Vitamin A is an essential vitamin required for vision, gene transcription, boosting immune function , and great skin health.
 A deficiency in vitamin A can... lead to blindness and increased viral infection, however deficiency is only considered a problem in developing countries where it is a leading cause of blindness in children.

Over consumption of vitamin A can lead to jaundice, nausea, loss of appetite, irritability, vomiting, and even hair loss. The current percent daily value for Vitamin A is 5000 international units (IU)