To Your Health

A. Sulfites are sulfur-based preservatives that are used to prevent discoloration of dried fruits and vegetables. Sulfites are also used to inhibit the growth of microorganisms in wine and to bleach flour. Sulfite allergy is not common but does occur. Nearly three quarters of asthma sufferers have mild to moderate reactions, and one quarter have severe reactions to the sulfite from wine.

Fresh fruits and vegetables do not ordinarily contain sulfite, and foods that contain sulfite are required by law to label it if they are sold interstate. If you have discovered that you are allergic to sulfite, in addition to the sulfite found in most wines and dried fruits, be aware that some salad bars or delis may use sulfite on fresh fruit salads to maintain their natural color. Dried fruit that is the same color as the fresh fruit most likely has had sulfite added. Although less appetizing, buy the dried fruit that is darker since these are less likely to have had sulfite added to them. Read labels on the prepared foods that you buy and look for any of the six names used for sulfites: sulfur dioxide, sodium sulfite, sodium bisulfite, potassium bisulfite, sodium metabisulfite, and potassium metabisulfite.

Sulfites have been implicated as the cause of breathing problems in some subjects with asthma. However, there is still no universally accepted explanation for why this happens. The cause may be a shortage of an enzyme called sulfite oxidase, which requires the trace mineral molybdenum in order to break down sulfites to harmless sulfates.

Molybdenum is an often-ignored but essential trace mineral for virtually all life forms. There are three important molybdenum-containing enzymes in the human body. In addition to sulfite oxidase, there are two other enzymes, one involved in the breakdown of DNA and RNA and the other in the breakdown of drugs and toxins. There is no official RDA for molybdenum. Dietary intake varies from 100 to 500 micrograms a day, principally from beans and peas, organ meats, and whole-grain cereals. Molybdenum is thought to be generally nontoxic in daily amounts under 10 to 15 milligrams.

Very high doses of B-12 may reduce sulfite sensitivity. In one study, vitamin B-12 supplementation was able to block sulfite-induced breathing difficulties in four out of five asthmatic children. When vitamin B-12 is being used as a drug, as in the treatment of sulfite-induced asthma, injections appear to be preferable to oral administration, so you would need your physician to supervise this treatment. It appears that very high serum concentrations are needed for vitamin B-12 to act as a drug, and this can be achieved only by injection. Although there is little published research, clinical observations suggest that orally administered vitamin B-12 is not particularly effective against asthma.

Avoidance of sulfite is easier if you sidestep wine and if your diet consists primarily of fresh foods. The well-documented benefits of wine can still be obtained from grape juice, although you will need to drink more juice, since wine is more concentrated.