Emerging evidence suggests that vitamin D, traditionally known for its role in bone health, plays a significant role in gastrointestinal (GI) health as well. Deficiency in this fat-soluble vitamin has been linked to a variety of GI diseases, including inflammatory bowel disease (IBD), diverticulitis, colorectal cancer, and liver disease.
Vitamin D is primarily synthesised through sun exposure, though diet and supplements contribute as well. Vitamin D binds to receptors in the gut, influencing immune function, inflammation regulation, and microbiome composition.
In IBD, vitamin D deficiency is common and appears to contribute to disease development rather than being solely a consequence. Low levels are associated with greater disease activity, higher relapse rates, and poor treatment responses. Supplementation has shown potential in reducing relapses, though evidence quality remains limited.
In diverticulitis, higher vitamin D levels are associated with reduced risk. Geographic studies show higher incidence in areas with less sun exposure, supporting a possible link between UV light, vitamin D status, and disease risk.
In colorectal cancer, low vitamin D levels are associated with increased risk and worse prognosis. Adequate levels, particularly from vitamin D3, may support DNA repair mechanisms through proteins like sirtuin 1. National cohort studies support a protective role of sufficient vitamin D intake.
In liver disease, vitamin D deficiency is especially common in people with a type of fatty liver disease linked to metabolic issues, called MASLD. Research suggests that vitamin D supplements might help by reducing liver scarring and fat buildup, making it a potentially helpful part of treatment.
Given the low risk and potential benefits, especially in GI-related conditions, Dr. Johnson recommends that clinicians consider targeted vitamin D testing and supplementation as part of a broader GI disease management strategy. As research continues to evolve, vitamin D’s role in gut health may warrant more prominent attention in clinical practice.
