Inflammatory bowel disease (IBD) is a common chronic inflammation in parts of the gastrointestinal tract with a prevalence rate of 0.1 to 0.4 % in the general population [1]. The most prevalent IBDs are Crohn's Disease (CD) and Ulcerative Colitis (UC). Recent studies have reported that the incidence and prevalence of this disease have been increasing in the last five decades [1], [2]. A recent study from Iran has predicted an emerging epidemic for the prevalence of IBD in the country [3].

The pathogenesis of IBDs including CD and UC is not completely known. The onset and development of intestinal inflammation can be attributed to different factors including genetic defects, familial history, host microbiome, environmental stimuli like smoking, air pollution, the use of birth control pills, and diet [4], [5]. Based on the current evidence, diet plays an important role in shaping the composition of enteric flora. Therefore, diet could be considered a preventive or therapeutic option [6].

For many patients living with UC, a proper diet plan involves eliminating foods that appear to raise the possibility of worsening the disease symptoms [7]. Gluten is a food component that has recently been suggested to play a possible role in the development and recurrence of UC [8]. Gluten is a water-insoluble protein that due to its abnormal structure is not fully digested by intestinal enzymes but produces peptides that stimulate the intestinal immune system. These changes lead to intestinal villi depletion, intestinal crypt gland hyperplasia, and malabsorption of certain foods [9]. There is a growing recognition of Non-celiac Gluten Sensitivity (NCGS) in IBD patients. Cross-sectional studies have shown that approximately one-third of these patients report NCGS diagnosis [8], [10]. Therefore, NCGS is defined as a condition induced by the ingestion of gluten leading to intestinal or extraintestinal symptoms [11]. In addition, some studies indicated that gluten may activate the innate immune system and decrease intestinal barrier function [12], [13]. Thus, based on its absorption pattern and immunogenicity, it may be reasonable to study gluten-free diets in IBD patients.

Although several cross-sectional studies have suggested that GFD may improve symptoms in IBD patients, there is a need for interventional studies to evaluate the effect of this diet in patients with mild to moderate UC [8]. This study aimed to evaluate the effect of a GFD on inflammatory markers, disease severity, and quality of life in patients with mild to moderate UC.