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.