FAO-WHO has held a calculation, that half of the carotenoids are absorbed by the body is converted into vitamin A, so only about one sixth of the carotene content in foodstuffs that will eventually be utilized by the body.
The units of measure for vitamin A that is used is the International Unit (IU) or International Units (SI). Currently the unit to be replaced with a dose of vitamin A retional equivalent (RE), because this unit is more precise and can provide a real picture of the circumstances, including consideration of the problem and the degree of absorption of carotene conversion to vitamin A.
1 RE = 1 og retinol (3.33 IU)
1 RE = 6 d og – carotene (10 IU)
1 RE = 12 og carotenoids (10 IU)
Too much vitamin A can cause hipervitaminosis, a state of intoxication caused by too much consumption of vitamin A, which when consumed 75,000 to 500,000 SI (45 to 300 mgr d-carotene) daily for a period of several months. Storage of vitamin A in the body. 95% of the reserves stored by the body vitamn A liver preformance.
As a result of Vitamin A deficiency
In the body of vitamin A plays a role in vision / eye, the surface epithelium, as well as help the growth process. The role of retinol in normal vision is very important because power is highly dependent eye sight by the presence of rhodopsin, a pigment that contains retinol.
(A) Impairment of vision
Vitamin A plays a role keeping the cornea to keep it healthy. Normal eye is usually issued mucus, the viscous liquid fatty issued mucosal epithelial cells that help prevent fat condensed issued mucosal epithelial cells thus helping to prevent infection.
When the body lacks vitamin A, epithelial cells will remove keratin, a protein that is insoluble in water and not mucus. When epithelial cells remove keratin, cells membrane will dry and harden, and the state is known as keratinization. The state would then take place when the cause of disease xerophthalmia.
Xeroftalmia are circumstances when a person experiencing a shortage of vitamin A, first keratinized eye conjunctiva, and cornea are also affected. When untreated, the eye will be blind. Marks the beginning of a vision impairment as a result of vitamin A deficiency is the declining ability to see light dala vague. A child suffering from vitamin A deficiency is usually when running in the vague light often bumped into existing objects in front of him.
This is because there are chemical changes that occur in the retina of the eye. Under normal circumstances the retina of the eye there is a substance called rhodopsin, which contains vitamin A needed in a series of visual stimuli acceptance at any time during the day If there is a deficiency of vitamin A, it means redopsin formation process will be disrupted. This is what is the causes of childhood rabunnya in a state of faint light or dusk light. Therefore, the disease is called night blindness or hemeralopi disease.
In both the manufacturing level will be reduced so that the tears of the eyes or mucous membranes become dry and konyuntiva appear many times. On the left and right parts of the eye will look shiny white stains like fish scales. And these spots are called Bitot spots. The symptoms of dryness is called xeroftalmi konyuntiva.
This disease can be cured without leaving scars or defects in the eye. When dlam extent this xeroftalmi children do not get treatment, then there is a greater danger, namely injury to the cornea. Sometimes it’s really great wound so that the whole cornea was destroyed. Such a situation is called keratomalasea. Patients will be blind at all.
(B) Epithelial Tissue Damage.
Vitamin A deficiency also causes a change – a change in the tissue lining (epithelium). This lining tissues would be hard because of the horn cells. Because of this, people who are not deficient in vitamin A is susceptible to respiratory disease or gastrointestinal tract.
(C) Growth Disorders
Lack of vitamin A can also disrupt the body’s growth. In addition, vitamin A deficiency may affect bone growth.
