Fat-soluble Vitamins
Vitamin A, D, E, And K are fat-soluble vitamins.
Vitamin A
Chemistry: 1. Vitamin A is unsaturated primary alcohol (Retinol). Structurally it is related to the plant pigment carotene.
2. Vit. A is derived from β-carotene. Hence, β-carotene is a pro-vitamin A. it requires bile salt and fat for absorption. Sources: 1. Chief sources are Fish liver oil (i.e. cod liver oil, shark liver oil), milk, cheese, and egg.
2. Animal oil like Ghee and Butter are good sources but vegetable oil does not contain Vit A.
3. Vegetables and fruits like carrot, tomato, spinach, mangoes, etc. are rich sources of Vit. A. Storage: vitamin A is stored mainly in the liver, little lungs and skin. Excretion: vitamin A is excreted through stools.
Functions of Vit. A
- Vitamin A is essential for body growth and weight.
- Vitamin A is very useful for the health of eyes, skin epithelia, and nervous system.
- Vitamin A aids in bone-cell formation along with vitamin D, Fertility and resistance against cold along with Vitamin C.
- Vitamin A is also responsible for the formation of rhodopsin (the light-sensitive chemical substance in rods odd retina).
Deficiency of Vitamin A results in:
- 1. Eyes: (i) prolonged deficiency of Vit. ‘A’ results in night blindness. this is due to the absence of re-synthesis of rhodopsin when exposed to light.
(ii) Deficiency of Vit. A leads to degeneration of the lachrymal gland of the eye causing Xerophthalmia. Its deficiency gives rise to red eyes and corneal ulcers. - 2. Alimentary system: Epithelial degenerate and give digestive disturbances in Vit. A deficiency.
- 3. Respiratory system: Deficiency of Vit. A leads to increased susceptibility or respiratory diseases like cold, pneumonia, and tuberculosis. Therefore Vit. A is called an anti-infective Vitamine.
- 4. Skeletal System: Vit. A deficiency leads to slow and irregular growth of bones and teeth.
- 5. Nervous System: Vit. A deficiency also adversely affects medullary sheaths of nerves.
- 6. Fertility: Vit, A deficiency adversely affects the normal ovulation in rats, this is not proved in humans. Still, it is used empirically to aid spermatogenesis in men and ovulation in women.
Hypervitaminosis: toxicity occurs when vitamin A is stored in the body more than required. Common symptoms noticed in man and animals are Changes in vision, bone pain and skin Changes.
Vitamin D
Chemistry: 1. Vitamin D is a sterol. it has more than 6 components, of them vit. D2 and D3 are the most potent.
2. vitamin D2 is ergocalciferol or 7-dehydrocholesterol which is an isomer of ergosterol. Ergosterol on irradiation by ultraviolet rays yields Calciferol.
3. Vit. D3 is cholecalciferol which is activated 7-dehydrocholesterol formed in human skin on exposure to sunlight.
4. Vitamin D is fat-soluble and thermostable. Sources: 1. The best yield of vitamin D3 is from ergosterol which is found under the skin, in the milk, butter and egg yolk in moderate quantities.
2. Liver and cod liver oil are also the moderate sources of Vitamin D.
Functions of Vitamin D
- Vitamin D plays an important role in the absorption, retention, and utilization of calcium and phosphorous in the body.
- Vitamin D aids proper teeth and bone formation.
- Vitamin D is an important hormone for the mineralization and formation of bones.
Deficiency of Vitamin D
vitamin D Deficiency gives rise to rickets in children and osteomalacia in adults. These diseases arise as a result of excessive excretion of calcium and phosphorous in feces.
- Rickets:
- Develop between 6-18 month of infancy
- The bones soften and blend under pressure and there is mal deposition of (calcium phosphate) Ca3(PO4)2.
- The skull bones show bossing and a Gap in the skull which does not calcify till the age of one and a half year.
- The delayed and irregular eruption of teeth occurs.
- the chest is flat, pointed or depressed.
- The pelvis is deformed.
- Legs may bend under pressure, giving deformed locomotion.
- Osteomalacia: Generally found in pregnant, lactating or multipara mothers with rapidly recurring deliveries. This occurs because of an excessive drain of calcium from the mother’s body.
- Adolescent rickets occurs at pre-puberty times when bones are growing fast.
Hypervitaminosis: develops after excessively large doses of vitamin D. Weight is lost, headache, vomits, etc. develops and abnormal calcium disposition occurs in the kidney, heart etc. The child develops uremia and may even die.
Vitamin E
Vit. E is Alpha-tochopherol. it is fat soluble and thermostable.
Sources of vitamin E are Soyabean, wheat sprouts, cornseed oil, Butter, milk and leafy vegetables.
Vit. E is fat soluble and thermostable. It is also called anti-sterility vitamin and ‘anti-oxidative vitamin’. It is used to prevent arteriosclerosis in old peoples, Promotes wound healing, and involves in the formation of RNA, DNA and RBC.
Function of vitamin E
- vitamin E prevents excessive oxidation of fatty acids that help to form cell structure. hence Vit. E is called ‘anti-oxidative vitamin’.
- vitamin E Helps in normal functioning of the vascular and nervous system. therefore it is used to prevent arteriosclerosis, i.e. thickening of the blood vessels in old peoples.
- vitamin E is necessary for the normality of reproductive system in rats. it prevents abortion in rats. Vit. E is also called anti-sterility vitamin
- Vitamin E is also involved in the formation of RNA, DNA and RBC.
- Vitamin E also promotes wound healing.
Deficiency of Vit. E
- Due to vitamin E deficiency in Rats, female rats abort and male rats do not show normal spermatogenesis. vitamin E might help to overcome abortion or miscarriage problems.
- In a bsence of vitamin’E’ muscular dystrophy occurs in rats.
Vitamin K
Chemically vitamin K belongs to the naphthaquinone family. Vitamin K1 and K2 are natural products.
Vitamin K is fat soluble and thermostable. Aids in coagulation of blood. given to mother before delivery to prevent haemorrhages in newborns. Synthesised by intestinal bacteria and store in liver. Bile salts required for its absorption.
Sources of ‘Vitamin K’ are vegetables like cabbage, tomato, Soyabean, alfa-alfa, spinach etc. Synthesised in considerable amounts by intestinal bacteria and stored in liver. Bile salts are a must for its absorption.
Function of Vitamin K
1. Vitamin K aids in coagulation of blood by keeping up prothrombin level in the blood. It also aids factor VII in cloting of the blood.
2. haemorrhages in newborns can be prevented by giving Vitamin K to the mother, before delivery.
Deficiency of Vitamin K
1. Vit. K deficiency produces hypoprothrombinaemia and haemorrhage in newborn babies and petechinal haemorrhage in man.
2. factor VII insufficiency due to Vit. K deficiency also produces bleeding.
Vitamine A, D, E and K are soluble in fat and are thermostable (Not decompose by excess heat).