Vitamin A (Retinol), (along with retinal and retinoic acid) is a fat-soluble, antioxidant vitamin important in vision and bone growth. It is sometimes used in the treatment of severe acne. As can be seen from the structure, this is a compound synthesized from isoprene.
A deficiency of vitamin A is not only disease causing, but it can kill. On the other hand, overdoses of vitamin A are also lethal. The livers of certain animals, especially those adapted to polar environments, often contain amounts of vitamin A that would be toxic to humans. The first documented death due to vitamin A poisioning was Xavier Mertz, a Swiss scientist who died in January 1913 on an Antarctic expedition that had lost its food supplies and fell to eating its sled dogs. Mertz consumed lethal amounts of vitamin A by eating sled dog liver. The liver of the polar bear also has enough vitamin A to kill a human being.
Deficiency of Vitamin A can cause night-blindness, pale, dry skin. Vitamin A is found in Carrot, Spinach, Milk and Egg. Vitamin A gets destroyed at about 40 degrees Celsius, hence these foods must be consumed raw in order to avail maximum benefit.
- Vitamin A information (http://www.talkwellness.org/vitamina.html)