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1 Vitamins History Purified diets of carbohydrate, protein, fat, minerals and water were not capable of normal growth “Accessory growth factors” Casimir Funk, a Polish biochemist, isolated an antiberberi substance from rice polishings Named it vitamine An amine Vital for life Vitamins Essential organic compounds required in very small amounts (micronutrients) involved in fundamental functions of the body Unrelated chemically Not only amines so “e” was dropped

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Page 1: Vitamins - Študentski.net · vitamins Fat-soluble Vitamins A, D, E and K Water-soluble B vitamins and vitamin C The Basics of Water-Soluble Vitamins Dissolve in water B vitamins

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Vitamins

HistoryPurified diets of carbohydrate, protein, fat, minerals and water were not capable of normal growth

“Accessory growth factors”

Casimir Funk, a Polish biochemist, isolated an antiberberi substance from rice polishings

Named it vitamineAn amineVital for life

Vitamins

Essential organic compounds required in very small amounts (micronutrients) involved in fundamental functions of the bodyUnrelated chemically

Not only amines so “e” was dropped

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VitaminsNot 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

VitaminsOrganic molecules in foodRequired in small amountsClassified based on solubility

Fat solubleWater soluble

Fat-soluble Vitamins

RetinolErgocalciferolCholecalciferolTocopherolPhylloquinone

AD2

D3

EK

Chemical nameVitamin

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Water-soluble Vitamins

ThiaminRiboflavinNicotinamide (niacin)Pantothenic acidPyridoxineBiotinFolacin (folic acid)CholineCyanocobalaminAscorbic acid

B complexB1

B2

B3

B5

B6

B7

B12

C

Chemical nameVitamin

Vitamins

All vitamins are metabolically essential but 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

Vitamins

Some function as vitamins after undergoing a chemical change

Provitamins (e.g., β-carotene to vitamin A)

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ClassificationBased on solubility in the laboratory, but solubility greatly influences how the body absorbs, transports and stores vitaminsFat-soluble

Vitamins A, D, E and KWater-soluble

B vitamins and vitamin C

The Basics of Water-Soluble Vitamins

Dissolve in waterB vitamins & vitamin CAbsorbed mostly in small intestine & stomachBioavailability

Nutritional status, other nutrients & substances in food, medications, age, illness

Circulated to liver in bloodNot stored in large quantities

The Basics of Water-Soluble Vitamins

Page 5: Vitamins - Študentski.net · vitamins Fat-soluble Vitamins A, D, E and K Water-soluble B vitamins and vitamin C The Basics of Water-Soluble Vitamins Dissolve in water B vitamins

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Naming the VitaminsFirst named vitamin A or BB-complex vitaminsGiven common names also

ThiaminRiboflavinNiacin

Chemical namesAscorbic acid

Memorizing B Vitamin Names & Numbers

Thiamin (Vitamin B1)Contains thiol & amine group

Thiamin pyrophosphate (TPP) or thiamin diphosphate

Thiamin triphosphate

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Bioavailability & Regulation of Thiamin in the Body

BioavailabilityIncreases when lowUses simple diffusion when high

Antithiamin factorsRaw fish, coffee, tea, berries, brussels sprouts, cabbage

Vitamin C prevents oxidationAlcohol inhibits thiaminExcess excreted in urine

Functions of ThiaminATP production

Synthesis of DNA & RNA

Noncoenzyme roles

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Thiamin Deficiency: Beriberi

“I can’t, I can’t”Prevalent in parts of the world that rely on unfortified, milled rice as stapleCauses weak & impaired immune functionTypes

Dry, wet, infantile, cerebral (Wernicke-Korsakoff syndrome)

Did you know…Riboflavin is easily destroyed by light so milk is packaged in cardboard or cloudy plastic containers so it is not destroyed.

