Adverse reactions to food fall into two main categories, food allergies, and food intolerances. Food allergies cause a response by the immune system. When a person has a food allergy, his or her body responds to something in food by treating it like a threatening foreign material. Immune system cells produce proteins called antibodies that act to disable this material. This process often causes inflammation and results undesirable symptoms that range from mild and annoying to life threatening. The reason why some people respond to certain foods and others do not is probably genetically based
Food intolerances, on the other hand, also cause adverse reactions, but these reactions do not involve the immune system and are not life threatening. Lactose (milk sugar) intolerance is an example of a food intolerance. It is caused by the body producing too little of the enzyme needed to digest lactose. Interestingly, although surveys show that in the United States up to 30% of families believe they have at least one member with a food allergy, the actual documented rate of food allergies is about 6% in infants and children and 3.7% in adults. On the other hand, in Hispanic, Jewish, and Southern European populations, the rate of lactose intolerance is about 70%, and it reaches 90% or more in Asian and African populations. Food intolerances are much more common, but true food allergies tend to be much more severe. In this article, food sensitivities are used to include both food allergies and food intolerance.
The most common symptoms of food sensitivities are nausea, diarrhea, bloating, excessive gas, hives, rashes, eczema, headaches, migraine, asthma, wheezing, and hay fever-like symptoms. These symptoms may occur immediately after eating the trigger food or may not develop for hours. Most immediate reactions are severe allergic responses that can result in anaphylactic shock, a condition in which the airways swell shut and the person cannot breathe. One study found that in about one-third of individuals in anaphylactic shock who were brought for treatment to the emergency room at the at the Mayo Clinic in Minnesota, the shock trigger had been a food. Foods most likely to cause immediate reactions are peanuts, tree nuts, and shellfish
Delayed symptoms are difficult to detect and are sometimes called “maskedrdquo; food sensitivities. The most common causes of delayed sensitivities are dairy products, egg, wheat, and soy, however, sensitivities vary widely and can be caused by many foods. The amount of a trigger food that it takes to cause a response varies considerably from person to person
A true elimination diet is very rigorous and needs to be implemented under the direction of a physician often in consultation with a dietitian or nutritionist. For the elimination diet to be useful, the patient must follow the diet strictly. Cheating invalidates the results
For 2–3 weeks, a person on the elimination diet eats only the following foods (This list may be modified by the physician):
* grains: rice and rice products, sago, tapioca, buckwheat products, millet products
* proteins: veal, lamb, chicken, turkey, rabbit, tuna, bream, whiting, dried peas, lentils
* fruit: peeled pears, peeled apples, pawpaw
* vegetables: potatoes, sweet potatoes, lettuce, parsley, bamboo shoots, celery, cabbage
* sweeteners and seasonings: sugar, maple syrup, sunflower oil, safflower oil, salt, garlic
* beverages: water, fresh pear juice
The individual must avoid all medicines containing aspirin (salicylates) and food colorings. After several weeks on these restricted foods, one new food is introduced in larger than normal amounts. This is the challenge food, and it is eaten for three days in a row. If no symptoms appear, the dieter continues to eat that food in normal amounts and adds another challenge food. If symptoms appear, the challenge food is stopped immediately and no new challenge food is introduced until symptoms disappear. During this time the dieter keeps a food journal, writing down everything that is eaten and any symptoms, either physical or emotional, that appear. It can take 2 to 3 months to work through all challenge foods.
