[MozarkDawg]

Question is, is food-additive Vit D as effective as skin-produced Vit D?

Apparently, as the nationwide deficiency causing rickets was what led to Vitamin D fortifying butter and milk decades ago, my understanding is that the cases dropped exponentially afterward.

[Battle Axe]

When did they put Vit D into milk and butter? Folks on the farm would still be drinking their own cow's milk and making their own butter and thus not get the benefits.