Vitamin D and E

Vitamin D

Synonyms. Antiricketic vitamin, sunshine vitamin, vitamin D group, vitamin D exists in two forms : Vitamin D2 (Ergocalciferol)— a synthetic derivative of a plant sterol and Vitamin D3 (Cholecalciferol)—a derivative of cholesterol.

Sources. Vitamin D is a steroid which is synthesized from cholesterol. Vitamin D2 is formed from plant sterol, ergosterol which occurs in yeast and other fungi in the presence of

ultraviolet light. Vitamin D3 formed from animal sterol, 7-dehydrocholesterol, which occurs in animal skin. Its synthesis also needs ultraviolet light. Egg

yolk, milk, butter and fish liver oils contain vitamin D. The highest amount of vitamin D is present in fish liver oils (e.g., cod liver oil). Thus vitamin D is found in large quantities in the same food stuffs as vitamin A.

Daily Requirement. 10 ug (= 400 IU— International Unit) for infants and growing children. In tropical countries with plenty of sunlight, smaller amounts may suffice. Adults need less amounts of vitamin D.

Functions.

(i) Vitamin D promotes absorption of calcium and phosphorous by the intestine.

(ii) It maintains the normal functioning of parathromone (hormone secreted by parathyroid glands)

(iii) It affects the metabolism of citric acid which is a normal constituent of many body tissues including bones.

(iv) Vitamin D has a specific function on kidney, tubular reabsorption of calcium and phosphate

(v) It exerts an anti-rachitic effect. Because it regulates metabolism of calcium and phosphorus, it effects normal growth of the body and formation of teeth and bones.

Vitamin D behaves more like a hormone than as the cofactor of an enzyme.

Deficiency Symptoms,

(i) Rickets in children (softness and deformities of bones like bow-legs and pigeon-chests)

(ii) Osteomalacia in adults (weak bones liable to easy fracture)

(iii) Dental caries (cavities in teeth).

Destroyed by : Oral contraceptives.

Hypervitaminosis D. Extremely large doses of vitamin D cause hypercalcemia, hyper-phosphatemia, anoerxia (loss of appetite), nausea, vomiting and diarrhoea.

Vitamin E

Synonyms. Tocopherol (Gr. tokos = child birth, pherein = to carry), Antisterility vitamin, Fertility vitamin, vitamin of Reproduction, Beauty vitamin, vitamin E group. Today, at least eight naturally occurring tocopherols are alpha, beta, gamma, zeta1, zeta2, eta, delta and epsilon. -Tocopherol has the highest vitamin activity. Sources. Tocopherols are known to occur in a variety of plant and animal tissues. Wheat germ and whole cereal are good source of vitamin E. The most important natural sources of tocopherols are vegetable oils, of these wheat germ oil has the highest concentration. Corn oil, cotton seed oil and safflower oil contain considerable amounts of tocopherols. Although fish liver oils are rich in vitamin A and D but they are poor sources of vitamin E. Lettuce (garden plant with crisp leaves used as salad) is good source of this vitamin. Of animal tissues, liver is usually the highest in vitamin E. Tocopherols are also found in animal body fat (adipose tissue).

Daily Requirement. About 20 mg.

Functions.

(i) Tocopherols are excellent antioxidants and thus maintain normal biomembrane structure. It inhibits oxidation of unsaturated fatty acids and vitamin A.

(ii) Vitamin E plays a specific role in selenium metabolism. Selenium is an essential component of the enzyme glutathione peroxidase that scavenges toxic hydroperoxy compounds in tissues,

(iii) It keeps skin healthy,

(iv) It also decreases fragility (weakness) of the erythrocytes (RBCs). Thus its deficiency also causes anaemia in which RBCs are devoid of haemoglobin,

(v) Vitamin E has anti cancer property. It is used for curing tumour cancer,

(vi) It maintains normal functioning of reproductive organs hence it is called fertility vitamin,

(vii) It maintains the muscles of the body, therefore, vitamin E should be a part of athlete’s diet,

(viii) Vitamin E is now used to prevent heart attacks and treat Alzheimer’s disease in some patients,

(ix) A derivative of vitamin E (one of the tocopherols) is said to be necessary for synthesis of coenzyme Q which is a component in the electron transport chain,

(x) It helps in development and cell formation. Thus it is needed in the diet of pregnant and lactating women and for the new born infants particularly premature infants,

(xi) Vitamin E is required for proper use of vitamin A in the body.

Destroyed by : Heat.

Hypervitaminosis E. Hypervitaminosis symptoms of vitamin E are not reported.

Deficiency Symptoms,

(i) Reproductive failure

(ii) Degeneration of muscles (muscular dystrophy)— a degenerative disease of skeletal muscles

(iii) Increased haemolysis (breakdown of erythrocytes— RBCs) leading to macrocytic anaemia (RBCs become larger)

(iv) Slow growth and degeneration of the renal tubules.