Celiac disease is a rare autoimmune disease that affects approximately 1% of the US population, though the condition is suspected to be underdiagnosed because some people do not develop the characteristic gastrointestinal symptoms associated with the disease, such as diarrhea and weight loss. In people with celiac disease, exposure to gluten (eg, from eating wheat, barley, and other grains) triggers the immune system to attack the lining of the intestine, making it difficult or impossible to absorb nutrients. It has been unclear what exactly causes individuals who are genetically predisposed to celiac disease to develop a reaction to gluten but a new study published in Frontiers in Pediatrics suggests it could be the popular food additive, microbial transglutaminase, which has been used in many processed foods, baked goods, and meat and dairy products, over the past 4 decades.
Microbial transglutaminase is an enzyme isolated from Streptoverticillium mobaraense that is used to improve food texture, palatability, and shelf-life. “Microbial transglutaminase can glue together proteins… This enzyme functions like the transglutaminase produced by our body, which is known to be the target of autoimmunity in celiac disease,” Aaron Lerner, a study author and visiting professor at the Aesku.Kipp Institute in Germany, said in a study-related statement.
Lerner explained that two major processes may be at play. First, gluten is difficult to digest, often leaving behind gluten protein fragments (peptides). These peptides are highly susceptible to transglutaminase and subsequently become transformed by them, creating a variety of new peptides. These new peptides resist further breakdown and become recognized as foreign bodies by human leukocyte antigen (HLA)-DQ receptors located inside the gut wall. Almost all cases of celiac disease are associated with one of two HLA-DQ genes: HLA-DQ2 or HLA-DQ8. Although celiac disease is rare, approximately 30% of people carry one of these genes, making them susceptible to celiac disease if the conditions are right. This is where environmental factors, such as microbial transglutaminase, may come into play.
The second process involves intestinal permeability. Lerner said microbial transglutaminase may directly modify the proteins that hold the intestinal barrier together, increasing intestinal permeability. This would allow more gluten-derived proteins and microbial transglutaminases to breach the intestinal barrier and cause an immune reaction.
Although further studies are needed to confirm these associations, Lerner suggests individuals with celiac disease might want to try to avoid foods that contain microbial transglutaminase. Per the United States Department of Agriculture website, microbial transglutaminase should be included in the ingredient labeling of any food product processed with this additive. “TG enzyme is not considered a processing aid that would be exempt from labeling. There are no exemptions to the USDA’s mandatory labeling requirement for this product,” the website states.