Food Intolerance or Allergy Adverse responses to food comprise a complex and confused area of scientific and medical investigation. A large amount of information has been compiled on the subject, and substantial differences exist in definition of terms, information, and action to be taken. Numerous examples exist where adverse reaction to food is misinterpreted or misdiagnosed. Malabsorption or intolerance may be interpreted as allergy. Likewise, allergy may be interpreted as malabsorption or food sensitivity. Any adverse response to food is most critical in infancy. The intestinal wall is not completely developed and is more permeable to intact large molecules. As a result, response is more severe and immediate in infants than in older children or adults. Also, digestive and immunological mechanisms for handling of food components are immature 1. An additional problem exists since infants cannot accurately communicate symptoms but can only indicate discomfort to the caregiver. Used accurately, the terms "food allergy" and "food sensitivity" refer to an immunologic response. On the other hand "food intolerance" may be used to describe a host of adverse responses to foods which may or may not include "food allergy". A first step is to differentiate between the descriptive terms used for each, and to maintain that terminology whether it be with patients or associates. This should not imply that either problem is not real or that one is greater than the other — only that they are different. A considerable portion of the medical literature surrounding the general subject of adverse reactions to foods uses terminology specific to the application involved. Efforts have been made by scientific bodies to provide a universal basis for discussion. For purposes of this discussion, the following general definitions will apply: 2,3,4,5,6 Adverse reaction to a Food: A general term to describe any abnormal Food Allergy, hypersensitivity: An abnormal immunologic reaction. Food Intolerance: An abnormal physiological response that is not immunologic. Several confounding factors contribute to the confusion in distinguishing among allergy, sensitivity and intolerance. The methods used to identify problems such as scratch tests with impure extracts, hair analysis, dowsing, cytotoxic testing and various electrical methods lack validation and most are scarcely credible. 7,8The only realistic way to make a diagnosis is use of an elimination diet followed by reintroduction of foods, one at a time. 9 Food Allergy— Food allergy is generally considered as an immune mediated response to foods, and is characterized by a host of symptoms. The most severe of these are anaphylaxis, abdominal pain, vomiting, diarrhea, urticaria, rhinitis and asthma. Food allergy does not encompass: 6 - The inability to digest or metabolize food components. Enzyme deficiencies are included in this category; one of the most common is lactase deficiency. - Sensitivity to specific food components. For example, sensitivity to sulfites is characterized by severe respiratory response. Some less well defined adverse responses to food components include reactions to certain food dyes and possibly to monosodium glutamate. - Food responses similar to allergy or sensitivity triggered by food toxins. Certain alkaloids, oxalates and pressor amines may result in adverse food sensitivity type reactions. - Adverse responses produced by indigestible materials. Excessive quantities of indigestible fiber components and high melting point fatty acids causing diarrhea fall into this category. The configuration of some food proteins and carbohydrates make them difficult to hydrolyze in the digestive system. Allergic responses are not uncommon. These fall into clearly defined categories, associated with the protein portion of the food. IgE mediated reactions occur in response to cow's milk, soy, peanut and egg, and less frequently to other nuts, fish, shellfish and poultry. Estimates of frequency vary from 2% to 7% — with the lower estimate probably for allergic reaction and the higher for an "undefined combination". The meaning of combination being the sum of food allergy and intolerance 10. The diagnoses include skin tests, RAST (Radioallergosorbent Test) and food challenges. Each of these has been criticized as being non-specific and unrelated to food intake. Prick tests are only valid to determine IgE mediated food allergies. Acute allergic reactions may be detected by RAST or prick tests. Celiac disease is a very specific form of immunologic reaction to gluten, and can often be validated by detection of circulating IgA antibodies to gliadin. A small bowel biopsy is the only way to accurately confirm that dysfunction. Food Intolerance — Food intolerance generally describes non-immunologic responses to food. These include a number of systemic inabilities to digest, metabolize or tolerate foods. Several are well known, others are relatively obscure. They may include inability to digest carbohydrates (most frequently lactose), protein (most frequently prolamines) and indigestible material (most frequently fiber). Specific responses, unique to each compound have been associated with aspirin (salicilates), tyramine (cheese) and octopamine in citrus fruits 6. Several of the food intolerances relate to enzyme deficiencies, which are more pronounced in infants and young children. Several are of genetic origin, however, and as such are not age related. Microbial Toxins/Environmental Contaminants — Toxic Materials— Numerous toxic materials found in foods may in some instances present symptoms similar to food sensitivity; alkaloids (mushrooms), hemagglutinins (beans), goitrogens (cabbage), pressor amines (bananas) and oxalates (rhubarb) are examples. Contaminants such as saxitoxins, ergot, aflatoxins, penicillin and pesticide must also be considered. Nitrates and nitrites from water and some foods and food treatments represent a potential hazard, and must be monitored. Several lists of the most commonly offending foods are available, but the importance and order does not always agree. An example of a "10 most frequent" sensitizing foods has been proposed in order of apparent priority; milk, nuts ( peanut, kola such as cola, chocolate), corn, egg white, pea (legume), citrus, tomato, wheat and artificial food color. The validity of any such list should be subjected to careful scrutiny 11. Fruits have been reported to cross react "closely, but not completely". The likely problems are eczema, urticaria and are common causes of asthma. Fruits should be suspected in patients with aphthous stomatitis (canker sores). A Finnish report evaluated fish and citrus allergy - fish as the most potent allergen and citrus as common with infants. Allergy can be delayed, but not significantly changed by the delay in introduction of solid foods 12. Breast feeding exclusively for the early feeding period has been suggested as a method to avoid the incidence of food intolerance later in development. A contrasting view has been presented as a result of controlled evaluation of feeding histories, which concluded that extended breast feeding and delayed introduction of offending foods did not protect against atopic eczema 13,14. Dietary and feeding practices have a vital importance, and are often overlooked. This is particularly true in the case of young infants whose tolerance and acceptability of a variety of foods has not been established. The tried-and-true feeding practices are breast or formula feeding exclusively for a reasonable time, introduction of single ingredient foods one at a time, observation of acceptance and tolerance before introduction of a new food and observation of any food related problems such as - diarrhea, vomiting, rash or gastric discomfort 15. In summary, a clear definition of terms used and further understanding of the identification and description of adverse responses to foods is needed. Considerable discomfort and inconvenience can be avoided with careful and precise identification of food problems. Removal of the offending food or substance from the diet remains the most effective method of addressing adverse responses, whether they are allergies, sensitivities or intolerances. Identification of susceptible individuals by family history or by screening is an essential step in the management of adverse food responses. References: 1. Lebenthal, E. Impact of Development of the Gastrointestinal Tract on Infant Feeding. J Pediatrics. 1983; 102: 1-9. 2. Bock SA. Food Sensitivity, A Critical Review and Practical Approach. Am J Dis Child 1980; 134: 973-982. 3. European Society for Paediatric Gastroenterology and Nutrition (ESPGAN). Diagnostic Criteria for Food Allergy with Predominately Intestinal Symptoms. J Ped Gastroenterology and Nutrition. 1992; 14:108-112. 4. FAO. FAO Technical Consultation on Food Allergies. 1995; Report D/W 0724. FAO Press.Rome Italy. 5. McCarty, E P and Frick, OL. Food Sensitivity: Keys to Diagnosis. J Pediatrics. 1983; 102: 645-652. 6. Present Knowledge in Nutrition. 7th Ed. ed .Zeigler, E., Filer, L. 1996; ILSI Press. Washington DC. 7. Stern M, and Walker W A. Food Allergy and Intolerance. Ped Clinics of North America. 1985; 32: 471-492. 8. Stern M., Gastrointestinal Allergy. in Pediatric Gastrointestinal Disease. ed. Walker, W. A. et al. Vol 1, Chapter 4, 557-574. 9. Bock SA, Atkins FM. Patterns of Food Hypersensitivity During Sixteen Years of Double-Blind, Placebo Controlled Food Challenges. J Pediatrics. 1990; 117: 561-567. 10. Bock S A. Prospective Appraisal of Complaints of Adverse Reactions to Foods in Children During the First 3 Years of Life. Pediatrics. 1987; 79: 683-688 . 11. Speer, F, Food Allergy: The 10 Common Offenders. Am Family Phys. 1976; 13: 106-112. 12. Saarinen UM, Kajosaari M. Does Dietary Elimination in Infancy Prevent or only Postpone a Food Allergy? A Study of Fish and Citrus Allergy in 375 Children. 1980; Lancet 1980: 166-167. 13. Kramer, M S. and Moroz B. Do Breast-Feeding and Delayed Introduction of Solid Foods Protect Against Subsequent Atopic Eczema?. J Pediatrics. 1981; 98: 546-550. 14. Steinman HA, Potter PC. The Precipitation of Symptoms by Common Foods in Children with Atopic Dermatitis. 1994 Allergy Proceedings; 15: 203-210. 15. American Academy of Pediatrics. Pediatric Nutrition Handbook. 1993.
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