Vitamin D deficiency is commonly diagnosed among patients with inflammatory bowel disease(IBD).Patients with IBD are at risk of low bone density and increased fractures due to low vitamin D levels,long standing disease,and frequent steroid exposures;as a result,it is well established that vitamin D supplementation in this population is important.There is increasing support for the role of vitamin D in strengthening the innate immune system by acting as an immunomodulator and reducing inflammation in experimental and human IBD.The active form of vitamin D,1,25(OH)D3,acts on T cells to promote T helper(Th)2/regulatory T responses over Th1/Th17 responses;suppresses dendritic cell inflammatory activity;induces antibacterial activity;and regulates cytokine production in favor of an antiinflammatory response.Murine and human IBD studies support a therapeutic role of vitamin D in IBD.Risk factors for vitamin D deficiency in this population include decreased sunlight exposure,disease duration,smoking,and genetics.Vitamin D normalization is associated with reduced risk of relapse,reduced risk of IBD-related surgeries,and improvement in quality of life.Vitamin D is an inexpensive supplement which has been shown to improve IBD outcomes.However,further research is required to determine optimal serum vitamin D levels which will achieve beneficial immune effects,and stronger evidence is needed to support the role of vitamin D in inducing disease response and remission,as well as maintaining this improvement in patients’disease states. Vitamin D deficiency is commonly diagnosed among patients with inflammatory bowel disease (IBD). Patients with IBD are at risk of low bone density and increased fractures due to low vitamin D levels, long standing disease, and frequent steroid exposures; as a result, it is well established that vitamin D supplementation in this population is important. Here is is increasing support for the role of vitamin D in strengthening the innate immune system by acting as an immunomodulator and reducing inflammation in experimental and human IBD. The active form of vitamin D, 1,25 (OH) D3, acts on T cells to promote T helper (Th) 2 / regulatory T responses over Th1 / Th17 responses; suppresses dendritic cell inflammatory activity; induces antibacterial activity; and regulates cytokine production in favor of an antiinflammatory response . Murine and human IBD studies supporting a therapeutic role of vitamin D in IBD. Risk factors for vitamin D deficiency in this population include decreased sunlight exposure, disease duration, smoking, and genetics. Vitamin D normalization is associated with reduced risk of relapse, reduced risk of IBD-related surgeries, and improvement in quality of life. Vitamin D is an inexpensive supplement which has been shown to improve IBD outcomes.However, further research is required to determine optimal serum vitamin D levels which will achieve beneficial immune effects, and stronger evidence is needed to support the role of vitamin D in inducing disease response and remission, as well as maintain this improvement in patients’ disease states.