People with asthma or allergies may find their symptoms alleviated by the simple strategy of avoiding chemical preservatives and artificial coloring. Sulfur dioxide, sodium bisulfite and sulfites are used to prevent dryness, stiffening and discoloration in dried fruits, frozen potatoes, shrimp, avocado dips, salads, vegetables, wine, beer and other foods.
According to Michael Murray, N.D., and Joseph Pizzorno, N.D., in their Encyclopedia of Natural Medicine, a restaurant customer can easily ingest up to 100 mg of metabisulphite in a single meal. Asthma attacks can be triggered by exposure to sulfites, tartrazine (an orange food dye) and benzoates (preservatives), and at least four deaths caused by sulfites have been reported to the Food and Drug Administration. Always check labels for additives and, in general, try to avoid processed foods that contain chemicals.
How can you tell if the food in a restaurant or supermarket has been treated with sulfites? If the management displays a sign claiming "no sulfites," it's probably true. In 1986, the FDA made the use of sulfites on fresh produce illegal, so salad bars are less a hazard than they used to be. Still, prepared foods may contain sulfites and it's best to be sure. The demand for a simple way of determining sulfite content inspired the development of sulfite test strips, which can be dipped into any food. The strips turn red, revealing the presence of sulfites, or green, showing that the food is sulfite-free.