Review article: vitamin D and inflammatory bowel disease – established concepts and future directions

Abstract

Summary Background Understanding of the role of vitamin D in health and disease has increased markedly in the past decade, with its involvement extending well beyond traditional roles in calcium and phosphate homeostasis and musculoskeletal health. This conceptual expansion has been underpinned by identification and exploration of components of this axis including vitamin D‐binding protein, key enzymes and receptors in multiple cell types, and a greater recognition of nonclassical autocrine and paracrine effects. Its influence in IBD remains uncertain. Aim To review the role of vitamin D in bone health, immune regulation and cancer prevention in IBD, and to outline practical issues and limitations of its use. Methods An extensive online literature review including PubMed and Medline. Results In patients with IBD, the vitamin D axis provides an important and often underutilised pathway to preserving bone health. Furthermore, an exciting body of clinical and basic science research demonstrates that these pathways may have an integral part to play in regulation of the immune response in IBD, through effects on the intestinal barrier, antigen presenting cells and adaptive T cells. The possibility of chemoprevention requires further study. The optimal target level of 25‐hydroxy vitamin D in patients with IBD is currently uncertain, as is the best therapeutic modality. Conclusions Study of vitamin D pathways may result in the development of relatively inexpensive therapeutic options to optimise patient outcomes. Further prospective clinical research is required to address efficacy and long‐term safety.

Vitamin D as a novel therapy in inflammatory bowel disease: new hope or false dawn?

“…Notably, in an open label study by Yang et al (47) , a series of inflammatory cytokines (TNF-α, IL-17 and IL-10) remained unchanged in response to vitamin D supplementation, even though circulating levels of 25(OH)D of 100 nmol/l were achieved. Others hypothesise that therapeutic response of vitamin D may be mediated in part by effects on the intestinal barrier (68,69) . Preliminary results (50) from our group suggest that vitamin D supplementation (50 μg (2000 IU)/d) may maintain intestinal permeability and barrier integrity in CD, but the findings from this pilot study require further investigation.…”

Lower Levels of Vitamin D Correlate With Clinical Disease Activity and Quality of Life in Inflammatory Bowel Disease

“…It has recently being linked to a number of other functions like anti-inflammatory and anti-carcinogenic pathways in the gastrointestinal tract (25) . In humans, sun exposure is responsible for up to 95% of vitamin D production (7) . Vitamin D deficiency was reported in 63% of patients with CD (30) and has been proposed to play a key role in IBD pathogenesis based on geographic distribution, seasonal variation in onset and exacerbations of IBD (12) .…”

“…Anorexia, food intolerance, malabsorption, reduction of outdoor activities, corticosteroid therapy, bowel resection and circulating cytokines are the consequences of gastrointestinal involvement and may lead to vitamin D deficiency (27) . The most stable measurable form of vitamin D in serum is 25-hydroxyvitamin D (25[OH]D) (7) . Screening for vitamin D deficiency requires a blood sample for measurement of serum 25(OH)D levels and is therefore practical and feasible in an outpatient setting (30) .…”

Maintaining Muscle Strength in Crohn’s Disease: Can a Vitamin D Daily Keep Muscle Loss Away?

“…Both anecdotally and based on the available literature, it is widely accepted that vitamin D deficiency is commonly seen in patients with CD, putatively due to ''direct'' effects of the pro-inflammatory milieu on absorption and binding, malabsorption secondary to small bowel mucosal disease or surgical resection, as well as ''indirect/illness'' effects such as reduced sunlight exposure, physical inactivity, and reduced dietary intake [8] (Fig. 1).…”