IMPACT OF ANTI-INFLAMMATORY DIET VERSUS HIGH-FIBER DIET ON SYMPTOMATIC REMISSION AND FECAL CALPROTECTIN IN INFLAMMATORY BOWEL DISEASE

Abstract BACKGROUND Diet is increasingly recognized as a modifiable factor in inflammatory bowel disease (IBD). The UCLA anti-inflammatory diet (AID) was developed by gastroenterology-specialized dietitians after a comprehensive review of anti-inflammatory nutrients in the research literature. The aim of this study was to compare the effectiveness of AID versus high-fiber diet in patients with IBD. METHODS A retrospective cohort study was conducted of adult patients of the UCLA IBD Center, who were seen by a registered dietitian between January 2022 through February 2024 and counseled to initiate AID or a fiber-rich diet. Demographics, disease characteristics, and medication use were abstracted from the electronic medical records. Disease activity was assessed using the Harvey–Bradshaw Index for Crohn’s disease (CD) and the Simple Clinical Colitis Activity Index for ulcerative colitis (UC). Primary endpoints were symptomatic remission and change in fecal calprotectin, as first measured between 2-12 months after baseline visit. Subgroup analyses excluded recent corticosteroid use and separately evaluated patients on biologics. Continuous variables were compared using t-tests and categorical variables using chi-square tests. RESULTS In the entire cohort (83 AID, 64 fiber), baseline demographics were generally similar, although imbalances were noted with race (p = 0.02), IBD type (AID: 52% CD, 48% UC; fiber: 78% CD, 22% UC; p = 0.002), and steroid exposure (37% vs 20%; p = 0.04). After excluding patients with recent steroid exposure (AID 52, fiber 51), groups were comparable except for IBD type (AID: 52% CD, 48% UC; fiber: 78% CD, 22% UC; p = 0.009). Symptomatic remission occurred significantly more often with AID vs. fiber in the overall cohort (81% vs. 38%; p < 0.001), subgroup off steroids (90% vs. 33%; p < 0.001), and biologic users (80% vs 31%; p < 0.001) (Fig.1). Calprotectin decreased significantly with AID but not fiber in the overall cohort (Δ − 374, p < 0.001 vs. −62, p = 0.60), with reductions persisting among those off steroids (Δ − 242, p = 0.036 vs. -63, p = 0.58) and in biologic users (Δ − 417, p < 0.001 vs. -80, p = 0.54) (Fig. 2). Between-group differences were significant overall (p = 0.03) and in biologic users (p = 0.03) but not in the subgroup off steroids (p = 0.20) (Fig. 2). CONCLUSION The AID was significantly associated with symptomatic remission and greater reductions in fecal calprotectin, when compared with high-fiber controls. These findings highlight the potential benefit of a holistic anti-inflammatory dietary approach over mere increase in fiber intake for improvement of clinical outcomes in IBD. Future efforts should focus on prospective validation, explore mechanisms linking diet and mucosal inflammation, and assess how dietary counseling may complement existing therapies.