Aging decreases the capacity of human skin to produce vitamin D3.
MacLaughlin J, Holick MF.
J Clin Invest. 1985 Oct;76(4):1536-8.
PMID: 2997282
doi:10.1172/JCI112134
An evaluation of surgically obtained skin (age range, 8-92 yr) revealed that there is an age-dependent decrease in the epidermal concentrations of provitamin D3 (7-dehydrocholesterol). To ascertain that aging indeed decreased the capacity of human skin to produce vitamin D3, some of the skin samples were exposed to ultraviolet radiation and the content of previtamin D3 was determined in the epidermis and dermis. The epidermis in the young and older subjects was the major site for the formation of previtamin D3, accounting for greater than 80% of the total previtamin D3 that was produced in the skin. A comparison of the amount of previtamin D3 produced in the skin from the 8- and 18-yr-old subjects with the amount produced in the skin from the 77- and 82-yr-old subjects revealed that aging can decrease by greater than twofold the capacity of the skin to produce previtamin D3. Recognition of this difference may be extremely important for the elderly, who infrequently expose a small area of skin to sunlight and who depend on this exposure for their vitamin D nutritional needs.
Food chain as origin of vitamin D in fish
D. Sunita Rao and N. Raghuramulu.
Comparative Biochemistry and Physiology Part A: Physiology
Volume 114, Issue 1, May 1996, Pages 15-19
doi:10.1016/0300-9629(95)02024-1
Plankton, the chief food source of fish, was assessed as the possible dietary origin of vitamin D in fish. The presence of vitamin D compounds were examined in fresh water phytoplankton and zooplankton employing a series of chromatographic procedures. Abundant amounts of provitamins D and vitamins D (D2 and D3) were found in the fresh water plankton. The high amount of vitamin D observed may be due to exposure of plankton to sunlight because the plankton were caught during the summer month. Thus, plankton may be an important contributor to vitamin D in fish.