The Effect of Vitamin D on Intestinal Inflammation and Faecal Microbiota in Patients with Ulcerative Colitis

Background and Aims

There is evidence vitamin D may be immunomodulatory and alter faecal microbiota, but results from clinical studies in humans to date have been inconclusive. This study aimed to assess the effect of vitamin D replacement in vitamin D deficient patients with and without ulcerative colitis (UC) on inflammation and faecal microbiota.

Methods

Vitamin D was replaced over 8 weeks in patients with active UC (defined by faecal calprotectin ≥100 µg/g), inactive UC (faecal calprotectin <100 µg/g), and non-IBD controls with baseline 25(OH) vitamin D <50 nmol/L, and markers of inflammation and faecal microbiota analysed.

Results

Eight patients with active UC, 9 with inactive UC and 8 non-IBD controls received 40,000 units cholecalciferol weekly for 8 weeks. Mean baseline 25(OH) vitamin D increased from 34 (range 12–49) nmol/L to 111 (71–158) nmol/L (p <0.001), with no difference across the groups (p = 0.32). In patients with active UC, faecal calprotectin levels reduced from median 275 to 111µg/g (p = 0.02), platelet count reduced (mean 375 to 313x10 ⁹/L, p = 0.03), and albumin increased (mean 43 to 45g/L, p = 0.04). These parameters did not change in patients with inactive UC or non-IBD controls. No changes in overall faecal bacterial diversity were noted although a significant increase in Enterobacteriaceae abundance was observed in patients with UC (p = 0.03).

Conclusions

Vitamin D supplementation was associated with reduced intestinal inflammation in patients with active UC, with a concomitant increase in Enterobacteriaceae but no change in overall faecal microbial diversity.