Definition
Vitamin A
Vitamin A is a fat-soluble vitamin that is stored in the liver.
There are two types of vitamin A that are found in the diet.
- Preformed vitamin A is found in animal products such as meat, fish, poultry and dairy foods.
- Pro-vitamin A is found in plant-based foods such as fruits and vegetables. The most common type of pro-vitamin A is beta-carotene.
Vitamin A helps form and maintain healthy teeth, skeletal and soft tissue, mucus membranes, and skin. It is also known as retinol because it produces the pigments in the retina of the eye.
Vitamin A promotes good vision, especially in low light. It may also be needed for reproduction and breast-feeding.
Retinol is an active form of vitamin A. It is found in animal liver, whole milk, and some fortified foods.
Carotenoids are dark-colored dyes (pigments) found in plant foods that can turn into a form of vitamin A. There are more than 500 known carotenoids. One such carotenoid is beta-carotene.
Source : Medline Plus
Sources
Vitamin A comes from animal sources, such as eggs, meat, fortified milk, cheese, cream, liver, kidney, cod, and halibut fish oil. However, all of these sources, except for skim milk that has been fortified with Vitamin A, are high in saturated fat and cholesterol.
The best sources of vitamin A are:
- Cod liver oil
- Eggs
- Fortified breakfast cereals
- Fortified skim milk
- Orange and yellow vegetables and fruits.
Other sources of beta-carotene such as broccoli, spinach, and most dark green, leafy vegetables.
The more intense the color of a fruit or vegetable, the higher the beta-carotene content. Vegetable sources of beta-carotene are fat- and cholesterol-free.
Source : Medline Plus
Vitamin A deficiency
Food vitamin A deficiency resulting from insufficient food intake in vitamin A content it mainly affects the eyes and can lead to blindness.
| Source: Adapted from Centers for Disease Control and Prevention, World Food Programme. A Manual: Measuring and interpreting malnutrition and mortality. Rome: WFP, 2005:28. | ||
| Serum retinol ( µg / dL ) |
Serum retinol ( μmol / L ) |
WHO definition |
| < 10 | < 0.35 | Severe |
| 10 - 19.9 | 0.35 - 0.69 | Moderate |
| 20 or above | 0.7 or above | None |
Xerophthalmia
Xerophthalmia, meaning drying of the eyes (from the Greek word xeros, meaning dry), is the term now used to cover the eye manifestations resulting from vitamin A deficiency.
Translated from FAO
Organ
The first organ affected is the conjunctiva, which dries and loses its shiny appearance. Then, the cornea is reached, softens and loses its ability to reflect light.
Symptoms
Night blindness is often the first evidence of vitamin A deficiency; the individual has a reduced ability to see in dim light. In many countries where xerophthalmia is endemic, there are local terms for night blindness. Parents may notice that their young child is clumsy in the dark or fails to recognize people in a poorly lit room. Night blindness occurs because vitamin A deficiency reduces the rhodopsin in the rods of the retina.
The next sign is drying of the conjunctiva, which is known as conjunctival xerosis. Patches of xerosis give the appearance of sandbanks at receding tide. The conjunctiva loses its shiny lustre and often becomes thickened, wrinkled and sometimes pigmented.
Sometimes accompanying the conjunctival xerosis are Bitot's spots, which are usually triangular-shaped, raised whitish plaques that occur in both eyes. When examined closely they look like a fine foam with many tiny bubbles. This foamy, sticky material can be wiped away. Bitot's spots in the absence of xerosis may have a cause other than vitamin A deficiency.
The next stage is corneal xerosis, drying of the corneal surface, which first appears hazy and then granular on simple eye examination. The drying is followed by a softening of the cornea, often with ulceration and areas of necrosis.
Translated from FAO
Frequency
Vitamin A deficiency is common in low-resource countries, particularly among refugees. For example, one-third of adolescent refugees in Nepal and up to two-thirds of African refugee children have been reported to have vitamin A deficiency.
Source : Kids New to Canada
Vitamin A deficiency is the most common cause of blindness in children in many endemic areas.
Xerophthalmia occurs almost entirely in children living in poverty. It is extremely rare to find cases in more affluent families, even in areas where xerophthalmia is prevalent. It is a disease related to low socio-economic status, low levels of female literacy, land shortages, inequity, poor availability of curative and preventive primary health care, high rates of infectious and parasitic diseases (often related to poor sanitation and water supplies) and grossly inadequate family food security.
Translated from FAO
Causes
Vitamin A deficiency can be caused by low dietary intake, malabsorption and increased utilisation or excretion associated with common illnesses. Despite established policies for supplementing and fortifying foods supplied at refugee camps, high rates of vitamin A deficiency persist. Refugee numbers, pressures on food supply and difficult logistics make implementation a challenge in many regions.
Source : Kids New to Canada
Low intake of vitamin A and carotene over an extended period is the most common cause of xerophthalmia. The condition may be influenced by other factors, however, e.g. intestinal parasitic infections, gastro-enteritis or malabsorption. Measles often precipitates xerophthalmia because it leads to lowered food intake (in which anorexia and stomatitis may be factors) and to increased metabolic demands for vitamin A. The virus may also affect the eye, aggravating lesions caused by vitamin A deficiency. PEM is also important as a cause or accompaniment of xerophthalmia. Data from Indonesia and elsewhere suggest that serious corneal involvement in xerophthalmia seldom occurs except in children who have moderate or severe PEM.
Source : FAO
Evolution
While most cases of vitamin A deficiency are not severe enough to have definite, observable symptoms, stressors such as measles, pneumonia or diarrhea can decrease levels further and result in serious disease. Vitamin A deficiency can affect vision, in a range from poor night vision to blindness, and there is an increased risk of death after measles, diarrhea or pneumonia.
The prevalence of blindness in children in Sudanese refugee camps has been estimated at 1.4 per 1000 children, with 40% of cases due to corneal opacities attributed mainly to vitamin A deficiency. 5 Additional consequences include impaired bone growth, weakened immune response and increased risk of mortality.
Source : Kids New to Canada
Prevention
In the long term, sustainable control will be achieved by increasing the production and consumption of foods rich in vitamin A and carotene by at-risk populations. Other methods include medicinal supplements, often consisting of high doses of vitamin A every four to six months; fortification of foods; and nutrition education.
Translated from FAO
Diagnosis
A dosage of Vitamin A can detect a deficiency.
An examination at the slit lamp can show atrophy and dryness of the conjunctiva in case of xerophthalmia.
Treatment
Effective treatment depends on early diagnosis, immediate dosing with vitamin A and proper treatment of other illnesses such as PEM, tuberculosis, infections and dehydration. Severe cases with corneal involvement should be treated as emergencies. Sometimes hours, and certainly days, may make the difference between reasonable vision and total blindness.
Treatment for children one year of age or over should consist of retinyl palmitate orally or retinyl palmitate.
When there is corneal involvement it is desirable to apply an antibiotic ointment such as topical bacitracin to both eyes six times per day. Appropriate systemic antibiotics should also be administered.
Provide a varied diet rich in vitamin A is also required.
Translated from FAO
