ostermayer on Nostr: vitamin D has never been isolated from humans in a form distinct from vitamin D₃ ...

vitamin D has never been isolated from humans in a form distinct from vitamin D₃ (cholecalciferol). In humans, only vitamin D₃ has been identified This compound is produced in the skin when 7‑dehydrocholesterol is irradiated by UV‑B light.

The term "vitamin D₁" was initially used but was later discovered to be an artifact—a mixture of vitamin D₂ and another compound


The first pure vitamin D to be isolated and identified was vitamin D₂ (ergocalciferol), but this was from plant/fungal sources (like irradiated yeast), not from humans


https://pmc.ncbi.nlm.nih.gov/articles/PMC9066576/

https://pmc.ncbi.nlm.nih.gov/articles/PMC3899558/