Lecture Outline Chapter 8 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

LectureLectureOutlineOutline

Chapter 8Chapter 8

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

VitaminsVitamins

Chapter 8Chapter 8 Insert photo from 1st page of chapter

Chapter Learning OutcomesChapter Learning Outcomes

1.1. Classify vitamins according to whether they are fat-Classify vitamins according to whether they are fat-soluble or water-soluble.soluble or water-soluble.

2.2. List major functions and sources for each vitamin.List major functions and sources for each vitamin.

3.3. Describe deficiency and/or toxicity signs and Describe deficiency and/or toxicity signs and symptoms for certain vitamins, including A, D, symptoms for certain vitamins, including A, D, thiamin, folate, and C.thiamin, folate, and C.

4.4. Discuss ways to conserve the vitamin content of Discuss ways to conserve the vitamin content of foods.foods.

5.5. Evaluate the use of vitamin supplements with respect Evaluate the use of vitamin supplements with respect to their potential health benefits and hazards.to their potential health benefits and hazards.

Quiz YourselfQuiz Yourself True or FalseTrue or False

1.1. Natural vitamins are better for you Natural vitamins are better for you because they have more biological activity because they have more biological activity than synthetic vitamins. T Fthan synthetic vitamins. T F

2.2. Certain vitamins are toxic. T FCertain vitamins are toxic. T F

3.3. Vitamin E is an antioxidant. T FVitamin E is an antioxidant. T F

4.4. Vitamins are a source of “quick” energy.Vitamins are a source of “quick” energy.

5.5. According to scientific research, taking According to scientific research, taking large doses of vitamin C daily prevents the large doses of vitamin C daily prevents the common cold. T Fcommon cold. T F

How Did You Do?How Did You Do?

1.1. FalseFalse In most instances, natural vitamins In most instances, natural vitamins have the same activity in the body as have the same activity in the body as synthetic vitamins. synthetic vitamins.

2.2. TrueTrue Certain vitamins are toxic. Certain vitamins are toxic.3.3. TrueTrue Vitamin E is an antioxidant.Vitamin E is an antioxidant.4.4. FalseFalse Vitamins are Vitamins are notnot a source of a source of

kilocalories.kilocalories.5.5. FalseFalse According to results of most According to results of most

scientific research, megadoses of vitamin scientific research, megadoses of vitamin C do C do notnot prevent the common cold. prevent the common cold.

Vitamins: Basic ConceptsVitamins: Basic Concepts

What is a vitamin?What is a vitamin?A complex A complex organicorganic compound that: compound that:

– The bodyThe body can’t make can’t make — or make enough to — or make enough to maintain good healthmaintain good health

– NaturallyNaturally occurs in common foods occurs in common foods– Deficiency condition Deficiency condition occurs when the vitamin occurs when the vitamin

is missing in the dietis missing in the diet– Good health isGood health is restoredrestored,, if deficiency disorder if deficiency disorder

is treated earlyis treated early

Vitamins: Basic ConceptsVitamins: Basic Concepts

• Most vitamins have more than 1 formMost vitamins have more than 1 form– Vitamin A = retinol, retinal, retinoic acidVitamin A = retinol, retinal, retinoic acid

• ProvitaminsProvitamins are are vitamin precursors vitamin precursors that do that do not function in the body until converted to not function in the body until converted to active forms.active forms.– Beta-caroteneBeta-carotene ( (plant pigmentplant pigment) = precursor to ) = precursor to

vitamin Avitamin A– TryptophanTryptophan = ( = (amino acidamino acid) precursor to B-vitamin ) precursor to B-vitamin

niacinniacin

How Vitamins Differ from How Vitamins Differ from Carbohydrate, Fat, and ProteinCarbohydrate, Fat, and Protein

VitaminsVitamins

OrganicOrganic

No CaloriesNo Calories

MicroMicronutrientsnutrients

Foods contain very Foods contain very small amounts small amounts

(milligrams or micrograms)(milligrams or micrograms)

