Vitamin D questions
There are a couple mini researach questions I have around Vitamin D. How different are humans with respect to Vitamin D, from other life forms or just other mammals. Also what does the synthesis pathway look like for Vitamin D (or more than one pathway if dietary is a separate pathway from skin). And how exactly does vitamin D enable immune function?
The names.
- Per 1 , “plasma concentration of 25-hydroxyvitamin D” is one “vitamin D” biomarker.
Fish
- Per 2, “Fish incorporates vitamin D2 and D3 through the diet.”
Roles of “Vitamin D”
- Also per 2] , “In mammals, vitamin D forms are involved in mineral metabolism, cell growth, tissue differentiation, and antibacterial immune response.”
Synthesis pathway for “Vitamin D”
- From 3, “The synthesis of vitamin D begins in the skin with activation of a precursor molecule by ultraviolet light from the sun. After that, the process moves to the liver for further chemical modification and then on to the kidneys for a final tweak.”
- And “Humans and other animals can synthesize this molecule right from cholesterol, something we always have plenty of” 3 .
Dietary vitamin D
- Hmm ok so according to 3, “Many animals, including humans, can escape this paradox by simply ingesting the activated vitamin D precursor. Dietary vitamin D still requires the activation steps in the liver and kidney, but at least it lets us stay out of the sunlight. Such supplementation has allowed humans to live in frigid climates and it is no coincidence that Arctic diets tend toward fish and whale blubber, two very rich sources of vitamin D.” So I’m reading here that if you eat the vitamin D precursor, you can skip out on the sun.
Dumb evolution Haha
- And from 3 , “it would make much more sense to house the enzymes for the synthesis of vitamin D within fat cells, which are often tucked right underneath the skin anyway, where the UV light is needed for the first step.” Indeed there is a list of these weird suboptimalities in life out there. Or do we just not understand what’s going on?