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Soy protein is widely used by the food industry for its functional benefits such as enhancing moisture retention. For this reason, considerable diligence is required by those who are allergic to soy protein because it is present in many commonly consumed foods. Fortunately, this diligence is required by relatively few individuals as overall, surveys indicate that the prevalence of soy allergy is lowest among the Big 8 food allergens.
Since 2004, the U.S. Food Allergen Labeling and Consumer Protection Act has mandated that the label of a food that contains an ingredient that is protein or is a derived protein from a “major food allergen” must include language noting the allergen included. The 8 foods classified as major allergens are thought to be responsible for 90% of the food-related allergic reactions among Americans.
When the Big 8 was established, relatively little prevalence data were available. However, as discussed below, over the past 10 years large surveys have provided considerable insight into the prevalence of food allergies among Canadian and U.S. children and adults.
The first report in the scientific literature of soy allergy dates to 1934, although in this case the allergic response was the result of airborne transfer of soy allergens among workers in a plant that milled soybeans.1 More than 30 potential soybean allergen sequences have been identified; 16 of which have been confirmed with some data to support sensitization and elicitation.2 However, IgE binding assays using immunoglobulins from soybean sensitive individuals reveal that about ⅔ of the total allergenic response is caused by 1 allergen, P34 (Gly m Bd 30K).3-5
The amount of soy protein required to elicit allergic responses in soy-sensitive individuals is generally much higher than for other food allergens.6 In fact, it may be more than an order of magnitude higher than observed for peanut allergy.7-9 Highly refined soybean oil is exempt from labeling because any residual trace amounts of protein that might be in soybean oil have been shown not to cause reactions in soy protein-sensitive individuals.10
Allergic reactions to soy are generally considered to be more moderate in comparison to other food allergens, although some cases of anaphylaxis have been reported in the literature. In 1999, Foucard et al.11 concluded that soy allergy has probably been underestimated as a cause of food anaphylaxis. This conclusion was based on a review of medical records of all fatal and life-threatening reactions sent to them by physicians in Sweden over a 3-year period. It was determined that 4 individuals suffered fatal allergic reactions in response to soy protein. However, 1 year later, Sicherer et al.12 suggested that these reactions were not caused by soy, per se, but instead because the soy-containing foods consumed were contaminated with trace quantities of peanut protein, lupine, or some other allergen. They noted that if these reactions were due to soy protein, Foucard et al.11 would have identified more fatal soy-allergic reactions in a single country than have been reported in the rest of the world.
Generating accurate prevalence data is challenging because for the most part it relies on self-reported data, that is, survey respondents report whether they are allergic to specific foods. In some cases, respondents also indicate whether their allergy was diagnosed by a physician, although the method of physician diagnosis is not necessarily reported. It is generally recognized that self-reported data overestimate prevalence when compared to more rigorous diagnostic methods.13 In some cases, surveys can partially control for this discrepancy by assessing whether the report of allergy is consistent with patient history.
Despite the limitations, recent North American surveys provide considerable insight into the prevalence of soy allergy. As shown in the table, among U.S. and Canadian adults, surveys consistently show that the prevalence of soy allergy is lower than the prevalence of the other 7 foods in the Big 8. For example, the prevalence of milk/ dairy allergy is between about 3 and 41 times greater than the prevalence of soy allergy. Estimates of the prevalence of soy allergy range from 1 to 6 per 1,000 adults.
The prevalence of food allergy is greater among children than adults, although recent data indicate that food allergies often begin in adulthood.14 As in adults, soy allergy prevalence among children is the lowest among the Big 8. Children tend to outgrow their allergies, although the rate and extent to which this outcome occursvaries.15 Estimates in the literature suggest 70% of children outgrow their soy allergy by age 10.15,16
Finally, concerns about soy allergy appear to be 1 reason many products targeting flexitarians and vegetarians are now made with pea protein rather than soy protein. Although pea protein has not been studied as extensively, it does cause allergic reactions. In fact, concentrating the protein—as is the case for pea protein isolate and pea protein concentrate— may lead to enhanced allergenicity.17 Canadian researchers recently described 6 cases of severe allergic reactions to foods containing concentrated sources of pea protein.17
Self-Reported Prevalence of Food Allergy Reported by US and Canadian Adults for Major Food Allergens (percent of population)
Years data collected
1. Duke WW. Soy bean as a possible important source of allergy. J Allergy Clin Immunol. 1934;5300-2.
2. Stevenson SE, Woods CA, Hong B, et al. Environmental effects on allergen levels in commercially grown non-genetically modified soybeans: assessing variation across north america. Front Plant Sci. 2012;3196.
