Vitamin A deficiency ( VAD ) or hypovitaminosis A is a deficiency of vitamin A in the blood and tissues. This is common in poor countries, but rarely seen in more advanced countries. Nyctalopia (night blindness) is one of the first signs of VAD. Xerophthalmia, keratomalacia, and complete blindness can also occur because vitamin A has a major role in phototransduction. Three forms of vitamin A include retinol, beta-carotene, and carotenoids.
Vitamin A deficiency is the leading cause of preventable preventable childhood blindness, and it is essential to achieve the Millennium Development Goal 4 to reduce child mortality rates. Approximately 250,000 to 500,000 undernourished children in developing countries are blinded every year because of vitamin A deficiency, about half of whom die within a year of being blind. The UN Special Session for Children in 2002 set the goal of eliminating VAD in 2010.
The prevalence of night blindness due to VAD is also high among pregnant women in many developing countries. VAD also contributes to maternal death and other adverse outcomes in pregnancy and lactation.
VAD also reduces the ability to fight infections. In countries where children are not immunized, infectious diseases such as measles have a higher mortality rate. As Alfred Sommer explains, even mild subclinical deficiencies can also be problematic, as it can increase the risk of children developing respiratory infections and diarrhea, reducing growth rates, slowing bone development, and reducing the likelihood of survival of serious illnesses.
VAD is thought to affect about a third of children under five years of age worldwide. It is estimated to claim the lives of 670,000 children under five years old. Around 250,000-500,000 children in developing countries are blinded annually due to VAD, with the highest prevalence in Southeast Asia and Africa. According to the World Health Organization (WHO), VAD is under control in the United States, but in developing countries, VAD is a significant problem. Globally, 65% of all children aged 6 to 59 months receive two doses of vitamin A by 2013, fully protecting them against VAD (80% in underdeveloped countries).
Video Vitamin A deficiency
Signs and symptoms
The common cause of blindness in developing countries is VAD. WHO estimates 13.8 million children have vision loss rates associated with VAD. Night blindness and worsening condition, xerophthalmia, is a marker of VAD, as it can cause impaired immune function, cancer, and birth defects. Collections of keratin in the conjunctiva, known as Bitot spots, are also visible. Imtiaz sign is the earliest ocular sign of VAD. The conjunctival epithelial defect occurs around the lateral aspect of the limbus in the subclinical stage of VAD. These conjunctival epithelial defects are not visible in the biomicroscope, but they take on a black stain and become visible after gradual kajal (surma); this is called "Imtiaz's sign". Vitamin A deficiency is one of the few hypovitaminoses involved in follicular hyperkeratosis.
Twilight
Night blindness is difficult for the eye to adjust to the dim light. Affected individuals can not distinguish images in low-level illumination. People with night blindness have poor eyesight in the dark, but behold normally when sufficient light is present.
VAD affects vision by inhibiting the production of rhodopsin, the pigment of the eye responsible for experiencing low light situations. Rhodopsin is found in the retina and consists of the retina (the active form of vitamin A) and opsin (protein). Because the body can not make the retina in sufficient quantities, a low vitamin A diet causes a decrease in the number of rhodopsin in the eye, because the retina is inadequate to bind with opsin. The result of night blindness.
Night blindness caused by VAD has been associated with loss of goblet cells in the conjunctiva, the membrane covering the outer surface of the eye. Goblet cells are responsible for removing mucus, and their absence produces xerophthalmia, a condition in which the eye fails to produce tears. The dead epithelial and microbial cells accumulate in the conjunctiva and form debris that can cause infection and possibly blindness.
