Dietary Determinants of Metabolic and Gut Microbial Health in Patients with Inflammatory Bowel Disease

Abstract

Background: Diet has been linked to gut dysbiosis and the onset, course, and response to treatment of patients with IBD and metabolic disease. Methods: This single-centre prospective case-control study investigated the relationship between dietary intake, metabolic profile, and stool microbial composition in 57 individuals with IBD in clinical remission and 24 healthy individuals (HC). Participants' baseline anthropometric measurements, serum metabolic parameters, lipid profiles, and oral and stool samples for microbiota testing were collected. Their dietary intake and physical activity were documented. A partially corrected correlation was performed to examine the associations between variables and p-values adjusted for multiple comparisons using the Benjamini-Hochberg equation (adj-p). Results: In participants with IBD, the intake of saturated fat correlated positively, and the intake of dietary fibre correlated negatively with anthropometric indices (saturated fat and BMI: r = 0.37, adj-p = 0.04, fibre and BMI: r = -0.45, adj-p = 0.01). Higher anthropometric indices were associated with poorer glucose control and a less favourable serum lipid profile (BMI and insulin: r = 0.48, p < 0.01, WHR and triglycerides: r = 0.57, p < 0.01). The stool microbiota of participants in the IBD group was less diverse and more similar to their oral microbiota than was observed in the HC group (Mann-Whitney U test p = 0.03). Within the IBD group, a higher intake of added sugar and processed meat and a higher serum insulin level was associated with lower stool microbial alpha diversity (processed meat intake and Shannon's diversity: r = -0.43, adj-p = 0.02; added sugar and Shannon's diversity: r = -0.39, adj-p = 0.03; insulin and Shannon's diversity: r = -0.45, adj-p = 0.02). Neither the dietary intake nor stool microbial composition correlated with the risk of disease flaring. Conclusions: Our findings suggest that dietary intake is associated with the metabolic health and gut microbial composition of IBD patients.

Keywords: Crohn’s disease; diet; dietary fibre; flare; inflammatory bowel diseases; metabolic risk; microbiota; processed meat; ulcerative colitis.

Figure 1

Flowchart of participants, with reasons for exclusion or withdrawal from the study. Legend: CD: Crohn’s disease, HC: healthy control, IBD: inflammatory bowel disease, mo: months.

Figure 2

IBD group classified by BMI class. Legend: Bar graph displaying mean number of steroid courses per group. BMI: Body Mass Index class of participants in the IBD group: Obese (BMI ≥ 30, Overweight BMI 25–29.9, Normal weight BMI 18.5–24.9), p: p-value assessed using the Kruskal–Wallis test.

Figure 3

In the HC and IBD groups bar graphs which compare participants’ oral-stool microbiome bacterial similarities as measured by the Bray–Curtis similarities statistic, with a higher number representative of a more similar oral-stool microbial composition. Legend: Comparison was performed using Mann–Whitney U test following Shapiro-Wilk testing for data distribution. Arrow to indicate IBD participant who followed a ketogenic diet which included a high intake of processed meat.