Regulation & Bioavailability of Riboflavin

Types:Free form

Can be absorbedBound to proteinCoenzyme (FMN or FAD)

Absorption through simple diffusion when intake high

Active transport when intake lowAnimal foods more bioavailableAlcohol inhibits absorptionExcess excreted in urine

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Coenzyme Functions of Riboflavin

Energy metabolismRedox reactionsFormation of ATP, water, carbon dioxideβ-oxidationConverts vitamin A & folate to active forms, tryptophan to niacinForms vitamin B6 & K

Riboflavin DeficiencyAriboflavinosis

Weakness, cheilosis, stomatitis, glossitis, anemia, confusion

AlcoholicsDiseases that interfere w/ riboflavin utilization

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Niacin (Vitamin B3)Forms

Nicotinic acidNicotinamide

Body uses both forms to make:NAD+

NADP

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Dietary Sources of Niacin1 mg niacin = 60 mg tryptophanNiacin equivalent

Combined amounts of niacin & tryptophan in foods

Bioavailability of NiacinAnimal products more bioavailable than plantIncreasing bioavailability

Treating grain products with alkaline substances cleaves protein from niacin

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Regulation of Niacin in Body

Small intestinal absorptionSimple diffusion when intake is highActive transport when intake is low

Circulated to liverAttached to transport proteins

Converted to NAD+ or NADP

Liver converts tryptophan to niacin when needed

Functions of NiacinCoenzymes catalyze redox reactions related to energy metabolismSynthesizes fatty acids, cholesterol, steroid hormones, & DNAMetabolizes vitamin C & folateNAD+

Protein synthesisMaintenance, replication & repair of DNAGlucose homeostasisCholesterol metabolism

Lower LDL & increase HDL

Niacin Deficiency: Pellagra“Rough skin”Four Ds

DermatitisDementiaDiarrheaDeath

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Tryptophan, Niacin, & Pellagra

Used to be thought of as infectious diseaseJoseph Goldberger

Studies done adding protein sources to diet

Prevented & treated disease through dietEnrichment programs developedRare in U.S.

Niacin ToxicityNicotinic acid (1 g/day)

Skin inflammationItchinessFlushingHeartburnNauseaIncreased plasma glucoseLiver damage

Regulation of Pantothenic Acid in the Body

BioavailabilityIncreases via active transport when intake is lowCirculated to liver via bloodNot stored in bodyCoenzyme form high in liver, kidney, heart, adrenal glands, & brain

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Functions of Pantothenic Acid in the Body

Use of glucose, amino acids, & fatty acids for ATP productionSynthesizes:

HemeCholesterolBile saltsPhospholipidsFatty acidsSteroid hormones

Pantothenic Acid Deficiency & Toxicity

DeficiencyRare“Burning feet syndrome”

ToxicityRareNausea & diarrhea

Vitamin B6

FormsPyridoxinePyridoxalPyridoxamine

Similar biological activities

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Regulation of Vitamin B6 in the Body

Absorbed in small intestine Circulated in blood to liver

Forms pyridoxal phosphate (PLP)Coenzyme form of B6

Stored in muscle & liver

Functions of Vitamin B6 in the Body

PLP coenzyme to metabolismProteins & amino acids via transamination

Synthesizes nonessential amino acidsProduces nonprotein substances

Converts tryptophan to niacin

Vitamin B6 Deficiency: Microcytic Hypochromic Anemia

Results in inadequate heme productionDecreases oxygen availability in tissuesImpairs ability to produce ATP via aerobic metabolism

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Vitamin B6 ToxicityExcess supplement use

Severe neurological problemsDifficulty walkingNumbness in hands & feet

Bioavailability of BiotinReduced by:

AvidinEgg whites

Alcohol

Extreme heat destroys biotin

Regulation of Biotin Enzymes cleave to protein-biotin complexes in small intestineProduced by large intestine bacteriaCirculates to liver via bloodSmall amounts stored in

MuscleLiverBrain

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Functions of BiotinCatalyzes carboxylation reactionsUse of amino acids & fatty acids in citric acid cycle for synthesis of fatty acidsGene expression