3. Ogawa T, Tsuji H, Bando N, et al. Identification of the soybean allergenic protein, Gly m Bd 30K, with the soybean seed 34-kDa oil-body-associated protein. Biosci Biotechnol Biochem. 1993;57(6):1030-3.
4. Helm RM, Cockrell G, Connaughton C, et al. Mutational analysis of the IgE-binding epitopes of P34/Gly m Bd 30K. J Allergy Clin Immunol. 2000;105(2 Pt 1):378-84.
5. Herman EM. Genetically modified soybeans and food allergies. J Exp Bot. 2003;54(386):1317-9.
6. Bindslev-Jensen C, Briggs D, Osterballe M. Can we determine a threshold level for allergenic foods by statistical analysis of published data in the literature? Allergy. 2002;57(8):741-6.
7. Ballmer-Weber BK, Holzhauser T, Scibilia J, et al. Clinical characteristics of soybean allergy in Europe: a double-blind, placebo-controlled food challenge study. J Allergy Clin Immunol. 2007;119(6):1489-96.
8. Hourihane JB, Kilburn SA, Nordlee JA, et al. An evaluation of the sensitivity of subjects with peanut allergy to very low doses of peanut protein: a randomized, double-blind, placebo-controlled food challenge study. J Allergy Clin Immunol. 1997;100(5):596-600.
9. Wensing M, Penninks AH, Hefle SL, et al. The distribution of individual threshold doses eliciting allergic reactions in a population with peanut allergy. J Allergy Clin Immunol. 2002;110(6):915-20.
10. Bush RK, Taylor SL, Nordlee JA, et al. Soybean oil is not allergenic to soybean-sensitive individuals. J Allergy Clin Immunol. 1985;76(2 Pt 1):242-5.
11. Foucard T, Malmheden Yman I. A study on severe food reactions in Sweden--is soy protein an underestimated cause of food anaphylaxis? Allergy. 1999;54(3):261-5.
12. Sicherer SH, Sampson HA, Burks AW. Peanut and soy allergy: a clinical and therapeutic dilemma. Allergy. 2000;55(6):515-21.
13. Sicherer SH, Sampson HA. Food allergy: A review and update on epidemiology, pathogenesis, diagnosis, prevention, and management. J Allergy Clin Immunol. 2018;141(1):41-58.
14. Gupta RS, Warren CM, Smith BM, et al. Prevalence and severity of food allergies among US adults. JAMA Netw Open. 2019;2(1):e185630.
15. Savage J, Sicherer S, Wood R. The Natural History of Food Allergy. The journal of allergy and clinical immunology In practice. 2016;4(2):196-203; quiz 4.
16. Savage JH, Kaeding AJ, Matsui EC, et al. The natural history of soy allergy. J Allergy Clin Immunol. 2010;125(3):683-6.
17. Lavine E, Ben-Shoshan M. Anaphylaxis to hidden pea protein: A Canadian pediatric case series. The journal of allergy and clinical immunology In practice. 2019.
18. McGowan EC, Peng RD, Salo PM, et al. Changes in food-specific IgE Over time in the National Health and Nutrition Examination Survey (NHANES). The journal of allergy and clinical immunology In practice. 2016;4(4):713-20.
19. Verrill L, Bruns R, Luccioli S. Prevalence of self-reported food allergy in U.S. adults: 2001, 2006, and 2010. Allergy Asthma Proc. 2015;36(6):458-67.
20. Soller L, Ben-Shoshan M, Harrington DW, et al. Overall prevalence of self-reported food allergy in Canada. J Allergy Clin Immunol. 2012;130(4):986-8.
Mark Messina, PhD, MS, is the co-owner of Nutrition Matters, Inc., a nutrition consulting company, and is an adjunct professor at Loma Linda University. His research focuses on the health effects of soyfoods and soybean components. He is chairman of The Soy Connection Editorial Board and executive director of the Soy Nutrition Institute.
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