Allergies & Soy Review

Soy protein has been rated 11th among foods in terms of allergenicity, although milk and eggs are also considered very allergenic foods (Wraith & Young, 1979). In healthy, non?allergic children, soy is generally less allergenic than cow's milk.

By Clare M. Hasler, Ph. D., Univ. of Il. U/C
(Revised December 2001)
Food allergy, or food hypersensitivity, is actually a group of disorders characterized by an abnormal immunologic response to certain foods, resulting in a variety of symptoms. About 1.5 percent of adults and up to 6 percent of children younger than 3 years in the United States - about 4 million people - have a true food allergy (Formanek, 2001). It is commonly believed that food allergies are increasing in prevalence. The most common foods to cause allergies in adults are shrimp, lobster, crab, and other shellfish; peanuts, walnuts and other tree nuts, fish, and eggs. In children, eggs, milk, peanuts, soy, and wheat are main culprits. According to the Food and Drug Administration, 90 percent of all allergic reactions in the United States are due to reactions to proteins in these foods. Additional "emerging" food allergens include tropical fruits, sesame seeds, psyllium, spices, and condiments (Ebo, 2001). In total, an estimated 150 Americans die each year from severe allergic reactions to food (Formanek, 2001).

Soy protein has been rated 11th among foods in terms of allergenicity, although milk and eggs are also considered very allergenic foods (Wraith & Young, 1979). In healthy, non-allergic children, soy is generally less allergenic than cow's milk. The incidence of cow's milk allergy ranges from 0.3 to 7.5% among infants. Allergy to soy is seen in 0.5% or less of this population (Eastham, 1989). Soy allergy is uncommon among adults.

The median age at which infants present with allergy to either soy or cow's milk is 3 months. The symptoms (in descending order of frequency) are: diarrhea, vomiting, irritability, atopic dermatitis, rhinitis (inflammation of the nasal mucous membrane) and asthma. However, by 3 years of age the majority of infants outgrow the symptoms. Overall, children usually outgrow their allergies to milk, egg, soy, and wheat, while allergies to peanuts, tree nuts, fish, and shrimp usually are not outgrown. A 1993-1996 survey of 61 cases of severe reactions by children to food in Sweden revealed that several youngsters who were allergic to peanuts also experienced soy anaphylaxis. Some young people with severe asthma and peanut allergy may also be allergic to soy, although there appears to be no obvious relationship between soy and milk allergies (Friedman and Brandon, 2001).

A recent study characterized food-allergic reactions in children ages 3-19 with known food allergies in schools and preschools to determine the mechanisms that are in place to prevent and treat those reactions. Of the 132 children in the study, 58% reported fool-allergic reactions in the past two years. Milk (32%) and peanut (29%) allergies were most common, while soy (3%) allergy was noted in 1 case (Nowak-Wegrzyn et al, 2001).

Although it is not completely certain which specific component of soy is responsible for allergic reactions, at least 15 allergenic proteins have been found in soybeans using the sera of soybean-sensitive patients (Ogawa et al., 1991). One study found the protein 2S globulin had the highest allergenic capacity (Shibasaki, 1980). In a review of soy and other protein sources and allergenicity, the main soy allergens reported were the 7S and 11S globulinic fractions containing conglycinin and glycinin. The IgE binding epitope on a seed vacuole protein (P34) identified as Glyn Bd 30 KD is a major soybean allergen in children with soy allergy. A minor allergen is the trypsin inhibitor, of which 80-90% is removed by heat used to prepare formula (Muraro, 2001).

Anyone allergic to soy will probably have to avoid all soy products, which include hydrolyzed vegetable protein, textured soy protein (also called textured vegetable protein, TVP), isolated soy protein, miso, natto, okara, soy cheese, soy sauces (teriyaki, tamari, shoyu), soy protein concentrates, isolates and flours, soynuts, soygrits, soy oil, tempeh, yuba, soy beverages, and tofu products. Avoid lecithin if it is made from soy oil instead of another type of plant oil. Soy meal and oil is utilized in a number of industrial products, including inks, soap and cosmetics. One has to read labels extremely carefully and if in doubt about a particular ingredient, contact the manufacturer. Most products have an address and/or phone number on them.

The way in which soyfoods are processed can affect allergenicity. In general, fermented soyfoods such as miso, tempeh, shoyu, tofu and natto are less allergenic than raw soybeans (Lalles & Peltre, 1996; Herian et al., 1993). Allergic reactions sometimes do not occur upon exposure to soy sauce because, in general, soy sauce is consumed in very low quantities and is low in protein (per gram) compared to other soy foods. Soybean oil that is completely free of protein should not produce allergic symptoms. For persons allergic to soy wanting to consume isoflavones, these are also present in other legumes in smaller
quantities.

Other recommended web resources on allergies include:
Food Allergy & Anaphylaxis Network: www.foodallergy.org
FDA Consumer: http://www.fda.gov
National Institute of Allergy and Infectious Diseases: www.niaid.nih.gov

References:
Eastman EJ. Soy protein allergy. In: Food Intolerance in Infancy: Allergology, Immunology, and Gastroenterology. Carnation Nutrition Education Services, v1, New York: Raven Press, 1989.

Ebo DG, Stevens WJ. Ige-mediated food allergy - Extensive review of the literature. Acta Clinica Belgica 2001;56(4):234-247.

Formanek R. Food allergies: When food becomes the enemy. FDA Consumer; July-August 2001:10-16.

Friedman M and Brandon D. Nutritional and health benefits of soy proteins. J. Agric. Food Chem. 2001;49(3):1069-1086.

Herian AM, Taylor SL, Bush RK. Allergenic reactivity of various soybean products as determined by RAST inhibition. J Food Science 1993;58:385-388.

Lalles JP, Peltre G. Biochemical features of grain legume allergens in humans and animals. Nutr Rev 1996:54:101-107.

Muraro MA. Soy and other protein sources. Pediatr Allergy Immunol 2001;12(Suppl 14):85-90.

Nowak-Wegrzyn A, Conover-Walker MK, and Wood RA. Fool-allergic reactions in schools and preschools. Archives of Pediatrics & Adolescent Medicine 2001;155(7):790-795.

Ogawa T. et al. Investigation of the IgE-binding proteins in soybeans by immumoblotting with the sera of the soybean-sensitive patients with atopic dermatitis. J Nutr. Sci. Vitaminol. 1991;37:555-565.

Shibasaki M, Suzuki S, Tajima S, Nemoto H, Kuroume T. Allerginicity of major components of soybean. Int Arch Allergy Appl Immun 1980;61:441-448.

Wraith DG, Young GVW. In: The Mast Cell: Its Role in Health and Disease. Piman Medical, London, 1979.

For more information about Dr. Hasler, see the Soy and Human Health Ask an Expert page.

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