What is vitamin A? What are the sources of vitamin A? What is the role of vitamin A in night vision? What is vitamin A toxicity?
Vitamin A(C20H30O) is the fat-soluble vitamin that is taken as nutrition in two forms the Preformed vitamin A and Provitamin A, the preformed vitamin A consists of retinal esters and retinol, these are not further metabolized in the cell and are stored as such.
Provitamin A consists of carotenoids. These are converted into retinol, which is later on changed to retinoic acid, intracellularly.
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| VITAMIN A: TYPES AND ITS INTRACELLULAR CONVERSION INTO RETINOIC ACID |
As it is fat-soluble it is converted into micells and absorbed by duodenal mucosa in the intestine once absorbed, it is not washed away easily. It is stored in the liver and fat tissue. Deficiency of vitamin A can only be observed by a relative dose-response test where plasma retinol level is measured before and after an administration of a small dose of vitamin A.
BIOLOGICAL ROLE OF VITAMIN A
It is involved in immune function.
It is required for healthy tooth formation
Proper cell division needs vitamin A
It is required for rhodopsin the pigment of the eye, so it is needed for night vision.
Pregnant ladies require vitamin A for healthy childbirth
Lactating women also require vitamin A for child health.
Which foods are rich in vitamin A?
Preformed vitamin A is mainly found in animal sources such as beef liver, fish oil, milk, and egg. Pro-formed Vitamin A is found in green vegetables, orange, and yellow fruits.
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| TWO DIFFERENT FORMS OF VITAMIN A AND THEIR SOURCES |
Food rich in vitamin A
Cod liver oil
Sweet potato
Carrot
Beef liver
Black Eyed Peas
Broccoli
Bell pepper
Mango
Yogurt
Pumpkin pie
Tomato juice
Cheese
Spinach
Deficiency of Vitamin A
Deficiency of Vitamin a results in dryness of the eye (Xerophthalmia)
Deficiency of Vitamin A in pregnant ladies results in a high risk of Nyctalopia or night blindness and reproductive disorders called teratogenesis.
Deficiency of Vitamin A in infants results in night blindness.
Blurred vision
Age-related macular degeneration is prevented and treated by vitamin A supplements.
WHY DO WE GET VITAMIN A DEFICIENCY?
Cystic fibrosis: People with cystic fibrosis have a high risk of Vitamin A deficiency as they have impaired absorption of fats.
Preterm birth also leads to vitamin A deficiency as these infants do not have a fully formed liver.
Deficiency in infants is mainly due to not getting an adequate amount of colostrum or breast milk.
In young children, deficiency occurs when they stop breastfeeding
People suffering from protein-calorie malnutrition and chronic diarrhea can suffer from vitamin A deficiency.
How to reduce deficiency of vitamin A
The infant should be given breast milk, lactating women should take yellow fruits and vegetables.
Prevented chronic diarrhea in children
Avoid alcohol
Avoid beverages with added sugar and sodium.
Keep your pancreas healthy.
Keep your liver healthy.
Toxicity of vitamin A
Excessive Vitamin a may lead to a fractured bone excessive, a dose of Vitamin A over the years tends to become weak preformed Vitamin A mainly leads to Vitamin A toxicity it also leads to
nausea, headache,
pain joints and muscle pain. This is because Vitamin A is a fat-soluble vitamin, excess of vitamin A is stored in the liver and fat tissue, so it tends to accumulate over the years. Further, it does not wash away easily these symptoms continue for a long time even if you stop taking vitamin A supplements.
Vitamin A toxicity is observed when we take the excess of preformed vitamin A i.e. retinal and retinol. not in the case of beta carotenoid intake.
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