Vitamin A - Use, Sources, Deficiency, Requirement - Nutrition And Health

 

Vitamin-A (Retinol)

What Is Vitamin-A :
Vitamin A, also known as retinol, is a fat-soluble vitamin that plays several essential roles in the body.
Vitamin A (Retinol) is a fat-soluble vitamin formed within the body (liver or intestinal mucosa) from carotene (the yellow pigments of plants, which are also called provitamin A). The liver has enough capacity to store Vitamin A to meet needs for 6 to 9 months.

Function of Vitamin-A :
1. Vision : 

Vitamin A is crucial for maintaining healthy vision, especially in low-light conditions. It is a key component of rhodopsin, a protein in the eyes that absorbs light.
2. Immune System : 

It supports the immune system by helping to form and maintain healthy skin and mucous membranes, which act as barriers against infections.
3. Cell Growth : 

It plays a role in the development and differentiation of cells, particularly in skin, tissues, and organs.
4. Reproduction : 

Vitamin A is important for reproduction and fetal development.
5. Skin Health : 

Retinol is used in skincare products for its ability to stimulate collagen production and reduce the appearance of wrinkles.

Sources of Vitamin-A :

1. Animal-based sources (Preformed Vitamin A or Retinol) :
- Liver (beef, chicken)
- Fish oils
- Dairy products (butter, cheese, milk)
- Egg yolks

2. Plant-based sources (Provitamin A or Beta-Carotene) :
- Carrots
- Sweet potatoes
- Spinach
- Kale
- Mangoes
- Apricots
In the body, beta-carotene (from plant sources) is converted into retinol, the active form of vitamin A.

Vitamin A Deficiency Symptoms :

Night Blindness : 

A deficiency in Vitamin A causes night blindness, which is the first clinical symptom of a deficiency.

Conjunctival Xerosis : 

Dryness of the conjunctiva (the membrane covering the eyeball and inner sides of the eyelids). It is often the first clinical sign of Vitamin A deficiency.

Bitot's Spot : 

Triangular, pearly white or yellowish, foamy spots on the conjunctiva on either side of the cornea.

Corneal Xerosis : 

The cornea becomes dry and eventually opaque, leading to a serious condition.

Keratomalacia : 

Liquefaction or extreme softening of the cornea, known as keratomalacia, which is a grave medical emergency.

All the above are ocular manifestations of Vitamin A deficiency, collectively referred to as    xerophthalmia (dry eye).

 

Causes of Blindness :

- In developed countries, blindness is most frequently caused by accidents, glaucoma, diabetic retinopathy, hypertensive retinopathy, and cataracts.
- In South-East Asia, including India, the principal cause of blindness is cataracts, responsible for 62.6% of cases.
- Vitamin A deficiency is a significant cause of childhood blindness, although this has been declining slowly.

Daily Requirement :
Infants : 350 µg
Preschool age group (1 to 6 years) : 400 µg
School age (7 to 12 years), adolescents, men, women (with or without pregnancy) : 600 µg
Women with lactation : 950 µg