The Water-Soluble Vitamins: B Vitamins and Vitamin C
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Transcript of The Water-Soluble Vitamins: B Vitamins and Vitamin C
Whitney & Rolfes – Understanding Nutrition, 12 th Edition
The Water-Soluble The Water-Soluble Vitamins: B Vitamins Vitamins: B Vitamins
and Vitamin Cand Vitamin CChapter 10
Whitney & Rolfes – Understanding Nutrition, 12 th Edition
The Vitamins – An The Vitamins – An OverviewOverview
Support nutritional health Vitamins differ from macronutrients
Structure Individual units
FunctionNo energy yielded
Food contents Similarities to macronutrient
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The Vitamins – An The Vitamins – An OverviewOverview
Bioavailability Quantity provided by food Amount absorbed and used by body Factors influencing bioavailability
Efficiency of digestionNutrition statusMethod of food preparationSource of nutrientOther foods consumed at same time
Whitney & Rolfes – Understanding Nutrition, 12 th Edition
The Vitamins – An The Vitamins – An OverviewOverview
Precursors Provitamins
Converted to active form in body
Organic nature Can be destroyed during storage and in
cooking
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The Vitamins – An The Vitamins – An OverviewOverview
Solubility Affects absorption, transport, and excretion Water-soluble
Move directly into bloodMost travel freely
Fat-solubleEnter lymph and then bloodRequire transport proteins
Consumption frequency of vitamins
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The Vitamins – An The Vitamins – An OverviewOverview
Toxicity More is not necessarily better Excessive intakes
Levels higher than UL
Whitney & Rolfes – Understanding Nutrition, 12 th Edition
The Vitamins – An The Vitamins – An OverviewOverview
Whitney & Rolfes – Understanding Nutrition, 12 th Edition
The B Vitamins – As The B Vitamins – As IndividualsIndividuals
Vitamins do not provide the body with fuel for energy
Coenzymes Assist enzymes with release of energy
Without coenzyme, an enzyme cannot function
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The B Vitamins – As The B Vitamins – As IndividualsIndividuals
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The B Vitamins – ThiaminThe B Vitamins – Thiamin
Part of coenzyme thiamin pyrophosphate (TPP) Energy metabolism
Conversion of pyruvate to acetyl CoATCA cycle
Nerve activity and muscle activity Recommendations
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The B Vitamins – ThiaminThe B Vitamins – Thiamin
Deficiency Malnourished and alcoholics Beriberi
Dry – nervous systemWet – cardiovascular system
Toxicity No adverse effects
No UL
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The B Vitamins – ThiaminThe B Vitamins – Thiamin
Whitney & Rolfes – Understanding Nutrition, 12 th Edition
The B Vitamins – ThiaminThe B Vitamins – Thiamin
Food sources Prolonged cooking destroys thiamin Leaches into water when boiling or
blanching foods Cooking methods that conserve thiamin
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The B Vitamins – ThiaminThe B Vitamins – Thiamin
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The B Vitamins – The B Vitamins – RiboflavinRiboflavin
Serves as coenzyme in energy metabolism Flavin mononucleotide (FMN) Flavin adenine dinucleotide (FAD)
Recommendations Deficiency
Inflammation of membranes Toxicity
No UL
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The B Vitamins – The B Vitamins – RiboflavinRiboflavin
Whitney & Rolfes – Understanding Nutrition, 12 th Edition
The B Vitamins – The B Vitamins – RiboflavinRiboflavin
Food sources Milk and milk products Other sources
Destruction of riboflavin Ultraviolet light Irradiation Not destroyed by cooking
Whitney & Rolfes – Understanding Nutrition, 12 th Edition
The B Vitamins – The B Vitamins – RiboflavinRiboflavin
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The B Vitamins – NiacinThe B Vitamins – Niacin
Two chemical structures Nicotinic acid Nicotinamide
Major form of niacin in blood
Two coenzyme forms – metabolic reactions Nicotinamide adenine dinucleotide (NAD)
Carries hydrogens and their electrons NADP (the phosphate form)
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The B Vitamins – NiacinThe B Vitamins – Niacin
Recommendations Body manufacturers from tryptophan
Only occurs after protein synthesis needs have been met
RDA is stated in niacin equivalents Deficiency
PellagraSymptoms
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The B Vitamins – NiacinThe B Vitamins – Niacin
Whitney & Rolfes – Understanding Nutrition, 12 th Edition
The B Vitamins – NiacinThe B Vitamins – Niacin
Toxicity Naturally occurring
No harm Supplements or drugs
“Niacin flush” Potential health benefits of large doses of
nicotinic acid Food sources
Less vulnerable to food preparation losses
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The B Vitamins – NiacinThe B Vitamins – Niacin
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The B Vitamins – BiotinThe B Vitamins – Biotin
Coenzyme that carries activated carbon dioxide Critical in TCA cycle
Delivers carbon to pyruvate to form oxaloacetate