Carbs, Fats, Proteins

Organic

Provides Calories

Macronutrients

Foods contain relatively large

amounts(grams)

Same

Differ

Vitamins Are MicronutrientsVitamins Are Micronutrients

Comparing Amounts Comparing Amounts of Nutrients in a of Nutrients in a

FoodFood• A slice of bread weighs A slice of bread weighs

about 1 oz (28 g) about 1 oz (28 g)

• Vitamins comprise only Vitamins comprise only ~0.005% (1.48 mg) of ~0.005% (1.48 mg) of the bread’s weightthe bread’s weight

• Insert slice of bread from page 224

Roles of VitaminsRoles of Vitamins

Vitamins may:Vitamins may:

– Have hormonal actionhormonal action (e.g., vitamin D)

– ParticipateParticipate in certain chemical reactions

– RegulateRegulate certain body processes– Cell division and development– Growth and maintenance of tissues

Vitamins and Their FunctionsVitamins and Their Functions

• Insert figure 8.1

Do Vitamins Supply Any Calories? Do Vitamins Supply Any Calories?

VitaminsVitamins do notdo not supply energy, but many supply energy, but many

participate in the chemical reactions that release participate in the chemical reactions that release the energy stored in macronutrients.the energy stored in macronutrients.

• OxidationOxidation = loss of electrons= loss of electrons

• ReductionReduction = gain of electrons= gain of electrons

• Oxidation reactions can form Oxidation reactions can form radicalsradicals (or “ (or “freefree radicalsradicals””), substances with unpaired electrons.), substances with unpaired electrons.

• AntioxidantsAntioxidants are substances that give up are substances that give up electrons to stabilize free radicals.electrons to stabilize free radicals.

What is an Antioxidant?What is an Antioxidant?

• Most free radicals Most free radicals are are highlyhighly reactive reactive substancessubstances – they have an they have an

unpaired electronunpaired electron

• A A free radicalfree radical can can remove an remove an electron from a electron from a more more stablestable molecule, such as molecule, such as DNADNA, a , a proteinprotein, or , or a a polyunsaturated polyunsaturated fatty acid.fatty acid.

Free RadicalFree Radical

Insert Figure 8.2

How Do Antioxidants Work?How Do Antioxidants Work?

• By giving upgiving up an electron to a free radical, an antioxidant protects other molecules.– Action stabilizes the free radical

• Beta-caroteneBeta-carotene and vitamins Evitamins E and CC function as antioxidants.

• Insert Figure 8.3Insert Figure 8.3

Antioxidant ActionAntioxidant Action

Classifying VitaminsClassifying Vitamins

Fat-solubleFat-soluble — AA, , DD, , EE,, and KK- Associated with lipids in foods and the body

- Don’t dissolve in water or urine- Stored in the body and may be toxic

Water-solubleWater-soluble — B B vitamins, CC, and cholinecholine- Dissolve in watery components of foods and the body

- Excreted in urine- Most are not stored to a major extent

- Generally non toxic

FatFat-Soluble-Soluble VitaminsVitamins

• Insert Table 8.1

Water-Water-solublesoluble

VitaminsVitamins • Insert Table 8.1

Sources of VitaminsSources of Vitamins

Natural SourcesNatural Sources: Plants, animals, fungi, and bacteria

SyntheticSynthetic:Made in laboratories by chemistsSynthesized by microbes in laboratories and extracted for commercial use

Most natural and synthetic forms have equal activity in the body except:Natural vitamin ENatural vitamin E: greater biological activity than syntheticSynthetic folateSynthetic folate: greater biological activity than natural

Vitamin Enrichment and FortificationVitamin Enrichment and Fortification

• EnrichmentEnrichment– Addition of specific amounts of thiamin, riboflavin,

niacin, folic acid, and the mineral iron to refined flour and milled grains

• Grains lose considerable amounts of their natural vitamin/mineral contents during refinement

• FortificationFortification– Addition of one or more nutrients to a wide array of

commonly eaten processed foods during their manufacturing

Vitamin AbsorptionVitamin Absorption

• Most absorption occurs in small intestine– Absorption is not 100% efficient.

