A Low Dietary Quality Index in a Newly Diagnosed Inflammatory Bowel Disease Cohort: Results from a Case-Control Study

Epidemiological evidence suggests a link between the risk of IBD and diet. Macro- and micro- nutrient intake, diet quality and dietary patterns may play a pivotal role in disease pathogenesis. We aimed to study the dietary intake of newly diagnosed IBD patients compared to non-IBD controls.

A cohort of newly diagnosed IBD patients were invited to complete the Scottish Collaborative Group Food Frequency Questionnaire (SCGFFQ) at their first clinic visit. Controls were recruited from non-IBD ambulatory patients, university students, and healthcare workers. The SCGFFQ estimates habitual diet over a 3-month period. Component nutrient data were calculated based on previous validation studies, deriving nutrient data by comparison of the SCGFFQ to actual weighted food records. Data on age, gender, ethnicity, and disease phenotype were collected. The intake of macro- and micro-nutrients was expressed as mean and standard deviation and compared using the Kruskal-Wallis test. Dietary patterns were derived using principal component analysis. Differences in the dietary patterns for age, gender, and ethnicity were analysed by logistic regression analysis. The diet quality was compared to the dietary recommendation values (DRVs) and measured using the diet quality index.

We enrolled 160 IBD cases (114 UC and 46 CD) and 126 non-IBD controls, and in the study, with a median age across the groups of 40 years (IQR = 24) for UC, 34 years (IQR = 29) for CD, and 36 years (IQR = 24) for non-IBD controls. The diet quality indexes for both UC and CD were low compared to controls: 59.0% (SD 18.0) for UC, 46.0% (SD 17.7) for CD, and 63.2% (SD 17.1) controls. UC patients had excessive total energy consumption (>2500 kcal/day) compared to the DRVs. UC patients reported higher retinol, vitamin D, riboflavin, niacin, vitamin B6, vitamin B12, and panthanoic acid intake, consistent with a diet rich in animal products and low in fruit/vegetable intake. This is likely driven by higher consumption of dietary patterns 2 (rich in carbohydrates, refined sugar and low fibre) and 5 (refined sugar and saturated fat) in the UC cohort. Dietary pattern 1 (variety of food items and oily fish) was less likely to be consumed by the CD population. CD patients tended to have a lower overall intake of both macro- and micro-nutrients.

The dietary patterns identified here are a proof of concept, and the next phase of the study would be to ideally monitor these patterns in a case-control cohort prospectively, and to further understand the mechanisms behind which dietary patterns influence IBD. Patients with newly diagnosed CD have low dietary quality and lower overall intake of macro- and micro-nutrients. This finding supports the role for dietetic attention early in newly diagnosed CD.