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NFS284 Chapter 10-12 Review Notes

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University of Toronto St. George
Nutritional Science
Tom Wolever

Nutrition: Science and Applications - Dehydration Chapter 10 – Water and electrolytes o Headache, fatigue, dry mouth and eyes, dark-colored urine, nausea, Chapter 11 – Major minerals confusion, disorientation, death Chapter 12 – Trace elements - Water intoxication o Hyponatremia = excessive intake of water during prolonged exercise Electrolytes  dilutes blood sodium  changes osmotic pressure  water - Sodium moves out of blood into tissue  organ swelling and damage o High proportion of sodium intake above the UL o Early symptoms of water intoxication are similar to dehydration o Low [Na+] outside the cell Minerals  inorganic elements needed by the body in small amounts o Regulation of blood pressure - Major minerals  Mg, P, Ca  ↓ BP  renin released from kidney  angiotensin - Trace minerals  Se, Mn, I, Cr, F, Zn, Fe converted into angiotensin II - Source of minerals in the Canadian diet o Natural sources  Angiotensin II  constricts blood vessels  ↑ BP  Angiotensin II  aldosterone released from o Fortified foods (e.g., iron, calcium, iodine) adrenal gland  sodium reabsorbed into the o Natural health products (e.g., calcium supplements) - Bioavailability kidneys  ↑ water retention  ↑ BP o Hypertension o Absorption  ↑ sodium intake  ↑ blood sodium levels  ↑ BP  Iron and calcium absorption is low  Sodium absorption is high  Most individuals: o ↑ BP  ↑ sodium excreted from the  RDA takes into account the absorption rates o Phytate, oxalate, and tannins decreases absorption by binding to the kidneys  ↑ water excretion  ↓ BP  Salt-sensitive individuals: minerals o ↑ BP  ↓ sodium excretion  ↑  Phytate (e.g., grains)  Ca, Zn, Fe, Mg  Oxalate (e.g., spinach)  Ca, Fe constriction of blood vessels  ↑ BP o No additional benefit of lowering sodium intake from UL = 2300 mg  Tannins (e.g., tea, coffee)  Ca, Fe to AI = 1500 mg - Minerals function as cofactors o Mineral cofactor + incomplete enzyme = active enzyme  May be potentially harmful for certain groups  Average sodium intake is above the UL = 2300 mg Calcium - Potassium - High prevalence of inadequate calcium intake - Required for bone structure and health o Potassium intake may or may not be adequate  <50% of the population has an intake greater than the AI o Components of bone  Hydroxyapatite o High [K+] inside the cell - Chloride  Mineral Physiology of pregnancy  Inorganic matrix  Rigid - High blood pressure o Gestational hypertension  Deposits on collagen o Pre-eclampsia (e.g., high BP, fluid retention, rapid weight gain)  Collagen o Eclampsia (e.g., seizures, death)  Protein - Not related to diet but calcium supplements may be beneficial  Organic matrix Water  Flexible - Water balance o Types of bone o Water intake  food, drink, metabolism  Trabecular bone (spongy) o Water output  feces, urine, evaporation  Cortical bone (compact) o Bone remodeling o ↑ calcium supplements with vitamin D) ≠ ↑ risk of myocardial  Bone formation  requires osteoblast (b = build bone) infarction  Bone resorption (breakdown)  requires osteoclast (c = - Calcium blood levels must be maintained in a very narrow range consume bone) o Regulation of calcium blood levels o Osteopenia  Calcium absorption in the intestines  Low bone density  Calcium reabsorption in the kidneys o Osteoporosis  Calcium release from the bone  Loss of both organic matrix (protein/collagen) and inorganic - When calcium blood levels are low, calcium is taken from the bone  matrix (mineral/hydroxyapatite) eventually, osteoporosis  Front edge of the vertebrae collapses more than the back - Calcium absorption edge, so the spine bends forward o Vitamin D  synthesize calcium transport proteins  Decline in height o Calcium transport proteins  carry calcium across enterocyte  Trabecular bone is crushed o Calcium pump requires ATP  move calcium into blood  Vulnerable to respiratory problems o Higher in infants (60%)  Increased changes of bone fractures o Lower in adults (25-30%) o Age-related bone loss o Increases during pregnancy  RDA for calcium is unchanged  As we grow, bone mass increases o Decreased by tannins, fibre, phytates, and oxalates  During puberty, bone mass increases rapidly - Vegetables low in oxalate are good sources of calcium (e.g., kale, collard, turnip, mustard, Chinese cabbage)  Men have higher peak bone mass  Women have lower peak bone mass - Non-bone related functions  After age 35, bone mass starts to decrease o Muscle contraction  After menopause, loss of bone mass is accelerated for o Neurotransmitter release about 5 years o Blood clotting  Estrogen stimulates osteoblast activity o Blood pressure regulation  Estrogen is produced from testosterone in men, - ↑ calcium intake = ↓ colon cancer (confirmed by observational studies) which declines gradually o Calcium binds with toxins in the colon, making them insoluble and biologically inactive
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