|
|
What Is Vitamin A
Vitamin A is the name given to a family of related fat-soluble compounds which include: retinol; retinal; beta-carotene; lutein; zeaxanthin; lycopene. It should be pointed out that, though these compounds all fall under the umbrella term of vitamin A, they have different properties and functions. In fact lycopene, lutein and zeaxanthin lack vitamin A activity but do exhibit other health enhancing properties. You should also be aware that vitamin A compounds fall under two categories: preformed vitamin A and provitamin A. So why should you care about the difference between preformed vitamin A and provitamin A? Well because of the way they are metabolised in the body. Retinol (preformed vitamin A) the most beneficial form of vitamin A can easily be taken in amounts toxic to the body. Beta-carotene on the other hand, as a provitamin A (meaning that they are transformed into vitamin A after certain metabolic reactions in the body) is only utilized on an as-needed-basis by the body. Simply put, your body only converts as much beta-carotene into vitamin A as it needs; for this reason you cannot ingest toxic levels of beta-carotene.
Vitamin A Functions
Vitamin A in adequate amounts is essential for healthy vision, healthy bones, reproduction, cell division and cell differentiation.
Promoting Healthy Vision
Vitamin A is required for the proper functioning of the retina of the eye and is absolutely necessary for the optimal integrity of the mucous membranes surrounding the eye. Vitamin A helps prevent night blindness and
Vision
You are probably aware that vitamin A is good for your sight, specifically night vision, but how does it actually achieve this? Well what is pretty well known is that insufficient levels of retinol (the most active form of vitamin A) results in so-called night blindnes. This is because retinol is required in the formation of 11-cis Retinal which crosses the interphotoreceptor matrix (in the eye) to the rod cells where it binds to a protein called opsin forming the visual pigment rhodopsin. Rhodopsin rich rod cells are superbly adapted to detecting very small amounts of light and hence play an extremely important role in night vision.
11-cis Retinal is converted via isomerization to all-trans retinal through the catalytic actions of a light photon and this process of isomerization triggers a cascade of events that ultimately result in the generation of an electrical signal to the optic nerve. The optic nerve in turn generates its own nerve impulse which is conveyed to the brain where it is interpreted as vision.
SUMMARY
Vitamin A in sufficient doses is necessary for healthy vision, especially at night and for optimal health of the eye apparatus..
Vision Bone Skin Immune System Cell Division / Differentiation Gene Expression Blood Anti-Cancer Activity Protein and Sugar Metabolism
|
|
