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SEMINAR BY:
DR. KRISHI MOHAN
INTERN (2006 BATCH)
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y Introduction
y Definition
y Classification
y Vitamin Ay Vitamin D
y Vitamin E
y
Vitamin Ky Bibliography
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y These are essential organic substancesy Yield no energy, but facilitate energy-yielding chemical reactionsy If absent from a diet, it will produce deficiency signs and
symptomsy Fat-soluble vitamins A, D, E, Ky Water-soluble vitamins B1 (Thiamin), B2 (Riboflavin), B3
(Niacin), B5 (Panthothenic acid), B6 (Pyridoxine), B9 (Biotin),B12 (Cyanocobalamin ), Folic acid and Vitamin Cy Preservation of vitamins in foods
y exposure to light, heat, air, water, and alkaline
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y Vitamins may be regarded as organic compoundsrequired in the diet in small amounts to performspecific biological functions for normal maintenance
of optimal growth and health of the organism
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VITAMINS
FAT SOLUBLE WATER SOLUBLE
NON B- COMPLEX
ENERGY RELEASING
B COMPLEX
HAEMATOPOIETIC
VITAMIN A
VITAMIN C
FOLIC ACID
VITAMIN D
THIAMINE B1
CYANOCOBALAMIN B12
VITAMIN E
PYRIDOXINE B6
RIBOFLAVIN B2VITAMIN K
BIOTIN B7
NIACIN B3
PANTOTHENIC ACID
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y found in fats and oilsy require bile for absorption
y enter the lymph, then the blood
y dissolve in organic solvents
y not readily excreted; can cause toxicity
y transported like fat in chylomicrons, VLDL, LDL
y held and stored in fatty tissuesy
daily requirements need not be met
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y 3 forms in the body
y retinol
y retinal
y retinoic acid
y collectively known as retinoidsy found in food derived from animals
Retinol, the alcohol form Retinal, the aldehyde form Retinoic acid, the acid form
Beta-carotene, a precursor
Cleavage at this point can
yield two molecules of vitamin A*
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The variety of functions performed by Vitamin Aare,
1. Vision
y Vision: The biochemical function for the same was
elucidated by George Wald (Nobel Prize 1968).y The event occur in a cyclic process known as
Rhodopsin Cycle or Walds Visual Cycle.
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DietDiet
carotene carotene RetinylestersRetinylesters
FFAFFA
RetinolRetinol
ChylomicronsChylomicrons
RetinolRetinol
RBPRBP
Retinol RBPRetinol RBP RBPRBP
Intestinal cell
carotene
Retinal
RetinolFFA
Retinylesters
Retina
All-trans retinol
All-trans retinal
Visual cycle
Target cell
Retinol
Retinoic acid
Specific proteins
Cell differentiation
Liver:All-trans
retinol
Retinylpalmitate(stored)
mRNA
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y Vision is based on absorption of light by photoreceptor cells in the eye.
y Vertebrates have two kinds of photoreceptor cell, called rods & cones
because of their distinctive shape.y Cones(300million)function in bright light and are responsible for color
vision.
y Rods(100 million) function in dim light but do not perceive color.
y Rods contain photoreceptor molecules called rhodopsin
y Rhodopsin consists of a protein opsin linked to 11-cis retinal (aprosthetic gp) which gives the rhodopsin its ability to absorb light.
y Absorbtionof light result in the isomerization of 11-cis retinal into all-trans retinal.
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y
Promote vision (retinal)y Maintenance of the corneay Converting light energy into nerve impulses
y Participate in protein synthesis and cell differentiationy Differentiation of epithelial and goblet cells
(retinoic acid)y Support reproduction and growthy Support immunity (retinoic acid and carotenoids)y Involved in bone growth and remodelingy Synthesis of glycoproteinsy
Antioxidant activity (-carotene)
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2. Retinol and retinoic acid function almost likesteroid hormones. They regulate proteinsynthesis and thus are involved in cell growth anddifferentiation.
