Although we can get vitamin D in other sources studies show that, for humans this substance isn't really a vitamin but a hormone. When the sunlight hits the skin, it activates a precursor in the skin which produces vitamin D3,25.According to Bryan Arling - General Internal Medicine practitioner, vitamins are substances that we take-in and needed by our body which cannot be produced ourselves while hormones are substances produced in some parts of our body for specific functions. Learn more on the link below.
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