Role Of Vitamin A In The Human Body

Vitamins are essential compounds that are required to maintain the fundamental functioning of the body. Vitamin A is a fat-soluble vitamin and is known to be an essential micronutrient for immunity, cellular differentiation, growth, reproduction, and vision. It is ingested in the diet in two ways- firstly as retinol from animal sources such as milk, meat, fish, liver, and eggs. Secondly, as a provitamin carotene from plant sources such as green leafy vegetables and red palm oil. In developing countries, deficiency of vitamin has been recognized as a public health concern and it negatively affects the health and survival of the infants, young children, and pregnant ladies. Deficiency of vitamin A includes various health consequences which include mild to serious effects on innate and acquired mechanism of resistance to infection, increased risk of mortality, and an increased burden of infectious morbidity.

Role Of Vitamin A In The Human Body

Vitamin A is one of the most important vitamins for the healthy body and it is best known to influence the immune system. An immune system consists of various cells,organs and the tissues that defends the body against any attack by the foreign invaders. Any impairment to this system can lead to various autoimmune diseases such as celiac disease, rheumatoid arthritis, and lupus. Vitamin A is considered to be an anti-infective vitamin as it is required for the normal functioning of the immune system. It plays a central role in the immune system which extends to both innate and adaptive immune response. Vitamin A is a group of organic compounds that includes retinol, retinal and retinoic acid. Vitamin A along with retinoic acid plays an important role in the development and differentiation of white blood cells, such as lymphocytes which plays a main role in the immune system.

Also, vitamin A increases the susceptibility to infections and infectious diseases. Diseases like diarrhea and shigella can be the result of an increased urinary loss of retinol and supplements of vitamin A has shown a positive effect and reduces the severity of diarrhea and shigella. Shigella is one of the leading diseases that causes diarrhea and is responsible for the death of millions of people. It invades the epithelial lining of the colon and causes severe inflammation and death of the cells of the lining of the colon.

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Vitamin A is highly associated with the healthy eyes and healthy vision. With regards to eyes, vitamin A mainly plays two roles, firstly in the retina and secondly to maintain the conjunctival mucosa and corneal stroma. The retina contains two different photoreceptors, the rods, and the cones. The rods are essential for vision in dim and low light and on the other hand, the cones are essential for vision in the bright light. Vitamin A acts as a backbone of the visual pigments for both rods and cones. A lack of vitamin A in the body can lead to changes in the normal mucosal surface and can also cause loss of goblet cells along with the replacement of normal epithelium. Also, severe deficiency of Vitamin A can lead to the development of the symptoms of xerophthalmia in individuals. Xerophthalmia is a medical condition which is characterized as a dryness of conjunctiva and cornea. It is a condition in which the eyes fail to produce tears.  

Vitamin A is also known to be involved in the development and growth and both an excess and deficiency of Vitamin A can lead to birth defects. Retinol and retinoic acids play a central role in the development of embryonic and during the development of fetal, it functions in the development of limbs and the formation of organs like eyes, ears, and heart. Also, retinoic acid regulates the expression of the gene for the growth hormone. Now it is clear that Vitamin A plays a key role in the development of embryonic but too much of retinoic acid can result in embryo lethality of malformation. Therefore, regulating the amount of retinoic acid is critically important.  

Vitamin A is required for maintaining healthy tissues in the reproductive tract. One of the studies showed that in the male reproductive system, deficiency of vitamin A causes the replacement of the epithelia of the epididymis, prostate and the seminal vesicle with stratified squamous keratinizing epithelium, and spermatogenesis ceases. In females, chronic deficiency of vitamin A affects women during their reproductive years.

Vitamins are essential for the proper functioning of the body and Vitamin A is one such vitamin that is responsible for the normal functioning of almost all the organs and it is essential for the growth and development of an infant as well. It is important to be aware of the ways in which a deficiency of this important vitamin can impact us.

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