3. It is essential to maintain healthy epithelial
tissue, because retinol and retinoic acid arerequired to prevent keratin synthesis.Further, retinyl phosphate is essential for the
formation of mucopolysaccharides compounds ofmucus secreted by epithelial cells to maintain
moist surface.
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7. Cholestrol synthesis requires Vitamin A.Mevalonate, an intermediate in the cholestrol
biosynthesis, is diverted for the synthesis ofcoenzyme Q in Vitamin A deficiency.
8. Carotenoids ( most important carotene)function as antioxidants and reduce the risk of
cancers initiated by free radicals and strongoxidants. carotene is found to be beneficialto prevent heart attacks. This is also attributedto the antioxidant property.
9. Decrease in gluconeogenesis in Vitamin Adeficiency is observed which is secondary tothe reduced synthesis of glucocorticoids.
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Vitamin A - Deficiency
In dim light, you can make out the details in
this room. You are using your rods for vision
A flash of bright light momentarily blinds
you as the pigment in the rods is bleached.
With inadequate vitamin A, you do not recoverbut remain blinded for many seconds.
You quickly recover and can seethe details again in a few seconds.
Night blindness: Leading cause of blindness in third world countries
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y Cell keratinizationy Dry skiny Xerophthalmia (dryness of cornea & conjunctiva)
curable early stage
after 8 days vitamin A
incurable late stages
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y Hyperkeratosis and hyperplasia of gingival tissues
y Hypoplastic and chalky white incisors
y Atrophy of odontoblasts
y Atrophy of salivary glands leading to xerostomia causingincrease in caries
y Crowding of teeth
y Stunting and thickening of the roots
y Dental caries
y Disturbances in differentiation and function of ameloblastsy Thick, regular labial dentin with interglobular spaces
y Thin, atubular lingual dentin
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y Upper safe levels are 4- to 10-fold higher thanrequirements in nonruminants and 30-50-foldhigher than requirements in ruminants
y Not readily excretedy Hypervitaminosis A in humans
y Polar explorers eating polar bear or seal liver
y Self-medication and overprescription
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y Not always essentialy Body can make it if
exposed to enoughsunlight
y Made from cholesterolin the skin
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y Not found naturally inmany foods
y Synthesized in body
y Plants (ergosterol)y Sun-cured forages
y Fluid milk products arefortified with vitamin D
y Oily fish
y Egg yolk
y Butter
y Liver
y Difficult for vegetarians
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yVitamin D = calciferol
yVitamin D2 = ergocalciferoly Completely synthetic form produced by the irradiation
of the plant steroid ergosteroly Plant source cannot be used by birds
yVitamin D3 = cholecalciferoly Produced photochemically by the action of sunlight or
ultraviolet light from the precursor sterol 7-
dehydrocholesteroly Animal source required by birds
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y Functionsy Bone development
y Calcium absorption (small intestine)
y Calcium resorption (bone and kidney)
y Maintain blood calcium levels
y Phosphorus absorption (small intestine)
y Hormoney Regulation of gene expression
y
Cell growth
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y Osteoclastsy Break down bone
y Calcium resorption
y Derived from stem cells
y Differentiate after stimulation by vitamin Dy Osteoblasts
y Bone-forming cells
y Secrete collagen, which calcifies
y Bone contains 6066% Ca by weighty Hydroxyapatite, Ca10(PO4)6(OH)2
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y Younger age groupy Rickets
y Failure of bones to grow properlyy Results in bowed legs or knock-
knees, outward bowed chest andknobs on ribs
y Older age groupy Osteomalacia: Adult form of rickets
y Softening of bones, bending of spine,and bowing of legs
y Osteoporosis (porous bones):y Vitamin D plays a major role along
with calciumy Loss of vitamin D activity with
advancing agey Associated with fractures very
serious for geriatrics
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y Hypoplasia and hypocalcification of enamel and dentin
y Calciotraumatic line seen during dentin formation is theearliest sign of deficiency.