Participates in gluconeogenesis and fatty acid synthesis
Participates in breakdown of fatty acids and amino acids
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The B Vitamins – NiacinThe B Vitamins – Niacin
Recommendations Adequate intake (AI)
Deficiencies Rare Symptoms
Toxicity No UL
Food sources
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The B Vitamins – The B Vitamins – Pantothenic AcidPantothenic Acid
Part of chemical structure of coenzyme A Roles in body
Recommendations AI
Deficiency Rare
Toxicity Food sources
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The B Vitamins – BThe B Vitamins – B66
Three forms Pyridoxal, pyridoxine, and pyridoxamine Conversion to coenzyme PLP
Amino acid metabolismUrea metabolismConversion of tryptophan to niacin or
serotoninSynthesis of heme, nucleic acids, & lecithin
Stored exclusively in muscle tissue
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The B Vitamins – BThe B Vitamins – B66
Recommendations Large doses
Deficiency Symptoms Alcohol & isoniazid
Toxicity Irreversible nerve degeneration
Food sources
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The B Vitamins – BThe B Vitamins – B66
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The B Vitamins – FolateThe B Vitamins – Folate
Known as folacin or folic acid Primary coenzyme form – THF
(tetrahydrofolate) Transfers single-carbon compounds during
metabolismConvert vitamin B12 to coenzyme form
Synthesize DNA
Regenerate methionine from homocysteine
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The B Vitamins – FolateThe B Vitamins – Folate
Whitney & Rolfes – Understanding Nutrition, 12 th Edition
The B Vitamins – FolateThe B Vitamins – Folate
Folate disposal Secretion by liver into bile
Enterohepatic circulationVulnerable to GI tract injuries
Recommendations Bioavailability of folate
Synthetics vs. food sources Increased need
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The B Vitamins – FolateThe B Vitamins – Folate
Neural tube defects Supplement use
1 month before conceptionThrough first trimester
Fortified grain products Congenital birth defects Safety concerns with fortification
Mask a vitamin B12 deficiency
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The B Vitamins – FolateThe B Vitamins – Folate
Heart disease Breakdown homocysteine
Blood clots and atherosclerotic lesions Risk for heart attacks, stroke, or death from
cardiovascular causes Cancer
Type of cancer Timing of supplementation
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The B Vitamins – FolateThe B Vitamins – Folate
Deficiency Impairs cell division and protein synthesis Red blood cells and GI tract cells falter
AnemiaGI tract deterioration
Primary deficiencies Secondary deficiencies
Drugs
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The B Vitamins – FolateThe B Vitamins – Folate
Toxicity Naturally occurring from food sources Fortified foods or supplements UL has been established
Food sources Heat and oxidation destroy folate
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The B Vitamins – FolateThe B Vitamins – Folate
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The B Vitamins – Vitamin The B Vitamins – Vitamin BB1212
Vitamin B12 and folate depend on each other for activation Regeneration of methionine, synthesis of
DNA, and synthesis of RNA
Individual roles of vitamin B12
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The B Vitamins – Vitamin The B Vitamins – Vitamin BB1212
Digestion and absorption Stomach Small intestine
Intrinsic factor
Transported in blood by specific binding proteins
Enterohepatic pathway Deficiency is rare
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The B Vitamins – Vitamin The B Vitamins – Vitamin BB1212
Recommendations Deficiency
Inadequate absorptionLack of hydrochloric acid or intrinsic factor
Pernicious anemia Vegan diets Anemia of folate deficiency Symptoms of vitamin B12 deficiency
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The B Vitamins – Vitamin The B Vitamins – Vitamin BB1212
Whitney & Rolfes – Understanding Nutrition, 12 th Edition
The B Vitamins – Vitamin The B Vitamins – Vitamin BB1212
Toxicity No adverse effects
No UL
Food sources Found almost exclusively from animal
products Bioavailability
Fish and milk
Destruction
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Vitamin-Like CompoundsVitamin-Like Compounds
Choline Manufactured from methionine in body
Conditionally essential nutrientAdequate intake (AI)
Common sources Deficiencies are rare Roles in the body
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Vitamin-Like CompoundsVitamin-Like Compounds
Inositol Part of cell membrane structures
Carnitine Transports long-chain fatty acids for
oxidation Both can be made by body
No recommendations established Both are widespread in foods
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The B Vitamins – In The B Vitamins – In ConcertConcert
Each B vitamin coenzyme is involved in energy metabolism Directly Indirectly
Deficiencies Single B-vitamin deficiencies seldom show
up in isolationBeriberi and pellagra
