¹Hyogo Medical University, Neuropsychiatry, Nishinomiya, Japan

Background: Gluten intolerance is a syndrome characterized by several physical and psychological symptoms such as abdominal pain, constipation, diarrhea, headache, foggy brain, tiredness, anxiety, and depression, related to the ingestion of gluten. Gluten intolerance is one of the gluten-related diseases. It is thought to differ in mechanism from autoimmune diseases such as celiac disease and allergies. We have already reported the association between treatment-resistant schizophrenia and gluten intolerance may be an aggravating factor in various psychiatric disorders.
Eating disorders are mental disorders that are often difficult to treat, especially when recovering from low weight. Low weight often results in constipation due to reduced gastrointestinal tract activity, but sometimes patients complain of diarrhea despite the absence of laxative abuse. Patients with avoidant/restrictive food intake disorder (ARFID) reduce their intake due to discomfort caused by eating food. Many patients with anorexia nervosa (AN) usually avoid carbohydrates including gluten.

Aims & Objectives: We hypothesized that gluten sensitivity might be associated with the development of underweight eating disorders and conducted this study.

Method: From 2020 to 2024, patients with underweight eating disorders who visited our inpatient/outpatient unit in Hyogo medical university hospital and age- and sex-matched healthy controls without subjective symptoms of gluten intolerance were recruited. We determined immunological gluten sensitivity using anti-gliadin IgG antibody, and psychiatric and physical symptoms were evaluated by medical interview and self-administered questionnaire. We excluded participants on a strict gluten-free diet because their anti-gliadin IgG antibody levels seem to be reduced. Anti-tissue transglutaminase IgA antibody was also measured to exclude patients with celiac disease. This study was approved by the ethics committee at Hyogo Medical University. Detailed explanations of the study procedures were provided to each participant at the time we received their informed consent.

Results: The sample consisted of 34 female patients with underweight eating disorders, including 23 patients with AN, 10 patients ARFID and 1 patient with other specified eating disorder, and 43 healthy controls participated. Immunological gluten sensitivity was significantly higher in underweight eating disorders than in healthy controls, 47%, 11.6%, respectively（P<0.001）. Positive rates of immunological gluten sensitivity in each group were 47.3% in AN and 40% in ARFID. Two patients with AN who were positive for anti-gliadin IgG antibodies were introduced to a gluten-free diet during outpatient treatment after immunological gluten sensitivity was detected and showed clear weight gain.

Discussion & Conclusions: Significantly higher immunological gluten sensitivity was found in underweight eating disorders, suggesting that immunological gluten sensitivity may be a factor in the development and maintenance of eating disorders.