condiments and Sauces: Mustard, ketchup, horseradish, pickled foods, relishes, and some gravies contain sulphites.
- Bottled juices: Lemon and lime juice concentrates commonly use sulphites as a preservative.
- Deli meats and Sausages: Processed meats are often preserved with sulphites.
- Seafood: Fresh or frozen crustaceans like shrimp and lobster can be treated with sulphur powder.
How to Avoid Sulphites in Food
For those with sensitivities, complete avoidance is the most effective management strategy.
- Read Labels Carefully: Always check the ingredient list for names like sulphur dioxide, potassium metabisulphite, and E-numbers like E220-E228.
- Beware of Cross-Contamination: Avoid bulk foods where contact with other items is possible. For example, dried fruit from a bulk bin could be contaminated by a sulphited product.
- Inquire at Restaurants: When eating out, ask staff if sulphites are used in the preparation of dishes, especially salads, dressings, and processed seafood.
- Cook from Scratch: Preparing meals at home with fresh, whole ingredients is the best way to control your diet and ensure no hidden sulphites are present.
Low Sulphite vs. High Sulphite Foods
| Food Category | Low/Sulphite-Free Foods | High Sulphite Foods |
|---|---|---|
| Beverages | Water, freshly squeezed juices, homemade tea | Wine, beer, bottled juices, soft drinks, ciders |
| Fruits | Most fresh fruits and berries, dried sultanas (check label) | Dried apricots, raisins, maraschino cherries, glazed fruit |
| Vegetables | Fresh vegetables | Frozen fries, dehydrated potatoes, canned vegetables, pickled foods |
| Meats | Fresh, unprocessed meats, poultry, and fish | Deli meats, hot dogs, sausages, processed seafood |
| Grains | Plain oats, rice, flour, pasta | Crackers, muesli, some pre-made baked goods |
| Condiments | Fresh herbs, spices, homemade sauces | Bottled salad dressings, ketchup, mustard, vinegar |
Conclusion: Making an Informed Decision
The question of "should I avoid sulphites in food?" is not a universal one. For most people without a pre-existing condition, sulphites are generally safe. However, if you have asthma or experience allergy-like symptoms such as hives, wheezing, or stomach upset after consuming processed foods or beverages, you may have a sulphite sensitivity. In such cases, adopting a sulphite-avoidance diet is the recommended course of action. For anyone considering a significant dietary change, it is always best to consult a healthcare professional or a registered dietitian to ensure your nutritional needs are met.
Considerations for Diagnosing and Managing Sulphite Sensitivity
Diagnosing sulphite sensitivity can be challenging, as there are no simple blood or skin tests available. Diagnosis often involves a medically supervised oral challenge, where small, increasing amounts of sulphites are administered under controlled hospital conditions. Another method is an exclusion and reintroduction diet, supervised by a dietitian, to monitor symptoms. Some studies have also explored the use of patch testing, but further research is needed. This highlights the importance of a proper medical evaluation for accurate diagnosis and management of any suspected sensitivity or allergy.
Visit the Anaphylaxis UK Fact Sheet on Sulphite Allergy for more information
Managing Your Sulphite Intake: Practical Steps
For those who have been diagnosed with sulphite sensitivity, managing your intake becomes a daily task. Beyond simply reading labels, it involves being a proactive consumer and asking questions. Be particularly cautious with foods from bulk bins, as ingredient information is often unclear and cross-contamination is a risk. When buying products from countries with different labeling laws, be extra vigilant, as regulations on sulphite declaration can vary. For example, in the UK, sulphites must be highlighted on labels if present at more than ten parts per million. Finally, remember that while sulphites are used to preserve food, switching to a diet of mostly fresh, unprocessed items will naturally lower your exposure. For instance, instead of dried fruit, opt for fresh fruit, and choose fresh cuts of meat over processed deli varieties.
Sulphites and the Gut Microbiome: An Emerging Concern
Beyond the immediate allergic reactions, some recent research has explored the long-term impact of sulphites on gut health, even in non-sensitive individuals. Studies indicate that sulphites can inhibit the growth of certain beneficial gut bacteria, potentially shifting the gut microbiome towards a less healthy balance. While this area requires more research, it adds another potential reason for those conscious of gut health to consider reducing their intake of sulphite-rich processed foods. The overall message remains consistent: a balanced diet emphasizing whole, unprocessed foods is best for most people, with added caution necessary for those with sensitivities.