Biotin DeficiencyUncommonSeen in:

Individuals who eat large quantities of raw egg whitesConditions impairing intestinal absorptionGenetic disorders

Signs & SymptomsDepression, hallucinations, skin irritations, infections, hair loss, poor muscle control, seizures, developmental delays in infants

Folate (Folacin)

Consists of:Nitrogen-containing double ring structureNitrogen-containing single ring structureGlutamic acid

Folic acidSynthetic formFortified foods & supplements

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Dietary Sources of FolateSince 1998All cereal products in U.S. fortified with folic acidHeat, light, & oxygen destroy folate

Bioavailability of Folate Depends on formInfluences

Genetic factorsDrugs

Absorption higher with:Fortified foodsSupplements

Dietary folate equivalents (DFE)

Regulation of Folate in Body

Glutamate units must be cleaved before absorbed

Converted to tetrahydrofolate (THF)Results in 5-methyl tetrahydrofolate

Circulated to liver via bloodLittle is stored

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Function of Folate: Single-Carbon Transfers

Coenzyme involved in transfer of single-carbon groups to form organic substances

Homocysteine to methioninePurines & pyrimidinesNormal growth & development

Focus on Life Cycle Nutrition: Folate, Neural Tube Defects, & Spina Bifida

Neural tube Spinal cord & brain

Defects result when:Closure of neural tube is incomplete

Spina bifida20 out of 100,000 babies

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Folate, Neural Tube Defects, & Spina Bifida

Folate supplementation decreases risk in some women

IOM recommends:That women capable of becoming pregnant take folic acid supplements and/or consume folic acid-fortified foods in addition to a varied diet

Folate Deficiency: Macrocytic Anemia

Red blood cells (RBC) remain immatureCells are large & contain organelles not found in mature RBC

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Folate DeficiencyAlcoholicsPeople w/ intestinal diseasesPeople taking certain medicationsElderlyGenetic variations

Regulation of Vitamin B12 in the Body

Must be cleaved before absorptionBound to R protein & intrinsic factorOnce absorbed, binds to transcobalaminCirculates to liver via bloodStored in liver

Functions of Vitamin B12

Coenzyme that catalyzes:Production of succinyl CoA

Uses amino acids & fatty acids for ATP production

Key for ruminants!!

Conversion of homocysteine to methionine

Allows use of folate

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Vitamin B12 Deficiency & Pernicious Anemia

VegansBreastfed infants of B12-deficient mothersElderly

Pernicious anemiaGastric cells stop intrinsic factor secretionInjections of B12 given

Signs & symptomsMacrocytic anemia, fatigue, difficulty sleeping, numbness, memory loss, severe neurological disturbances

Folate, Vitamin B12, & Anemia

B12 DeficiencyCaused by secondary folate deficiency

Folate “masks” B12 deficiency

Regulation of Vitamin C in the Body

Absorption in small intestine via active transportUses glucose transport proteinHigh intakes

Absorbed by simple diffusion in stomach & small intestine

Circulates to liver via bloodExcess excreted in urine

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Functions of Vitamin CAntioxidant

Accepts & donates electrons

Involved in a variety of redox reactions

The “Recharging” of Enzymes

ExamplesCollagen

Synthesis of carnitine

Synthesis of hormonesCholecystokinin Gastrin

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BioavailabilityEnhances absorption of:

IronCopperChromium

Consuming vitamin C sources with these minerals increases their bioavailabilityExample

Orange juice + iron-enriched cereal

Vitamin C & Protection from Free Radical Damage

Free radicalsCharged substances that have unpaired electrons in their outer shells Break DNA & oxidize fatty acids found in cell membranes

Vitamin CDestroys free radicals

Vitamin C & Protection from Free Radical Damage

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Vitamin C, the Common Cold, & Other Diseases

Suggested that large vitamin C doses benefit immune systemMore research needed:

Common coldCancerHeart diseaseCataracts

Vitamin C Deficiency & Toxicity

DeficiencyScurvy

Signs & symptomsBleeding gumsSkin irritationsBruisingPoor wound healing

ToxicityNauseaDiarrheaCrampingKidney stones

Choline: A “New” Essential Vitamin?

