Water Soluble Vitamins Flashcards
Vitamin C Chemical Name
Ascorbic Acid; Dehydroascorbic acid
Vitamin C RDA
90 mg/day for men
75 mg/day for women
Vitamin C absorption
Ascorbic acid by specific active transport system
Dehydroascorbic acid passively absorbed
Efficiency decreases with high intake
Food with Vitamin C
citrus fruits, peppers and green vegetables
Vitamin C storage
Serum and tissues: Pituitary and adrenal glands, eye, brain, kidneys, lungs, liver
Vitamin C excretion
urine
Functions of Vitamin C
antioxidant (in water based fluids) reducing agent- affects iron absorption Synthesis of body compounds: collagen Enhance immune system (free radical reduction) Detox of drugs and carcinigens
Vitamin C and E relationship
restores Vitamin E to active form so that it can continue to act as an antioxident
Collagen synthesis
fibrous protein giving strength to connective tissues; important in wound healing
Vitamin C and immune response
Supplemental vitamin C can reduce the severity and duration of illness- due to antioxidant properties
Vitamin C deficiency
Scurvy: Fatigue, pinpoint hemorrhages (petichiae)
Bleeding gums, poor wound healing, joint pain, fractures
Anemia, atherosclerotic plaques, depression
Who is at risk for Vitamin C deficiency
Alcoholics, elderly men, low fruit/veg intake, (smokers)
Vitamin C toxicity
GI distress, only achieved with supplementation
Measuring Vitamin C status
Serum ascorbic acid; leukocyte ascorbic acid (reflects tissue stores)
B Vitamins
Thiamin, Riboflavin, Niacin, B6, B12, Folate, Pantothenic Acid, Biotin
Thiamin Chemical Names
Thiamin pyrophosphate (TPP) is coenzyme
Thiamin Absorption
Active transport into bloodstream, passive if high
Thiamin Transport
via RBC in blood
Thiamin Storage
storage is poor, 50% in skeletal muscle
Thiamin Excretion
urine
Thiamin Function
Energy metabolism: takes part in decarboxylation and converting pyruvate to Acetyl CoA
Pentose synthesis: Transketolation, generates 5 C structures and helps with DNA and RNA
Nerve conduction: may affect release of acetylcholine
Thiamin Deficiency
Beri Beri: Peripheral neuropathy
Wernicke-Korsakoff Syndrome: Involuntary eye movement; double vision, ataxia: staggering, poor muscle coordination, mental confusion, “drunken stupor”
Thiamin Toxicity
No real toxicity, some issues with parenteral administration and can have a pharmacological affect with metabolic diseases
Thiamin Measurement
Functional assay, Transketolase in RBC (Blood)
Riboflavin (B2) Chemical name
Part of Coenzymes:
Flavin adenine dinucleotide (FAD)
Flavin mononucleotide (FMN)
Thiamin Absorption
Active transport into bloodstream, passive if high
Thiamin Transport
via RBC in blood
Thiamin Storage
storage is poor, 50% in skeletal muscle
Thiamin Excretion
urine
Thiamin Function
Energy metabolism: takes part in decarboxylation and converting pyruvate to Acetyl CoA
Pentose synthesis: Transketolation, generates 5 C structures and helps with DNA and RNA
Nerve conduction: may affect release of acetylcholine
Thiamin Deficiency
Beri Beri: Peripheral neuropathy
Wernicke-Korsakoff Syndrome: Involuntary eye movement; double vision, ataxia: staggering, poor muscle coordination, mental confusion, “drunken stupor”
Thiamin Toxicity
No real toxicity, some issues with parenteral administration and can have a pharmacological affect with metabolic diseases
Thiamin Measurement
Functional assay, Transketolase in RBC (Blood)
Riboflavin (B2) Chemical name
Flavin adenine diphosphate
Flavin mononucleotide
Riboflavin Absorption
Active transport (passive if high)
Riboflavin transport
via protein carrier in blood (albumin)
Riboflavin storage
some storage in tissues: heart, liver, kidney
Riboflavin excretion
via urine
Riboflavin Functions
accepts/donates electrons
participates in oxidation-reduction reactions (in ETC and TCA cycle); catabolism of fatty acids
Niacin storage
from liver to tissues where it is converted to NAD and NADH
Who is at risk for Riboflavin deficiency?
