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Chapter 10: The Water-Soluble Vitamins. Overview of Water-Soluble Vitamins. Dissolve in water Easily destroyed or washed out during food storage and preparation. Are easily absorbed and excreted Not stored in the body tissues and must be replaced each day. Seldom reach toxic levels. - PowerPoint PPT Presentation
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Chapter 10: The Water-Soluble Vitamins
Overview of Water-Soluble Vitamins
Dissolve in water Easily destroyed or washed out during food
storage and preparation. Are easily absorbed and excreted Not stored in the body tissues and must be
replaced each day. Seldom reach toxic levels
Overview of Water-Soluble Vitamins Many B-complex vitamins needed for energy
metabolism and form an integral part of coenzymes Help the body metabolize CHO, lipids and
amino acids Thiamin pyrophosphate – TPP (thiamin) Flavin Adenine Dinucleotide (FAD), Flavin Mononucleotide
(FMN)(riboflavin) Nicotinamide Adenine Dinucleotide (NAD), Nicotinamide
adenine dinucleotide phosphate (NADP)(niacin) Coenzyme A (pantothenic acid) Pyridoxal phosphate (PLP) (Vitamin B-6) Tetrahydrofolic acid (folate) Cofactor (biotin)
Enrichment Act of 1941 and 1998
Many nutrients lost through milling process of grains
Grain/cereal products are enriched with Thiamin, riboflavin, niacin, folate, iron Enriched grains still deficient in B-6, magnesium
and zinc Whole grains contain original nutrients
Distinction between water-soluble and fat-soluble vitamins
Fat-soluble vitamins Water-soluble vitamins
Absorption Lymph first, then the blood Direct absorption into the blood
Transport Protein carriers used by many Freely transported
Requirements
Periodic doses required Frequent doses required
Storage Stored in cells associated with fat
Circulate in water-filled parts of the body
Excretion Less readily excreted, tend to remain in fat-storage sites
Excreted in urine by kidneys
Toxicity Toxic levels likely when consuming supplements
Toxic levels possible when consuming supplements
Thiamin
Functions as a coenzyme: Thiamin pyrophosphate (TPP) In metabolism of CHO; & amino acids Decarboxylation of alpha keto acids (page 227)
Enzyme is Transketolase: coverts glucose to a 5-carbon sugar
Food Sources of Thiamin
Wide variety of food White bread, pork, hot dogs, luncheon meat,
cold cereal Enriched grains/ whole grains
RDA For Thiamin
1.1 mg/day for women 1.2 mg/day for men Most exceed RDA in diet Surplus is rapidly lost in urine; non toxic
Deficiency of Thiamin Beriberi
first observed in the Far East where polished rice replaced rice where bran remained intact.
characterized by loss of sensation in the hands and feet, muscular
weakness, advancing paralysis,and abnormal heart action.
Peripheral neuropathy Dry beriberi
Weakness, nerve degeneration, irritability, poor arm/leg coordination, loss of nerve transmission
Wet beriberi Edema, enlarge heart, heart failure
Wenicke-Koisakoff Syndrome
Mainly in alcoholics Alcohol diminishes thiamin absorption Alcohol increases thiamin excretion Poor quality diet
Involuntary eye movement; double vision Ataxia: staggering, poor muscle
coordination Mental confusion, “drunken stupor”
Riboflavin Coenzymes:
Flavin mononucleotide (FMN) Flavin adenine dinucleotide (FAD)
Oxidation-reduction reactions Electron transport chain Citric Acid Cycle Catabolism of fatty acids: beta oxidation FMN shuttles hydrogen ions and electrons to
into the electron transport chain
Food Sources of Riboflavin
Milk/products Enriched grains Liver Oyster Brewer’s yeast Sensitive to uv radiation (sunlight) Stored in paper, opaque plastic containers
RDA for Riboflavin
1.1 mg/day for women 1.3 mg/day for men Average intake is above RDA Toxicity not documented
Deficiency of Riboflavin
Ariboflavinosis Glossitis, cheilosis, seborrheic dermatitis,
stomatitis, eye disorder, throat disorder, nervous system disorder
Niacin
Nicotinic acid (niacin) & nicotinamide (niacinamide)
Coenzyme Nicotinamide adenine dinucleotide (NAD) Nicotinamide adenine dinucleotide phosphate
(NADP) Oxidation-reduction reaction
Food Sources of Niacin Mushroom Enriched grains Beef, chicken, turkey, fish, eggs,milk
Amino acid tryptophan can be converted to niacin Heat stable; little cooking loss 60mg tryptophan can be converted into 1 mg
niacin Estimate by dividing the total gram of protein by
6
Deficiency of Niacin Pellagra
3 Ds: Dermatitis, dementia, diarrhea appeared in Europe in early 1700s when corn
became staple food corn lacks niacin and tryptophan
Niacin as a Medicine
75-100 x RDA can lower LDL and increase HDL Slow/ reverse progression of atherosclerosis
with diet and exercise Toxicity effects
Flushing of skin, itching, nausea, liver damage
Content Review
How are water-soluble vitamins different from fat-soluble vitamins?
