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Vitamin A (Retinol)

Vitamin A (Retinol) Description and Overview:

Vitamin A is the name for a group of fat-soluble compounds that have a similar structure. This group includes retinol, retinal, retinyl esters, retinoic acid, and carotene. The most easily used type of vitamin A is retinol, often called preformed vitamin A as it is the active form in the body.

Vitamin A is a very versatile nutrient which serves a wide range functions. It is best known for being essential for good eye health. It also aids in the formation and maintainenance of healthy teeth and bones, body tissues including skin, and mucous membranes. It may play an important role in guarding against damage caused by oxidation (free radicals) which can contribute to premature aging, arthritis, cancer, cardiovascular disease, and infection, among other things.. Vitamin A is vital for normal cell growth and cell differentiation. It also serves necessary functions related to reproduction. Read more about the benefits and functions of vitamin A and signs of vitamin A deficiency.

Vitamin A is naturally found in two forms - preformed vitamin A and provitamin A, also known as carotene. Sources can be separted into two broad categories - animal sources and vegetable sources. Animal sources including things like eggs and meat. Vitamin A, in a form called retinyl palmitate, can be obtained from beef, calf, and chicken liver; and fish liver oils as well as many dairy products. Vegetable sources, which come in the form of beta-carotene, generally contain neither fat nor cholesterol. Read more about sources of vitamin A and the daily requirement of vitamin A.

An overdose of vitamin A can be damaging to the bones and thin skin, resulting in weakness and brittleness. It can also result in tiredness and vomiting. Read more about vitamin A overdose.

 

The precursors of vitamin A (retinol) are carotenoids (usually beta-carotene). Retinol, retinal, and retinoic acid are called retinoids. Retinal converted in the body to retinoic acid, a type of vitamin A which affects gene transcription. Beta-carotene, along with the other carotenoids that can be changed by the body into retinol, are called provitamin A carotenoids.

The structure of vitamin A is similar to carotene. Carotene is changed into vitamin A by the liver. It is then carried throughout the body with fat. This form of the vitamin can then be stored in fat tissues.

The body can get vitamin A via two methods. The first is by producing it from carotene, a vitamin precursor obtained from vegetables like carrots, squash, and spinach. The second is by absorbing vitamin A from animal sources. During digestion, retinol is inserted into chylomicrons as the ester form, and then these particles facilitate transportation to the liver. Storage of vitamin A in liver cells takes place through the ester derivative, however when retinol is required by other body tissues, it is de-esterifed and released into the bloodstream as an alcohol.

Retinol then connects to a serum carrier, retinol-binding protein, to be carried to relevant body tissues. A binding protein located within cells, cellular retinoic acid binding protein, functions to store and transport retinoic acid within cells.

Vitamin A (Retinol) Articles:

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More Information:

Vitamin A (Retinol) Benefits, Functions, Signs of Deficiency

Vitamin A (Retinol) Daily Requirement, Dietary Sources

 

 

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