Featured article in the Fall 2016 Issue of Nutrition Close-Up; written by Apeksha Gulvady, PhD
Our present decade presents a very different food allergy landscape than it did about 35 years ago in terms of prevalence, types and severity of food-allergic reactions, diagnostic tools, and even recommendations for prevention. Take prevalence in the United States for instance. Although the rates of perceived prevalence have remained at around 20% through the ages, the actual incidence has gradually risen from <1% in the 1980s up to about 5% of the general population and 8% of U.S. children in recent years.1-4 And while the number of individuals affected by food allergies continues to grow across the globe, particularly in developing countries, the United States alone accounts for as many as 15 million people with food allergies today.1
Of the estimated 5.9 million U.S. children who have a food allergy, 30% have been found to be allergic to multiple foods. The most common allergenic foods include milk, egg and soy (which children are likely to outgrow); peanuts, tree nuts and shellfish (whose allergies are typically carried over into adulthood); plus, wheat and fish.1,5 Even trace amounts of these foods have the potential to trigger a reaction ranging from a mild response, like coughing, to the more severe and potentially fatal anaphylaxis.5 Nearly 40% of children with food allergies have a history of severe reactions.4
Food allergies can be classified as IgEmediated, non-IgE, cell-mediated, or mixed IgE- and cell-mediated, with generalized, cutaneous, ocular, gastrointestinal, cardiovascular or respiratory symptoms.2,6 Egg allergies, which are induced by egg proteins, can be IgE antibody-mediated or mixed IgE- and cell-mediated disorders, the former being more common in children.7 Egg whites contain more than 20 different cross-reacting proteins and glycoproteins, which may bind to human immunoglobulin E (a class of antibodies found in mammals) to varying extents, and result in inflammatory reactions. Cutaneous symptoms have been found to be the most common reaction type, but gastrointestinal or respiratory tract manifestations have been reported as well.6 In addition, mediation by different phenotypes of IgE, primarily conformational (3-dimensional) epitopes or sequential (linear) epitopes, can determine whether the egg allergy may be outgrown, or carried into adulthood, respectively.6
With no cures available for food allergies, management of the condition has traditionally largely focused on prevention of reactions. Thus far this has been achieved in three ways: strictly avoiding allergenic foods; adopting nutritional support; and prompt recognition of symptoms when accidental exposure occurs that is immediately followed by treatment.
However, strict avoidance of eggs may be challenging from both a nutrition and health perspective. Eggs uniquely combine nutrient density, affordability, availability, and versatility. One large egg provides 14 essential nutrients, including many shortfall nutrients, and as high-quality a protein source as exists. Moreover, the wide range of nutrients found in eggs gives them an important role in achieving an array of positive health benefits, including weight management, muscle strength, healthy pregnancy, brain function, eye health and more. Particularly in the case of pregnant or breastfeeding women, the choline, high quality protein, iron, and folate in eggs may help decrease rates of congenital abnormalities.
The American Academy of Pediatrics (AAP) had previously recommended that eggs should not be introduced until after two years of age in high-risk families, but the recommendation has since been withdrawn. The most recent AAP position is that there is also little evidence that delaying timing of the introduction of complementary foods beyond 4-6 months of age prevents the occurrence of atopic disease. Thus, it is now generally accepted by the American Academy of Pediatrics that delaying the introduction of food allergens into an infants diet beyond 47 months may be ineffective after all, and may in fact increase risk of allergy.8 Importantly, the AAP recommends that food allergens should not be avoided during pregnancy or breastfeeding.8 Recent research also supports the idea that early exposure of the fetus to small quantities of egg allergens, via maternal consumption, may in fact induce tolerance to the allergen and thereby reduce risk of reaction in the early childhood years.9
As the number of food allergy sufferers continues to grow, researchers are continuing to make great advances in developing new tools for diagnosis, uncovering the basis of food allergy mechanisms and tolerance. Further research can eventually help define the best management practices and hopefully find the much needed cure.
Apeksha Gulvady, PhD, is a nutrition scientist specializing in science-based communications for a broad range of food, nutrition and biomedical areas.
References:
1. Food Allergy Facts and Statistics for the US. Food Allergy research and Education. Available at: http://www.foodallergy.org/file/facts-stats.pdf. Accessed September 13, 2016
2. Nowak-Wegrzyn A, Sampson HA. Adverse reactions to foods. Med Clin North Am. 2006 Jan;90(1):97-127.
3. Sicherer SH, Sampson HA. Food allergy. J Allergy Clin Immunol, 125 (2 Suppl. 2) (2010), pp. S116S125
4. Gupta RS, Springston EE, Warrier MR, et al. The prevalence, severity, and distribution of childhood food allergy in the United States. Pediatrics. 2011 Jul;128(1):e9-17.
5. Gupta RS, Lau CH, Sita EE, Smith B, Greenhawt MJ. Factors associated with reported food allergy tolerance among US children. Ann Allergy Asthma Immunol. 2013
Sep;111(3):194-198.e4.
6. Sampson HA. Food allergy: Past, present and future. Allergol Int. 2016 Sep 6. [Epub ahead of print]
7. Caubet JC, Wang J. Current understanding of egg allergy. Pediatr Clin North Am. 2011 Apr;58(2):427-43.
8. Greer FR, Sicherer SH, Burks AW. American Academy of Pediatrics Committee on Nutrition, American Academy of Pediatrics Section on Allergy and Immunology. Effects of early nutritional interventions on the development of atopic disease in infants and children: the role of maternal dietary restriction, breastfeeding, timing of introduction of complementary foods, and hydrolyzed formulas. Pediatrics. 2008;121:183-91.
9. Lack G. Update on risk factors for food allergy. J Allergy Clin Immunol. 2012 May;129(5):1187-97.
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