Understanding Vitamin A
Vitamin A is fat-soluble vitamin that comes from two sources, namely retinoids and provitamin carotenoids. Retinoids, such as retinal and retinoic acid, found in animal sources like liver, kidney, eggs, and dairy products.
Carotenoids such as beta-carotene (which has the highest activity of vitamin A) found in plants such as dark or yellow vegetables and carrots.The main biological function of vitamin A (as retinal metabolites) is in a cycle of vision. The study also showed that vitamin A may reduce the death rate from measles, prevent some cancers, helps growth and development, and enhance immune function. Vitamin A deficiency is rare in industrialized nations but remains a problem in developing countries.
Food sources of vitamin A
Vitamin A is found in dairy products, fish, dark-colored vegetables and fruits. Vegetables rich in vitamin A include carrots, sweet potatoes, pumpkin, spinach and cantaloupe. Milk, cheese, butter and eggs also contain vitamin A. Consumption of five servings of fruits and vegetables per day supplies 5-6 milligrams per day of provitamin A carotenoids, which provides about 50-65% of vitamin A for adults.
Benefits and functions of vitamin A
Vitamin A is essential for the maintenance of the epithelial cells of the cornea and vision. Vitamin A also helps the growth and reproduction of bones and teeth. In addition vitamin A also plays a role in the formation and regulation of hormones and helps protect the body against cancer (beta carotene).
Symptoms and signs of vitamin A deficiency
The first signs and symptoms of vitamin A deficiency is night blindness usually (difficulty seeing at night). Then there will be deposition of foamy (Bitot spots) in the whites of the eyes (sclera) and cornea can harden and form scar tissue (xeroftalmia), which can cause permanent blindness. Vitamin A deficiency also causes skin inflammation (dermatitis) and increase the likelihood of infection. Some patients experience anemia.Vitamin A deficiency can also prevent the growth of bones, or cause changes in bone shape, forming cracks and damage to the teeth and the cessation of growth of tooth-forming cells. In addition, vitamin A deficiency can affect bone and nervous system, and can lead to paralysis.
Dose of the daily requirement of vitamin A
Daily requirement of vitamin A recommendation by the U.S. Recommended Daily Allowance (RDA) for adults is: 900 micrograms per day (3,000 IU) for men and 700 micrograms per day (2,300 IU) for women. For pregnant women 19 years and older, 770 micrograms per day (2,600 IU) is recommended. For lactating women 19 years and older, 1,300 micrograms per day (4300 IU) is recommended.For children - children under 18 years of vitamin A upon the recommendation of the U.S.
Recommended Daily Allowance (RDA) is: for children aged 1-3 years, 300 micrograms per day (1,000 IU) for children aged 4-8 years, 400 micrograms per day (1,300 IU), and for children aged 9-13 years 600 micrograms per day (2,000 IU).
Vitamin A toxicity
Vitamin A poisoning occurs when the binding protein has been fulfilled so that the vitamin A that is free to attack the body's cells.This does not occur if the vitamin comes from the daily diet, but this can happen when someone is using supplements of vitamin A.vitamin A toxicity have less specific symptoms such as headaches, dizziness, fatigue, malaise, blurred vision, bone pain and swelling, nausea, and / or vomiting. Poisoning can cause severe eye damage, high levels of calcium, and liver damage.
From various sources
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