The Link between Vitamin D and Irritable Bowel Syndrome

Background: Irritable bowel syndrome (IBS) and other functional gastrointestinal disorders are common and can significantly affect quality of life. This study aimed to evaluate the efficacy of vitamin D3 supplementation in treating IBS symptoms using the IBS Symptom Severity Score (SSS), and to assess the relationship between serum 25-hydroxyvitamin D (25-OH vitamin D) levels and IBS. Methods: This observational cross-sectional study included 130 participants aged ≥18 years attending the Internal Medicine outpatient clinic at Benha University Hospitals. They were divided into two equal groups: Group A (65 IBS patients) and Group B (65 healthy controls). Blood samples were collected to measure serum 25-OH vitamin D levels. IBS patients were also assessed using the IBS-SSS. Results: Vitamin D deficiency was significantly more prevalent in the IBS group (36.92%) compared to the control group (26.15%) (P = 0.028). Among IBS subtypes, the constipation-predominant type (IBS-C) showed the highest prevalence of deficiency (78.46%) compared to IBS-D (13.48%) and IBS-M (7.59%). Following vitamin D supplementation, the IBS group demonstrated a significant increase in vitamin D levels and a marked decrease in SSS scores (P < 0.001 for both). No significant correlations were found between vitamin D levels and age, BMI, hemoglobin, WBCs, platelets, liver enzymes, creatinine, or urea. However, vitamin D levels were inversely correlated with SSS (r = -0.196, P = 0.025). Conclusion: Vitamin D supplementation appears to alleviate IBS symptoms. IBS patients tend to have lower serum vitamin D levels, with an inverse relationship between vitamin D levels and symptom severity.