• Absorption generally increases when more of the vitamin is needed:– Growth (e.g., during infancy and

adolescence)– Pregnancy– Lactation (milk production)

Vitamin AbsorptionVitamin Absorption

• Fat soluble are absorbed with dietary fat– Some fat is needed in the diet.

• Diseases that affect the GI tract can reduce vitamin absorption.– Cystic fibrosisCystic fibrosis (CF) interferes with fat

digestion and fat-soluble vitamin absorption • People with CF and other intestinal

diseases may need to take supplemental sources of vitamins.

Vitamin Deficiency and Toxicity Vitamin Deficiency and Toxicity DisordersDisorders

• Deficiencies result from poor diets or certain health conditions.– In the United States, severe deficiencies are

uncommon because of:• Food preservation practices• Food enrichment and fortification• Widespread availability of fruits and vegetables

• According to dietary surveys: at least 2525% of Americans consume inadequate amounts of AA, EE, and C.C.

Populations at Risk for Vitamin Populations at Risk for Vitamin Deficiency (U.S.)Deficiency (U.S.)

• AlcoholicsAlcoholics• ElderlyElderly• Hospitalized (long-term)Hospitalized (long-term)• Anorexia nervosaAnorexia nervosa• Certain gastrointestinal Certain gastrointestinal

disordersdisorders• Rare metabolic conditionsRare metabolic conditions

Preserving Vitamin Content of FoodsPreserving Vitamin Content of Foods

Are fresh fruits and vegetables better Are fresh fruits and vegetables better sources of vitamins than canned or sources of vitamins than canned or frozen product?frozen product?

It depends…It depends… Two main factors that influence vitamin Two main factors that influence vitamin

retention in product are:retention in product are:

1) Length of time since harvest1) Length of time since harvest

2) Storage conditions since harvest2) Storage conditions since harvest

Which Vitamins are Susceptible to Which Vitamins are Susceptible to Loss?Loss?

• Vitamin CVitamin C, , thiaminthiamin, , andand folatefolate are are easily easily destroyeddestroyed by improper storage and by improper storage and preparation practices.preparation practices.

• NiacinNiacin and and vitamin Dvitamin D tend to be very tend to be very stable.stable.

Ways to Maximize Vitamin Ways to Maximize Vitamin Contents of FoodsContents of Foods

• Avoid buying wilted, bruised, or shriveled Avoid buying wilted, bruised, or shriveled produce.produce.

• Store at near freezing temperatures, in high Store at near freezing temperatures, in high humidity and air-tight containers.humidity and air-tight containers.

• Cook in small amounts of water.Cook in small amounts of water.• Avoid cutting foods that will be cooked into Avoid cutting foods that will be cooked into

small pieces. small pieces. • Use quick cooking methods such as Use quick cooking methods such as

microwaving, steaming, and stir-frying.microwaving, steaming, and stir-frying.• Freeze produce to preserve vitamins.Freeze produce to preserve vitamins.

• Insert Table 8.2Insert Table 8.2

Summary: Fat-Soluble Summary: Fat-Soluble VitaminsVitamins


MyPyramid: Fat-Soluble VitaminsMyPyramid: Fat-Soluble Vitamins

Vitamin AVitamin A

RetinolRetinol (preformed Apreformed A) Most active form of the vitamin In animal foods

Beta-caroteneBeta-carotene (provitamin Aprovitamin A) One of a few carotenoidscarotenoids (plant pigments) that the

body can convert to retinol

Major functionsMajor functions– Normal vision and reproduction– Cellular growth– Immune system function– Epithelial cell production and maintenance

Vitamin AVitamin A

• What is What is night blindnessnight blindness??– The inability to see in dim lightThe inability to see in dim light– An early sign of vitamin A deficiencyAn early sign of vitamin A deficiency

• The retina, the light- sensitive area inside each The retina, the light- sensitive area inside each eye, contains rods and cones, specialized nerve eye, contains rods and cones, specialized nerve cells essential for vision. cells essential for vision.

