Transcript Water Soluble Vitamins 2

Water-Soluble Vitamins
Water soluble
Readily excreted – expensive urine
Can be lost from food by cooking/storage
Typically work as part of enzymes in metabolism
Relatively high absorption rate
Severe deficiencies rare
Vitamins – Niacin, Thiamine, Folic Acid, Riboflavin, B12,
and C.
Enrichment Act of 1941 and 1998
Milling of rice, wheat, oats, etc…
significantly reduces nutritional quality
Whole grains contain original nutrients
Enrich with
thiamin, riboflavin, niacin, folate, iron
Enriched grains still
deficient in B-6, magnesium and zinc
Thiamin
Destroyed by alkaline and heat
Coenzyme: Thiamin pyrophosphate (TPP)
Absorbed in the jejunum by a carrier-mediated system
Transported by RBC in the blood
Deficiency
Beriberi
Weakness, nerve degeneration, irritability, poor
arm/leg coordination, loss of nerve transmission
Edema, enlarge heart, heart failure
Food Sources of Thiamin
Wide variety of food
White bread, pork, hot dogs, luncheon meat, cold cereal
Enriched grains/ whole grains
Thiaminase found in raw fish
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
Riboflavin
Coenzymes:
Flavin mononucleotide (FMN)
Flavin adenine dinucleotide (FAD)
Oxidation-reduction reactions
Electron transport chain
Citric Acid Cycle
Catabolism of fatty acids
Absorption, Transport, & Metabolism of
Riboflavin
HCL in the stomach release riboflavin from its
bound forms
Absorption
Active or facilitated transport during low to
moderate intake
Passive absorption during high intake
Increase with intake
Transported by a protein carrier in the blood
Functions of Riboflavin
Accepts electrons
Electron Transport Chain
FAD
FADH2
Succinate
Fumarate
Citric Acid Cycle
Participates in beta oxidation
FMN shuttles hydrogen ions and electrons to into the electron
transport chain
Metabolism of oxidized glutathione
Deficiency of Riboflavin
Ariboflavinosis
Glossitis, cheilosis, seborrheic dermatitis, stomatitis, eye
disorder, throat disorder, nervous system disorder
Occurs within 2 months
Usually in combination with other deficiencies
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Glossitis (Fig. 10-4)
Who is at Risk For Deficiency?
Rare
Low milk/dairy intake
Alcoholics
Long term phenobarbital use
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
Niacin
Nicotinic acid (niacin) & nicotinamide (niacinamide)
Coenzyme
Nicotinamide adenine dinucleotide (NAD)
Nicotinamide adenine dinucleotide phosphate
(NADP)
Oxidation-reduction reaction
Metabolic reactions
Absorption, Transport and Storage of Niacin
Readily absorbed from the stomach and small
intestine
Absorption: active transport and passive diffusion
Transported from the liver to all of the tissues where
it is converted to the coenzymes
Deficiency of Niacin
Pellagra
3 Ds
Occurs in 50-60 days
Decrease appetite & weight
Prevented with an adequate protein diet
Enrichment Act of 1941
Only dietary deficiency disease to reach epidemic proportions
in the U.S.
Who is at risk?
