Although the exact cause of asthma is largely unknown, there are some aggravating factors that can bring on an asthma attack. One such factor is allergies. Despite allergies having been identified as a trigger of asthma, allergies alone will not cause asthma. In fact, not all allergic people have asthma and many asthmatics are not allergic.

Allergies occur when the body's defence system or immune system is too aggressive, and harmless substances are erroneously identified as hazardous. The term allergies can include allergies to pollen, mould, house dust, and occasionally certain medications or foods. In the latter instance, certain foods or food preservatives may trigger asthmatic reactions in sensitive individuals.

Food allergy itself is generally quite uncommon, affecting only about one percent of children and 0.05 percent of adults. More common food allergy symptoms than asthma are hives, eczema and intestinal complaints like cramping, vomiting and diarrhoea.

Furthermore, inhaled food allergens such as mites, cat fur and pollen are more likely to trigger an asthma attack than are foodstuffs. In other words, food allergy is not a particularly common cause of asthma.

However, when a particular food has been identified as an allergen, elimination of that particular food substance from the daily diet is usually necessary and is the most effective approach. The most common food allergens that may induce an asthma attack in those sensitive to them are food preservatives. Others that may play a role include wheat, nuts, eggs, milk, fish and chocolate.

Food preservatives

Although the vast majority of additives and preservatives have been tested by many laboratories throughout the world and appear to be safe, some individuals may be sensitive to them. In fact, it has been estimated that approximately 5 percent of asthmatics are sensitive to sulphur-containing compounds (especially sulphites) that are readily found in foods.

Sulphur-containing compounds have been added for many years to a number of foods for the purpose of colour bleaching and prevention of oxidation and microbial infestation. When sulphites are present in a final food product in amounts more than 10 parts per million, the food label must carry the chemical name and purpose of the additive (eg potassium bisulphate as a preservative).

Because sulphites destroy vitamin B1, they are not permitted in foods that are considered to be significant sources of this vitamin — primarily meats, some fish and crab.

Sulphite-sensitive individuals can avoid offending foods by reading labels on packaged foods. However, such protection is not available with regard to sulphite-treated foods that are served as "fresh", such as salad-bar ingredients and menu items that are delivered to restaurants in pre-prepared forms. Sulphites are used in these cases to preserve the crispness of salad greens and the whiteness of peeled uncooked potatoes.

Possible sources of sulphites in foodstuffs include:

  • Beverages: soft drinks, fruit juices (especially citrus drinks, grape juice)
  • Alcohol: wine, beer, cocktail mixes
  • Condiments: vinegar, pickles, salad dressings
  • Dips: avocado and other dips
  • Fish: canned or fresh shrimps, shellfish
  • Fresh fruit or veg: grapes, fresh pre-cut potatoes
  • Processed fruits: dried fruit, fruit juice concentrates, purees, dried coconut
  • Processed veggies: instant mashed potatoes, restaurant salad bars, dried veggies, canned or pickled veggies, purees
  • Processed meats: sausages, boerewors, cold meats, paté
  • Puddings: fruit fillings, gelatin
  • Grain products: cornstarch, gravies, instant noodle mixes
  • Soups: dried or canned soups
  • Syrups: molasses, corn or maple syrup, jams

    Asthma can also be triggered by the preservative sodium benzoate (found in fruit juices, soft drinks and foods with fruit), colourants like tartrazine, flavour enhancers like MSG and salicylates, found in aspirin.

    Additional dietary triggers that have been linked to asthma include:

  • Consumption of very cold foods or icy drinks
  • Stomach distension caused by overeating
  • Dehydration
  • Hot, spicy foods, like chilli or hot mustard

    New developments

    One study has found that fish oil, particularly omega-3 fatty acids, may help reduce the severity of asthma attacks, possibly due to their anti-inflammatory properties. Another study has found low magnesium status in people with bronchial asthma — it has been proposed that magnesium may inhibit bronchial constriction in asthmatics. More research in both of these areas is needed.

    If you or a member of your family suffers from food-related asthma, here are some tips to follow:

  • Eat small frequent meals
  • Ensure adequate fluid intake
  • Omit any identified food allergens
  • Consume sufficient amounts of vitamins A, C, B6 and zinc, all of which are involved with competence of the immune system.


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