Vitamin D deficiency and graft-versus-host disease in hematopoietic stem cell transplant population

Vitamins are the organic compounds that have long been known to play a significant role in our body by functioning as hormones and antioxidants. Vitamin D, a fat-soluble vitamin, is the main regulator of calcium hemostasis in our body. At the same time, it is also known to show its potential effects on the immune system by modulating the differentiation, activation, and proliferation of T and B lymphocytes. The immunomodulatory properties of vitamin D are also known to have a crucial role in the prevention and treatment of graft-versus-host disease. Patients undergoing hematopoietic stem cell transplantation are particularly at risk of vitamin D deficiency. This review article expands our understanding of vitamin D, its immunomodulatory effects, and its role in prevention and treatment of graft-versus-host disease.