SULFITE ALLERGY AND INTOLERANCE
Sulfite sensitivity affects only a small group of people, but its effects can be devastating. The people most affected are asthmatics, and a significant number of deaths from a sulfite-induced attack have had a direct impact on the use of sulfites in foods and drugs. Consequently, the use of sulfites in foods and drugs has changed considerably over the past ten years. Whereas previously sulfites were used extensively as preservatives, keeping manufactured and natural foods free from disease-causing microorganisms and preventing spoilage, now they have been replaced by other preservatives in many products, and where no effective replacement is available, labeling laws have become stricter. Nevertheless, the sulfite-sensitive person needs to remain vigilant an identifying the foods, beverages, and drugs that may contain sulfites and to carefully avoid them. This chapter will provide you with details of why sulfites cause adverse reactions, where sulfites can be found, and how to avoid all sources of sulfites in your diet, without compromising your nutrition.
Sensitivity to sulfites is most common in people with asthma. Of these people, individuals who are dependent on steroids to control their asthma are considered most at risk for sulfite sensitivity. Although the incidence of adverse reactions to sulfites is estimated to be as high as 1% of the U.S. population, sulfite sensitivity in people without asthma is considered rare. Reported symptoms have occurred in most organ systems, including the lungs, gastrointestinal tract, and skin and mucous membranes. Reports of life-threatening anaphylactic reactions in persons with asthma are very rare. The major risk is a life-threatening asthma attack.
Symptoms reported to be due to sulfite sensitivity include
♦ Asthma in asthmatics
♦ Severe respiratory reactions, including bronchospasm, wheezing, and a feeling of tightness in the chest
♦ Flushing, feeling of temperature change
♦ Onset of hypotension (low blood pressure)
♦ Gastrointestinal symptoms (abdominal pain, diarrhea, nausea, vomiting)
♦ Difficulty in swallowing
♦ Dizziness, loss of consciousness
♦ Urticaria (hives); angioedema (swelling, especially of the mouth and face)
♦ Contact dermatitis
♦ Anaphylaxis (in persons with asthma); anaphylactoid reaction (in persons without asthma)
There is no evidence that avoiding all dietary sources of sulfites improves asthma. For people who are not sensitive to sulfites, exposure to sulfites poses very little risk. Toxicity studies in volunteers showed that ingestion of 400 milligrams of sulfites daily for 25 days produced no adverse effects.
People with impaired kidney and liver function should avoid sulfites because the enzymes in the kidney and liver that are required to break down sulfites will be inadequate, resulting in sulfite excess and development of symptoms of sulfite intolerance listed above.
How Sulfites Cause Adverse Reactions
Respiratory symptoms caused by sulfites are thought to be caused by sulfur dioxide, which acts as a direct irritant on hypersensitive airways. Sulfur dioxide is released from sulfurous acid, which forms when sulfites dissolve in water. This effect is enhanced when the sulfite is present in an acidic food. Persons with asthma can have severe bronchospasm after inhaling as little as one part per million of sulfur dioxide. Wheezing, flushing, and other symptoms of asthma have been brought on by the inhalation of the vapors from a bag of dried apricots.
Research suggests an IgE-mediated reaction in which sulfite acts as a hapten, combining with protein to form a neoantigen that prompts the immune system to make antigen-specific IgE. However, because the levels of IgE, eosinophils, and histamine are normal in most people who have symptoms of sulfite sensitivity and because sulfite-specific IgE has not been demonstrated in most sensitive people listed, scientists consider that IgE-mediated reactions are very rare, or at least unlikely, as a cause of sulfite sensitivity.
When sulfite enters the body, it is converted quite quickly to sulfate by enzymes. Sulfates are not reactive and thus do not cause any symptoms.
A deficiency in the enzyme sulfite oxidase, which converts sulfite to sulfate, has been suggested as a possible cause of abnormally high levels of sulfites, which may provoke a reaction. However, this hypothesis has not yet been definitively proven to be the main mechanism causing sulfite sensitivity in research studies.
Use of Sulfites in Foods and Medications
Sulfites are used as preservatives in beverages, fruits, vegetables, prepared and pre-sliced foods, and packaged snack foods. The active component is sulfur dioxide, which has been used as a preservative since Roman times, especially for wine. Today it is the most versatile food additive in use.