• Rods and cones need vitamin A to function Rods and cones need vitamin A to function properlyproperly..


Vitamin A Vitamin A and and

VisionVision


Vitamin A Content of Selected Vitamin A Content of Selected FoodsFoods

Vitamin AVitamin A• Dietary AdequacyDietary Adequacy

– RDA: 700 - 900 mcg RAERDA: 700 - 900 mcg RAE

• Vitamin A DeficiencyVitamin A Deficiency– Certain epithelial cells produce too much Certain epithelial cells produce too much keratinkeratin

• Keratin Keratin -- tough protein found in hair, nails, and tough protein found in hair, nails, and outermost layers of skinoutermost layers of skin

– Excess keratin:Excess keratin:• Skin becomes rough and bumpySkin becomes rough and bumpy• Inner eyelid cells that secrete mucus to protect Inner eyelid cells that secrete mucus to protect

cornea become keratinized.cornea become keratinized.– Can result in Can result in xeropthalmiaxeropthalmia “dry eye” “dry eye”

XerophthalmiaXerophthalmia

If uIf untreated, vitamin A deficiency ntreated, vitamin A deficiency eventually leads to blindness.eventually leads to blindness.

What is Carotenemia? What is Carotenemia?

CarotenemiaCarotenemia

– YellowingYellowing of skin due to excessive of skin due to excessive beta-carotene intakebeta-carotene intake• May occur in infants who eat too much May occur in infants who eat too much

orange/yellow or dark green baby foods: orange/yellow or dark green baby foods: carrots, apricots, winter squash, sweet carrots, apricots, winter squash, sweet potatoes, peas, green beans, etcpotatoes, peas, green beans, etc. .

– Typically harmlessTypically harmless

Vitamin DVitamin D

RicketsRickets: : vitamin D deficiencyvitamin D deficiency in children in children - Results in soft bones that do not grow - Results in soft bones that do not grow properly and become misshapenproperly and become misshapen


Vitamin D: The “Sunshine Vitamin” Vitamin D: The “Sunshine Vitamin” Synthesis and FunctionsSynthesis and Functions

Why Is Vitamin D Necessary?Why Is Vitamin D Necessary?

Vitamin DVitamin D is needed foris needed for:: – Metabolism of calcium and phosphorus Metabolism of calcium and phosphorus – Production and maintenance of healthy bonesProduction and maintenance of healthy bones

Parathyroid hormoneParathyroid hormone ( (PTHPTH))– Released when blood calcium levels drop Released when blood calcium levels drop – Stimulates kidneys to increase active vitamin D Stimulates kidneys to increase active vitamin D

production and decrease urinary calcium excretionproduction and decrease urinary calcium excretion

• Insert Figure Insert Figure 8.118.11

Maintaining Normal Blood Calcium LevelsMaintaining Normal Blood Calcium Levels

People who live south ofPeople who live south of

the 37the 37thth parallel and are parallel and are

outdoors when sunlightoutdoors when sunlight

is most intense are mostis most intense are most

likely synthesizinglikely synthesizing

adequate adequate previtamin Dprevitamin D..

Vitamin D and SunlightVitamin D and Sunlight

Insert Figure 8.12

• Dietary AdequacyDietary Adequacy– AI: 5 mcg/day (200 IU) for people < 50 AI: 5 mcg/day (200 IU) for people < 50

years of age years of age

• Vitamin D DeficiencyVitamin D Deficiency– RicketsRickets

• Rare in the U.S. because many foods Rare in the U.S. because many foods are fortified with vitamin D are fortified with vitamin D

• May develop in breastfed infantsMay develop in breastfed infants– Osteomalacia Osteomalacia -- “adult rickets”-- “adult rickets”

Vitamin D Adequacy and DeficiencyVitamin D Adequacy and Deficiency

• Upper Limit (UL) Upper Limit (UL) – 50 mcg/day (2000 IU)50 mcg/day (2000 IU)

• Vitamin D toxicityVitamin D toxicity– Too much calcium is absorbedToo much calcium is absorbed

• The excess calcium is deposited in soft The excess calcium is deposited in soft tissues including kidneys, heart, and blood tissues including kidneys, heart, and blood vessels.vessels.

