Ex.6 - Micronutrients (59-60) Flashcards
Daily values
Determined by FDA for a daily diet of 2,000 calories a day
-Originally based on RDA in 1968
Dietary reference intakes
System of nutrition recommendations from the institute of medicine of the National Academies
-Dietary reference intakes: Guiding principles for nutrition labeling and Fortification (2003)
-Replaced original recommended dietary allowance (RDA)
-Provides several different types of reference values:
-Estimated average requirement (EAR)
-Recommended dietary allowance (RDA)
-Adequate intake (AI)
Tolerable upper intake levels: (UL)
Dietary reference intakes explained
Estimated average requirement (EAR)
-The amount of nutrient estimated to meet the need of 50% of the healthy individuals in an age and gender group
Recommended dietary allowance (RDA)
-Two standard deviations above the EAR
-Sufficient to meet the need of nearly all (97-98%) healthy individuals in a group
Adequate intake (AI)
-Used when scientific evidence is inadequate to set an EAR
-Approximations of the average nutrient intake by a healthy population
Tolerable upper intake level (UL)
-The max level of daily intake of a nutrient w/o any health risk
Micronutrients
Vitamins:
Fat-soluble: Vitamin A, Vitamin D, Vitamin E, Vitamin K
Water soluble: group of vitamin’s B and C
Minerals;
Macrominerals: Ca2+ and Mg2+
Trace minerals: iron, iodine, zinc, copper, selenium chromium, manganese, molybdenum, fluoride, boron
Vitamins
Organic compounds that are essential in the diet to promote and regulate body function
When insufficient in diet, deficiency symptoms occur
Named alphabetically in the order of their discovery:
-B vitamins were initially thought to be one chemical substance
-Only B6 and B12 are referred to by the numbers
Grouped into fat and water soluble vitamins
-Each group shares similar absorption, excretion, and storage properties
Vitamins and names
B1 - thiamin
B2 - Riboflavin
B3 - Niacin
B5 - Panthoenic acid
B6 - Pyridoxine
B7 - Biotin
B9 - Folic acid
B12 - Cobalamin
Vitamin A
Retinol, retinal and retinoic acid
Produced from Carotenoids, organic pigments in plants
Cis-retinal reversibly associates with opsins and function as light sensor
-Vitamin A deficiency may cause night blindness
Vitamin A - Retinoic Acid
Retinoic acid function as hormones, regulating cell growth, and differentiation
-Associates with nuclear receptors: Retinoic acid receptors (RARs) and retinoid X receptors (RXR)
-Carotenoids are effective antioxidants; may reduce the risk of cancers
-Stored in the liver as retinol palmitate
-Dietary sources: dark green and yellow vegetables, liver, egg yolk, butter, and whole milk
Deficiency is rare, but
40-60% of Americans Consume less than 2/3 of RDA
Vitamin D
Function as steroid hormones maintaining calcium homeostasis
Synthesized from an intermediate in cholesterol biosynthesis
Produced photochemically in the skin
Insufficient exposure to sunlight may cause vitamin D deficiency
-Rickets in young children and osteomalacia in adults
-Dietary sources: Vitamin D milk, saltwater, fish, liver and egg yolk
Vitamin E
Occurs in diet as tocopherols and tocotrienols
Naturally occurring antioxidants protecting unsat fatty acids
Accumulate in circulating lipoproteins, cell membranes, and fat deposits
Reduce the risk of CV disease by preventing oxidation of LDL
-The oxidized form of LDL is atherogenic
Dietary sources: Vegetable oils rich in polyunsaturated fatty acids
Deficiency is rare
Vitamin K
Carboxyglutamic acid residues allow proteins to bind Ca2+
-Essential for blood clotting
-Several proteins involved in blood coagulation require y-carboxyglutamic acid residues for Ca2+ binding (ex. Prothrombin)
Essential for bone mineralization
-Several proteins in bone require y-carboxyglutamic acid residues for binding to hydroxyapatatite (Osteocalcin)
Vitamin K cont
In the carboxylation rxn, Vitamin K is converted to an inactive epoxide for m
Regeneration of the active form REQUIRES vitamin K epoxide reductase
Warfarin
-Anticoagulant, vitamin K antagonist
-Prevent thrombosis
-Inhibits K epoxide reductase
Dietary sources:
-Vitamin K1 in green vegetables
-Vitamin K2 synthesized by intestinal bacteria
deficiency is rare
Thiamin - B1
Thiamin pyrophosphate - functions as a cofactor in enzymatic catalysis
-Thiazole ring forms carbanion, a strong nucleophile
-ex: pyruvate dehydrogenase, (Pyruvate-> acetyl CoA)
thiamin Triphosphate - function in transmission of nerve impulse in peripheral nerve membranes
Severe thiamin deficiency is known as beriberi
-Characterized by muscular atrophy and weakness
-May occur in populations exclusively relying on polished rice for food or in alcoholics
Riboflavin (B2)
Precursor of cofactors used in many redox rxns
-Flavin adenine dinucleotide (FAD)
Flavin mononucleotide (FMN)
Riboflavin deficiency is very rare
-Symptoms; angular cheilitis, glossitis, and scaly dermatitis
Usually seen in chronic alcoholics
Rich in milk, meat, eggs, and cereal products
Niacin - B3
niacin (nicotinic acid) and Niacinamide (nicotinamide) in diet
