Vitamin D Synthesis: Acute Effect of Sun Exposure

The effects of acute exposure to sun are sunburn and synthesis of vitamin D. vitamin D is one of the vitamin (other vitamin which is synthesized in the body is vitamin K in the gut, by gut flora but not adequate for human requirement) which human body can synthesize in the body in adequate amount and vitamin D is required by human body for good health state. Vitamin-health is an important aspect for good health state and vitamin D is vital for this.

How vitamin D is synthesized in the skin?

Upon exposure of skin to sunlight (UV-B or ultraviolet B, which consists of wavelengths between 290 and 320 nm), there occurs photolysis of epidermal 7-dehydrocholesterol converting it to pre-vitamin D_3. This pre-vitamin D₃ than then undergoes isomerization which is temperature-dependent to form the stable hormone vitamin D₃. This stable hormone vitamin D₃ then diffuses to the blood vessels of the dermis (the inner layer of skin) and circulates systemically where it is converted to the functional hormone 1,25-dihydroxyvitamin D₃ or 1,25(OH)₂D₃ (this active form is used by human body for good vitamin-health). Vitamin D metabolites from the circulation or those produced in the skin itself can augment epidermal differentiation signaling.

There is controversy regarding the importance of sun exposure in vitamin D synthesis. Bu at present, what is more important is, to emphasize that the use of sunscreens does not substantially diminish vitamin D levels. Aging can substantially decreases the ability of human skin to produce vitamin D₃ photo catalytically, the widespread use of sunscreens that filter out UV-B has led to concern that vitamin D deficiency may become a significant clinical problem in the elderly. But vitamin D is also available in many food sources and elderly people might suffer from vitamin D deficiency due to use of sunscreen that filter UV-B rays is unfounded.