Different Bowel Habit Subtypes of Irritable Bowel Syndrome May Response Different to Vitamin D Supplementation Regarding Inflammatory Cytokines, Oxidative Stress Biomarkers and Clinical Symptoms

Background: Considering the variations in clinical characteristics and pathophysiological mechanisms among irritable bowel syndrome (IBS) subtypes, it is a well-established fact that the response to treatments are different.

Objective: We evaluated the effect of vitamin D on inflammatory cytokines, oxidative stress biomarkers in IBS. Furthermore, we analyzed the effect of vitamin D in different subtypes of IBS.

Methods: A total of ninety IBS patients, as defined by the Rome III criteria, participated in this double blind, randomized, placebo-controlled 6-month intervention. Participants were randomly categorized to receive either 50,000 IU vitamin D₃ or a placebo fortnightly. Patients were further sub-classified as diarrhea predominant (IBS-D), constipation-predominant (IBS-C), and alternating bowel habits (IBS-A). Gastrointestinal (GI) symptoms, biochemical factors (such as IL-17, IL-10, TNFα, malondialdehyde (MDA) and total antioxidant capacity (TAC)) were assessed.

Results: Following vitamin D supplementation, the serum IL-17 and MDA levels significantly decreased, TAC and IL-10 levels significantly increased compared to the placebo group. When comparing different subtypes, the serum TNFα and IL-17 levels significantly (P < 0.05) decreased in IBS-D, whereas IL-10, MDA and TAC significantly (P < 0.05) changed in all the subtypes. Following vitamin D supplementation, abdominal pain, abdominal distention, flatulence and overall GI symptoms were significantly (P < 0.05) decreased in IBS-D patients with no significant changes in other subtypes.

Conclusion: Vitamin D has anti-inflammatory and antioxidant effects in patients with IBS. Vitamin D supplementation could ameliorate the GI symptoms in IBS-D. Thus, the present study suggests the beneficial effect of vitamin D in IBS-D.