alcoholics, phenobarbitol users, no milk intake
Riboflavin RDA
- 1 mg/d for women
1. 3 mg/d for men
Foods high in riboflavin
milk products, enriched or whole grains, liver
Measuring Riboflavin
Functional assay, Glutathione reductase activity in RBCs (blood)
Niacin RDA
14 NE/day for women
16 NE/day for men
Foods high in Niacin
all protein containing foods, beef, pork, poultry, fish, milk, eggs, peanut butter, nuts, whole and enriched grains
Niacin absorption
stomach and small intestine, active transport (passive if concentration is high)
Niacin transport
30% protein bound
Niacin storage
from liver to tissues where it is converted to NAD and NADH
Niacin excretion
via urine as other metabolites
Niacin Functions
participates in oxidation reduction reactions
participates in energy metabolism (glycolysis, TCA, ETC)
Niacin deficiency
Pellagra: only US malnutrition epidemic, in Southeastern US due to corn being the major food source in diet; cured in 1917 (Goldberger)
affects skin, GI tract, CNS; worsened by sun exposure
Vitamin B6 storage
liver and muscle tissue
Result of Pellagra in US
Enrichment Act of 1941
Vitamin B6 excretion
urine
Niacin toxicity
no toxicity from food alone
Supplementation: niacin flush, GI disturbances, liver damage
used pharmacologically to lower LDL and raise HDL
Measuring Niacin
No functional test, measure metabolites in urine: ratio of 2 major products of niacin metabolism
Vitamin B6 Chemical name/main coenzyme
Pyridoxal phosphate (PLP)
Vitamin B6 RDA
1.3 - 1.7 mg/day for adults (differs based on protein intake and medications)
B6 toxicity
Nerve damage causing numbness
Muscle weakness, inability to walk Convulsions Skin lesions Depression, fatigue, irritability, headaches *mostly due to supplementation
Measuring B6 status
*Erythrocyte transketolase activities (functional); Plasma PLP (blood), urinary 4- pyridoxic acid
Vitamin B6 storage
mostly taken up by liver
Vitamin B6 transport
protein bound in blood (albumin)
B12 Foods
produced by microorganisms (bacteria, fungi, algae); only food source is animal products: organ meat, seafood, meat, poultry, eggs, cheese, milk, fortified cereals
Vitamin B6 functions
Amino acid metabolism (transamination, deamination)
Neurotransmitter synthesis
Heme synthesis (erythropoiesis)
Vitamin B6 and homocysteine metabolism
AA that is not in food, metabolic intermediate that can lead to athlerosclerosis
B6 (and B12 and folate) metabolize homocysteine and lower levels in the body
B6 deficiency
Microcytic hypochromic anemia: Small cells with little color
Who is at risk for B6 deficiency
Alcoholics (acetaldehyde)
Infants, elderly
Renal patients
B6 toxicity
Nerve damage causing numbness
Muscle weakness, inability to walk Convulsions Skin lesions Depression, fatigue, irritability, headaches *mostly due to supplementation
Measuring B6 status
*Erythrocyte transketolase activities (functional); Plasma PLP (blood), urinary 4- pyridoxic acid
Ineffective B12 absorption
Achlorhydria- slow stomach acid Low IF Increasing age Bacterial overgrowth Medications to reduce acid production Malabsorption problems
B12 RDA
2.4 ug/ day for adults
B12 Foods
produced by microorganisms (bacteria, fungi, algae); only food source is animal products
R Protein
produced by salivary glands, binds with B12 in stomach acid which protects B12 from being consumed by intestinal bacteria. Protease (trypsin from pancreas) cleaves R protein off of B12 in small intestine
Intrinsic Factor
binds with B12 in small intestine and is absorbed into blood stream and bound to the transport protein transcobalamin
B12 absorption
B12-IF complex absorbed slowly via receptors, Calcium is involved. Passive diffusion if concentration is high
Folate Chemical Name
Folate, Folic acid, folacin
Coenzyme form: Tetrahydrofolate (THF)
B12 storage
stored in liver for years
B12 excretion
via bile, very little in urine
Ineffective B12 absorption
Achlorhydria- slow stomach acid Low IF Increasing age Bacterial overgrowth Medications to reduce acid production Malabsorption problems
B12 Functions
DNA synthesis Cell division Folate metabolism: Conversion of homocysteine to methionine Nerve function: maintains myelin sheath Odd numbered fatty acid catabolism
B12 deficiency
Pernicious anemia
Nerve degradation
Elevated homocysteine
Folate excretion
via urine and bile
Who is at risk for B12 deficiency?
Elderly (gastric dysfunction): Atrophic gastritis, Hypochlorhydria
Alcoholics
Gastrectomy patients
Intestinal tapeworm infestation
Strict vegetarians: Can take 20-30 years in adults, Can take < 1 year in infants born to vegan mothers
Measuring B12
Total B12 serum (blood); Methymalonic acid (urine), Shilling test for B12 deficiency from poor absorption
Folate Chemical Name
Folate, Folic acid, folacin
Coenzyme form: Tetrahydrofolate
Folate RDA
400 μg/day for adults
Foods with Folate
fortified breakfast cereals and grains, leafy and green vegetables, beans, legumes, orange juice, liver
Folate absorption
Absorbed in the monoglutamate form with the help of folate conjugase (impeded by Zn deficiency and conjugase inhibitors: legumes, cabbage)
Actively absorbed during low to moderate intake
Passively absorbed during high intake
Folate transport
Delivered to the liver where it is changed back to the polyglutamate form
Folate storage
liver
Folate excretion
via urine and bile
Folate Functions
DNA synthesis: transfer of single carbon units, synthesis of adenine and guanine (B12 and folate work together- needed to recycle THF)
Amino Acid metabolism: Neurotransmitter formation, Homocysteine metabolism
Folate Deficiency
Megaloblastic anemia
Neural Tube Defects
Elevated risk of heart disease
Increased cancer risk
Megaloblastic anemia
Decreased DNA synthesis
Failure of cells to divide
Neural Tube Defects
Spina bifida, anencephaly; important to take folate supplements during pregnancy
1996- Folate fortification became mandatory in Bread products, flour, corn grits, cornmeal, farina, rice, macaroni, and noodles
Who is at risk for folate deficiency
Pregnant women Alcoholics Elderly Use of certain medications: antacids, oral contraceptives, chemotherapy, epilepsy IBS, malabsorption people in low income communities
Measuring folate status
Plasma, serum, RBC levels (blood), FIGLU excretion (urine)