IOMDesignated choline as essential in some situations

Certain populations at risk? conditionally essentialSome do not consider it a vitamin

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Dietary Sources of CholinePlant & animal foods

Eggs, liver, legumes, pork

LecithinMayonnaise & salad dressings

Regulation of Choline in the Body

Unbound choline absorbed in small intestineCirculates to liver via bloodLecithin

Cleaved from glycerol backbone by pancreatic enzymesTaken up by intestinal cells & reconstituted into lecithin moleculesReleased into lymphBecomes LDL

Made in body by methionine

Functions of Choline in Body

Synthesizes phospholipids & acetylcholineComponent of cell membranes & lipoproteinsMuscle controlStructural roleMetabolic reactions

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Choline Deficiency & ToxicityDeficiency

? liver damage in adult menToxicity

Fishy body odor, perspiration, salivation, low blood glucose, liver damage

Carnitine

Conditionally essential for infants

Classification being debated

Animal sourcesMeat, milk, & human milk

Regulation & Functions of Carnitine in the body

Absorbed in small intestineProduced from methionine & lysineAssists fatty acids to cross membranes

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Carnitine Deficiency & Toxicity

DeficiencyRare Genetic conditions

Muscle weakness, hypoglycemia, heart irregularities

ToxicityNone known

Summary

Summary

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Fat-Soluble VitaminsOrganic substances that dissolve in lipids & are vital to healthMicronutrientsVitamins A, D, E, & KKey players in:

Cell growthMaturationGene regulation

Basics of Fat-Soluble Vitamins

Absorbed in small intestineRequires lipids & bileCirculated in lymph via chylomicronsBecome part of lipoproteins or bound to transport proteinsAntioxidant propertiesStored in body

Vitamin A & the Carotenoids

RetinoidsRetinol (preformed vitamin A)

Most potent formCan be synthesized from retinal

RetinalCan be converted to retinoic acid

Retinoic acid

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CarotenoidsTypes

Provitamin A carotenoidsBeta-caroteneCan be converted to vitamin A

Nonprovitamin A carotenoidsCannot be converted to vitamin ALycopene, astaxianthin, zeaxanthin, luteinConsidered phytochemicals

Dietary Sources of Vitamin A & Provitamin A Carotenoids

Retinol activity equivalent (RAE)1 RAE = 12 micrograms beta-carotene & 1 microgram retinol

Preformed vitamin AOrgan meats, liver, fatty fish, dairy products

Provitamin AYellow, orange, red fruits/veg, leafy greens

Regulation of Vitamin A & Carotenoids in Body

Contained in chylomicronsEnter lymphJoin blood at thoracic ductDelivered to adipose tissue, muscle, & eyeWhat is not used, taken back to liver

Carotenoids packaged into VLDLsVitamin A attached to retinol binding proteins & transthyretin

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Vitamin A Synthesis 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

Functions of Vitamin ACell differentiation

Maintaining healthy immune system

Building strong bones

Vision

Vitamin A & Vision

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Night BlindnessInadequate amounts of retinal to re-form rhodopsin

Compound in retina that consists of the protein opsin & vitamin cis-retinal that is needed for night vision

Night vision becomes difficult

Vitamin A & Cell Differentiation

Vitamin A, Growth & Reproduction

Regulates cell differentiationExample

During embryonic growth, vitamin A assists in differentiation & maturation of tissues & organs

Needed for successful reproduction

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Vitamin A & the Immune Function

Maintains protective barriersEpithelial tissues

Helps produces lymphocytes & antibodies

Deficiencies – increased rate of infectious disease & illness

Vitamin A, the Carotenoids, & Cancer

Epidemiological studiesDiets rich in vitamin A or carotenoids associated with lower risk of some types of cancersLong-term, high-dose supplementation of beta-carotene in combination with other dietary factors increases incidence of lung & colorectal cancer

RecommendationDo not take vitamin A &/or beta-carotene supplements to reduce cancer risk

Vitamin A & Bone HealthRequired for processes with osteoclasts & osteoblasts

Favors bone formation

High preformed vitamin A intakeMay lead to greater risk of bone fractures in older people

Research needed?

