Fat Soluble Vitamins

The fat soluble Vitamins are the Vitamin A, Vitamin D, Vitamin E and Vitamin K.


Chemically, vitamin A is called retinol. It occurs in two forms-oxidized and reduced. The reduced form is called retinol1 and the oxidized form is called retinol2 or dehydroretinol.

Sources of fat soluble Vitamin A

Vitamin A is obtained from both plant and animal sources. Plants do not contain vitamin A as such; rather they store the pro-vitamin of retinol called carotene. Carotene is abundantly found in ripe fruits and vegetables e.g., carrot, tomato, mango, sweet potato etc., and green leafy vegetables e.g., cabbage, lettuce etc. Animals store vitamin A as such in their liver, fat, kidney etc., The fish liver oils such as cod liver oil, shark liver oil, halibut liver oil etc. or liver are the richest source of vitamin A. Fatty meat, milk, butter, ghee, egg yolk are also good sources of this Fat Soluble Vitamins.

Functions of Vitamin A

Vitamin A is required for synthesis of visual pigments of rods and cones that are responsible for vision. It maintains the structural and functional integrity of epithelial cells particularly the mucous membranes of cornea, conjunctiva, lacrimal gland, salivary gland, pharynx, respiratory tract, tongue etc. This vitamin also helps in growth, reproduction and metabolism. Vitamin A keeps the skin smooth, healthy and moist and helps in the functioning of cutaneous glands and hair follicle.

Deficiency symptoms of Vitamin A

Night blindness is one of the most important and early detectable symptoms of vitamin A deficiency. If the deficiency is prolonged, this may finally lead to complete blindness. Another early detectable symptom of the fat soluble vitamins A deficiency is dryness and roughness of skin particularly in the sides and back of the thighs and lateral part of the forearms that look like toad's skin. Retardation of growth in the young animals, degeneration of epithelial tissues leading to secondary infections, kidney stones etc. are the other symptoms.

Symptoms of Hypervitaminosis A

Hypervitammosis- A leads to headache, nausea, vomiting and drowsiness. In chronic cases resulting from prolonged intake of excess vitamin A, the symptoms include loss of appetite, dry itchy skin, loss of hair, cracking of lips, generalized weakness and pain in bones and joints.


Vitamin D is one of the fat soluble vitamins, Chemically it is known as sterol and since in the body it is related mainly with calcium metabolism. It is also called calciferol. There are two types of Vitamin D, those are Vitamin D2 and D3.

Functions of Vitamin D

Among the fat soluble vitamins the main function of vitamin D is to help in metabolism and utilization of calcium and phosphorus in the body. To perform this function, it stimulates— (i) absorption of Ca and P from intestine, (ii) deposition of calcium salts on bone-sand teeth for their growth and development, and (iii) re-absorption of Ca from renal tubules.

Deficiency symptoms of Vitamin D

Deficiency of vitamin D leads to rickets in young and osteomalacia in adults.

Symptoms of Hypervitaminosis D

Intake of excessively high amounts of vitamin D brings about increased blood level of Ca and P. As a results of this, various soft tissues e.g., arteries, kidney, heart, lung etc., become calcified. Renal calcification may cause failure of urine formation leading to toxicity and death.


Another of fat soluble vitamins the vitamin E chemically is an alcohol and is called tochopherol. It is also known as anti-sterility vitamin or fertility vitamin clinically, because in its absence animals fail to reproduce.

Functions of vitamin E

It helps in reproduction. In males, it is required for growth and maintenance of testicular germinal epithelium. In females, it helps to maintain sex cycles and pregnancy. It is required for maintaining the normal structure and function of skeletal muscles. Vitamin E is an antioxidant.

Deficiency symptoms of vitamin E

The chief symptom of vitamin E deficiency is sterility, characterised by degeneration of germinal epithelium in males and impairment of sex cycles and pregnancy in females. Another symptom of vitamin E deficiency is muscular weakness and dystrophy.


Vitamin K another of the fat soluble vitamins is clinically known as coagulation factor. Natural vitamin K occurs in two forms called vitamin K1 and K2 are chemically called phylloquinone and farnoquinone respectively.

Functions of Vitamin K

Vitamin K helps in coagulation of blood by promoting synthesis of prothrombin and some other coagulation factors in- liver. It may be involved in mitochondrial oxidative phosphorylation.

Deficiency symptoms of vitamin K

Vitamin K which is one of the fat soluble vitamins leads to the body an abnormally increased coagulation time and a tendency of spontaneous hemorrhage due to a fall in plasma level of prothrombin and other clotting factors.
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