Vitamin D and symptom severity in individuals with irritable bowel syndrome

Abstract
Vitamin D is typically associated with bone health, but there is increasing evidence that vitamin D deficiency plays a role in the risk and severity of several diseases including inflammatory bowel disease and cancer, and an association between low vitamin D status and irritable bowel syndrome (IBS) has been suggested. IBS is a chronic, relapsing functional disorder of the gut which has a considerable burden of cost to the NHS and to the individual living with this condition. The aetiology of IBS is unknown and the treatment that can be offered is not always effective. Treatment with vitamin D may be a relatively inexpensive and acceptable form of therapy. The aim of this thesis were to (i) to review the literature for evidence of a relationship between vitamin D and IBS, (ii) to investigate the efficacy of a sublingual/buccal vitamin D spray compared to vitamin D capsule, (iii) and to conduct a randomised control trial to investigate the possible effect of a 3000IU/ day vitamin D3 sublingual spray on symptom severity and quality of life with individuals with IBS.
Methods:
The systematic literature search was completed using PRISMA guidelines to identify the current available research investigating an association between vitamin D and IBS. Three databases; Pubmed, Medline and Web of Science were used. A supplementary search was conducted using the same method to assess the literature published post 2018. In addition, we conducted an efficacy study comparing 2 vitamin D preparations: capsule and sublingual spray. This study recruited 75 healthy participants and randomly allocated 25 participants to one of the three treatments. Participants received; placebo capsule/active spray, active capsule/placebo spray or placebo capsule/placebo spray. Blood samples were collected at baseline, day 3, 7, 14, 21 and 28 using whole blood spot kits (Sandwell and Birmingham Hospitals) for the analysis of vitamin D status. The final study was a randomised, double blinded, placebo-controlled trial with 135 free living participants with a diagnosis of IBS to examine the effect of a 3000IU/day vitamin D3 supplement for 12 weeks on symptom severity and quality of life in individuals with IBS. Fingerprick blood samples were collected and whole blood 25(OH)D was measured using liquid chromatography tandem mass spectrometry. Vitamin D status and quality of life was determined at baseline and exit. Quality of life was determined at baseline and exit using the IBS quality of life questionnaire and symptom severity was assessed fortnightly across the study using the IBS symptom severity score questionnaire (2). Habitual dietary intake of vitamin D was measured using the EPIC Food Frequency Questionnaire.

Results:
The systematic review yielded 7 studies; 3 intervention and 4 observation studies. The evidence from these studies suggest a beneficial effect of a vitamin D supplement on symptom severity and quality of life in people with IBS. The supplementary search generated a further 3 randomised controlled trials. These studies agree with the original review’s findings that individuals with IBS may have improvement in their symptomology by supplementing with vitamin D. The efficacy study found a sublingual vitamin D spray to be as effective as a capsule at raising whole blood 25(OH)D concentrations. Baseline measurements of 25(OH)D concentrations showed a high prevalence ofvitamin D insufficiency (44.6%) among participants. The data also suggests that rates of change of vitamin D status in response to supplementation are higher in individuals with lower levels of 25(OH)D. The RCT showed there was a significant improvement in the vitamin D status of participants randomised to receive active vitamin D (p=0.005) after 12 weeks. No difference was seen in symptom severity and quality of life between arms at baseline and exit (p=0.824, p=0.415 respectively). There was no association between change in vitamin D status and change in symptom severity (r= -0.071, p=0.434), nor increase in vitamin D and change in quality of life (r=-0.031, p=0.733). This analysis found a weak but significant correlation between baseline serum concentrations of 25(OH)D and dietary intake of vitamin D (p=0.046, r=0.17).
Conclusions:
The results confirm that there is a prevalence of low 25(OH)D concentrations in individuals with IBS, and this warrants correction, if only for general health. The sublingual vitamin D spray proved to be an effective mode of delivery for raising 25(OH)D concentrations, which may be beneficial to those who have swallowing difficulties or malabsorption issues. We found no benefit of vitamin D supplementation on IBS symptom severity or quality of life. Low dietary intakes of vitamin D present in the general population.