Celiac disease (CD) is an autoimmune enteropathy triggered by dietary gluten in genetically susceptible individuals. Gluten is commonly present in cereals such as wheat, barley, rye, and spelt (1). The global prevalence of CD based on serologic (i.e., presence of particular antibodies) test results is 1.4% and based on biopsies showing villous abnormalities, it is 0.7% (2). There is evidence suggesting that the incidence of CD has increased over the latter half of the 20th century and into the 21st century throughout the Western world (3). The increased incidence of CD has also been observed in the U.S. (4).
However, these relatively low incidence rates are misaligned with the results of a Gallop poll conducted in 2015 that showed 20% of Americans opt for a gluten-free diet and 17% say they avoid gluten-free foods (5). Although some Americans may avoid gluten because they think it is a healthy choice in general, others may avoid it because they have non-celiac gluten sensitivity, which is defined as a non-allergic and non-autoimmune condition in which the consumption of gluten can lead to symptoms similar to those seen in CD (6). Non-celiac gluten sensitivity, a less-known clinical entity, has been estimated to have a prevalence of up to 6% in the United States (7).
Soybeans do not contain gluten. And yet, in 1999, Faulkner-Hogg et al. (8) reported that soy triggered symptoms upon introduction to CD patients after they followed a strict gluten-free diet. In fact, of the 24 patients examined, 12 reacted to soy. Soy provoked flatulence, bloating, abdominal pain, and headache. In a personal communication a decade ago, one of these authors commented that although follow-up work had not been published, clinical experience since that report has continued to show that soy causes symptoms in CD patients.
Before that publication, Haeney et al. reported that CD patients who responded poorly to a gluten-free diet had significant anti-soya antibodies compared to patients with other gastrointestinal diseases. These authors suggested that CD patients may have an associated dietary soy sensitivity which could adversely influence their response to gluten withdrawal.
However, in contrast to these reports, a 2019 study found that in pediatric patients with both CD and eosinophilic esophagitis, soy was found to be well-tolerated, which led the authors to conclude that reintroducing this food first — or trialing a soy-inclusive elimination diet — is a viable treatment strategy (9).
So, what might account for some CD patients reacting to soy? There are several possibilities, but one of the most likely is cross-contamination. Comingling of grain can occur because of the use of shared harvesting, transporting, and processing equipment (10). Soybeans are typically rotated with other crops to improve soil conditions, one of which is wheat (11).
A 2010 publication showed that of the two soy flours analyzed, one contained only 92 parts per million gluten, whereas the other contained 2,925 parts per million (12). This finding illustrates the huge variation in gluten contamination within the same product category, and that some soy products may cause reactions in patients with CD. For comparison, <20 parts per million is generally considered “gluten-free” according to the U.S. FDA (13).
In conclusion, soybeans themselves are free of gluten. Soy sauce and miso can contain gluten, but gluten-free versions are available. If you have CD and are worried about consuming soy products, you should look for products labeled gluten-free as a precaution.
References:
1. Fasano A, Catassi C. Clinical practice. Celiac disease. N. Engl. J. Med. 2012;367(25):2419-26 doi: 10.1056/NEJMcp1113994 [published Online First: 2012/12/21].
2. Singh P, Arora A, Strand TA, et al. Global prevalence of celiac disease: Systematic review and meta-analysis. Clin Gastroenterol Hepatol 2018;16(6):823-36 e2 doi: 10.1016/j.cgh.2017.06.037 [published Online First: 2018/03/20].
3. King JA, Jeong J, Underwood FE, et al. Incidence of celiac disease is increasing over time: A systematic review and meta-analysis. Am. J. Gastroenterol. 2020;115(4):507-25 doi: 10.14309/ajg.0000000000000523 [published Online First: 2020/02/06].
4. Dahiya DS, Al-Haddad M, Perisetti A, et al. Celiac disease hospitalizations: an emerging challenge in the United States. Ann Gastroenterol 2022;35(4):383-92 doi: 10.20524/aog.2022.0724 [published Online First: 2022/07/06].
5. Riffkin ROiFAIG-FFi, https://prezi.com/fuws7phgltkb/ DAfU, one-in-five-americans-include-gluten-free-foods-in-diet/. One in Five Americans Include Gluten-Free Foods in Diet. 2017.
6. Volta U, Tovoli F, Cicola R, et al. Serological tests in gluten sensitivity (nonceliac gluten intolerance). J. Clin. Gastroenterol. 2012;46(8):680-5 doi: 10.1097/MCG.0b013e3182372541 [published Online First: 2011/12/06].
7. Igbinedion SO, Ansari J, Vasikaran A, et al. Non-celiac gluten sensitivity: All wheat attack is not celiac. World journal of gastroenterology 2017;23(40):7201-10 doi: 10.3748/wjg.v23.i40.7201 [published Online First: 2017/11/17].
8. Faulkner-Hogg KB, Selby WS, Loblay RH. Dietary analysis in symptomatic patients with coeliac disease on a gluten-free diet: the role of trace amounts of gluten and non-gluten food intolerances. Scand. J. Gastroenterol. 1999;34(8):784-9 [published Online First: 1999/09/28].
9. Patton T, Chugh A, Padhye L, DeGeeter C, Guandalini S. Pediatric celiac disease and eosinophilic esophagitis: Outcome of dietary therapy. J. Pediatr. Gastroenterol. Nutr. 2019;69(2):e43-e48 doi: 10.1097/MPG.0000000000002343 [published Online First: 2019/03/29].
10. Thompson T. Gluten contamination of commercial oat products in the United States. N. Engl. J. Med. 2004;351(19):2021-2 doi: 10.1056/NEJM200411043511924 [published Online First: 2004/11/05].
11. Janovicek K, Hooker D, Weersink A, Vyn R, Deen B. Corn and soybean yields and returns are greater in rotations with wheat. Agron. J. 2021;113(2):1691-711.
12. Thompson T, Lee AR, Grace T. Gluten contamination of grains, seeds, and flours in the United States: a pilot study. J. Am. Diet. Assoc. 2010;110(6):937-40 doi: 10.1016/j.jada.2010.03.014 [published Online First: 2010/05/26].
13. ‘Gluten-Free’ Means What It Says. US Food and Drug Administration. Accessed February 6, 2025. https://www.fda.gov/consumers/consumer-updates/gluten-free-means-what-it-says.
This blog is supported by SNI Global and U.S. Soy.
