Vitamin constituents of our diet are well known to affect the immune system. Vitamin D has essential roles in bone metabolism and modulating immune processes mainly lymphocyte activation by its proliferation. Vitamin D deficiency could be considerably diminished with ample exposure to sun and with the use of vitamin supplements. UVB photons are absorbed from sun by 7 dehydrocholesterol present in skin and transforms it into provitamin D3 and finally coverts to vitamin D3.Once vitamin D3 is formed it is metabolized to 25 hydroxyvitamin D3 in liver and then to 1, 25 dihydroxy vitamin D3 in kidney which is its biologically active form. Vitamin D deficiency could heighten the risk of rickets in children while it causes osteoporosis in adults. Vitamin D deficiency can also accelerate the risk of deadly cancer, cardiovascular disease, multiple sclerosis and kidney disease. An essential level of 80nmol/L 25 hydroxyvitamin D should be maintained in blood concentration. Sunscreen blocks UVB radiation and some UVA radiation to enter the skin thereby reducing the ability of skin to produce vitamin D3. 1,25(OH)2D or calcitriol, a hormonal substitue of vitamin D plays a vital role in cellular proliferation and differentiation of many normal as well as malignant cells.
Key words: Vitamin D, 1,25(OH)2D , Sunlight.