Fat Soluble Vitamin A: Structure, Metabolism, Deficiency

Fat Soluble Vitamin A: Structure, Metabolism, Deficiency

Vitamins are organic substances that cannot be synthesized within the body and are essential for the maintenance of normal structure and function of cells.

Classification of vitamins into two groups

  • Fat-soluble vitamins
  • Water-soluble vitamins

Fat-soluble vitamin A

Vitamin A is a fat-soluble organic compound or Retinol is a scientific name of vitamin A.

Retinol, Retinal, Retinoic acid Structure

Fat-soluble Vitamin A the main pro-vitamin for vitamin A is beta carotene.

And this is derived from carrot. Beta carotene is processed in several ways.

Beta Carotene


It has 2 beta-ionone ring and also has a poly paranoid chain which joining these 2 beta-ionone ring.

These poly paranoid chains would be cleaved and somatically in specific regions to give rise to retinol.

So from one beta carotene essentially two molecules of vitamin A can be converted into two different formats.

Like retinol and retinal interchange with each other and from retinal convert to retinoic acid.

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How the fat-soluble vitamin A is absorbed and processed by our digestive system? And how it is utilized by our body?

When we eat the carrot. It is getting digested and the beta-carotene is getting somehow metabolized into the intestine.

Inside the intestine the beta-carotene further processed an enzyme known as di-oxygenase would be cleaved to retinol.

From there it goes to the liver, inside the liver cells it is stored in a format of retinol palmitate.

Now whenever it required is released in the blood and with specific retinol-binding protein.

Vitamin a deficiency diseases


Lack of vitamin A, inability to synthesize sufficient, quantities of rhodopsin.

Moderate deficiency leads to loss of vision in low light (“night blindness”) conditions, while severe deficiency can lead to severe dryness and opacity of the cornea (xerophthalmia).

Dry Skin:

Retinol is an very essential compound for skin cell production, and also protects the skin from harmful radiation due to its activity as an antioxidant, which helps in the prevention of cancer.

Lack of vitamin A, Abnormal function of many epithelial cells causes skin to become drowsy, dry, and lose luster.

Also decrease the synthesis of thyroid hormones


Due to deficiency of vitamin a, children may have repeated infections in the lungs.


Diseases like digestion also result from deficiency of vitamin a.

Daily Recommendation Of Vitamin A

  • 1 to 3 year old 1000IU
  • 4 to 8 year old 1300IU
  • 9 to 13 year old 2000IU
  • 14 to 18 year old 2300IU
  • 18+ year-old men 3000IU
  • 18+ year-old women 2300IU

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Benefits of Vitamin A


It makes the muscles strong by speeding up the light of the eyes.


Retinol is a good source for the normal growth and development of bones.


Due to this, the skin remains soft and youthful. Keeps pimples and skin cancer away.


Vitamin A is necessary to maintain calcium levels in the blood and strengthen the bones.


All cells need Vitamin A to produce energy.


Vitamin A prevents cancer cells from growing. This aided in the prevention of cancer of the breast, lungs, skin, bladder, and uterus.


Vitamins increase immunity. Especially after birth in children, retinol dose is given so that disease-resistant power is strong and they can fight against diseases.

Vitamin A In Carrot

Vitamin A in carrot , retinol, Beta Carotene
Carrot is a source of provitamin A or a pre-vitamin A.

Carrots are a great source of vitamin A. Indeed are any vegetables are good sources of vitamin A.

Carrot or veggies are actually contain something called beta carotene.

This is not vitamin A it’s a carotenoid which is a provitamin A or a pre-vitamin A.

When you eat carotene it takes several more biochemical steps in your body to even turn beta carotene into actual real vitamin A .

This pre-vitamin A is locked up in the fiber of the vegetable.

Vitamin A essential vitamin we have to have it but carrot or veggies are not a true source of vitamin A.

So the true source of usable real vitamin a are pastured butter, egg yolks, and pastured meat.

There are mainly 5 types of Vitamins in carrot

a) Folate
b) VitaminB6
c) Vitamin c
d) Vitamin k
e) Vitamin a

Vitamins In Milk

vitamins, protein , and minerals in milk
Vitamin A in milk

Milk is a good source of high-quality protein which can be divided into two categories casein and whey proteins.

Most of the proteins in milk are categorized as casein which has a number of health benefits milk fat unprocessed milk is 4 percent fat but the content in commercial milk varies.

The vitamins and minerals necessary to sustain growth and development, milk contains all.

Milk is a good source number of important vitamins and minerals, including:

  • Vitamin B 12
  • Thiamin
  • Riboflavin
  • Niacin
  • Vitamin c
  • Folate
  • Pantothenic acid
  • Vitamin B6
  • Vitamin A
  • Zinc
  • Magnesium
  • Selenium
  • Vitamin D
  • Calcium
  • Phosphorus

Vitamin A In Egg

vitamin a in egg
How much vitamin A is in eggs?

Eggs offer a number of different nutritional and health benefits for those who consume this dairy product.

It is important to know the protein, vitamin, and many other mineral information for the foods we consume.

In a 100 gram serving, eggs contain about 729 IU’s of vitamin A this means that eggs offer roughly 15% of your daily value of vitamin A.

Depending on your own daily caloric needs and goals, in a 100 gram.

Clearly, eggs are a good source of vitamin A and can be consumed by those individuals looking to increase their vitamin A in their diet.

5 Vitamins In Egg

  • Folate
  • Vitamin a
  • Pantothenic acid
  • Vitamin B12
  • Riboflavin

Vitamin A Sources

Vitamin A is derived from carrots, is the major source of Vitamin A among the vegetables.

  • Cheese
  • Eggs
  • Papaya
  • Pepper
  • Pumpkin
  • Avocado

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Vitamin A For Acne

Basically vitamin A is a retinoid .

In the bottom layers where the cells are produced in the dermic layer, it will regenerate new cells to create new and fresh skin.

And this will push out the old ones to the surface and this the cycle that keeps recurring.

Our skin normally sheds & regenerates every 30 days.

It takes 14-21 days for retinoid to increase the skin’s cell turnover.

Vitamin A Excess Symptoms

a) Anorexia with weight loss
b) Alopecia with seborrheic lesions
c) Aching bones with limited movements
d) Abdominal hepatomegaly

Vitamin A toxicity, occurs when you have too much vitamin A in your body over a short period of time.

This condition may be acute or chronic.

Symptoms include changes to vision, back pain, and skin problem.

This kind of toxicity can lead to liver damage and increased pressure on your brain.

Causes Of Hypervitaminosis A

Excess amounts of vitamin A are stored in your liver, and it accumulates over time.

Most people develop vitamin A by taking high-dose dietary supplements, possibly due to megavitamin therapy.

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