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


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



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



Precursors Provitamins

Converted to active form in body

Organic nature Can be destroyed during storage and in

cooking



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



Toxicity More is not necessarily better Excessive intakes

Levels higher than UL




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


The B Vitamins – As The B Vitamins – As IndividualsIndividuals


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



Deficiency Malnourished and alcoholics Beriberi

Dry – nervous systemWet – cardiovascular system

Toxicity No adverse effects

No UL





Food sources Prolonged cooking destroys thiamin Leaches into water when boiling or

blanching foods Cooking methods that conserve thiamin




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





Food sources Milk and milk products Other sources

Destruction of riboflavin Ultraviolet light Irradiation Not destroyed by cooking




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)



Recommendations Body manufacturers from tryptophan

Only occurs after protein synthesis needs have been met

RDA is stated in niacin equivalents Deficiency

PellagraSymptoms





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




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



Recommendations Adequate intake (AI)

Deficiencies Rare Symptoms

Toxicity No UL

Food sources


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


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



Recommendations Large doses

Deficiency Symptoms Alcohol & isoniazid

Toxicity Irreversible nerve degeneration

Food sources




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





Folate disposal Secretion by liver into bile

Enterohepatic circulationVulnerable to GI tract injuries

Recommendations Bioavailability of folate

Synthetics vs. food sources Increased need



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



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



Deficiency Impairs cell division and protein synthesis Red blood cells and GI tract cells falter

AnemiaGI tract deterioration

Primary deficiencies Secondary deficiencies

Drugs



Toxicity Naturally occurring from food sources Fortified foods or supplements UL has been established

Food sources Heat and oxidation destroy folate




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



Digestion and absorption Stomach Small intestine

Intrinsic factor

Transported in blood by specific binding proteins

Enterohepatic pathway Deficiency is rare



Recommendations Deficiency

Inadequate absorptionLack of hydrochloric acid or intrinsic factor

Pernicious anemia Vegan diets Anemia of folate deficiency Symptoms of vitamin B12 deficiency





Toxicity No adverse effects

No UL

Food sources Found almost exclusively from animal

products Bioavailability

Fish and milk

Destruction


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


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


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






Toxicities Excess eliminated through urine excretion Homeostasis disruption

Toxicities develop

Food sources First choice should be foods rather than

supplements


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





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



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


Vitamin C – Vitamin C – Recommendations Recommendations

Prevent overt symptoms of scurvy

Absorption maximum 200 mg

Higher vitamin C levels for smokers


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


Vitamin C – Deficiency Vitamin C – Deficiency


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


Vitamin C – Food SourcesVitamin C – Food Sources

Fruits and vegetables Potatoes

Vulnerable to heat and oxygen Used as antioxidant by food manufacturers


Vitamin C – Food SourcesVitamin C – Food Sources


Highlight 10Highlight 10

Vitamin and Mineral Supplements


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


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


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


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


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


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


Misleading ClaimsMisleading Claims

Organic or natural vitamins High potency claims Marketing strategy

Fake vitamins “Green” pills Stress relief

Internet advertising Cost


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

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The Water-Soluble Vitamins: B Vitamins and Vitamin C

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