Vitamin D ToxicityVitamin D Toxicity

Alpha-tocopherolAlpha-tocopherol

• Functions:Functions: – Major fat-soluble antioxidant found in cellMajor fat-soluble antioxidant found in cell

• Protects polyunsaturated fatty acidsProtects polyunsaturated fatty acids– Improves vitamin A absorptionImproves vitamin A absorption– Maintains nervous system and immune Maintains nervous system and immune

system functionsystem function

Vitamin E Vitamin E


Selected Food Sources of Selected Food Sources of Vitamin EVitamin E

• Dietary AdequacyDietary Adequacy– RDA: 15 mg/day RDA: 15 mg/day

• Vitamin E Deficiency Vitamin E Deficiency – HemolysisHemolysis (breaking apart) of RBC (breaking apart) of RBC

• Due to oxidation of polyunsaturated fatty acids Due to oxidation of polyunsaturated fatty acids in cell membranein cell membrane

• Vitamin E ToxicityVitamin E Toxicity– Upper Limit (UL) 1000 mg/dayUpper Limit (UL) 1000 mg/day– Excess may interfere with vitamin K’s role Excess may interfere with vitamin K’s role

in blood clottingin blood clotting

Vitamin E Adequacy, Vitamin E Adequacy, Deficiency, and ToxicityDeficiency, and Toxicity

Water-Soluble VitaminsWater-Soluble Vitamins

Most function asMost function ascomponents ofcomponents ofspecific specific coenzymescoenzymes

• CoenzymesCoenzymes:: small small molecules that molecules that regulate chemical regulate chemical reactions by reactions by interacting with interacting with enzymesenzymes

• Insert Figure 8.16

Coenzymes are comprised Coenzymes are comprised of B vitamin and a nitrogen-of B vitamin and a nitrogen-

containing substancecontaining substance

Coenzyme Coenzyme FunctionFunction

Once activated, theOnce activated, the

enzyme-coenzymeenzyme-coenzyme

complex enables thecomplex enables the

reaction to occur.reaction to occur.

Insert figure 8.16


Water-Soluble VitaminsWater-Soluble Vitamins


MyPyramid and the Water-Soluble VitaminsMyPyramid and the Water-Soluble Vitamins

• FunctionsFunctions– Part of coenzyme involved in Part of coenzyme involved in release of energy release of energy

from carbohydratesfrom carbohydrates– Metabolism of certain amino acidsMetabolism of certain amino acids– Synthesis of Synthesis of neurotransmittersneurotransmitters

• Dietary AdequacyDietary Adequacy– RDA = 1.2 mg/day (men) 1.2 mg/day (women)RDA = 1.2 mg/day (men) 1.2 mg/day (women)

• DeficiencyDeficiency– Not storedNot stored

• deficiency symptoms can occur within in a few daysdeficiency symptoms can occur within in a few days

ThiaminThiamin

BeriberiBeriberi

• Thiamin deficiencyThiamin deficiency

conditioncondition

• People are weak, have People are weak, have poor muscular poor muscular coordination, and may coordination, and may develop cardiovascular develop cardiovascular problems and edema.problems and edema.