y
Hypomineralized dentiny Increased width to predentin
y Odontoblastic disorganization
y Enlarged pulp and pulp horns
yTooth defects more severe in males
y Permanent teeth affected predominantly
y Short, wedge shaped roots with delayed apical closure
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y Interglobular calcification in dentin, especially atapices
y Enamel hypoplasia
y Enlarged pulp chambers
y Irregular dentinal tubules
y
Small crowns and short blunted rootsy Pitted enamel surfaces
y Retarded jaw, tooth and condyle development
y Generalized jaw bone resorption
y Loss of the periodontal ligament
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y Calcification of soft tissuey Lungs, heart, blood vesselsy Hardening of arteries (calcification)
y Hypercalcemiay Normal is ~ 10 mg/dly Excess blood calcium leads to stone formation in kidneys
y Lack of appetite
y Excessive thirst and urination
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Type II (age-related) osteoporosisy Loss of bone mass
y Limited ability to absorb vitamin D or produce it
y 10-20 ug vitamin D/ day plus calcium decrease bonefracture
y Risk for hypercalcemia
Psoriasisy Skin disorder
y Topical treatment
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y Tocopherols
yAmount absorbed is dependent on fat intakey Incorporated into micellesy Requires bile and fat digesting enzymes
y Transported via chylomicrons to the liver
y Transported via VLDL, LDL, HDL from the liver
y Found concentrated in areas where fat is found
y Excreted via bile and urine (much in feces due tolimited absorption)
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y Plant oils
y Wheat germ
y Asparagus
y
Peanutsy Margarine
y Nuts and seeds
y Actual amount is
dependent on harvesting,processing, storage andcooking
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y Antioxidanty Free radical scavenger
y Protects cell membranesy Protects LDL from oxidationy Protection of double bonds in
polyunsaturated fatty acidsy Prevention of rancidityy Works in conjunction with
selenium
y Protects lungs from
pollutantsy Protects DNAy Protects heart
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y Protects the double bonds in saturated fat
y Role in iron metabolism
y Inhibits LDL oxidation
y Inhibits protein kinase C activity
y Enhance release ofprostacyclin
y Maintenance of nervous tissue and immune function
y No specific role in metabolic reaction
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y 15 mg/day for women and men
y (=22 IU of natural source or 33 IU of synthetic form)
y Average intake meets RDA
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y Supplements up to 800 IU is probably harmless
y Upper Level is 1,000 mg/day of any form ofsupplementary alpha-tocopherol
y Upper Level is 1500 IU (natural sources) or 1100 IU(synthetic forms)
y Inhibit vitamin K metabolism and anticoagulants
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y 40%-80% of dietary vitamin K is absorbed
y Absorption requires bile and pancreatic enzymes
y Role in the coagulation processy Calcium-binding potential
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y Liver
y Green leafy vegetables
y Broccoli
y Peas
y Green beansy Resistant to cooking losses
y Limited vitamin K storedin the body
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y K1, phylloquinoney Chloroplasts in plants
y K2, menaquinone
y Bacterial synthesis
y K3, menadioney Synthetic, water soluble formy Complexed to improve stability
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y Clotting factors aresynthesized in the liver asinactive precursors - vitamin Kconverts them to their activeformsy Conversion of prothrombin to
thrombin, an active enzyme
y Formation of fibrinogen tofibrin, leading to clot
formationy Stimulates bone formation and
decreases bone resorption
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y 90 ug/day for women
y 120 ug/day for men
y RDA met by most
y
Excess vitamins A and E interferes with vitamin Ky Newborns are injected with vitamin K(breast milk is a
poor source)
y Toxicity unlikely; readily excreted
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y Primary deficiency rare; secondary deficiencyoccurs when fat absorption is impaired (e.g., cysticfibrosis, Crohns disease) or following long-term orhigh-dose administration of antibiotics (they killthe bacteria in large intestine)y Newborn babies with sterile GI tract; single vitamin K
dose given to prevent hemorrhage
y Prolonged clotting time
y Generalized hemorrhages
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y Excessive gingival bleeding
y Dental caries
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y Not common except with over-supplementationy Phylloquinone and menaquinone are relatively nontoxic
y Jaundice; brain damage
y Menadione toxic to skin and respiratory tract in highdoses
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