Converted to cofactors, NAD and NADP
-Electron acceptors or hydrogen donors
-Essential in many redox rxns and cellular respiration
-NAD is also used for ADP-ribosylation
Severe deficiency is known as pellagra
-Dermatitis, diarrhea, and dementia
Rare: Primarily seen in alcoholics, patients w/severe malabsorption, and elderly on very restricted diets
Rich in meats, peanuts, and enriched cereals
Pyridoxine (B6)
Pyridoxine, Pyridoxamine and pyridoxal in diet
Converted to a cofactor, pyridoxal phosphate
-Synthesis of neurotransmitters
-Synthesis of sphingolipids
Deficiency:
-Mild: Irritability, nervousness, and depression
-Severe: Peripheral, neuropathy and convulsions
Rich in meat, vegetables and whole-grain cereals
A significant fraction of US population consumes less than recommended intake
Biotin (B7)
Serves as a cofactor for activation of carbon dioxide in carboxylase enzymes
-Ex: Acetyl-CoA carboxylase (aacetyl-CoA-> malonyl-CoA)
Covalently bound to lysine side chains in enzymes
Rich in a wide range of food sources
Deficiency is rare
-May occur when raw egg white is consumed regularly; avidin in egg white forms a tight complex with biotin
_Common in pregnant women
Folic acid (B9)
Converted to tetrahydrofolate a one-carbon carrier in enzyme rxns
Used in synthesis of Amino acids and nucleotides
Essential for DNA synthesis and cellular proliferation
Rich in a wide range of food sources
Deficiency inhibits DNA synthesis
-Produces abnormal red blood cells - anemia
-Increases the risk of birth defects, especially neural tube defect
-Common in alcoholics
Cobalamin (B12)
Contains Co in a coordination state of six
Exists as a complex w/proteins
Required for two rxns in human
-Methionine synthase (homocysteine -> methionine
-Methymalyonyl-CoA-> succinyl-CoA)
When insufficient, homocysteine and methylmalonic acid accumulate, which causes anemia and neurological damage
Deficiency is rare except in patients with severe malabsorption diseases and long-term vegetarians
Vitamin C
Ascorbic Acid
Functions as a cofactor for several oxidases
-Required for hydroxylation of lysine and proline side chains, which is necessary for collagen stability
-Proper collagen stability is essential for maintenance of normal connective tissue, wound healing ,and bone formation
Nonenzymatic reducing agent
-Aids in absorption of iron by reducing it to Fe2+ in the stomach
-Protects vitamin A, vitamin E, and some B vitamins from oxidation
Vitamin C deficiency
Capillary fragility (mild)
-Easy bruising
-Decreased immunocompetence
Scurvy (severe)
-Decreased wound healing
-Osteoporosis
-Hemorrhaging
-Anemia
Smokers require more vitamin C
The use of megadoses of vitamin C to prevent and to cure common cold is controversial
Calcium
Most abundant mineral in the body
-Makes bones
-Serves as a second messenger
-Required for many enzymes
-Essential for blood coagulation and muscle contractility
Maintenance of constant serum level is vital
-Elaborate homeostatic control system
-Bones serve as reservoir
-Dietary insufficiency results in net loss of Ca2+ from the bones
-Vitamin D is required for optimal utilization of Ca2+
-Exercise facilitates Ca2+ utilization for bone formation
Calcium continued
Symptoms of Ca2+ deficiency resembles vitamin D deficiency
May contribute to osteoporosis
-Achieving max bone density from age 10-35 critical in reducing risk of osteoporosis later
-Proper calcium intake from the diet and exercise maximizes bone density
Mild deficiency may cause muscle cramps
-Significant portion of low income children and adult females do not get adequate Ca2+
Dietary sources:
-Dairy products
Nuts, beans, seeds, and seaweeds
Iron
Required for O2 transport, energy metabolism, cell proliferation and immune defense
Blood loss including menstruation increases need
-Need 2 fold more than adult males
Iron homeostasis = tightly regulated
-Essential for life but also extremely toxic
-Free iron generates free radicals
-Normally sequestered in the cell by ferritin and in the blood by transferrin
-Iron deficiency anemia is widespread in children and menstruating females
Trace minerals- Iodine
Used for synthesis of thyroid hormones
The best natural food source is seafood
Deficiency was endemic in inland populations
-Goiter
-Cretinism
Routinely added to table salt
Trace minerals- Zinc
Required for many mealloenzymes and zinc finger proteins
-Deficiency in children results in poor growth and impairment of sex development
Deficiency may cause poor wound healing, dermatitis, and impaired immune function
-Zinc intake may be marginal for many individuals
Trace minerals- Copper
Required for many enzymes
Ex- Lysyl oxidase, necessary for collagen cross linking
-Deficiency may cause anemia, bone demineralization, and blood vessel fragility
Trace minerals - Selenium
Incorporated into ~25 selenoproteins in humans
Contain Selenocysteine residues, which are incorporated during translation
Selenocystyl-tRNA binds to UGA codons in MRNA with a special sequence in 3’ -untranslated region
Deficiency is rare