Insert figure 8.18


Selected Food Sources of Selected Food Sources of ThiaminThiamin

• FunctionsFunctions– Coenzyme for metabolism of carbohydrate, Coenzyme for metabolism of carbohydrate,

lipids, and amino acidslipids, and amino acids

• Dietary AdequacyDietary Adequacy– RDA = 1.3 mg/day (males) 1.1 mg/day RDA = 1.3 mg/day (males) 1.1 mg/day

(females)(females)

• DeficiencyDeficiency– May occur in people who do not drink milk May occur in people who do not drink milk

or eat enriched grainsor eat enriched grains

RiboflavinRiboflavin


Selected Food Sources of Selected Food Sources of RiboflavinRiboflavin

• FunctionsFunctions– Part of two coenzymes that participate in at Part of two coenzymes that participate in at

least 200 reactionsleast 200 reactions

• Dietary AdequacyDietary Adequacy– RDA = 14-16 mg/dayRDA = 14-16 mg/day

• DeficiencyDeficiency– Pellagra—the “Pellagra—the “4 D’s4 D’s” of pellagra” of pellagra

DDermatitis, ermatitis, DDiarrhea, iarrhea, DDementia, ementia, DDeatheath

NiacinNiacin

Insert Table 8.9Insert Table 8.9

Selected Food Sources of Selected Food Sources of NiacinNiacin

• FunctionsFunctions– Part of coenzyme needed for amino acid Part of coenzyme needed for amino acid

metabolismmetabolism

• Dietary AdequacyDietary Adequacy– RDA = 1.3 to 1.7 mg/day RDA = 1.3 to 1.7 mg/day

• DeficiencyDeficiency– Rarely occurs, but signs and symptoms Rarely occurs, but signs and symptoms

include:include:• Dermatitis, anemia, convulsions, depression, Dermatitis, anemia, convulsions, depression,

and confusionand confusion

Vitamin B-6Vitamin B-6

Insert Table 8.10Insert Table 8.10

Selected Food Sources of B-6Selected Food Sources of B-6

• Folic Acid (synthetic) and FolacinFolic Acid (synthetic) and Folacin• FunctionsFunctions

– Part of coenzyme Part of coenzyme tetrahydrofolic acidtetrahydrofolic acid ( (THFATHFA))• THFA involved in DNA and amino acid THFA involved in DNA and amino acid

metabolismmetabolism• Conversion of homocysteine to methionineConversion of homocysteine to methionine

• Good Food Sources of FolateGood Food Sources of Folate– Leafy green vegetables, liver, legumes, asparagus, Leafy green vegetables, liver, legumes, asparagus,

broccoli, and orangesbroccoli, and oranges

• Dietary AdequacyDietary Adequacy– RDA = 400 mcg DFE/dayRDA = 400 mcg DFE/day

FolateFolate


Selected Food Sources of Selected Food Sources of FolateFolate

• DeficiencyDeficiency– Affects cells that rapidly divide, such as RBCsAffects cells that rapidly divide, such as RBCs

• Mature RBCs do not have nuclei and live ~ 4 Mature RBCs do not have nuclei and live ~ 4 monthsmonths

– without folate, RBC precursor cells enlarge, without folate, RBC precursor cells enlarge, but cannot divide (DNA is needed for division)but cannot divide (DNA is needed for division)

• Bone marrow releases some large, immature, Bone marrow releases some large, immature,

abnormal RBCs with nuclei (abnormal RBCs with nuclei (megaloblasts)megaloblasts)

into the blood stream.into the blood stream.

FolateFolate


Red Blood Cell (RBC) ProductionRed Blood Cell (RBC) Production

• During the first few weeks During the first few weeks after conception, the after conception, the neural neural tubetube forms. forms.– Neural tube develops Neural tube develops

into the into the brain and spinal brain and spinal cord.cord.

• Folate-deficient pregnant Folate-deficient pregnant women are at risk of giving women are at risk of giving birth to infants with birth to infants with neural neural tube defects.tube defects.

Neural Tube DefectsNeural Tube Defects

Two Common Types of Two Common Types of Neural Tube DefectsNeural Tube Defects

• Spina bifidaSpina bifida– Spinal bones do not form Spinal bones do not form

properly before birth and fail properly before birth and fail to enclose the spinal cord.to enclose the spinal cord.

• AnencephalyAnencephaly– Brain does not form properly Brain does not form properly

or is missing.or is missing.

