Saturday, April 11, 2020

Vitamin A : Sources, Functions in Our Body, Daily Requirement, Deficiency Symptoms, Hypervitaminosis of Vitamin A

Vitamin A : Sources, Functions in Our Body, Daily Requirement, Deficiency Symptoms, Hypervitaminosis of Vitamin A

Vitamin A : Sources, Functions in Our Body, Daily Requirement, Deficiency Symptoms, Hypervitaminosis of Vitamin A
"Vitamin A"

Vitamin A is a fat soluble vitamin which is highly important for our sound health. Vitamin A has key role in maintaining a good health of our vision, our immune system and cell growth. Vitamin A covers both a pre-formed (or active) vitamin - retinol, and a provitamin - beta carotene, some of which is converter to retinol in the intestinal mucosa and liver. Whereas the active form of Vitamin A (Retinol) only comes from fat soluble sources.

Sources of Vitamin A :

Vitamin A widely distributed in animal and plant foods –

(a) Animal based foods which are rich in active form of Vitamin A (Retinol),
(b) Plant based foods with Provitamin beta carotene.

(a) Animal foods :

Sources of active Vitamin A (Retinol) are liver, egg, butter, cheese, whole milk, marine fish, meat etc. Let's read some important facts–
  • Beef Liver - Liver is the richest source of Vitamin A in its active form (Retinol). This is one of the most nutrient dense organ meats available. Research shows that only 100 gm of liver provides 1,049 % of the recommended daily value of Vitamin A.

  • Cord Liver Oil - One teaspoon of Cord liver oil provides 150 % of your daily value of Vitamin A. Cord Liver Oil should only be purchased if it is extra virgin and has not been heat treated.

  • Egg - Vitamin A (Retinol) can also be found in eggs, especially within the yolk. One large egg provides 17 % of your daily value of Vitamin A.

  • Butter - One tablespoon of butter contains 11 % of your daily value of Vitamin A.

  • King Mackerel - This delicious marine fish provides 28 % of your daily value of Vitamin A in the active form of Retinol. It is also a rich source of Omega 3 fatty acids which lower inflammation throughout the entire body.

(b) Plant Foods :

The cheapest source of Vitamin A is green leafy vegetables such as spinach and amaranth which are found in great abundance in nature throughout the year. The darker the green leaves, the higher its carotene content. Vitamin A also occurs in most green and yellow fruits and vegetables such as papaya, mango, pumpkin and in some roots like carrots. The most important and effective carotenoid is beta carotene which has the highest Vitamin A activity. Let's read some important facts–
  • Carotenes are converted to Vitamin A (Retinol) in the small intestine and liver. Unfortunately, only 3-6% of the intake of beta carotene is converted into the active form.

  • It is also noted that this action is poorly accomplished in malnourished children and those suffering from diarrhea.

  • Mango - One medium sized mango contains 20% of the daily value of Provitamin A (Beta carotene).

  • Kale - Kale is one of the most nutrient dense super foods on the planet. It also contains antioxidants and one cup supplies 98 % of your daily value of Provitamin A.

  • Pumpkin (Winter Squash) - One cup of cooked squash or pumpkin contains 62 % of your daily value of Provitamin A.

  • Collard Greens - One medium sized cup of cooked collards contains 80 % of your daily value of Provitamin A.

  • Carrots : One medium carrot contains 44 % of your daily value of Provitamin A (Beta carotene), along with a host of other important nutrients.

  • Sweet Potato : One medium sized cup of cooked sweet potato contains 204 % of your daily value of Provitamin A.

Read more :
 Vitamin : Definition, Characteristics, Types of Vitamins & Antivitamin and Provitam

Vitamin D : Sources, Functions of Vitamin D, Daily Requirement in our body, Deficiency Symptoms, Hypervitaminosis of Vitamin D

Vitamin C : Sources, Daily Requirements, Functions In Our Body, Deficiency, Hipervitaminosis

Functions of Vitamin A :

Vitamin A participates in many bodily functions –
  1. Vitamin A contributes to the production of retinal pigments (Rhodopsin) which are needed for vision in dim light.
  2. Vitamin A is necessary for maintaining the integrity and normal functioning of glandular and epithelial tissue which lines intestinal, respiratory and urinary tracts as well as the skin and eyes.
  3. Vitamin A also participates in body growth especially skeleton growth.
  4. Vitamin A also acts as anti-infective. There is increase susceptibility to infection and lowered immune response in Vitamin A deficiency.
  5. Vitamin A helps in the digestion of carbohydrates.
  6. Vitamin A is also plays an important role in Gene Transmission and protein formation.

Daily Requirement of Vitamin A :



  • For Adult Women – 700 micrograms or 2330 IU
  • For Adult Men – 900 micrograms or 3000 IU
  • For children of ages 4 years to 8 years – 400 micrograms or 1330 IU
  • For children of ages 9 years to 13 years – 600 micrograms or 2000 IU
(IU = International Unit, 1 IU = 0.3 micrograms)


Note : The daily intake of Vitamin A must not exceed 3000 micrograms or 10000 IU for adults. Otherwise, it causes toxicity. During pregnancy, intake of more 20000 IU Vitamin A daily is associated with fatal malformations.


Deficiency of Vitamin A :

A lack of insufficient intake of Vitamin A through proper diet over a long time leads to the deficiency of Vitamin A or Hypovitaminosis of Vitamin A in your body.
  • The characteristics of Vitamin A deficiency are predominantly ocular. They include Nightblindness, Conjunctival xerosis, Bitot's spots, corneal xerosis and keratomalacia.

  • Nightblindness is the difficulty or problem for the eyes to see in dim light. Vitamin A has a vital role in production of Rhodopsin which helps to see in dim light.

  • In Conjunctival xerosis, conjunctiva becomes dry and non-wettable. Instead of looking smooth and shiny, it appears muddy and wrinkled.

  • Bitot's spots are triangular, pearly-white or yellowish, foamy spots on the bulbar conjunctiva on either side of the cornea.

  • Corneal xerosis is a particularly serious case. The cornea appears very dull, dry and non-wettable and eventually opaque. There has possibility of being corneal ulceration.

  • Keratomalacia of cornea is a grave medical emergency. If this case, the cornea become soft and may burst open. This process is a rapid one. If the eye collapses, the vision is lost.


  • Due to deficiency of Vitamin A, normal body growth may be disrupted.

  • Skin becomes thick, dry and itchy. The sebaceous gland and the Sweat gland become damaged and the hair follicle closes with keratin. Thus, the human skin becomes as uneven as the frog skin.

  • Lack of Vitamin A damaged the epithelial tissues of Kidney and Urinary tract. There is a possibility of forming stone in the kedney.

  • As the deficiency of Vitamin A leads to damage of epithelial tissues, there increases the chances to be infected easily.

Hypervitaminosis of Vitamin A :

Symptoms of hypervitaminosis of vitamin A are seen in people who are eating more vitamin A than normal daily requirement. The symptoms are:
  • Nausea and vomiting
  • Sleepiness
  • Decrease of body weight
  • Hair loss
  • Wounds in the eye
  • Low activation of the sexual gland

Click here to read about Vitamin B1 (Thiamine)

Click here to read about "Vitamin B2" or "Riboflavin".

1 comment:

  1. Very informative... Thanks for sharing.

    ReplyDelete