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Functions of CarotenoidsInfluences immune system

Antioxidant functionRegulation of gene expressionMaintenance of normal cell turnoverDecreases risk for certain diseases

Focus on Foods: Fruits, Vegetables, Carotenoids, & Health

LuteinMay decrease growth of breast tumors

LycopeneRelated to lower risk of prostate cancer

Lutein & zeaxanthinRelated to decreased risk of macular degeneration

Make your plate colorful!Beta-carotene

Carrots, sweet potatoes

LycopeneTomatoes, pink grapefruit, apricots, watermelon

LuteinDark green leafy vegetables

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Vitamin A DeficiencyUncommon in industrialized countries

Secondary vitamin A deficiency

Cystic fibrosisAlcoholics

Vitamin A Deficiency Disorder (VADD)

Increased risk of infection

Night blindness

XerophthalmiaDry eyes & scarringBitot’s spotsBlindness

HyperkeratosisSkin is rough, bumpy, irritated

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Focus on Diet & Health: Vitamin A & International Child Health

100-400 million children have VADDNonindustrialized countriesVitamin A supplementation decreases morbidity & mortality

WHO Recommends supplementation after 6 months in needed regions

Biotechnology

Biotechnology: Golden Rice

Vitamin A & Carotenoid ToxicityUpper safe levels are 4-10x requirements in nonruminants and 30x in ruminantsHypervitaminosis A in humans

Polar explorers eating polar bear or seal liverSelf-medication and overprescription

Blurred visionLiver abnormalitiesReduced bone strengthBirth defectsIncrease risk of lung cancerHypercarotenemia

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Vitamin D

Conditionally essential

FormsErgocalciferol (D2)

Plant sources & supplements

Cholecalciferol (D3)Animal foods & made by body

Regulation, Metabolism, & Synthesis of Vitamin D

Packaged into micellesAbsorbed into enterocyteIncorporated into chylomicronsLymph, then bloodRemnants taken to liver“Sunshine vitamin”

Synthesis of Vitamin D

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Influences on Vitamin D Synthesis

Areas with smog, overcast weather, very short daysDarker skinSunscreenAge-related changes

Activation of Vitamin D

Functions of Vitamin DRegulation of:

Blood calcium concentration

Gene expression

Cell differentiation

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Vitamin D & Calcium Homeostasis

Vitamin D, Cell Differentiation, & Cancer

Movement of vitamin D into nucleusStimulation of genes coding for specific proteinsExamples

Bone health GI function? prevention of colon, breast, skin, prostate cancers

Vitamin D DeficiencyRicketsOsteomalaciaOsteoporosisPeople over 50:

Get > 15 minutes sun exposure/dayIncrease vitamin D intake

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Vitamin D ToxicityHypercalcemia

OversupplementationDeposits of calcium in soft tissuesAffects function of nervous systemPromotes bone lossDeath

Vitamin E

8 different compounds

alpha-tocopherolMost biologically active

Regulation of Vitamin E in Body

Requires bile & synthesis of micellesCirculated in chylomicrons via lymph & bloodLiver

Repackaged into VLDLs

ExcessStored in adipose tissue

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Cell Membrane Structure

Vitamin E & CancerAntioxidants protect DNA from free radical damage? if vitamin E might prevent or cure cancerDiets high in vitamin E

