ELI5 Vitamin D - what do you mean it's not a vitamin?

ELI5 Explain Like I'm 5: Bite sized answers to stuff you should know about - in a mini podcast

How does the body get vitamin D from the sun? Why is vitamin D not actually a vitamin? Why do we need it? What foods are high in vitamin D? What happens if we get too much? Why are there so many types of vitamin B (e.g. B1, B2, B3, B6, B9, etc), but only one type of some other vitamins (such as C and D)?

... We explain like i'm five!

Thank you to the r/explainlikeimfive community as always and in particular the following users whose questions and comments formed the basis of this discussion: mbisme, mcmustang51, monstrag, gnonthgol, myhandsunclean, mitobear, lasseft, greygreygrey12, vizsla_velcro, splitegg & schnutzel.

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