Vitamin A - Food Sources and Deficiency Symptoms
Vitamin A is also called retinol, is a group of compounds that play an important role in vision, bone growth, reproduction, cell division, and cell differentiation. It promotes healthy surface linings of the eyes and the respiratory, urinary, and intestinal tracts. Vitamin A also helps the skin and mucous membranes function as a barrier to bacteria and viruses.
It can be obtained from either animal or vegetable sources. The animal form is divided between retinol and dehydroretinol whereas the vegetable carotene can be split into four very potent groups - alpha-carotene, beta-carotene, gamma-carotene and crypto-carotene.
Vitamin A, is a fat-soluble vitamin, which maintains mucous membranes. It helps you see in dim light and prevents xerophthalmia. Essential to the tissues lining lungs, digestive organs and genitourinary tract. Helps bones grow normally. Maintains membranes of body cells. Important for reproduction.
Yhe other names of vitamin A are as: Retinol, retinoic acid, carotenoids, carotene, beta-carotene, vitamin-A palmitate, vitamin-A acetate.
Functions of Vitamin A:
The possible functions are as:-
- Vision: Vitamin A is required for night vision, and for a healthy skin. Vitamin A is a fat-soluble vitamin that helps you see normally in the dark and promotes the growth and health of all body cells and tissues. The retina is located at the back of the eye. When light passes through the lens, it is sensed by the retina and converted to a nerve impulse for interpretation by the brain. Retinol is transported to the retina via the circulation, where it moves into retinal pigment epithelial cells.
- Regulation of gene expression: Retinoic acid and its isomers act as hormones to affect gene expression and thereby influence numerous physiological processes. All- trans RA and 9- cis RA are transported to the nucleus of the cell bound to cytoplasmic retinoic acid-binding proteins .
- It assists the immune system, and because of its antioxidant properties is great to protect against pollution and cancer formation and other diseases.
- It also assists your sense of taste as well as helping the digestive and urinary tract and many believe that it helps slow aging.
- It is required for development and maintenance of the epithelial cells, in the mucus membranes, and your skin, and is important in the formation of bone and teeth, storage of fat and the synthesis of protein and glycogen.
- It also protects against infection by keeping healthy the skin and tissues in the mouth, stomach, intestines and respiratory and uro-genital tract.
- Assists maintaining health skin and mucous membranes protecting the body's major organs.
Deficiency of Vitamin A:
- A deficiency of vitamin A may lead to eye problems with dryness of the conjunctiva and cornea, dry skin and hair, night blindness as well as poor growth.
- Dry itchy eyes that tire easily are normally a warning of too little vitamin A. If the deficiency become severe, the cornea can ulcerate and permanent blindness can follow.
- The eyes are obvious indicators of vitamin A deficiency. One of the first symptoms is night blindness.
- Other eye indicators of vitamin A deficiency include susceptibility to colds, flu, bacterial and viral infections, especially of the respiratory and urinary tract, are indicators of Vitamin A deficiency.
Sources of Vitamin A:
The possible sources are as:-
- Vitamin A is present in many animal tissues, and is readily absorbed from such dietary sources in the terminal small intestine. Liver is clearly the richest dietary source of vitamin A. Vitamin A is stored in the liver as retinyl esters and, when needed, exported into blood, where it is carried by retinol binding protein for delivery to other tissues.
- Vitamin A is found in milk, cheese, cream, liver, kidney, and cod and halibut fish oils. Beta-carotene comes from carrots, pumpkin, sweet potatoes, winter squashes, cantaloupe, pink grapefruit, apricots, broccoli, and spinach. The more intense the color of a fruit or vegetable, the higher the beta-carotene content.
- Vitamin A is found in dark green and yellow vegetables and yellow fruits, such as broccoli spinach and turnip greens.