Many of the B vitamins all function as a coenzyme, what is a coenzyme?
What disease is associated with a deficiency of niacin?
What disease is associated with a deficiency of thiamin?
What is the Enrichment Act? What nutrients are involved?
Pantothenic Acid Part of Coenzyme-A Essential for metabolism of CHO, fat,
protein
Glucose
Fatty acids Acetyl-CoA Amino Acids
Alcohol
Food Sources of Pantothenic Acid
Meat Milk Mushroom Liver Peanut Adequate Intake = 5 mg/day Average intake meets AI
Biotin Free and bound form Biocytin (protein bound form)
Freed by Biotinidase in small intestine Infant with genetic defect : low levels of
biotinidase Metabolism of CHO, fat, protein (C
skeleton) DNA synthesis
Functions of Biotin
Required to convert pyruvate to oxaloacetate (TCA cycle) and thus ATP production.
Required for fatty acid synthesis Breaks down leucine Sources
Widely distributed in foods and is produced by intestinal bacteria
Liver, egg yolk , whole grains, cauliflower are good food sources
Avidin in raw egg whites bind biotin
Biotin Needs
Adequate Intake is 30 ug/day for adults This may overestimate the amount
needed for adults No Upper Limit for biotin
Biotin Deficiency
Rare High intake of raw egg white diet Alcoholics Biotinidase deficiency Anticonvulsant drug use Signs & symptoms: skin rash, hair loss,
convulsion, neurological disorders, impaired growth in children
Vitamin B-6 family: Pyridoxal, Pyridoxine, Pyridoxamine
Main coenzyme form: pyridoxal phosphate (PLP)
Activate enzymes needed for metabolism of CHO, fat , protein
Transamination Synthesis of hemoglobin and oxygen binding
and white blood cells Synthesis of neurotransmitters
Functions of Vitamin B-6 Participates in 100+ enzymatic reactions Decarboxylation of amino acid (decarboxylase) Transamination reaction (transaminase) Structural rearrangement of amino acids (racemase) Heme synthesis CHO metabolism Lipid metabolism Neurotransmitter Synthesis Conversion of tryptophan to niacin
Other Role of Vitamin B-6
Homocysteine From the metabolism of methionine Produces toxic effect on arterial walls
(atherosclerosis) Metabolized by vitamins B-6, B-12 and folate
Food Sources of Vitamin B-6
Meat, fish, poultry Whole grains (not enriched back) Banana Spinach Avocado Potato Heat and alkaline sensitive
RDA for Vitamin B-6
1.3 - 1.7 mg/day for adults Daily Value set at 2 mg Average intake is more than the RDA
Deficiency of Vitamin B-6
Microcytic hypochromic anemia Seborrheic dermatitis Convulsion, depression, confusion Reduced immune response Peripheral nerve damage
Factors That Affect B-6 Requirement
Alcohol reduces PLP formation
L-DOPA-medication used to treat Parkinson’s disease and
Isoniazid-antituberculosis medication Reduce blood concentration of PLP Need extra vitamin B-6
B-6 As A Medicine?
