2009 Cengage-Wadsworth Chapter 11 Macrominerals

2009 Cengage-Wadsworth

Chapter 11

Macrominerals


Calcium

• Sources– Dairy, some seafoods

• Digestion, absorption, & transport– Digestion

• Present in relatively insoluble salts• If solubilized, can bind to other

compounds


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


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


Calcium

• Functions & mechanisms of action– Cortical bone vs. trabecular bone– Bone mineralization– Other roles

• Blood clotting• Nerve conduction• Muscle contraction• Enzyme regulation• Membrane permeability


Calcium

• Interactions with other nutrients– Phosphorus– Protein– Sodium– Caffeine– Iron– Lead– Fatty acids


Calcium

• Excretion– Urine, feces, skin

• Adequate Intake– 19-50 years: 1,000 mg– 51 & >: 1,200 mg

• Deficiency– Osteoporosis– Hypertension, colon cancer, obesity


Calcium

• Toxicity– UL = 2,500 mg

• Assessment of nutriture– Serum calcium - tightly regulated by

hormones– Bone densitometry– Neuron activation– Dual-energy X-ray absorptiometry


Phosphorus

• Sources– Meat, poultry, fish, eggs, dairy

• Digestion, absorption, transport, & storage– Digestion

• Hydrolyzed to inorganic phosphate


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


Phosphorus

• Functions & mechanisms of action– Bone mineralization– Nucleotide/nucleoside phophates

• Structural roles• Energy storage & transfer• Intracellular second messenger

– Phosphoproteins– Structural roles


Phosphorus

– Acid-base balance– Oxygen availability

• Excretion– Urine (67%-90%) & feces (10%-33%)

• Recommended Dietary Allowance– 19 years & >: 700 mg


Phosphorus

• Deficiency– Rare; renal patients, refeeding

• Toxicity– UL = 9-70: 4 g; >70: 3 g

• Assessment of nutriture– Serum concentrations– Urinary excretions


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


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


Magnesium

• Interactions with other nutrients– Calcium– Phosphorus– Potassium– Protein

• Excretion– Urine, feces (mostly unabsorbed)


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


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


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


Sodium

– Transport• Free in blood

– Functions• Maintenance of fluid balance• Nerve transmission/impulse conduction• Muscle contraction


Sodium

• Interactions with other nutrients– Calcium

• Excretion– Primarily urine, sweat

• Deficiency– Excessive sweating


Sodium

• Adequate Intake & assessment of nutriture– AI = 1500 mg– UL = 2300 mg– Ion-selective electrode potentiometry

• Used on blood & other body fluids


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


Potassium

• Interactions with other nutrients– Calcium

• Excretion– Urine (~90%), feces

• Deficiency & toxicity– Hyperkalemia - high serum potassium– Hypokalemia - low serum potassium


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


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


Chloride

• Functions– Major electrolyte– Gastric hydrochloric acid– Phagocytosis

– Exchange anion for HCO3- in RBC

• Excretion– 3 routes: GI tract, skin, kidneys


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


Perspective 11

Macrominerals & Hypertension


Hypertension

• Sodium• Potassium• Calcium• Magnesium• Other dietary factors

Documents

2009 Cengage-Wadsworth Chapter 11 Macrominerals