BACKGROUND: Advice to avoid dietary emulsifiers in Crohn's disease (CD) is based on preclinical data. AIMS: To examine the effect of diets high (HED) and low (LED) in emulsifiers in the food supply on disease activity in CD. METHODS: In a double-blinded, randomised feeding study, we randomised adults with symptomatic, sonographically active CD with ileal involvement on ≥ 2 months' stable medical therapy to 4 weeks of a HED or LED modelled on Australian healthy eating guidelines. We measured the Harvey-Bradshaw Index (HBI), sonographic indices (IBUS-SAS, bowel wall thickness), quality of life (QOL) and fatigue at baseline and study completion. RESULTS: We randomised 24 patients, mean age 37 (95% CI 32, 41) years, 12 male, HBI 6 (6, 8), bowel wall thickness 6.0 (5.5-6.6) mm. Adherence was >
95%. Clinical remission (HBI <
5) occurred in 9/12 on HED and 7/12 on LED
2 and 3, respectively, withdrew early with increasing gastrointestinal symptoms. IBUS-SAS fell from 51 (35, 68) to 33 (15, 51) on HED (p = 0.014) and from 57 (38, 76) to 44 (29, 59) on LED (p = 0.01). Bowel wall thickness reduced by 34% on HED and 15% on LED in those who completed the study. QOL and fatigue improved on both diets (p ≤ 0.05). There were no statistically significant differences in outcomes between diets. CONCLUSIONS: In the context of a healthy diet, the emulsifier content had no influence over disease activity over 4 weeks in patients with CD. Recommendations to avoid emulsifiers in patients with active CD are not supported. Australian New Zealand Clinical Trials Registry (ACTRN12619001099112).