Irritable Bowel Syndrome (IBS) is a common functional disorder of the gastrointestinal tract, affecting 17% overall of the UK population(Reference Ford and Talley1). The aetiology of this disorder is unknown, although it has been linked to environmental, psychological and social factors(Reference Longo, Ford, Lacy and Talley2). Vitamin D deficiency and insufficiency is common within the IBS population(Reference Williams, Williams and Corfe3), and vitamin D has been hypothesized as a potential remedy. We sought to test whether vitamin D supplementation improved symptoms or quality of life in IBS.
One hundred and thirty six volunteers were randomised to receive either a vitamin D (3000IU p.d.) or placebo oral spray in a 12-week double-blind, placebo-controlled, parallel design study. Power calculation was estimated from a pilot study(Reference Khayyat and Attar4) Quality of life (QoL) and serum vitamin D were determined at baseline and exit, symptom severity was assessed fortnightly across the study. Data were analysed using SPSS (IBM SPSS Statistics for Windows, V.23; IBM Corp.).
One hundred and twenty five participants (n = 66, treatment, n = 59, placebo) were included in the final analysis. Baseline data showed no differences in baseline demographics or symptomology between groups. After 12 weeks there was a significant improvement in the vitamin D status of participants randomised to receive vitamin D (p = 0.005, t-test). Symptom severity was assessed across the study by trial arm. There was no difference between active and placebo (p = 0.845, repeated measured ANOVA). QoL showed no difference between baseline and exit for either trial arm (p = 0.415, t-test. There was no association between increase in vitamin D and change in symptoms (r = −0.071 p = 0.434, Spearman's rho), nor increase in vitamin D and change in quality of life (r = −0.031p = 0.733, Spearman's rho).
Vitamin D insufficiency was prevalent in this sample(Reference Williams, Williams and Corfe6) confirming previous studies. Supplementation was efficacious. Patients with IBS should be tested for vitamin D status and, where appropriate, supplemented. In contrast to previous reports, this study shows no benefit of vitamin D supplementation on IBS symptomology.
