Vitamin A is perhaps the most important vitamin. It is called retinol and is easily transformed into the human body in retinoic acid, which is an effective way. It exists in two main ways: all-trans retinoic acid (ATRA, the most important) and 9-cis retinoic acid (9-cis RA).
An obvious function of vitamin A is like a big compound of proteins (called Rhodopsin) in eyes that react to light and make vision possible. Most functions of this vitamin, however, is performed by its receptors, which are transcription factors of the nuclear receptor family. For these receptors, retinoic acid can affect almost every function in the human cell. Knowing this, it is easy to understand why the vitamin must be consumed in normal amounts.
More recent studies are showing that the vitamin acts as an antioxidant (it combats the free radicals that accelerate aging and are associated with some diseases). However, caution should be exercised in the use of vitamin A, for excess is harmful.
Scientific Name = Retinol or Axeroftol.
Index [hide]
1 Consequences of deficiency
1.1 Causes of disabilities
2 Consumption exaggerated
3 Foods rich in Vitamin A
4 References
[edit]Consequences of deficiency
Structure of retinol (vitamin A).
The avitaminosis which is related to Vitamin A deficiency is xerophthalmia. One of the epithelium severely affected is the eye of the lining, leading to xerophthalmia. Xerophthalmia is the generic name given to various ocular signs and symptoms of hypovitaminosis A. The earliest clinical manifestation of xerophthalmia is night blindness, where the child can not look good adaptation in poorly lit; more pronounced manifestations of xerophthalmia are Bitot's spots, usually located on the exposed part of the conjunctiva and xerosis; in later stages the cornea is also affected being the corneal xerosis, characterized by the loss of brightness assuming granular appearance and ulceration of the cornea, ulceration can lead to progressive necrosis and destruction of the eyeball leading to blindness, irreversible, which is called Keratomalacia. Other complications related to vitamin A deficiency include poor vision at night (night-blindness), sensitivity to light (photophobia), reduction of smell and taste, dryness and infection in the skin and mucous membranes (xeroderma), stress, thickening of corneal injuries and skin cancer in the eye. Xerophthalmia is different from night-blindness, is being called the 'night blindness' and that, dry eyes, which promotes the increased friction between the eyelid and the eye, causing ulcerations in the epithelium of the eye. The vitamin A deficiency also causes hyperplasia (uncontrolled multiplication of cells) and metaplasia (loss of cell shape), and the emergence of opportunistic diseases. Frequent infections may indicate deficiency, since a lack of vitamin A reduces the body's ability to defend itself from diseases.
[edit]Causes of disability
Lack of breastfeeding or weaning early: the milk is rich in vitamin A and is the ideal food for children under two years old.
Insufficient consumption of foods rich in vitamin A.
Insufficient consumption of foods containing fat: the human body needs a quantity of dietary fat to keep several functions essential for its proper functioning. One is to allow the absorption of some fat soluble vitamins (vitamins A, D, E and K).
Frequent infections: infections that affect children lead to a decrease in appetite: The child begins to eat less food may arise a deficiency of Vitamin A. Moreover, the infection causes the body's need for vitamin A are higher, leading to reduced inventories in the body and triggering or worsening the state nutrition.
[edit]Consumption exaggerated
By ingesting excessive manifestations may be as dry skin, rough and scaly, cracking lips, follicular keratosis, bone and joint pain, headaches, dizziness and nausea, falling hair, muscle cramps, injuries, liver and stops growth. May also arise lack of appetite, edema, fatigue, irritability, and bleeding. Increase in the spleen and liver, abnormal liver function tests, reduced levels of cholesterol and HDL cholesterol may also occur. Great care should be given to products containing the retinoic acid used in the treatment of acne.
The precursors of vitamin A have a significant influence on the amount of vitamin A that must be ingested. There are compounds related to vitamin that can be converted within the body into vitamin active (pro-vitamins). Some carotenoids are pro-vitamin A, the most important beta-carotene, followed by alpha-carotene. As the excess of vitamin A is stored in the body reaching cause toxic levels, may be resorted to carotenoids that can be consumed in doses considerably higher without an accumulation is harmful.
Consumption of beta-carotene of about 30 mg / day increases the likelihood of lung cancer and prostate. Smokers and people who have suffered exposure to asbestos should not consume supplements of beta-carotene.[2]
[edit]Foods rich in Vitamin A
Are foods rich in vitamin A foods of animal and plant:
Liver
Butter
Milk
Egg yolk
Sardine
Cheese fat
Cod-liver oil
Avocado
Chard
Cashew
Peach
Papaya
Escarole
Melon
Carrot
Leaf Broccoli
Sweet potato
Kale
Spinach
Pumpkin
Tomato
Mango
Beta-carotene (provitamin A) are fat soluble, so the absorption of vitamin A is improved if these foods are eaten with fat (like vegetable oils). Cooking for a few minutes, until the cell walls to rupture and release color also increase absorption. um abraço a todos e ate a proxima .
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