Sources of Vitamins D:

Vitamin D is mainly found in fish liver oil, milk, ghee, butter, etc. It is also synthesized by the skin when ultraviolet (UV) radiation from the sun is used to convert a cholesterol derivative into vitamin D.

Deficiency symptoms of vitamins D:

Long-term deficiency of vitamin D affects the bones.

Rickets:

In children, vitamin D deficiency leads to rickets, a condition in which bones weaken and bow under pressure.

Osteomalacia, or "soft bones,":

In adults, vitamin D deficiency causes Osteomalacia, or "soft bones," increasing the risk for fractures in bones.