Brief Definition
Vitamin A belongs to the group of fat soluble vitamins (soluble in fat) is essential for the organism.
This vitamin is present in foods of animal origin as a pre-formed vitamin A and retinol is called while the plant appears as provitamin A, also known as carotenoids that stands out among the beta carotene.
Beta carotene are natural pigments that are found in fruits and vegetables red, orange and yellow, or in dark green vegetables. Beta-carotene is a chemical form required by the body for the formation of vitamin-A.
Approximately 80 and 90% of the retinol esters are absorbed while the beta carotene they do between 40 to 60%. The majority of vitamin A, almost 90% is stored in the liver, the remainder being deposited in the lungs, kidneys and body fat.
Functions of vitamin A and retinol in the body:
* Skeletal system: it is necessary for growth and bone development.
* Cell development: essential for growth, maintenance and repair of mucosal cells, epithelial, skin, vision, nails, hair and tooth enamel.
* Immune system: helps in the prevention of infectious diseases, especially respiratory creating protective barriers against different microorganisms. It stimulates immune functions, including antibody response and the activity of several cells produced by bone marrow involved in defending the body as phagocytes and lymphocytes. Therefore promotes the repair of infected tissues and increases resistance to infection.
* Reproductive System: helps in the normal function of reproduction, contributing to the production of sperm as well as normal female reproductive cycle. Due to its vital role in cell growth, vitamin A helps the changes that occur in the cells and tissues during development of the fetus to develop normally.
* Vision: It is essential for vision, since the Retinol helps improve night vision, preventing certain visual disturbances such as cataracts, glaucoma, vision loss, blindness twilight, also helps fight bacterial infections such as conjunctivitis.
* Antioxidant: Prevents cellular aging and the onset of cancer, since being a natural antioxidant eliminates free radicals and protects DNA from the mutagenic action.
The main sources of vitamin A include:
In the animal kingdom: dairy products, egg yolks and fish liver oil.
In plants: In all the plants yellow to red, or dark greens, carrots, sweet potatoes, pumpkins, squash, peppers, spinach, radicchio, lettuce, broccoli, Brussels sprouts, tomato, asparagus
In fruit: apricots, peaches, cantaloupe, papaya, mango, papaya
Consequences of lack or deficiency of vitamin A
Lack of vitamin A enters brings some consequences which are the following:
* Eye disorders: blindness can result crepuscular, ie visual acuity decreases at dusk, extreme sensitivity to light as well as dryness, opacity of the cornea ulcers, called xerophthalmia, which can lead to blindness
* Low immunity (low defenses) increased susceptibility to bacterial, parasitic or viral infections since vitamin A contributes to the maintenance of mucosal integrity. Lacking she disappears barrier against infection. Immune system cells are also affected which may lead to increased pre-cancerous cells of epithelial tissues of the mouth, throat and lungs
* Bony changes: inhibits growth, gives skeletal malformations, increases the likelihood of developing diseases in joints due to hindering bone regeneration.
* Skin disorder: causes Hypercornification, ie the skin becomes rough, dry, scaly (chicken skin, toad skin), hair becomes brittle and dry nails as
* Other: general fatigue and loss of appetite, weight loss, impaired hearing, taste and smell, reproductive alterations.
Toxicity – Toxic effects of excessive intake of vitamin A
Hypervitaminosis A refers to an abnormal deposition in the body in large amounts of vitamin A (retinol).
Normally this is given by the excessive intake of vitamin supplements.
Several adverse effects among which are:
* Defects at birth is when the supplement that has high doses of retinol ingested for a while, several days or weeks and especially during the first trimester of pregnancy.
* Abnormalities in the liver.
* Reduced bone mineral density.
* Central nervous system disorders.
Signs and symptoms of toxicity or hypervitaminosis (excess vitamin A) may be:
Anorexia, weight loss, vomiting and nausea, blurred vision, irritability, hepatomegaly, alopecia, headaches, insomnia, weakness, poor muscle strength amenorrhea (cessation of menstrual period), hydrocephalus and cranial hypertension in children.
A sign of danger is lacking hipercarotenosis. Excessive consumption of vegetables may produce. Excess carotene deposits under the skin giving a yellowing of palms.
Beta carotene is generally considered safe and not associated with adverse effects. Their conversion to vitamin A decreases when it deposits in the body are sufficient. Hipercarotenosis can only produce, which is not considered hazardous to health. When you reduce this excessive intake, the skin color returns to normal.
Have been established tolerable upper intake levels (tolerable upper intake levels: UL) to prevent the risk of toxicity with vitamin A. The adverse effects of higher intakes are increased to the maximum level tolerable.
These levels are not applicable to people suffering from malnutrition and who regularly receive vitamin A nor in individuals who are treated with vitamin A to treat various diseases such as retinitis pigmentosa
Recommendations related to vitamin A
* Vitamin A is stable at ordinary temperatures for storage and cooking.
* It is relatively stable to light and heat but is destroyed by oxidation (when exposed to oxygen is lost vitamin)
* The bioavailability of carotenoids increases through cooking (al dente), but when it is over the opposite effect, ie decreases significantly.
* The frying of foods rich in vitamin A, as this is soluble in fat. Pass carotene and retinol in the middle lost fat vitamin content of food consumed.
* Eat vegetables dehydration because it reduces the amount of carotenoids.
* The presence of vitamin E and other antioxidants also increase the bioavailability of vitamin A.
* Vegetarians who consume no dairy products or eggs need carotenoids to meet their need for vitamin A. This needs to include in your daily diet at least 5 servings of fruits and vegetables preferring those with green leaves and fruits orange or yellow
* Excess alcohol irritates the digestive tract and thus inhibit the absorption of vitamin A
credit to: Ms. Marcela Licata
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Tags: beta-carotene, carotenoids, deficiency, fat soluble, functions, toxicity, Vitamin A
