Vitamin D is one of the 13 vitamins discovered in the early 20th century by doctors studying nutritional deficiency diseases. Ever since, scientists have defined vitamins as organic compounds that must be obtained from dietary sources because they are not produced by the body's tissues.

Although vitamin D is firmly enshrined as one of the four fat-soluble vitamins, it is not technically a vitamin. It breaks the other rules for vitamins because it's produced in the human body, it's absent from all natural foods except fish and egg yolks, and even when it's obtained from foods, it must be transformed by the body before it can do any good.

What is vitamin D?

The natural type is produced in the skin from a universally present form of cholesterol, 7-dehydrocholesterol. Sunlight is the key: Its ultraviolet B (UVB) energy converts the precursor to vitamin D

How your body makes vitamin D
The sun's energy turns a chemical in your skin into vitamin D which is carried to your liver and then your kidneys to transform it to active vitamin D.

Warning signs of Vitamin D Deficiency - - -

https://www.youtube.com/watch?v=y3CWTlT7hQo