IMPORTANCE AND DEFICIENCY OF VITAMIN A IN HUMAN BODY

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 Introduction

Vitamin A is called Retinol and its is a fat soluble vitamin. It is very important for Vision, immune system, growth, reproduction and cellular differentiation  and epithelial tissue. 

It is exist in two forms

* Retinoid (preformed vitamin A)

It is active form of vitamin A and obtained from animal source

*Carotenoids ( provitamin A)

 Carotenoids are plant sources and body convert it into Vitamin A

* In chemical structure of vitamin A it share it structure with polyene chain with a beta-ionone ring and allow them to absorb light through these steps it participate in vision

Function of vitamin A in human body

1.Vision

Vitamin A is exist in two form Retinol and Retinal

Retinol 

It store in liver and converted into retinal where it combine with rhodopsin and allow them to send signal to brain for vision purpose

Retinal.

 And retinal also combine with different opsin to enhance colour vision

Retinal

It is an active form of Vitamin A where it directly combine with opsin and rhodopsin to allow color vision and transfer signal to brain for vision respectively

2. Immune function

It enhance  the  first defence  line of human body e.g  it maintain the integrity  of skin, epithelium of lung and GIT.

* Support white blood cell function especially T and B lymphocytes 

3. Reproduction

* In male it support spermatogenesis

* In female it support follicular development, ovulation and development of fetal during pregnancy 


4. Antioxidant activity

Vitamin A itself and beta-carotene act as antioxidant.

* Neutrilize reactive oxygen specie

* Prevent DNA damage

* Prevent lipid  peroxidation

Besides  Vitamin A Vitamin E also functioning as a antioxidant for more about vitamin E visit this sitehttps://healthduhs.blogspot.com/2026/02/vitamin-e-and-their-importance-in-human.html

5. Cellular growth

Its very important for cellular growth e.g tissue development  heart, lung and kidney

* Retinoic acid binds to nuclear receptor and began expression of gene

Source of vitamin A

1. Retinol

* Active form of vitamin A  produced by animal source

* Liver

*  Beef

* Chicken

* Fish

* Egg yolks

* whole milk

* Butter

* Cheese

* Fish oil


2. Beta-carotene

* It is a plant source vitamin A and body convert it into  retinol

* Carrot

* Sweet potato

* Papaya

* Mango

* Pumpkin

* Spinach

 Amount of Vitamin A recommended for a normal body

* 0-12 Months = 500 µg

*  1-8 Year= 400 µg

*   9-13year= 600 µg

*   14-18 =800µg

* More than 18=770 µg

Deficiency of vitamin A

1. Eye and vision problem

* Xerophathalmia

Dryness of eyes

* Night blindness

Unable to see in dim light

* Keratomalacia

Softening and ulceration of cornea

* Bitot's spot

 White patches on the conjectiva

2. Problem of skin and mucous membrane

* Dryness of mouth and respiratory system which lead toward  increased risk of infection

* Dry and rough skin

3. Problems related to growth

* Delayed bone development 

* Reproductive issue in children

* Impaired growth in children


4. Problem of immune system

* Increase susceptibility to infection 

*  Poor wound healing

Treatment of vitamin A deficiency

* Increase intake of vitamin A rich food

* Intake fortified  food

*  Foot with high fat increase the absorption of vitamin A

* WHO recommended doses for Vitamin A deficiency

6-11 month=30mg

11-59 month=60mg

* High dose therapy can reverse the deficiency but in some case it cause Hypervitaminosis

For about other vitamins e.g vitamin B12 visit this site 

https://healthduhs.blogspot.com/2026/02/role-of-vitamin-b12-and-its-related.html


Reference


 WHO -World Health Organisation
NIH- National Institute Of Health)

 CDC- Centre for Disease Control and prevention


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