Vitamin D and Inflammatory Bowel Disease
By Renata Trister DO
A relationship between vitamin D and Inflammatory Bowel Diseases (IBD) has recently been proposed. Vitamin D has several important actions beyond the bone maintenance. Vitamin D also exerts various effects on the immune system. Vitamin D deficiency has been implicated in the development of IBD such as Crohn’s Disease (CD). Current research also suggests a role for vitamin D in modulating some IBD complications, including osteopenia, colorectal neoplasia, and depression.
Vitamin D is well established as a regulator of calcium homeostasis. Recently, literature has linked vitamin D to a number of other conditions, including cancer, cardiovascular disease, and autoimmune diseases such as multiple sclerosis, diabetes mellitus, and
Crohn’s disease (CD). The incidence of Crohn’s disease, in general, appears to rise with increasing distance from the equator. Those residing in temperate climates have less exposure to sunlight, which is responsible for up to 95% of vitamin D production in humans. Vitamin D deficiency is found in 22 to 70% of patients with CD and has been proposed to play a key role in its pathogenesis.
Vitamin D deficiencies are common in patients with IBD. Normal levels of vitamin D are approximately 30 ng/mL. Levels between 20 and 30 ng/mL are considered insufficient, and anything below 20 ng/mL is considered deficient. The prevalence of vitamin D deficiency in inflammatory bowel disease (IBD) varies in different studies.
Laboratory experiments in various mice models have also shown that animals are more susceptible to colitis and that such colitis can be treated by vitamin D supplementation. These findings suggest, that there is at least a significant component of vitamin D level perhaps contributing to the development of IBD; vitamin D deficiency is not purely a consequence of prolonged, undertreated IBD or bowel damage, but is rather an artifact of immune dysregulation.
A growing body of literature has linked disease severity to low vitamin D levels. For example, a comparison of 3000 people with Crohn’s disease or ulcerative colitis and examined vitamin D levels showed that there is a gradation in the risk of surgery in people who had normal, insufficient, and deficient levels of vitamin D. People who had insufficient levels of vitamin D (20-30 ng/mL) had a higher risk of surgery and hospitalization, and people with levels lower than 20 ng/mL had an even higher risk of surgery and hospitalization.
Vitamin D can be considered a hormone with a number of effects on the immune system that are responsible for mediating susceptibility to infections and perhaps malignancy. Studies have suggested that vitamin D levels may be important in how patients respond to pathogens. Studies have linked low vitamin D levels with an increased risk of cancer, particularly colon cancer, in people with IBD. Low vitamin D levels are also linked to a higher risk of Clostridium difficile infection.
It is important to further evaluate the relationship of vitamin D deficiency and IBD to determine which one comes first. Prolonged bowel damage can cause IBD, with growing evidence and laboratory data suggesting that vitamin D is a potential mediator of several immune responses, the connection between Vitamin D levels and subsequent development of autoimmune conditions should not be disregarded. It is important to understand the role of vitamin D in the treatment of IBD itself, and not just for the treatment of vitamin D deficiency. We also need to better understand the optimal dose of vitamin D supplementation, and whether there are factors such as genetics that influence response to such supplementation. It is also important to define what the optimal vitamin D level should be in patients with IBD, and whether there should be a different adequate level when looking at inflammation. There is also growing evidence supporting the relationship between the gut microbiome and Vitamin D axis in autoimmunity. Bacterial induced modifications in Vitamin D metabolism can have vast effects on Vitamin D levels and Vitamin D Receptor signaling. Probiotics promote Vitamin D Receptor expression and its antimicrobial effects. This can be beneficial in treating colonic inflammation. Proper Vitamin D balance may restore healthy gut microbiome and decrease inflammation.