Photobiology of Vitamin D

Vitamin D supplementation guidelines

“…The predominant natural source of vitamin D3 in humans is production in the skin where 7-DHC follows a two step-reaction involving ultraviolet-B (UV-B) irradiation to form previtamin D3 followed by a subsequent thermal isomerization to vitamin D3 (20). Both vitamin D3 and vitamin D2 may be obtained in a lesser extent from varied diet and in more significant amounts from fortified foods and supplements.…”

Assessment of vitamin D status – a changing landscape

“…Absorption of this energy breaks the bond between carbons 9 and 10 to form an unstable 9, 10 seco-steroid, known as previtamin D3 [21]. The removal of this bond allows previtamin D3 to spontaneously rotate around the bond between carbons 5 and 6, which forms a more thermodynamically stable isomer, vitamin D3.…”

“…The removal of this bond allows previtamin D3 to spontaneously rotate around the bond between carbons 5 and 6, which forms a more thermodynamically stable isomer, vitamin D3. The molecular interactions of the previtamin D3 with the lipid bilayer of the cell membrane helps to hold the previtamin D3 in a conformation (s-cis, s-cis) that facilitates this isomerization process, which has a half-life in vivo of 2.5 h [21,22]. The isomerization process interrupts the hydrophobic and hydrophilic interactions that hold the molecule within the cell membrane and isomerization therefore expels the vitamin D3 into the interstitial fluid [23].…”

Second Trimester Sunlight and Asthma: Evidence from Two Independent Studies

“…Similarly, in the northern hemisphere, vitamin D levels are known to follow strong seasonal cycles of being highest in the summer and lowest in the winter as the number of sunlight hours varies (and the pattern is reversed in the southern hemisphere; Chen, 1999). Isolated data from small scale studies have similarly found seasonal fluctuations in the vitamin D level of both pregnant women and their newborns (Disanto et al, 2013;Bodnar et al, 2007).…”