Neural Tube DefectsNeural Tube Defects

• FunctionsFunctions– Part of coenzymes needed for:Part of coenzymes needed for:

• Folate metabolismFolate metabolism• Maintenance of Maintenance of myelin sheathsmyelin sheaths

• Absorption of Dietary B-12Absorption of Dietary B-12– B-12 in food is bound to proteinsB-12 in food is bound to proteins

• HCL and pepsin required to release B-12 from HCL and pepsin required to release B-12 from proteinsproteins

– B-12 must bind to B-12 must bind to intrinsic factorintrinsic factor for for absorption.absorption.



Vitamin B-12 AbsorptionVitamin B-12 Absorption


Selected Food Sources of Selected Food Sources of Vitamin B-12Vitamin B-12

• Dietary AdequacyDietary Adequacy– RDA = 2.4 mcg/day RDA = 2.4 mcg/day

• DeficiencyDeficiency– Pernicious AnemiaPernicious Anemia

• Genetic defect reduces production of intrinsic Genetic defect reduces production of intrinsic factor and results in poor B-12 absorption.factor and results in poor B-12 absorption.

• Signs and symptoms:Signs and symptoms:– megaloblastic anemia, nerve damage, weakness, megaloblastic anemia, nerve damage, weakness,

sore tongue, memory loss, confusion, difficulty walking sore tongue, memory loss, confusion, difficulty walking and maintaining balance, and eventual deathand maintaining balance, and eventual death


• Functions — not part of a coenzymeFunctions — not part of a coenzyme– CollagenCollagen synthesis synthesis

• protein that gives strength to connective tissuesprotein that gives strength to connective tissues

– Antioxidant Antioxidant activityactivity– Other Roles:Other Roles:

• Immune system functioning Immune system functioning • Synthesis of bile, and certain neurotransmitters Synthesis of bile, and certain neurotransmitters

and hormonesand hormones

• Dietary AdequacyDietary Adequacy– RDA = 75 to 90 mg/day (smokers have higher RDA = 75 to 90 mg/day (smokers have higher

RDAs)RDAs)

Vitamin CVitamin C


Selected Food Sources of Selected Food Sources of Vitamin CVitamin C

ToxicityToxicity• UL is 2000 mg/dayUL is 2000 mg/day• Kidneys excrete excess amounts of the vitamin and Kidneys excrete excess amounts of the vitamin and

oxalateoxalate, a byproduct of vitamin C metabolism, a byproduct of vitamin C metabolism– Increases risk of oxalate kidney stones, particularly in Increases risk of oxalate kidney stones, particularly in

susceptible persons susceptible persons

DeficiencyDeficiency• ScurvyScurvy

– Very rare in U.S., because about 10 mg/day prevents scurvyVery rare in U.S., because about 10 mg/day prevents scurvy – Signs and symptoms: poor wound healing, pinpoint Signs and symptoms: poor wound healing, pinpoint

hemorrhages, bleeding gums, bruises, and depressionhemorrhages, bleeding gums, bruises, and depression

Vitamin CVitamin C

Chapter 8 HighlightChapter 8 HighlightMegadosing on VitaminsMegadosing on Vitamins

Niacin As Medicine?Niacin As Medicine?

• Uses Uses – Given to lower LDL cholesterol and raise Given to lower LDL cholesterol and raise

HDL cholesterolHDL cholesterol

• Side effectsSide effects– Flushing of skin on face and chest, itchy Flushing of skin on face and chest, itchy

skin, GI tract upset, and liver damageskin, GI tract upset, and liver damage

Vitamin B-6 As Medicine?Vitamin B-6 As Medicine? • UsesUses

– Claims include help for symptoms of PMS and Claims include help for symptoms of PMS and carpal tunnel syndrome.carpal tunnel syndrome.