PMS B-6 to increase the level of serotonin Improve depression Not a reliable treatment
Toxicity potential Can lead to irreversible nerve damage
with > 200 mg/day Upper level set at 100 mg/day
Folate (Folic acid, Folacin)
Consists of pteridine group, para-aminobenzoic acid (PABA), and glutamic acid
Coenzyme form: tetrahydorfolic acid (THFA) Produce many identical deficiency signs and
symptoms as vitamin B-12 Vitamin B-12 is needed to recycle folate
coenzyme
Absorption, Metabolism of Folate Absorbed in the monoglutamate form with the
help of folate conjugase Actively absorbed during low to moderate intake Passively absorbed during high intake Delivered to the liver where it is changed back to
the polyglutamate form Mostly stored in the liver Excreted in the urine and bile (enterohepatic circulation)
Functions of Folate
DNA synthesis Transfer of single carbon units Synthesis of adenine and guanine Anticancer drug methotrexate
Homocysteine metabolism Neurotransmitter formation Amino acid metabolism
Food Sources of Folate
Liver Fortified breakfast cereals Grains, legumes Foliage vegetables Susceptible to heat, oxidation, ultraviolet
light
RDA for Folate
400 ug/day for adults Daily Value is set at 400 ug Dietary folate equivalents (DFE)
are units to express folate needs throughout life except during child bearing years
DFE = [(total synthetic folate) x 1.7] + total food folate intake
Deficiency of Folate
Similar signs and symptoms of vitamin B-12 deficiency
Pregnant women Alcoholics
Interferes with the enterohepatic circulation of bile/folate
Megaloblastic Anemia
Neural Tube Defects
Spina bifida Anencephaly Importance of folate
before and during pregnancy
Toxicity of Folate
Epilepsy Skin, respiratory disorder FDA limits nonprescription supplements to
400 ug per tablet for non-pregnant adults OTC Prenatal supplement contains 800 ug Upper Level for synthetic folate is 1 mg Excess can mask vitamin B-12 deficiency
Vitamin B-12
Cyanocobalamin, methlcobalamin, 5-deoxyadenosylcobalamin Contains cobalt Folate metabolism Synthesized exclusively by bacteria, fungi, and
algae Maintenance of the myelin sheaths Rearrange 3-carbon chain fatty acids so can
enter the Citric Acid Cycle
Absorption of Vitamin B-12
Therapy for Ineffective Absorption
Many factors can disrupt this process Monthly injections of vitamin B-12 Vitamin B-12 nasal gel Megadoses of vitamin B-12 to allow for
passive diffusion
Food Sources of Vitamin B-12
Synthesized by bacteria, fungi and algae (Stored primarily in the liver) Animal products Organ meat Seafood Eggs Hot dogs Milk
RDA for Vitamin B-12
2.4 ug/ day for adults and elderly adults
Average intake exceeds RDA B-12 stored in the liver; little is lost Non-toxic
Functions of Vitamin B-12
Helps convert methylmalonyl CoA to succinyl CoA (citric acid cycle)
Recycles folate coenzymes Nerve functions
Maintains myelin sheath Megalobalstic anemia
Deficiency of Vitamin B-12 Pernicious anemia
Nerve degeneration, weakness Tingling/numbness in the extremities
(parasthesia) Paralysis and death Looks like folate deficiency
Usually due to decreased absorption ability Achlorhydria, especially in elderly
Homocysteine and the B Vitamins
Choline
Absorbed from the small intestine All tissues contain choline Excess choline is converted to
betaine
Functions of Choline
Precursor for acetylecholine (neurotransmitter) Precursor for phospholipids (such as lecithin) Involved in the export of VLDL from the liver Precursor for the methyl donor betaine Assist in the conversion of homocysteine to
methionine
Food Sources of Choline
Widely distributed Milk Liver Eggs Peanuts Lecithins added to food Deficiency rare
Needs for Choline Adequate Intake is 550 mg/day for adult
males Adequate Intake is 425 mg/day for adult
females Normal consumption is ~700-1000 mg/day High doses associated with fishy body odor,
vomiting, salivation, sweating, hypotension, GI effects
Upper Level is set at 3.5 g/day (3500 mg/day)
Deficiency of Choline
Decrease choline stores Liver damage (fatty livers)
Vitamin C
Ascorbic acid (reduced form), dehydroascorbic acid (oxidized form)
Synthesized by most animals (not by human) Absorbed by a specific energy dependant
transport system Passive transport if intake is high Decrease absorption with high intakes Excess excreted
Functions of Vitamin C
Reducing agent (antioxidant) Iron absorption Synthesis of carnitine, tryptophan to serotonin,
thyroxine, cortiscosteroids, aldosterone, cholesterol to bile acids
Immune functions Synthesis of other compounds Questionable as to vitamin C’s role as an
antioxidant in people
Collagen Synthesis
Food Sources of Vitamin C
Citrus fruits Potatoes Green peppers Cauliflower Broccoli Strawberries Romaine lettuce Spinach
Easily lost through cooking
