Overweight and vitamin D deficiency are common in patients with irritable bowel syndrome - a cross-sectional study.

Background: Irritable bowel syndrome (IBS) is a common disease with unknown etiology. Poor dietary intake with nutritional deficiency and overweight have been described to increase the risk of IBS. The aim of the present study was to compare weight and circulating levels of micronutrients in IBS compared with healthy controls.

Design: Cross-sectional study.

Methods: Patients diagnosed with IBS and healthy volunteers were recruited. Participants had to complete a dietary diary book and the questionnaires Rome IV, IBS-severity scoring system (IBS-SSS), and visual analog scale for IBS (VAS-IBS). Weight and height were measured, and blood samples were drawn. C-reactive protein (CRP), cobalamin, folate, iron, total iron-binding capacity (TIBC), and 25-hydroxy (25-OH) vitamin D were analyzed. Differences were calculated between groups and generalized linear model for regressions was adjusted for false discovery rate (FDR).

Results: IBS patients (n = 260) were elder than controls (n = 50) (44.00 (33.25-56.00) vs. 37.85 (30.18-45.48) years; p = 0.012). After adjustment for age, both weight (β: 5.880; 95% CI: 1.433-10.327; p = 0.010, FDR = 0.020) and body mass index (BMI) (β: 2.02; 95% CI: 0.68-3.36; p = 0.003, FDR = 0.012) were higher in patients. Among IBS participants, 48.1% were overweight/obese compared with 26.0% in controls (p = 0.007). Diarrhea-predominated IBS had highest weight (p < 0.001) and BMI (p = 0.077). CRP and cobalamin were higher in patients than controls (p = 0.010 vs. p = 0.007), whereas folate was highest in controls (p = 0.001). IBS patients had lower intake of vegetables (p = 0.026), dairy products (p = 0.004), and cereals (p = 0.010) compared with controls. Despite 21.5% of IBS patients were taking vitamin D supplements, 23.65% of them had vitamin D levels below 50 nmol/L, compared with 26.0% observed in the control group (p = 0.720). Vitamin D levels were lower in overweight than in normal weight IBS patients (60 (48-73) nmol/L vs. 65 (53-78) nmol/L, p = 0.022). Vitamin D correlated with cobalamin and folate but correlated inversely with TIBC and BMI. IBS patients had a high degree of gastrointestinal and extraintestinal symptoms, which were inversely associated with iron levels. Extraintestinal symptoms were associated with increased BMI.

Conclusion: IBS patients were often overweight or obese, with low vitamin D levels. High burden of extraintestinal symptoms were associated with overweight and lower iron levels.

Registration: ClinicalTrials.gov, NCT05192603 (Date of registration 11/29/2021) and NCT03306381 (Date of registration 09/18/2017), respectively.