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