Sensitive to heat Sensitive to iron,
copper, oxygen
RDA for Vitamin C
90 mg/day for male adults 75 mg/day for female adults +35 mg/day for smokers Average intake ~72 mg/day Fairly nontoxic (at <1 gm) Upper level is 2 gm/day Excess intake will not cure the common cold
Deficiency of Vitamin C
Scurvy Deficient for 20-40 days Fatigue, pinpoint hemorrhages Bleeding gums and joints, hemorrhages Associated with poverty
Vitamin-Like Compounds
Carnitine Inositol Taurine Lipoic acid Synthesized in the body at the expense of
amino acids and other nutrients
Carnitine
Found in meat and dairy products Synthesized in the liver from amino acids
lysine and methionine Transports fatty acids into the
mitochondria Aids in the removal of excess organic
acids
Inositol
Myo-inositol Found in animal products Synthesized from glucose Precursors to eicosanoids Metabolizes calcium ions Metabolism is altered in people with
diabetics, multiple sclerosis, kidney failure, certain cancers
Taurine Found only in animal products Synthesized from methionine and cysteine Associated with the photoreceptor in the eye Antioxidant activity in the white blood cell and
pulmonary tissue CNS function, platelet aggregation, cardiac
contraction, insulin action, cell differentiation and growth
Lipoic Acid
Found in meats, liver, and yeast Redox agent Needed in reactions in which CO2 is lost
from a substrate Regenerates vitamin C and glutathione
Bogus “Vitamins”
Para-aminobenzoic acid (PABA) Part of folate, but not able to make folate A part of a B-complex family for bacteria
Laetrile “Vitamin B-17” Contains cyanide, promoted as a cancer cure
Bioflavonoids “Vitamin P” --no nutritional requirement
Pangamic Acid “Vitamin B-15” and is illegal
Cancer
Many diseases Formation of tumors (neoplasms)
Benign Malignant
Types of Cancers
Carcinomas Cells that covers the body, including the secretory
organs Sarcomas
Connective tissues and bones Leukemias
Blood forming tissues Lymphomas
Lymph nodes or lymphoid tissues
Cancer Deaths
Carcinogenesis
Protooncogenes Genes that cause a resting cell to divide
Tumor Suppressor Genes Genes that prevent cells from dividing P53 gene finds error on the DNA and repairs it
Oncogene The cancer gene A protoonocogene out of control
DNA Repair Mechanism
Cell Replication
Telomeres Caps at the ends of chromosomes
Telomerase Enzyme that maintains the length and completeness Daughter cells are slightly shorter and telomerase
activity decreases Cell undergoes apoptosis
Malignant tumor cells, the telomerase activity increases—the cells can live indefinitely
Cancer Initiation, Promotion, and Progression
Cytochrome P-450
Prevents cancer initiation In the liver and intestinal cells Converts dangerous
compounds into harmless water-soluble metabolites
Cancer Initiation
Exposure to carcinogen Alteration of DNA Is relatively short
Cancer Promotion
May last for months or years Damage is “locked” in Cell division increases
Promoters: estrogen, alcohol, maybe dietary fat
Decrease time available for repair
Cancer Progression
Final stage Cancer cells proliferate and form a mass Invade surrounding tissue Metastasize to other tissues Heredity can only explain a small
percentage of cancers Environment contributes to most cancer
Role of Diet Excessive intake of calories increases the
risk of cancer Excessive body fat affects sex hormone
production High intake of fruits and vegetables is
associated with lower risk High intake of meats and protein is
associated with higher risk Excessive alcohol increases the risk Excessive charcoal broiling increases risk Nitrosamines (from nitrite) increases risk Mycotoxins (from fungi) increases risk
Fat and Cancer
The National Academy of Sciences recommends 30% of total calories from fat
Effects of the type of fat to cancer There are still wide gaps in knowledge
linking fat and cancer Excessive intake is a more likely cause
Calcium,Vitamin D and Cancer
Calcium intake is inversely related to cancer
Calcium binds to bile acids in the colon Vitamin D inhibits progression of
cancerous polyps Vitamin D inhibits rapid colon/rectal cell
growth in patients with ulcerative colitis
Recommendations to Reduce the Risk for Cancer
Remain physically active Avoid obesity Engage in physical training that promotes lean
muscle mass Consume abundance of fruits and vegetables Consume plenty of low-fat/nonfat dairy products Avoid high intakes of red meat and animal fat Avoid excessive alcohol
Warning Signs (CAUTION)
Early detection is critical Unexplained weight loss A change in bowel or bladder habits A sore that does not heal Unusual bleeding or discharge A thickening or lump in the breast or elsewhere Indigestion or difficulty in swallowing An obvious change in a wart or a mole A nagging cough or hoarseness