(Untreated) corn as main staple, poor diet,
Hartnup disease, alcoholics
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Dermatitis of Pellegra (Fig. 10-5)
Food Sources of Niacin
Mushroom
Enriched grains
Beef, chicken, turkey, fish
Heat stable; little cooking loss
60mg tryptophan can be converted into 1 mg niacin
RDA for Niacin
14 NE/day for women
16 NE/day for men
Niacin as a Medicine
75-100 x RDA can lower LDL and TG and increase HDL
Slow/ reverse progression of atheroscelerosis with diet and
exercise
Toxicity effects
Flushing of skin, itching, nausea, liver damage
Biotin
Free and bound form
Biocytin (protein bound form)
Biotinidase in small intestine
Metabolism of CHO, fat, protein (C skeleton)
DNA synthesis
Functions of Biotin
Assists in the addition of CO2 to substances
Carboxylation of acetyl-CoA to form malonyl-CoA for the
elongation of a fatty acid chain
Addition of CO2 to pyruvate to yield oxaloacetate
Breaks down leucine
Allows 3 essential amino acids to be oxidized for energy
Food Sources of Biotin
Cauliflower, yolk, liver, peanuts, cheese
Intestinal synthesis of biotin
Biotin content only available for a small number of foods
Unsure as to bioavailablity of synthesized biotin
We excrete more than we consume
Avidin inhibits absorption
> a dozen of raw eggs a day to cause this effect
Biotin Needs
Adequate Intake is 30 ug/day for adults
This may overestimate the amount needed for adults
No Upper Limit for biotin
Who is at Risk For 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: 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
Deficiency of Vitamin B-6
Microcytic hypochromic anemia
Seborrheic dermatitis
Convulsion, depression, confusion
Reduce immune response
Peripheral nerve damage
Who is at risk?
Elderly
Alcoholics
Alcohol decreases absorption
Destroy the coenzyme form
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 mg/day for adults
1.7 mg/day for men over 50
1.5 mg/day for women over 50
Daily Value set at 2 mg
Average intake is more than the RDA
Factors That Affect B-6 Requirement
L-DOPA-medication used to treat Parkinson’s disease and
Isoniazid-antituberculosis medication
Reduce blood concentration of PLP
Need extra vitamin B-6
Preeclampsia
Reduce blood concentration of PLP
Will supplementation will reduce preeclampsia?
B-6 As A Medicine?
PMS
B-6 to increase the level of serotonin
Improve depression
Not a reliable treatment
Carpal tunnel syndrome
Toxicity potential
Can lead to irreversible nerve damage with > 200 mg/day
Folate (Folic acid, Folacin)
Consists of pteridine group, para-aminobenzoic acid (PABA),
and glutamic acid
Coenzyme form: tetrahydorfolic acid (THFA)
Functions of Folate
DNA synthesis
Transfer of single carbon units
Synthesis of adenine and guanine
Anticancer drug methotrexate
Homocysteine metabolism
Neurotransmitter formation
Deficiency of Folate
Similar signs and symptoms of vitamin B-12 deficiency
Pregnant women
Alcoholics
Interferes with the enterohepatic circulation of bile/folate
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Neural Tube Defects
(Fig. 10-8)
Spina bifida
Anencephaly
Importance of folate before
and during pregnancy
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
Vitamin B-12
Cyanocobalamin. methlcobalamin,
5-deoxyadenosylcobalamin
Contains cobalt
Folate metabolism
Maintenance of the myelin sheaths
Rearrange 3-carbon chain fatty acids so can enter the Citric
Acid Cycle
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Absorption of Vitamin B-12 (Fig. 10-10)
Functions of Vitamin B-12
Helps convert methylmalonyl CoA to succinyl CoA (citric acid
cycle)
RBC formation
Nerve functions
Maintains myelin sheath
Megalobalstic anemia
Deficiency of Vitamin B-12
Pernicious anemia
Never 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
Injection of B-12 needed
Takes ~20 years on a deficient diet to see nerve destruction
Who is at Risk For Deficiency?
Vegans
Breastfed infants of vegan moms
Elderly
Individuals with AIDS or HIV
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
Non-toxic
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
Cancer prevention?
Collagen synthesis
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Collagen Synthesis (Fig. 10-12)
Antioxidant
Can donate and accept hydrogen atoms readily
Water-soluble intracellular and extracellular
antioxidant
Must be constantly enzymatically regenerated
Needs are higher for smokers
Deficiency of Vitamin C
Scurvy
Deficient for 20-40 days
Fatigue, pinpoint hemorrhages
Bleeding gums and joints. Hemorrhages
Associated with poverty
Rebound scurvy
immediate halt to excess vitamin C supplements
Who is at risk?
Infants, elderly men
Alcoholics, smokers
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 g/day
Warning to people with hemochromatosis, oxalate kidney
stones