Reducing night blindness requires an increase in vitamin A status in the at-risk population. Food supplements and fortification have proven to be effective interventions. Additional treatment for night blindness includes large doses of vitamin A (200,000 IU) in the form of retinyl palmitate to be taken by mouth, given two to four times a year. Intramuscular injections are poorly absorbed and ineffective in providing adequate vitamin A availability. Fortification of foods with vitamin A is expensive, but can be done on wheat, sugar, and milk. Households may avoid foods fortified by changing diet. The consumption of carotenoids-rich yellow-orange fruits and vegetables, especially beta-carotene, provides provitamin A precursors that can prevent night blindness associated with VAD. However, the conversion of carotene into retinol varies from person to person and the bioavailability of carotene in the diet varies.
Maps Vitamin A deficiency
Source
The richest source of vitamin A (retinol) is the liver (beef liver - one ounce provides about 8,000 IUs) and cod liver oil - a teaspoon provides about 4,500 IUs).
Cause
In addition to dietary problems, other causes of VAD are known. Iron deficiency can affect vitamin A uptake; Other causes include fibrosis, pancreatic insufficiency, inflammatory bowel disease, and small intestine bypass surgery. Excessive alcohol consumption can consume vitamin A, and a stressful liver may be more susceptible to vitamin A toxicity. People who consume large amounts of alcohol should seek medical advice before taking vitamin A supplements. In general, people should also seek medical advice before taking supplements vitamin A if they have conditions associated with fat malabsorption such as pancreatitis, cystic fibrosis, tropical canker sores, and biliary obstruction. Other causes of vitamin A deficiency are inadequate intake, fat malabsorption, or liver disorders. Deficiencies damage immunity and hematopoiesis and cause rashes and distinctive ocular effects (eg, xerophthalmia, night blindness).
Infection rate
Along with poor diet, a large number of infections and diseases are present in many developing communities. Infections severely deplete vitamin A reserves and vitamin A deficiencies make the individual more susceptible to infection; increased documentation of xerophthalmia has been seen after epidemic measles and various stages of xerophthalmia to be a good reference point for deficiency rates (with increased mortality with eye disease severity). In a longitudinal study of preschool children in Indonesia, susceptibility to disease increased nine times when VAD weight was present.
The reason for the increased rate of infection in vitamin A deficiency populations is that T-killer cells require retinoids to proliferate properly. Retinoic acid binds to specific gene promoter regions, thus activating the process of transcription and cell replication. A vitamin A deficiency diet will have a very limited surplus of retinol, so cell proliferation and replication will be suppressed, contributing to the reduced number of T cells and lymphocytes. This oppression results in a lack of an immune reaction if pathogens become present in the body and consequently a greater susceptibility to disease incubation.
VAD and infections worsen each other, so with infection, vitamin A levels are depleted, which in turn reduces vitamin A absorption. Very often seen with VAD is protein energy malnutrition, where retinol binding protein (RBP) synthesis decreases, resulting in reduced retinol uptake. This causes the inability to use any vitamin A because the RBP is absent, so retinol can not be transported to the liver, maximizing VAD.
Diagnosis
Treatment
Treatment of VAD can be done by oral form and injection, generally as vitamin A palmitate.
- As an oral form, vitamin A supplementation is effective in reducing the risk of morbidity, especially from severe diarrhea, and reducing mortality from measles and all causes of death. Vitamin A supplementation in under-five children at risk of VAD can reduce all causes of death by 23%. Some countries where VAD is a public health problem overcome elimination by incorporating vitamin A supplements available in capsule form with national immunization day (NID) for polio or measles eradication. In addition, delivery of vitamin A supplements, during integrated child health events such as child's health days, has helped ensure high coverage of vitamin A supplementation in a large number of underdeveloped countries. Child health events allow many countries in West and Central Africa to achieve more than 80% of vitamin A supplementation coverage. According to UNICEF data, by 2013 worldwide, 65% of children between the ages of 6 and 59 months are fully protected with two vitamin supplements A high dose. Vitamin A capsules cost about US $ 0.02. The capsules are easy to handle; they do not need to be stored in a refrigerator or vaccine container. When appropriate doses are given, vitamin A is safe and has no negative effect on seroconversion levels for polio vaccine or oral measles. However, since the benefits of vitamin A supplements are temporary, children need them regularly every four to six months. Since NIDs provide only one dose per year, the distribution of vitamin A associated with NID should be complemented by other programs to maintain vitamin A in children. High maternal supplementation benefits breastfed mothers and infants: high-dose vitamin A supplementation from breastfeeding mothers in the first month's postpartum may provide breast-fed infants with the right amount of vitamin A through breast milk. However, high doses of supplementation in pregnant women should be avoided as they may lead to miscarriage and birth defects.
