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VITAMINS
HistoryHistory
Purified diets of carbohydrate, protein, fat, minerals and water were not capable of normal growthgrowth
“Accessory growth factors”
Casimir Funk a Polish biochemist isolated an Casimir Funk, a Polish biochemist, isolated an antiberiberi substance from rice polishings
Named it vitamineNamed it vitamineAn amineVital for life
Vit iVitamins
Essential organic compounds required in very small amounts (micronutrients) very small amounts (micronutrients) involved in fundamental functions of the bodyyUnrelated chemically
Not only amines so “e” was dropped
VitaminsVitamins
Not metabolic fuels (like glucose or fatty acids) or structural nutrients (like amino ) (acids)
Regulators (catalysts) of reactions, some of which are involved in energy metabolism
VitaminsVitamins
All vitamins are metabolically essential but not all required in the dietbut not all required in the diet
Most mammals can synthesize vitamin C; not humans and primatesNo mammal can synthesize B vitamins but rumen bacteria do
VitaminsVitamins
Some function as vitamins after undergoing a chemical changeundergoing a chemical change
Provitamins (e.g., β-carotene to vitamin A)
ClassificationClassification
Based on solubility in the laboratory, but solubility greatly influences how the body b b t t d t it iabsorbs, transports and stores vitamins
Fat-solubleVitamins A D E and KVitamins A, D, E and K
Water-solubleB vitamins and vitamin C v ta s a d v ta C
Fat soluble VitaminsFat-soluble Vitamins
Absorbed with dietary fat in small intestine40-90% absorption efficiencyAbsorption typically regulated by need
↑need ↑absorptionTransported away from small intestine in chylomicra via blood and lymph
Fat soluble VitaminsFat-soluble VitaminsLiver either stores the vitamin or repackages it for delivery to other cells
Excess vitamin Excess vitamin accumulates in liver and adiposeToxicities can occur; Toxicities can occur; almost always associated with supplement use (not foods)foods)
Water soluble VitaminsWater-soluble Vitamins
Ab b d h ll i iAbsorbed at the small intestineAbsorption often highly regulated by either other vitamins or binding proteins in the small other vitamins or binding proteins in the small intestineTransported away from small intestine in bloodbloodTypically not stored; instead, kidney filters excess into urine
Thus, more important to get these vitamins daily.Toxicities almost unheard of
Vitamins in Feeds and FoodsVitamins in Feeds and FoodsFound in ALL TYPES Found in ALL TYPES of foods; not just fruits and vegetables.In general, processing can decrease amount of vitamins in food.
The Fat-Soluble VitaminsA, D, E and K
Vitamin A: The RetinoidsVitamin A: The Retinoids
3 forms of vitamin A important for health
R i lRetinalRetinoic acidRetinol (key player; can b t d t th be converted to other forms)
β-carotene (a carotenoid or pigment) carotenoid or pigment) in yellow/orange foods is a potent provitamin AA
Vitamin A:S th i d StSynthesis and Storage
β-carotene is converted to vitamin A in the intestinal mucosa90% is stored in liver, mainly as the ester, retinyl palmitateCarotenoids can be stored in adipose tissue
Vitamin A : SSources
Animal sourcesLiverMilkEggsEggs
Plant sourcesCarrotsSpinachbroccoliDark-green or orange-
C30H30ODark green or orangeyellow colored fruits & vegetables
Vitamin A : F tiFunctions
Vision, especially night visionCell growth (retinoic acid)I itImmunityReproduction
R l f Vit i A i Vi iRole of Vitamin A in Vision
Visual Pigment
CarotenoidsCarotenoidsAdditi l h i l i Additional physiologic effects
Serving as an “antioxidant”R Remove excess “electrons” from cell systemElectrons (free radicals) damage cells and DNA
Can cause mutations
Protecting from cancer (related to antioxidant (related to antioxidant function?)Protecting from heart disease?
Vitamin A :Req irementsRequirements
f b l d ffTo account for metabolic differences between vit A and its carotenoid precursors
equivalents of 1 μg retinol (RAE = retinol equivalents of 1 μg retinol (RAE = retinol activity equivalent)12 μg β carotene and 24 μg α carotene = 1 12 μg β carotene and 24 μg α carotene = 1 RAE
900 RAE900 RAE700 RAE (higher during lactation)
Vitamin A :D fi iDeficiency
Main symptomsy pNight blindnessHyperkeratosisImpaired immune pfunction
Rare in industrialized worldworldLeading cause of blindness in areas of povertypoverty
Vitamin A :E i i t kExcessive intake
Retinol intake > 1000 μg/d bone fx riskRetinol intake 3000 μg/d during early pregnancy risk of birth defect 15000 μg/d itching, scaling of skin, malaise, loss of appetite, ICP ( nausea, vomiting, headaches, seizures, coma and death)
hHypervitaminosis A in humansPolar explorers eating polar bear or seal liverS lf di ti d i tiSelf-medication and overprescription
Vitamin D
l lNot always essentialBody can make it if exposed to enough sunlight!Made from cholesterol in the skin!Made from cholesterol in the skin!
