The effect of dietary emulsifiers and thickeners on intestinal barrier function and its response to acute stress in healthy adult humans: A randomised controlled feeding study

Background: Although dietary emulsifiers are implicated in the pathogenesis of Crohn's disease, their effect has not been studied in humans. Aim: To determine the effects of high- and low-emulsifier diets (HED, LED) on intestinal barrier function in healthy subjects in unstressed and acutely stressed states. Methods: We conducted a single-blinded, cross-over, controlled feeding trial in 22 healthy adults. After recording 7 days of their habitual diet, we randomised participants to HED or LED with ≥3-week washout between diets. On dietary completion, acute stress was induced via intravenous corticotrophin-releasing hormone. We assessed dietary adherence, effects on 2-h urinary lactulose: rhamnose ratio (LRR), serum concentrations of lipopolysaccharide-binding protein, soluble-CD14 and markers of epithelial injury and inflammation. Results: Dietary adherence was excellent. In an unstressed state, median (interquartile range) LRR during HED was 0.030 (0.018–0.042); on LED, this was 0.042 (0.029–0.078; p = 0.04). LPB concentrations were lower on HED than LED (p = 0.026), but no differences were observed for epithelial injury or inflammation. Under acute stress, LRR increased by 89% (−1% to 486%) on HED (p = 0.004), differing (p = 0.001) from 39% (1%–90%) decrease on LED (p = 0.009). Soluble-CD14 also increased (p < 0.001). The LED had a prolonged carry-over effect on suppressing HED-induced changes during stress. Similar changes in LRR and soluble-CD14 were observed when HED was used as the first diet (both p < 0.01). Conclusion: High intake of emulsifiers improved barrier function in the unstressed state, but increased intestinal permeability to stress, without evidence of inflammation. A LED was protective of the stress effect.