Vitamin A



"On the world scale, the most important consequence of vitamin A deficiency is blindness."
- Davidson’s Principle and Practice of Medince. Page 319.

The report continues "Each year, approximately 500,000 new cases of blindness occur in young children," all due to lack of this vitamin . What a grim statistics!

Vitamin A, an essential fat-soluble antioxidant vitamin, is crucial for clear vision, healthy skin, as well as for the development and maintenance of strong bones and teeth.

Vitamin A actually describes a group of micronutrients belonging to retinol family called retinoids. Well known retinoids include retinoic acid and 11 – cis retinaldehyde which make up the initial part of the rods in the retina at the back of the eye.

Preformed forms are found only in animal sources, while plants contains related chemical substances that still needs to be converted to the real forms after ingestion.One of such forms is carotenes or carotenoids.

Over 600 carotenes have been identified. 30 - 50 have been found to have Vitamin A activity, which is why carotenes are included in the discussion. Examples of carotenes found in food commonly include alpha-carotenes, beta-carotenes, and beta-cryptoxanthine. Carotene is sold as beta carotene supplement.

Carotenes are naturally-occurring, brightly coloured plant pigments that are important in the photosynthesis process. Carotenes are what help protect plants as well as the body against the potentially damaging effects of free radicals.

Vitamin A is stored in the Liver, and the liver can store up to three years worth of vitamin A requirement.

Excess vitamin A is dangerous, and can kill. Animal sources of vitamin occurs as real retinols, and are up to six times more potent than plant sources of vitamin A.


Functions of Vitamin A

The functions and benefit of vitamin A include:

As an Antioxidant - Protects Against Cancer and Aging

Vitamin A and carotene are anti –oxidants. They help protect the body against free radicals and even eliminate their effect where possible.

For clarity, free radicals refer to some very powerful chemicals that have the ability to add or remove oxygen to or from the structures of normal chemical in the body. This can be comparable to what happens when rust appears on a car called oxidation.

Simply put, free radicals causes oxidation to normal cells just as damp would cause the surface of a metal to rust. If this goes on unchecked, it easily results in the development of many diseases like cancer, heart disease, macular degeneration, diabetes, arthritis, Alzheimer's disease and cataracts.

Antioxidants are able to take away the power of free radicals. In other words, the free radical's ability to oxidize cells is eliminated.

In a recent study at Kyoto Prefectural University of Medicine (Published September 11 2006), 75 people with a liver disease that can progress to full blown liver cancer were divided into two groups. A group of 30 patients were given a daily dose of mandarin (very rich in vitamin A)juice for one full year, while the other group of 45 were not given.

After one year, none of those who had mandarin (vitamin A) developed liver cancer, while up to 10 percent of the other 45 developed liver cancer!

Vision

Apart from its anti-oxidant function, vitamin A also makes up part of the chemical that makes us to see in the retina (back of the eye).

There are two forms of vitamin A that are involved in ensuring good vision.

As mentioned earlier, 11-cis retinal forms part of the rod of the retinal in a chemical complex called rhodopsin. This rhodopsin contains a protein called opsin and retinal.

Once we are exposed to light, this chemical complex (rhodopsin) breaks down to its constituents (opsin and vitamin A). This break sends electrical signal to our brain, which is translated to vision.

Once this happens, new rhodopsin complex needs to be formed. Lack of vitamin A means that they would be very poor amount (if any) to help in the formation of rhodopsin. Eating enough of this vitamin helps you see in the dark and avoid night blindness.

Retinoic acid is another form of vitamin A very important for vision. It is needed to maintain the cornea, that transparent part just covering the eye. This is because it helps in the production of special lubricant called glycoprotein. Lack of retinoic acid would lead to triangular spots showing on the transparent part of the eye called bitot’s spot, which could lead to blindness.

Growth and Development

This marvellous vitamin plays a very important role in growth; growth of every single cell and organ in our body. It is involved in the control of our genetic blue print in overseeing division of cells as well as maturation of these cells. Right from conception, it ensures proper development of the unborn baby, up to adult hood.

It also helps keep the mucous membranes inside the throat, lungs, eyes, mouth, digestive tract, kidneys, bladder and reproductive system healthy.

These and its overall effect on the skin in its ability to ward off wrinkles is why this vitamin has been referred to as an 'anti-aging' vitamin.

Strong Immunity

Vitamin A is, due to its role in cell division and maturation, it is necessary in the production of blood and the white blood cells that protects us against infections.

It also helps cells lining the throat, lungs, eyes, mouth, digestive tract, kidneys, bladder and reproductive system healthy by helping them in production and secretion of mucus. This mucus helps trap dust and bugs which are then eliminated. When deficiency of this vitamin occurs, these cells are unable to produce mucus, they become dry, and children with this deficiency suffer more from colds, cough and respiratory tract infections, diarrhoea, urinary tract infections, and have increased chances of dying when they catch any of the just mentioned infections.You can buy a selection of vitamin A capsules and liquid vitamin A at very low price from Amazon. You can also browse major vitamin shops like ,or compare prices at

You can read further about this vitamin in the sections below from food sources containing vitamin A, vitamin A supplements, its role in acne to issues of overdose and toxicity.


Vitamin A Rich Foods


Supplements of this Vitamin


Recommended Daily Allowance


Vitamin A for Acne


Deficiency


Overdose and Toxicity


All other Vitamins



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