Personalized Research on Diet in Ulcerative Colitis and Crohn’s Disease (PRODUCE): A Series of N-of-1 Diet Trials

Evidence about Specific Carbohydrate Diet (SCD) for inflammatory bowel disease (IBD) is limited. We conducted 54 single-subject, double-crossover N-of-1 trials comparing SCD to a modified SCD (MSCD) and comparing each to the participant's baseline, usual diet (UD).Across 19 sites, we recruited patients 7-18 years with IBD and active inflammation. Following a 2-week baseline (UD), patients were randomized to one of two sequences of four alternating 8-week SCD and MSCD periods. Outcomes included fecal calprotectin and patient-reported symptoms. We report posterior probabilities from Bayesian models comparing diets.Twenty-one (39%) participants completed the trial, 9 (17%) completed a single crossover, and 24 (44%) withdrew. Withdrawal or early completion occurred commonly (lack of response (n=11), adverse events (n=11) and not desiring to continue (n=6)). SCD and MSCD performed similarly for most individuals. On average, there was <1% probability of a clinically meaningful difference in IBD symptoms between SCD and MSCD. The average treatment difference was -0.3 (95% CrI -1.2, 0.75). There was no significant difference in the ratio of fecal calprotectin geometric means comparing SCD and MSCD [0.77 (95% CrI 0.51, 1.10)]. Some individuals had improvement in symptoms and fecal calprotectin compared to their UD, while others did not.SCD and MSCD did not consistently improve symptoms or inflammation, although some individuals may have benefited. However, there are inherent difficulties in examining dietary changes that complicate study design and ultimately conclusions regarding effectiveness.