Dietary Exposures and Interventions in Inflammatory Bowel Disease: Current Evidence and Emerging Concepts

Abstract

Diet is intimately linked to the gastrointestinal (GI) tract and has potent effects on intestinal immune homeostasis. Inflammatory bowel disease (IBD) is characterized by chronic inflammation of the GI tract. The therapeutic implications of diet in patients with IBD have received significant attention in recent years. In this review, we provide a contemporary and comprehensive overview of dietary exposures and interventions in IBD. Epidemiological studies suggest that ultra-processed foods, food additives, and emulsifiers are associated with a higher incidence of IBD. Exclusion and elimination diets are associated with improved symptoms in patients with IBD, but no effects on objective markers of inflammation. Specific dietary interventions (e.g., Mediterranean, specific carbohydrate, high fiber, ketogenic, anti-inflammatory diets) have been shown to reduce symptoms, improve inflammatory biomarkers, and quality of life metrics to varying degrees, but these studies are limited by study design, underpowering, heterogeneity, and confounding. To date, there is no robust evidence that any dietary intervention alone may replace standard therapies in patients with IBD. However, diet may play an adjunct role to induce or maintain clinical remission with standard IBD therapies. The results of novel dietary trials in IBD such as personalized fiber, intermittent fasting, and time-restricted diets are eagerly awaited.

Keywords: Crohn’s disease; clinical trials; diet; epidemiology; food; inflammatory bowel disease; ulcerative colitis.

Figure 1

Ultra-processed Foods and Food Additives in IBD. (A) Additives and their effects on IBD: Excessive salt and artificial sweeteners can promote intestinal inflammation and induce colitis. Higher salt concentrations have been shown to increase intestinal permeability, increase inflammatory cytokine production through a reduction in fecal short-chain fatty acid production and depletion of Lactobacillus, and exacerbate chemically induced colitis in experimental models. Artificial sweeteners in UPFs may also induce gut inflammation, as seen in mice models of spontaneous ileitis with sucralose/maltodextrin supplementation. Azo dyes red 40 and yellow 6, the most abundant synthetic food coloring used by the food industry, can trigger IBD-like colitis in genetically susceptible mice. Consumption of ≥3 servings/week of soft drinks, consumption of ≥100 g/day of refined, sweetened foods, and consumption of ≥100 g/day of salty snacks were all associated with a higher risk of IBD. (B) Common Emulsifiers P80 and CMC effects on Gut and Microbiome: P80 and CMC are the most studied emulsifiers. They have been found to cause similar alterations to human gut microbiomes as does IBD. CMC and P80 are found in edible oils, ice creams, cake mixes, icing, and chocolate syrup, but ingestion of them has led to reduced numbers of beneficial Bifidobacterium and important SCFA producers—Faecalibacterium and Subdoligranulum—and Clostridium leptum. These same microbiota alterations by P80 and CMC in mice led to chronic intestinal inflammation.

Figure 2

Elimination and Exclusion Diets in IBD.

Figure 3

Specific Dietary Interventions in IBD: Mediterranean Diet (MD), Specific Carbohydrate Diet (SCD), and Anti-Inflammatory Diet (AID).

Figure 4

Specific Dietary Interventions in IBD: Ketogenic Diet (KD) and Plant-Based Diet (PBD) in IBD.