USES OF SULFUR DIOXIDE (SULFITES) INCLUDE
♦ Prevention of food spoilage by
- Inhibiting the growth of microorganisms, especially enterobacteria such as Salmonella
- Inhibiting enzymatic and nonenzymatic browning in food plants
- Antioxidant effects (keeping oxygen from changing the food’s color or flavor)
- Preserving the red color of meat by preventing oxidation of myoglobin to metamyoglobin
- Preventing discoloration of shrimps and lobsters by inhibiting the enzyme tyros inase
♦ Bleaching of flour, maraschino cherries, citrus peel
♦ Physical modification of dough by modifying the gluten of the flour. This reduces the elasticity of the dough and reduces the time required for mixing and standing of the dough in making batches of baked goods.
♦ Stabilization of vitamin C
♦ Inhibition of nitrosamine formation (e.g., in cooking barley to make malt)
Sulfites are also used as preservatives in some medications, including inhalable and injectable drugs, where they act as antioxidants. Some forms of epinephrine (adrenaline) contain sulfite as a preservative. However, the action of epinephrine appears to overcome any adverse effects of sulfite, and administration of epinephrine in anaphylactic emergencies is the recommended treatment.
Cooking foods does not cause sulfites to lose their effect. In addition, because sulfites bind to several substances in foods, such as protein, starch, and sugars, washing foods, even if a detergent is used, will not remove all traces of sulfites.
Sulfates in foods do not cause the same adverse reactions as sulfites. Persons who are sensitive to sulfites need not avoid sulfates.
Detection of Sulfites in Foods
Chemically treated strips have been developed to test foods for the presence of sulfites. However, because of the high number of false-positive and false-negative results obtained with these test strips, their use is not recommended.
Government Regulations on the Use of Sulfites
“Sulfiting agents or sulfites, traditionally used as food preservatives, are causing concern among consumers. For most Canadians, this use of sulfites is harmless to health. For a few individuals, these substances can cause a severe adverse reaction.”
The use of sulfites on fresh fruit and vegetables, except sliced potatoes and raw grapes, has been banned in the United States by Food and Drug Administration regulation since 1986 and in Canada since 1987. Canadian regulations state that “no person shall sell any fresh fruit or vegetable that is intended to be consumed raw, except grapes, if sulfurous acid or any salt thereof has been added thereto.”
Sulfites are permitted for use in the form of
| Sodium metabisulfite |
| Potassium metabisulfite |
| Sodium bisulfite |
| Potassium bisulfite |
| Sodium sulfite |
| Sodium dithionite |
| Sulfurous acid |
| Sulfur dioxide |
A specified level of sulfites (calculated in parts per million) may be added to the following foods and beverages, because no suitable alternatives are currently available:
Fruits and Vegetables
| Dried fruits and vegetables |
| Fruit juices (except frozen concentrated orange juice) |
| Frozen sliced apples |
| Frozen sliced mushrooms |
| Grapes |
| Sliced potatoes |
Beverages
| Alcoholic |
| De-alcoholized wines and beers |
Sweeteners
| Glucose solids and syrup |
| Dextrose (used in making confectionery) |
| Molasses |
Fish
| Crustaceans | (shellfish) |
Others
| Jams, jellies, marmalades (sulfite is in the pectin) |
| Mincemeat |
| Pickles and relishes |
| Tomato paste, pulp, ketchup, puree |
| Gelatin |
| Pectin |
| Snack foods |
| Candies and confectioneries |
| Frozen pizza dough |
| Frozen pastry shells |
Note that
♦ Not all manufacturers of these products use sulfites.
♦ Canadian government regulations require that if sulfites are used, they must be listed on the label.
♦ U.S. government regulations state that if any food contains 10 parts per million or more, the sulfite must be identified in the ingredient list on the label.
Some foods do not require labels. The presence of sulfites in the following may not be listed:
♦ Some bulk foods
♦ Individually sold candies
♦ Individually portioned foods such as those sold in vending machines, mobile canteens, and delis
♦ If the sulfite is in a secondary ingredient in a manufactured food. For example, if one of the ingredients in a prepared cake is jam that contains sulfites, the jam must be listed, but not the sulfite contained in it. This is because the final level of sulfite in the finished product is below the amount required by law to be disclosed.
When eating in restaurants, ask whether sulfiting agents are present in the foods.
Alcoholic beverages
In Canada at present, ingredients of alcoholic beverages, including sulfites, need not be listed on the label. In the United States, if sulfite levels are 10 parts per million or more in wine, distilled spirits, and malt beverages, sulfites must be listed on the labels.
Medications
Sulfites are used in a wide range of medications and pharmaceuticals. The Compendium of Pharmaceuticals and Specialties (CPS) provides a list of sulfite-containing products. Consult your pharmacist about the sulfite content of any medications you require.
Other Sources of Sulfites
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