Form of vit D in foods :Vit D3 (most common)( )Vit D2 (less common)
FunctionsPromotes intestinal absorption of Ca and its retention in the body Influences growth of bone & conn tissues Influences growth of bone & conn tissues
Vitamin D :R i tRequirements
Adults : at least 5 μg/day, 3 times as much with advanced age
Vitamin D :SSources
Fluid milk products are pfortified with vitamins DOily fishEgg yolkEgg yolkButterLiverDifficult for vegetariansA young person gets a full day’s supplies from 10 – 15’ day s supplies from 10 – 15 exposure to summer sun (UV-B, 290-315 nm), older person needs several times person needs several times longer
Vitamin D:D fi iDeficiency
ChildrenChildrenRickets
Failure of bones to grow properly.a lu e o bo es to g ow p ope ly.Characterized by bone deformities in lower limbs (bowlegs) & chest.
AdultsAdultsOsteoporosis (porous bones)
Associated with fractures very serious for the elderlyAssociated with fractures very serious for the elderly
Vitamin D :E i i t kExcessive intake
Prolonged consumption of several hundred μg /day hypercalcemia & soft tissue calcificationThousands μg/day coma & death in extreme cases
Vitamin EVitamin E
FunctionsAntioxidant (inactivates oxygen free radicals in membranes, lipoproteins, etc) lipoproteins, etc)
Protects cell membranes from free radicalsProtects lungs from Protects lungs from pollutantsOthers?
Vitamin E :R i tRequirements
Ad lt t l t 15 /dAdults : at least 15 mg/dPregnancy, breast feeding & high intake of PUFA slightly increase needPUFA slightly increase need
Vitamin E :SSources
Plant sourcesWheat germSunflower oilsSunflower oilsNuts
Little in animal sourcesBeef fed high levels of vitamin Beef fed high levels of vitamin E right before slaughter so now a source
Improves shelf lifeImproves shelf life
Vitamin E :D fi iDeficiency
Very rare, except in people who have difficulty absorbing fat Limited evidence that inadequate intakes atherosclerosis, Parkinson’s & Alzheimer’s di t t i i i disease, cancer, cataract, impair immune function
Vitamin E :E i i t kExcessive intake
Hi h d ( 1000 f l t High doses (> 1000 mg of any supplement form) can interfere with blood clotting risk of hemorrhagic strokerisk of hemorrhagic strokeThis adds to anticlotting effects of coumadins & salicylatescoumadins & salicylates
Vit i KVitamin K
FunctionsBlood clotting gPromoting mineralization of bone Regulation cell division & differentiation
Vitamin K :R i tRequirements
Newborn infants should get at least one supplemental dose to prevent cerebral h hhemorrhageAdequate daily intakes :
90 μg/day120 μg/day
Vitamin K :SSources
Bacteria in the large intestine (10-15%) or rumenPlant sources
Green leafy vegetablesy gSome oilsBroccoli
Animal sourcesAnimal sourcesMilk
Vitamin K :D fi iDeficiency
Very rare, except in people who have difficulty absorbing fat (e.g., cystic fibrosis Crohn’s disease) or using lots of fibrosis, Crohn’s disease) or using lots of antibiotics (they kill the bacteria in large intestine)intestine)Symptom: bleeding
Vitamin B1 (Thiamin)Vitamin B1 (Thiamin)
Function :Function :coenz in decarboxylation of α-keto acids & in transketolation in HMPin transketolation in HMP
Conditions predisposing to deficiency :Conditions predisposing to deficiency :alcohol abuse; inadeq diet, esp withsuperimposed glucose load; superimposed glucose load; gastric by pass surgery
Vitamin B1 (Thiamin) :Vitamin B1 (Thiamin) :
R 0 4 / 1000 k lReq : 0,4 / 1000 kalDeficiency : Wet beri-beri, dry beri-beri, alcoholic polyneuropathy Wernickealcoholic polyneuropathy, Wernicke-Korsakoff syndromeTh/ : 10 15 mg/day up to 100 mg/dayTh/ : 10 – 15 mg/day up to 100 mg/dayToxicity : none documented up to 200 x RDA
Vit i B2 ( ib fl i )Vitamin B2 (riboflavin)
f d h d d f hIn foods with dairy products meat, fish, eggs, liverIs a permitted colouring (yellow) agent for Is a permitted colouring (yellow) agent for foods but because its light sensitivity used infreqHigh intake harmless yellow discolouration of the urinePrecursor of flavin mononucleotides (FMN) & flavin-adenine dinucleotide) essential for several enzymesseveral enzymes
Vit i B3 ( i i )Vitamin B3 (niacin)
Can be obtained from diet or can be synthesised in the body from the essential y yamino acid tryptophan1 mg niacin ~ 60 mg tryptophang g yp pFound in red meat, liver, eggs, milkIs a component of coenz NAD & NADPp
Vit i B3 ( i i )Vitamin B3 (niacin)
Deficiency : pellagra 3D(dermatitis, diarrhoea & dementia)( , )
Epidemics on a diet based upon maizeHigh doses reduce high plasma cholesterol High doses reduce high plasma cholesterol
flushing, itching, nausea & vomiting
Vit i B6 ( id i )Vitamin B6 (pyridoxine)
3 biologically active substances found in food : pyridoxine, pyridoxal & pyridoxamineLiver, eggs, meat, fish, green leafy vegetables, fruitsOvert def is rare
Vit i B12 ( b l i )Vitamin B12 (cobalamins)Synthesised in micro-organisms (bacteria, fungi Synthesised in micro organisms (bacteria, fungi & algae)Present in meat, fish, eggs & milk, , gg
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