– Weak or no scientific support for claims Weak or no scientific support for claims

• Side effects of high doses Side effects of high doses – Severe sensory nerve damageSevere sensory nerve damage– Walking difficultiesWalking difficulties– Numbness of hands and feetNumbness of hands and feet

• Because of side effects, Because of side effects, notnot recommended recommended for treating PMSfor treating PMS

Folic Acid As Medicine?Folic Acid As Medicine?

• UseUse

– Lowers blood homocysteine levels when taken with Lowers blood homocysteine levels when taken with B-12 and B-6B-12 and B-6

• CVDCVD– Recent studies of subjects with CVD suggest folic acid Recent studies of subjects with CVD suggest folic acid

supplements do not reduce risk of having heart another heart supplements do not reduce risk of having heart another heart attack.attack.

• Alzheimer’s diseaseAlzheimer’s disease» May be a relationship between mild cognitive impairment May be a relationship between mild cognitive impairment

and folate deficiency or elevated blood homocysteineand folate deficiency or elevated blood homocysteine

» More research is needed to determine whether taking More research is needed to determine whether taking supplements to lower homocysteine can reduce risk of supplements to lower homocysteine can reduce risk of cognitive decline or slow progression of Alzheimer’s.cognitive decline or slow progression of Alzheimer’s.

Vitamin C As Medicine?Vitamin C As Medicine?

• UsesUses– Does not prevent common cold but may Does not prevent common cold but may

reduce reduce severityseverity of the infection of the infection

– Reduces oxidation of LDL cholesterolReduces oxidation of LDL cholesterol• More research is needed to determine whether More research is needed to determine whether

high doses help reduce CVD risk high doses help reduce CVD risk

– More research is needed to determine More research is needed to determine whether vitamin C helps reduce cancer risk or whether vitamin C helps reduce cancer risk or aids in cancer treatmentaids in cancer treatment

Carotenoids As Medicine?Carotenoids As Medicine? • Uses Uses

– CancerCancer• Older studies suggested diets rich in carotenoids were Older studies suggested diets rich in carotenoids were

associated with lower risk of cancers.associated with lower risk of cancers.– Dietary supplements containing beta-carotene failed to show Dietary supplements containing beta-carotene failed to show

benefit– may be harmful.benefit– may be harmful.

• Diets rich in fruits and vegetables associated with lower CVD Diets rich in fruits and vegetables associated with lower CVD riskrisk

– Dietary supplements containing beta-carotene and other Dietary supplements containing beta-carotene and other carotenoids fail to show benefit.carotenoids fail to show benefit.

– Age-related Macular Degeneration (AMD)Age-related Macular Degeneration (AMD)• Diets that supply high amounts of certain carotenoids may Diets that supply high amounts of certain carotenoids may

lower risk of lower risk of AMD.AMD.

Vitamin E As Medicine?Vitamin E As Medicine? • Questionable Benefits Questionable Benefits

– Recent studies did not support taking Recent studies did not support taking vitamin E (alpha-tocopherol) supplements vitamin E (alpha-tocopherol) supplements to reduce risk of heart attacks, cancer, to reduce risk of heart attacks, cancer, macular degeneration, and cognitive macular degeneration, and cognitive impairment.impairment.

– Future studies using other forms of Future studies using other forms of vitamin E may provide scientific support vitamin E may provide scientific support for taking the vitamin to prevent or treat for taking the vitamin to prevent or treat certain diseases.certain diseases.

Some Final ThoughtsSome Final Thoughts

• U.S. Preventive Services Task ForceU.S. Preventive Services Task Force::

““Taking vitamins does not replace the need to eat Taking vitamins does not replace the need to eat a healthy diet.”a healthy diet.”

• Consuming a wide Consuming a wide varietyvariety of vitamins, of vitamins, antioxidants, and phytochemical in their antioxidants, and phytochemical in their natural natural state and concentrationsstate and concentrations may be the most may be the most effective way to lower risk of CVD, cancer, and effective way to lower risk of CVD, cancer, and other serious chronic diseases.other serious chronic diseases.

Lecture Outline Chapter 8 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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