Whitney & Rolfes – Understanding Nutrition, 12 th Edition
Whitney & Rolfes – Understanding Nutrition, 12 th Edition
The B Vitamins – In The B Vitamins – In ConcertConcert
Whitney & Rolfes – Understanding Nutrition, 12 th Edition
The B Vitamins – In The B Vitamins – In ConcertConcert
Toxicities Excess eliminated through urine excretion Homeostasis disruption
Toxicities develop
Food sources First choice should be foods rather than
supplements
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Vitamin C – Roles Vitamin C – Roles
Antioxidant Defends against free radicals
Loses electrons easily Vitamin C recycling Protects tissues from oxidative stress
Disease prevention Enhances iron absorption
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Vitamin C – Roles Vitamin C – Roles
Whitney & Rolfes – Understanding Nutrition, 12 th Edition
Vitamin C – Roles Vitamin C – Roles
Cofactor in collagen formation Matrix for bone and tooth formation Conversion of proline to hydroxyproline
Cofactor in other reactions Hydroxylation of carnitine Conversion of tryptophan to serotonin Conversion of tyrosine to norepinephrine Making hormones
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Vitamin C – Roles Vitamin C – Roles
In stress Adrenal glands release vitamin C and
hormones into blood Types of stress that increase vitamin C
Prevention and treatment of common cold Conflicting and controversial research Deactivates histamine
Disease prevention
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Vitamin C – Vitamin C – Recommendations Recommendations
Prevent overt symptoms of scurvy
Absorption maximum 200 mg
Higher vitamin C levels for smokers
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Vitamin C – Deficiency Vitamin C – Deficiency
Notable signs of deficiency Gums bleed easily around teeth Capillaries under skin break spontaneously
Scurvy Other physical signs Psychological signs Sudden death
Whitney & Rolfes – Understanding Nutrition, 12 th Edition
Vitamin C – Deficiency Vitamin C – Deficiency
Whitney & Rolfes – Understanding Nutrition, 12 th Edition
Vitamin C – Toxicity Vitamin C – Toxicity
Supplementation side effects Diarrhea GI distress
UL Interference with medical regimens Medical conditions in which high doses of
vitamin C should not be consumed
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Vitamin C – Food SourcesVitamin C – Food Sources
Fruits and vegetables Potatoes
Vulnerable to heat and oxygen Used as antioxidant by food manufacturers
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Vitamin C – Food SourcesVitamin C – Food Sources
Whitney & Rolfes – Understanding Nutrition, 12 th Edition
Highlight 10Highlight 10
Vitamin and Mineral Supplements
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Vitamin and Mineral Vitamin and Mineral SupplementsSupplements
Taken as dietary insurance Costly but harmless practice Costly and harmful to health practice
Mostly self-prescribed Physician recommendation Improving food choices is preferred course
of action Registered Dietitian
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Arguments for Arguments for SupplementsSupplements
Correct overt deficiencies Therapeutic doses prescribed by physician
Acting as drug
Support increased nutrient needs Certain stages of life
Improve nutrition status Improve body defenses Reduce disease risks
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Who Needs Who Needs Supplements?Supplements?
Specific nutrient deficiencies
Low energy intakes Vegans and older
adults with atrophic gastritis
Lactose intolerance Certain medications
Certain stages of life cycle
Inadequate milk intake, sun exposure, or dark skin
Medical conditions that interfere with nutrients in body
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Arguments Against Arguments Against SupplementsSupplements
Toxicity Supplement users are more likely to have
excessive intakes Issues with children
Life-threatening misinformation No guarantee of supplement effectiveness
Unknown needs “Ideal” supplements
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Arguments Against Arguments Against SupplementsSupplements
False sense of security Other invalid reasons
Today’s health problemsOvernutritionPoor lifestyle choices
Bioavailability and antagonistic actions Nutrients may interfere with one another’s
actionMake dietary modifications first
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Selection of SupplementsSelection of Supplements
Follow directions carefully Single, balanced vitamin-mineral
supplement U.S. Pharmacopeia (USP) logo
Logo assurances Two basic questions
Form Contents
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Misleading ClaimsMisleading Claims
Organic or natural vitamins High potency claims Marketing strategy
Fake vitamins “Green” pills Stress relief
Internet advertising Cost
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Regulation of Regulation of SupplementsSupplements
Food and Drug Administration (FDA) Dietary Supplement Health and Education
Act of 1994 Enable consumers to make informed choices Same general labeling requirements as
foods Net effect: deregulation of supplement
industry