Associated with decreased cancer riskLittle experimental evidence

Vitamin E & CataractsCloudy growths that develop on the lens of the eyeCauses vision to become cloudyCan lead to blindnessEvidence suggests:

Older people who take vitamin E supplements are at lower risk for developing cataracts

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Vitamin E & Heart DiseaseSlows rate of plaque formationSupplementation

400 mg/dayCauses overall increased risk of mortality

RecommendationTaking vitamin E supplements to decrease risk of heart disease is discouraged

Vitamin E DeficiencyUncommonReports in:

Infants fed formulas with inadequate vitamin EGenetic abnormalitiesFat malabsorption

SymptomsNeuromuscular problems, loss of coordination, muscular painHemolytic anemia

Vitamin E ToxicityRare

Very high doses:Hemorrhages

Genetic differences

Caution:Vitamin E supplements

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Vitamin K

Refers to 3 compounds:Phylloquinone (K1)

Food & supplementsMenaquinone (K2)

Produced by bacteria in large intestine

Menadione (K3)Produced commercially

Regulation of Vitamin K in the Body

Absorbed via micellesIncorporated into chylomicronsEnters lymph & then blood

Vitamin K produced in large intestineEnters epithelial cells by simple diffusion

LiverPackages dietary & bacterially produced forms into lipoproteins

Functions of Vitamin K: Coagulation

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Did you know…Vitamin K also catalyzes carboxylation of other proteins for bone & tooth development

Binds calcium

If you take a calcium supplement, take a look at the label. More than likely, vitamin K is an ingredient!

Nutrient-Drug Interactions & Vitamin K

Long-term antibiotic useKills intestinal bacteriaIncreases risk for deficiency

Coumadin (warfarin)“Thins the blood”Decreases activity of vitamin KEat a balanced dietLimit foods high in vitamin K to one serving each day

Dicoumarol found in moldy sweet cloverSweet clover disease

Vitamin K Deficiency & Toxicity

RareInfantsDiseases that cause lipid malabsorptionProlonged antibiotic use

Deficiency signsExcessive bleeding

Few toxic effects

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Vitamin K Injections During Infancy

Infants born with low storesLarge intestine lacks vitamin K-producing bacteriaHuman milk contains low levels

Vitamin K deficiency bleeding (VKDB)Mostly in breastfed infants5-10 babies/100,000 born

Vitamin C(ascorbic acid)

Energy releasing Hematopoietic Other

B-complex vitamins

Water-soluble vitamins

Thiamin (B1)Riboflavin (B2)Niacin (B3)Panthothenic acidBiotinVitamin B6

Folic acidVitamin B12Vitamin B6Pathothenic acid

Vitamin B6Thiamin (B1)Folic acidVitamin B12Niacin (B3)

Fat-soluble VitaminsAbsorbed 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 (depending on size)

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Fat-soluble Vitamins, Cont.Liver either stores the vitamin or repackages it for delivery to other cells

Excess vitamin accumulates in liver and adiposeToxicities can occur; almost always associated with supplement use (not foods)

Water-soluble VitaminsAbsorbed at the small intestineAbsorption often highly regulated by either other vitamins or binding proteins in the small intestineTransported away from small intestine in bloodTypically not stored; instead, kidney filters excess into urine

Thus, more important to get these vitamins daily.Toxicities almost unheard of

Vitamin Supplements: Making Wise Choices

Dietary supplements not approved by FDA for safety & effectivenessResponsibility of:

Manufacturers Distributors

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Sorting Fact from FictionOffice of Dietary Supplementshttp://ods.od.nih.govRemember:

Safety firstThink twice about chasing the latest headlineLearn to spot false claimsMore may not be better“Natural” does not always mean safe

When Should You Consider Taking A Supplement?

Food availability limitedNot consuming certain foodsPeriods of rapid growth & developmentEconomic situations are difficultUse of low-calorie diet

Remember…Supplements should never replace medications or a variety of foods

Do not exceed ULs

Keep a record of all dietary supplements taken & share with healthcare provider