- Food fortification is also useful for improving VAD. Various oily and dry forms of the retinol, retinyl acetate, and retinyl palmitate esters are available for fortified vitamin A foods. Margarine and oil are the ideal foods for fortification of vitamin A. They protect vitamin A from oxidation during storage and immediate absorption of vitamin A. Beta- carotene and retinyl acetate or retinyl palmitate are used as a form of vitamin A for fortification of vitamins from fat-based foods. Fortification of sugar with retinyl palmitate as a form of vitamin A has been widely used throughout Central America. Cereal flour, milk powder, and liquid milk are also used as food vehicles for vitamin A fortification. Genetic engineering is another method of food fortification, and this has been achieved with golden rice, but resistance to genetically engineered food has prevented its use in July 2012.
- Dietary diversification can also control VAD. Nonanimal sources of vitamin A containing vitamin A are predicted for intake of more than 80% for most individuals in developing countries. Increased consumption of vitamin A-rich foods from animals other than fruits and vegetables has a beneficial effect on VAD. Researchers at the US Agricultural Research Service have been able to identify genetic sequences in maize associated with higher levels of beta-carotene, vitamin A precursors. They found that breeders may cross certain variations of maize to produce crops with an 18-rate increase in beta-carotene. Such advances in plant nutrient breeding may one day assist VAD-related diseases in developing countries.
Global Initiative
The global effort to support the national government in handling VAD is led by the Global Alliance for Vitamin A (GAVA), an informal partnership between A2Z, the Canadian International Development Agency, Helen Keller International, the Micronutrien Initiative, UNICEF, USAID and the World Bank. The GAVA Combined Activities are coordinated by the Micronutrient Initiative.
Vitamin Angels has committed to eradicating childhood blindness due to VAD on this planet in 2020. Operation 20/20 was launched in 2007 and will cover 18 countries. The program gives children two high-dose vitamin A and antiparasitic supplements (twice a year for four years), which feeds children nutritionally during the most vulnerable years to prevent them from becoming blind and suffering from other life-threatening diseases. to VAD.
About 75% of vitamin A needed for supplementation activities by developing countries is supplied by the Micronutrien Initiative with support from the Canadian International Development Agency.
An estimated 1.25 million deaths due to VAD have been avoided in 40 countries since 1998.
In 2008, an estimated annual investment of US $ 60 million in supplements of vitamin A and zinc would yield benefits of more than US $ 1 billion per year, with each dollar spent generating more than US $ 17. This combined intervention is classified by the Consensus Copenhagen 2008 as the world's best development investment.
Epidemiology
See also
- Children's blindness
- Gold rice
- Retinol
- St. Jerome's description of vitamin A deficiency
- Vitamins
References
Further reading
- UNICEF, Vitamin A Supplementation: A Decade of Progress, UNICEF, New York, 2007.
- Flour Fortification Initiative, GAIN, Micronutrien Initiative, USAID, World Bank, UNICEF, Future Investing: Exclamation Unite for Deficiency Vitamins and Minerals Act, 2009.
- UNICEF, Improving Child Nutrition: Achievable goals for global progress, UNICEF, New York, 2013.
External links
- Micronutrien Initiative
- UNICEF Data on Vitamin A Deficiency and Supplementation
- Helen Keller International
- A2Z
- World Health Organization Database on Vitamin A Deficiency
- Vitamin A Deficiency in IAPB
Source of the article : Wikipedia
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