Can Patients with Celiac Disease Safely Consume Soy? What the Evidence Shows

By Mark Messina, PhD, MS

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.¹The prevalence of CD has steadily increased in the latter half of the 20th century and into the 21st century.² The increased incidence of CD noted globally, has also been observed in the U.S.³ Estimates are that global prevalence ranges from between 0.7% and 2.9% in the general population. Prevalence is higher in females and well-defined at-risk groups, such as relatives of affected individuals and patients with autoimmune comorbidities.⁴In addition to CD, non-celiac gluten sensitivity (NCGS) has been estimated to have a U.S. prevalence of up to 6%.⁵ NCGS is a clinical entity characterized by the absence of CD and wheat allergy in patients that trigger reproducible symptomatic responses to gluten-containing foods.

Soybeans do not contain gluten. Nevertheless, there is confusion about whether patients with CD can consume soy foods. At least two observations are likely to contribute to this confusion. Most traditional soy sauces contain gluten as they are made from wheat, soybeans, salt, and water. However, some gluten-free soy sauce options are available. Interestingly, a 2018 analysis found that despite being made with wheat, the presence of gluten in soy sauce was undetectable, perhaps because the protein was hydrolyzed during fermentation.⁶

In 1999, Faulkner-Hogg et al.⁷ reported that consuming soy triggered symptoms in CD patients after they followed a strict gluten-free diet. In fact, of the 24 patients examined, 12 reacted to soy. A decade ago, one author reported in personal correspondence that, although no follow-up studies had been published, clinical experience still indicated that soy triggers symptoms in CD patients. However, in contrast to this report, a 2019 study found that in pediatric patients with both CD and eosinophilic esophagitis, soy was 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.⁸

These contrasting findings may be a result of possible cross-contact of soy flour with wheat. In 2010, Thompson et al.⁹ found that of the two soy flours analyzed, one contained only 92 parts per million gluten, whereas the other contained 2,925 parts per million. These values indicate the potentially huge variation in gluten cross-contact 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.¹⁰ Finally, it is possible that some CD patients are also allergic to soy protein, although the incidence of soy allergy is quite low in comparison to the other major food allergens.¹¹

Before that 2010 publication, Haeney et al.¹²reported that CD patients who responded poorly to a gluten-free diet had significant anti-soya antibodies in comparison 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.

Practical Guidance for Patients and Clients

So, what might account for some CD patients reacting to soy? There are several possibilities, but one of the most likely is cross-contact. Comingling of grain can occur because of the use of shared harvesting, transporting, and processing equipment.¹³ Soybeans are typically rotated with other crops to improve soil conditions, one of which is wheat.¹⁴

If you have CD, and are concerned about consuming soy products, look for products labeled or certified as gluten-free.

REFERENCES

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CAN PATIENTS WITH CELIAC DISEASE SAFELY CONSUME SOY? WHAT THE EVIDENCE SHOWS

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