Vitamin A is a group of fat-soluble organic compounds that include retinol, retinal, and retinoic acid. The vitamin is essential for many bodily functions such as a strong immune system, good skin, and, most importantly, proper vision.
The two primary types of vitamin A found in foods are retinol and provitamin A. Retinol is commonly found in animal products such as meat, fish, eggs, and dairy products.
At the same time, the body converts carotenoids such as alpha-carotene and beta-carotene, which can be found in plant foods such as green, red, yellow, and orange fruits, into vitamin A.
Vitamin A Deficiency, also known as hypovitaminosis A, is the insufficient amount of vitamin A in tissues and blood. It is prevalent in low-income, developing countries, especially amongst children and women of reproductive age.
One of the most common symptoms of vitamin A deficiency is Nyctalopia (night blindness), which may eventually lead to complete blindness. Other effects of vitamin A deficiency include Xerophthalmia and keratomalacia.
According to the World Health Organization, vitamin A deficiency is the leading case of preventable blindness in children. It also increases the risk of diseases and death from severe infections in children and may increase the risk of maternal mortality.
There are nearly half a million malnourished children in developing countries who go blind for lack of vitamin A annually, and some die within a year of becoming blind.
Insufficient amounts of vitamin A impairs the body’s ability to fight infections. There are higher fatality rates of infectious diseases such as measles and chickenpox in countries where children are not vaccinated.
Vitamin A deficiency may also increase children’s risk of developing diarrhea and respiratory infections, arrested bone development, decrease growth rate, and decrease the likelihood of survival from severe diseases.
The highest prevalence of vitamin A deficiency occurs in Africa and Southeast Asia.
Vitamin A deficiency is primarily caused by insufficient amounts of the vitamin in diets. Other causes of vitamin A deficiency include:
- Iron deficiency which affects the uptake of vitamin A
- Inflammatory bowel disease
- Pancreatic insufficiency
- Small-bowel bypass surgery
- Disorders of fat malabsorption such as pancreatitis, cystic fibrosis, and biliary obstruction.
- Liver disorders
- Suppressed synthesis of retinol-binding protein due to protein energy malnutrition
- Excess intake of alcohol which depletes vitamin A levels and stresses the liver.
Signs and Symptoms of Vitamin A Deficiency
This is the inability of the eyes to adjust to dim light. People afflicted with night blindness or Nyctalopia cannot distinguish images at low light levels.
They have poor vision in the dark and can only see when there is adequate light.
This occurs when the production of rhodopsin, the eye pigment responsible for sensing low-light situations, is depleted. Vitamin A is needed for the production of this pigment; insufficient amounts of the vitamin would lead to reduced production of rhodopsin.
Increased rate of infection
The absence of vitamin A leads to a reduced number of T-cells and lymphocytes, leading to a weak immune system that is open to infections.
Impaired healing of wounds
Vitamin A promotes the production of collagen, an essential component for healthy skin. Wounds that do not heal properly after injury may be caused by insufficient amounts of Vitamin A.
Studies have shown that oral vitamin A improved the collagen production in rats. This occurred even though the rats were on steroids which are capable of inhibiting wound healing
Furthermore, these studies in humans show similar results. Older men who treated wounds with topical vitamin A had a 50% reduction in the size of their injuries. This is in comparison with men who did not use the cream.
Vitamin is responsible for the proper functioning and development of the body. Children with inadequate amounts of vitamin A may experience stunted growth. Studies conducted in children in developing countries have shown that vitamin A supplements can improve growth.
However, vitamin A supplements should be taken in combination with other nutrients to have a more significant impact on growth.
Lack of vitamin A can lead lead to dry corneas and even complete blindness in severe cases. This is characterized by marks known as Bitot’s spots.
Not being able to produce tears is one of the earliest symptoms of vitamin A deficiency. Infants and children in Southeast Asia, Africa, and India are at the most risk of developing dry eyes.
However, vitamin A supplement can help to improve this condition.
Since vitamin A is necessary for the production of collagen and the repair of skin cells, a lack of it may consequently lead to skin problems such as eczema and acne.
Eczema is a condition that causes the skin to be dry, itchy, and inflamed. Studies have shown that vitamin A is effective in treating eczema. Although skin problems may be attributed to many other causes, chronic deficiency of vitamin A may be one of them.
Diagnosis of Vitamin A Deficiency
The diagnosis is made based on the clinical symptoms of vitamin A deficiency. Methods of assessing vitamin A levels in the body include the measurement of plasma retinol levels, plasma and urinary retinoic levels, and levels of vitamin A in breastmilk.
Treatment of vitamin A deficiency can be done using oral and injectable forms of the vitamin. Oral supplements are effective in reducing the risk of morbidity, especially from severe diarrhea.
Also, fortifying food with oily and dry forms of vitamin A is useful in improving vitamin A deficiency. Retinyl acetates, retinol esters, and retinyl palmitate can be used for the fortification of food.
Food sources rich vitamin A that can be used to treat the deficiency include:
- Cod liver oil
- Fortified skim milk
- Orange and yellow vegetables and fruits
- Fortified breakfast cereals
Among all these, livers are the richest animal sources of vitamin A. 100 grams of beef liver provides around 32,000 IUs of vitamin A.