Vitamin A
Retinol, the dietary form of vitamin A, is a fat-soluble, antioxidant vitamin important in vision and bone growth. It belongs to the family of chemical compounds known as retinoids. A metabolic product of retinol, all-trans-retinoic acid, is used in the treatment of acne. Another metabolite, retinal, is used in vision functions.
As can be seen from the structure, retinol is derived from isoprene.
Either deficiency or overdose of vitamin A can be harmful or fatal.
Deficiency of vitamin A can cause night-blindness, pale, dry skin. Vitamin A is found in carrots, spinach, milk and eggs. Vitamin A gets destroyed at about 40 degrees Celsius, hence these foods must be consumed raw in order to avail maximum benefit. It is also present in many foods in a dimerized form, carotene. The body converts carotene into vitamin A as it is needed, therefore high levels of carotene are not toxic as plain vitamin A can be.
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 poisoning 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 the dogs' livers. The liver of the polar bear also has enough vitamin A to kill a human being.
George Wald won the 1967 Nobel Prize in Physiology or Medicine for his work with retina pigments, including the role of vitamin A in the retina.
External links:
- http://ods.od.nih.gov/factsheets/cc/vita.html
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