Definition

• “Substances distinct from major components of food, required in minute quantities and whose absence cause specific deficiency diseases”.

General characteristics of vitamins

1. Vitamins are widespread occurrence in nature, both in plant and animal worlds.

2. The plants can synthesize all the vitamins whereas only few vitamins are synthesized in the animals.

3. Human body can synthesize some vitamins, e.g., vitamin A.

4. Most of vitamins have been artificially synthesized.

5. Vitamins are partly destroyed and are partly excreted.

6. All the cells of body store vitamins to some extent.

7. Vitamins are nonantigenic.

8. Vitamins are effective when taken orally.

9. Vitamins carry out functions in very low concentrations.

10. Synthetically-made vitamins are just as nutritionally good as natural vitamins.

Vitamin Classification

• Fat-soluble vitamins– Dissolve in substances such as ether and benzene

but not readily in water– Include vitamins A, D, E, and K

• Water-soluble vitamins– Vitamins that dissolve in water– Include B vitamins and vitamin C

VITAMIN D• The sunshine vitamin.• Fat soluble vitamin.• Is often called antirachitic factor in food.• Resemble sterols in structure and function like

a hormone.

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2 sources • - 90% synthesised in skin via UVB light exposure

• - Cholecalciferol (vitD3 = inactive) • - 10% from food – Ergocalciferol (vit D2=

inactive)

Activation in liver and kidneys to CALCITRIOL.

History

Work Scientists Years

Discovered by Mellanby 1919

First Demonstrated its existence

Elmer McCollum 1922

Discovered its chemical nature

H. Steenbock and A.F. Hess

1924

Isolated and named as calciferol

Augus 1931

Properties of Vitamin D

• Vitamin D is a white and odourless crystalline substance.

• It is fairly heat resistant.• Relatively resistant to oxidation.• It is not affected by acids and alkalies.• Vitamin D in foods and in food concentrates is not

easily destroyed by heating.

Structure of Vitamin D

Rich dietary sources of Vitamin D

• The best natural sources of vitamin D are the liver oils of many fishes as cod and halibut.

• Egg yolk is fair good source of vitamin D.

• Vitamin D2 plant origin.• Vitamin D3 is the animal origin and

can be produced from 7-dehydrocholestarol is also by irradiating with UV light.

Vitamin D can be provided to the body in three ways:

1. Consumption of natural foods.

2. By irradiating foods (like yeast) that contain precursors of vitamin D and fortification of foods (milk, butter etc.)

3. Exposure of skin to sunlight for synthesis of vitamin D.

Rich sources of Vitamin D per 100 g of edible portions

Fish and poultry Mcg

Cod-liver oil 175

Shark-liver oil 50

Halibut-liver oil 5-100

Eggs 1.5

Ghee 2.5

Butter 1.0

Note: Sunlight is the most important source of this vitamin.

Deficiency symptoms of Vitamin D

• Vitamin D deficiency occurs in strict vegetarians, chronic alcoholics, individuals with liver and kidney diseases or fat malabsorption syndromes.

• Deficiency of vitamin D leads to mineralization of bone.

• Rickets is a primarily a disease of growing bones.

• A study conducted by the Indian Social Institute, New Delhi (1981) shows that about 168 children per 1000 of live births die of rickets in India.

Osteomalacia

• The bones become softer than the rachitic bones and the C/P ratio does not remain constant.

• The disease is prevalent in India, China & Arab, particularly among women because of custom that keeps them indoor and also prevents them from exposure to sun.

Idiopathic Steatorrhea or Celiac Disease

• This is like osteomalacia.• The disease is characterised by demineralization of

the bones which may result in dwarfism.• In fact, Celiac Disease is indirectly a vitamin d

deficiency.• The fat is not absorbed in the intestine and is passed

out in stools along with calcium salts and vitamin D.

Demineralization of Bone• Overdosing of calciferol to the children and adults as

well produces Demineralization of Bone.• Serum concentrations of both calcium and phosphate

are greatly raised, resulting in metabolic calcification of many soft tissues and the formation of renal calculi.

• The latter disorder may block the renal tubules causing hydronephrosis.

Hypoparathyroidism

• Deficiency of parathyroid hormone (PTH) results in hypocalcemin and hyperphosphatemia.

• Lack of vitamin D may lead to teeth decay, pyorrhea, brittle or soft bones, retarded growth, and poor bone formation in children.

• It may causes muscular weakness, lack of vigour, deficient assimilation of minerals, and premature ageing.

• Lack of this vitamin in children can also give rise to improper activity of parathyroid gland, and result in convulsions.

Metabolic and Biochemical functions

• The provitamin D3 can be synthesised within the human body.

• The increased need of this vitamin D is usually felt in growth and in pregnancy to provide for the needs of foetus.

• Vitamin D plays an important role in calcification of bones and teeth.

• It encourages the absorption of calcium and phosphate salts.

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• Vitamin D2 and D3 as such are not biologically active.

• They are metabolised identically in the body and converted in active forms of vitamin D.

• Calcitrol is the biologically active form of vitamin D, it regulates the plasma levels of calcium and phosphate.

• Calcitrol acts at 3 levels (intestine, kidney and bone) to maintain plasma calcium.

Healing and Therapeutic properties

1. Rickets Vitamin D plays a very important role in the

prevention and treatment of rickets. The therapeutic dose varies from25 to 125

mcg per day, depending on the severity of the disease.

2. Renal Rickets (Renal osteodystrophy)

• This is in patients with chronic renal failure.• Renal Rickets is mainly clue to decreased

synthesis of calcitriol in kidney.• It can be treated by administration of calcitriol.

3. Bone Repair

• Any excess of calcium stored in the long bones serves as reserve for bone repair when needed.

• Vitamin D also contributes substantially towards bone repair by increasing calcium absorption through the intestinal wall

• This vitamin also regulates the deposition of minerals in bones and teeth.

4. Tooth Decay

• Vitamin D has been found beneficial in the treatment of tooth Decay.

• Mellanby proved the importance of this vitamin for tooth nutrition in children.

5. Arthritis

• Vitamin D is considered extremely beneficial in the treatment of arthritis.

• It needs to be taken with calcium for the body to be able to utilise it efficiently.

RECOMMENDED DIETARY ALLOWANCE

• The daily requirement of vitamin D is 400 IU or 10 mcg of cholecalciferol.

• In countries with good sunlight (like India), the RDA for vitamin D is 200 IU (or 5 mcg cholecalciferol).

• For older people, pregnant women and lactating mothers 400 units are adequate.

• Vitamin D requirement is greatly influenced by the amount of ultraviolet light to which the individual is exposed.

• For adults exposure to sunlight for 30 minutes a day is believed to satisfy the daily requirement (about 10 mcg) of vitamin D.

Precautions

• Dosage of over 125 mcg taken daily may adversely affect some individuals.

• Abnormal calcium deposits may also be foud in the blood-vesselwalls, liver, lungs, kidneys, and stomach.