Vitamin D and Immune System

Vitamin D interaction with immune system is one of the most well-established non-classical effects of Vitamin D. Vitamin D can modulate the innate and adaptive immune responses. The ability of Vitamin D to influence normal human immunity will be highly dependent on the vitamin D status of individuals; therefore, deficiency or insufficiency of Vitamin D is associated with increased autoimmunity and infection. The 25-hydroxyvitamin D3 (25OHD3) is the main circulating metabolite of Vitamin D and is the most reliable measurement of an individual’s Vitamin D status. The Vitamin D supplements in deficient individuals will have beneficial immune-modulatory effects on the autoimmune status.

Vitamin D3 itself is biologically inactive. Thus, after being synthesized in the skin, vitamin D3 binds to the vitamin D-binding protein (DBP) in the blood to be transported into the liver where the first hydroxylation at position 25 occurs producing the major circulating metabolite 25-hydroxy vitamin D3 (25(OH)D3)