2009 cengage-wadsworth chapter 11 macrominerals
TRANSCRIPT
2009 Cengage-Wadsworth
Chapter 11
Macrominerals
2009 Cengage-Wadsworth
Calcium
• Sources– Dairy, some seafoods
• Digestion, absorption, & transport– Digestion
• Present in relatively insoluble salts• If solubilized, can bind to other
compounds
2009 Cengage-Wadsworth
Calcium
• Absorption - 2 processes– Duodenum & proximal jejunum; saturable,
requires energy, involves calcium-binding transport protein (CBP), stimulated by calcitriol & low-calcium diets
– Small intestine, mostly jejunum & ileum; paracellular; passive diffusion, requires no carrier
– Factors influencing absorption» Vitamin D, lactose, phytate, oxalate,
divalent cations, fatty acids, type of supplement
2009 Cengage-Wadsworth
Calcium
• Transport– Bound to proteins (e.g. albumin, prealbumin),
complexed with sulfate, free
• Regulation of calcium concentrations– Extracellular calcium concentration regulation
» PTH» Calcitriol» Calcitonin
– Intracellular calcium concentration regulation
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Calcium
• Functions & mechanisms of action– Cortical bone vs. trabecular bone– Bone mineralization– Other roles
• Blood clotting• Nerve conduction• Muscle contraction• Enzyme regulation• Membrane permeability
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Calcium
• Interactions with other nutrients– Phosphorus– Protein– Sodium– Caffeine– Iron– Lead– Fatty acids
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Calcium
• Excretion– Urine, feces, skin
• Adequate Intake– 19-50 years: 1,000 mg– 51 & >: 1,200 mg
• Deficiency– Osteoporosis– Hypertension, colon cancer, obesity
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Calcium
• Toxicity– UL = 2,500 mg
• Assessment of nutriture– Serum calcium - tightly regulated by
hormones– Bone densitometry– Neuron activation– Dual-energy X-ray absorptiometry
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Phosphorus
• Sources– Meat, poultry, fish, eggs, dairy
• Digestion, absorption, transport, & storage– Digestion
• Hydrolyzed to inorganic phosphate
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Phosphorus
• Absorption - 2 processes– Saturable, carrier-mediated transport system
dependent on sodium & enhanced by calcitriol– Concentration-dependent facilitated diffusion– Factors influencing absorption
» Vitamin D, phytate, other minerals
• Transport & storage– Transported in inorganic & organic forms– In all cells, most in bone & muscle
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Phosphorus
• Functions & mechanisms of action– Bone mineralization– Nucleotide/nucleoside phophates
• Structural roles• Energy storage & transfer• Intracellular second messenger
– Phosphoproteins– Structural roles
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Phosphorus
– Acid-base balance– Oxygen availability
• Excretion– Urine (67%-90%) & feces (10%-33%)
• Recommended Dietary Allowance– 19 years & >: 700 mg
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Phosphorus
• Deficiency– Rare; renal patients, refeeding
• Toxicity– UL = 9-70: 4 g; >70: 3 g
• Assessment of nutriture– Serum concentrations– Urinary excretions
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Magnesium
• Sources– Coffee, tea, cocoa– Nuts, legumes, whole grains
• Absorption & transport– Absorption - 2 systems
• Saturable, carrier-mediated active transporter - low intakes
• Simple diffusion - higher intakes• Factors influencing absorption
2009 Cengage-Wadsworth
Magnesium
– Transport• 50%-55% free, 33% bound to protein,
13% complexed with ions
• Functions & mechanisms of action– Bone lattice & surface– >300 enzyme reactions as structural
cofactor or allosteric activator
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Magnesium
• Interactions with other nutrients– Calcium– Phosphorus– Potassium– Protein
• Excretion– Urine, feces (mostly unabsorbed)
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Magnesium
• Recommended Dietary Allowance– 19-30 years
• Men: 400 mg; women: 310 mg• Pregnancy: 350 mg; lactation; 310 mg
– 31 & >• Men: 420 mg; women: 320 mg• Pregnancy: 360 mg; lactation: 320 mg
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Magnesium
• Deficiency– Usually associated with illness
• Toxicity– UL = 350 mg (non-food sources)
• Assessment of nutriture– Serum concentrations– Renal excretion before & after
administration of Mg load
2009 Cengage-Wadsworth
Sodium
• Sources– Added salt
• Absorption, transport, & function– 3 pathways for absorption
• Na+/glucose cotransport system - whole small intestine
• Electroneutral Na+ & Cl- cotransport system - small intestine & proximal colon
• Electrogenic Na absorption mechanism - colon
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Sodium
– Transport• Free in blood
– Functions• Maintenance of fluid balance• Nerve transmission/impulse conduction• Muscle contraction
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Sodium
• Interactions with other nutrients– Calcium
• Excretion– Primarily urine, sweat
• Deficiency– Excessive sweating
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Sodium
• Adequate Intake & assessment of nutriture– AI = 1500 mg– UL = 2300 mg– Ion-selective electrode potentiometry
• Used on blood & other body fluids
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Potassium
• Sources– Unprocessed foods; some fruits &
vegetables, legumes, nuts, seeds
• Absorption, transport, & function– Absorbed by passive diffusion or K+/ H+-
ATPase pump– Contractility of smooth, skeletal & cardiac
muscle– Excitability of nerve tissue– Maintenance of electrolyte & pH balance
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Potassium
• Interactions with other nutrients– Calcium
• Excretion– Urine (~90%), feces
• Deficiency & toxicity– Hyperkalemia - high serum potassium– Hypokalemia - low serum potassium
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Potassium
• Adequate Intake & assessment of nutriture– AI = 4,700 mg– No UL for K from foods– Plasma K concentrations determined
by ion-selective electrode potentiometry
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Chloride
• Sources– Salt, eggs, fresh meat, seafood
• Absorption, transport, & secretion– Absorption similar to that of Na– Major secretory product of stomach
• Electrogenic Cl- secretion
– Disfunctional Cl transport - cystic fibrosis
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Chloride
• Functions– Major electrolyte– Gastric hydrochloric acid– Phagocytosis
– Exchange anion for HCO3- in RBC
• Excretion– 3 routes: GI tract, skin, kidneys
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Chloride
• Deficiency– Severe diarrhea & vomiting
• Adequate Intake & assessment of nutriture– AI = 2300 mg– UL = 3.6 g– Serum concentration
• Ion-selective electrode potentiometry• Coulometric titration
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Perspective 11
Macrominerals & Hypertension
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Hypertension
• Sodium• Potassium• Calcium• Magnesium• Other dietary factors