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Minerals

Minerals. Dr Reed Berger Nutrition Course Director Visiting Clinical Professor GI/Nutrition. General Lecture Format. -test questions will come from clinical correlations-- these will be relevant in clinical training and practice -items with *** and those with photos are important!!.

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Minerals

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  1. Minerals Dr Reed Berger Nutrition Course Director Visiting Clinical Professor GI/Nutrition

  2. General Lecture Format • -test questions will come from clinical correlations--these will be relevant in clinical training and practice • -items with *** and those with photos are important!!

  3. Minerals • A naturally occurring , homogeneous, inorganic substance required by humans in amts of 100 mg/day or more • -functions • -high and low serum levels • -absorption • -excretion • -deficiency • -toxicity

  4. calcium

  5. Calcium -most abundant mineral in the body -99% of calcium is in the bones and teeth -the remaining 1% is in the blood and ECF in cells and soft tissues

  6. Skeletal Calcium -if there is no reserve, calcium is drawn from bone—leading to deficiency

  7. Serum levels: 8.8 to 10.8 mg/dl • **when albumin is low (malnutrition, liver dz), calcium is decreased • Ratio: for each gram albumin is decreased below 4, add 0.8 to calcium

  8. -ionized calcium is increased in acidosis and decreased in alkalosis (increased bicarb binds calcium) • ***-example: in resp alkalosis, total serum calcium is normal, but ionized is low—always check ionized level with acid/base disorders

  9. Functions • -building and maintaining bones and teeth • -transport fxn of cell membranes and membrane stabilizer • ***-nerve transmission and regulation of heartbeat—use calcium gluconate IV to treat hyperkalemia (EKG—peaked T waves) • -ionized form initiates formation of the blood clot • -cofactor in conversion of prothrombin to thrombin

  10. Absorption • -***absorbed mainly in the acidic part of the duodenum • -absorption is decreased in the lower GI tract which is more alkaline • 20-30% of digested calcium is absorbed • Absorption is thru 1,25 (OH)2D3 (vit D derivative)--stimulates production of calcium binding protein and alk phos • -unabsorbed form is excreted in feces

  11. Factors that increase calcium absorption • -***more efficiently absorbed when the body is deficient • -best absorbed in acidic environment (upper duodenum) • -HCL in stomach allows better absorption in the proximal duodenum • -taking calcium with food increases abs • -fat increases intestinal transit time and increases absorption

  12. Factors that decrease absorption • -***lack of vitamin D • -oxalic acid forms insoluble complex which decreases absorption (rhubarb, spinach, chard, beet greens) • -phytic acid found in outer husks of cereal grains also form insoluble complex • -alkaline medium decreases abs.(lower GI tract) • Aging decreases absorption

  13. Maintenance of serum level • -parathormone (PTH) by the parathyroid gland and thyrocalcitonin secreted by the thyroid gland maintain serum levels • -***with decreased serum calcium levels, PTH increases and causes transfer of calcium from bone to blood to increase serum levels • -decreased levels also cause kidney to reabsorb calcium more efficiently (might normally be excreted in the urine) and to increase intestinal absorption • -when blood levels are increased, calcitonin acts by the opposite mechanisms as PTH to decrease serum levels

  14. Maintenance of serum level cont’d • ***-always need to correct low Mg level before treating a low calcium level • -hypomagnesemia decreases tissue responsiveness to PTH

  15. Causes of hypocalcemia -***malabsorption -small bowel bypass, short bowel -vit D deficiency -alcoholism -***chronic renal insufficiency -***diuretic therapy

  16. Causes of hypocalcemia cont’d -hypoparathyroidism -***hypomagnesemia -sepsis -pseudohypoparathyroidism -calcitonin secretion with medullary carcinoma of the thyroid

  17. Causes of hypocalcemia cont’d -***associated with low serum albumin (ionized calcium will be wnl) -decreased end organ response to vit D -hyperphosphatemia -***aminoglycosides, plicamycin, loop diuretics, foscarnet

  18. Causes of hypercalcemia -milk-alkali syndrome -vit D or vit A excess -primary hyperparathyroidism -secondary hyperparathyroidism (renal insuff, malabsorption) -acromegaly -adrenal insufficiency

  19. Causes of hypercalcemia cont’d ***Neoplastic Disease -tumors producing PTH-related proteins (ovary, kidney, lung) -***mets to bone -lymphoproliferative disease including multiple myeloma -secretion of prostaglandins and osteolytic factors

  20. Causes of hypercalcemia cont’d -***thiazide diuretic -sarcoidosis -paget’s disease of bone -***immobilization -familial hypocalciuric hypercalcemia -complications of renal transplant -iatrogenic

  21. Excretion • -normal is 65-70% of ingested calcium to be excreted in the feces and urine • -strenuous exercise increases loss (in sweat) • -***immobility with bed rest and space travel increase calcium loss because of lack of bone tension

  22. RDA • -see handout

  23. sources

  24. Deficiency • 1)***bone—to be discussed in osteoporosis lecture • 2) tetany—decreased serum levels increase the irritability of nerve fibers resulting in muscle spasms, fatal laryngospasm • ***-Chvostek’s sign: contraction of the facial m. after tapping the facial n. • ***-Trousseau’s sign: carpal spasm after occlusion of the brachial a. with blood pressure cuff for 3 min • 3) HTN—controversial • 4) prolonged QT--arrythmias

  25. Toxicity • -***polyuria, constipation, bone pain, azotemia, coma • -”stones, bones(bone pain), groans, psychiatric overtones”

  26. Phosphorus • Levels maintained by parathyroid gland

  27. Functions • -structure of teeth and bones • -essential component in cell membranes, nucleic acids, phospholipids • -phosphorylation of glucose • -buffer system in ICF and kidney

  28. absorption -best occurs when calcium and phos are ingested in equal amts (milk) -vit D also increases absorption

  29. RDA • -see table (and for all RDA’s)

  30. sources

  31. Sources ***dietary sources should be restricted in renal disease (usually see increased phos, decreased Ca) • -protein sources • -meat, poultry, fish, eggs, legumes, nuts, milk, cereals, grains

  32. Renal Disease

  33. Causes of hypophosphatemia -starvation -TPN with inadequate phos content -malabsorption, small bowel bypass -vit D deficient and vit D resistant osteomalacia

  34. Causes of hypophosphatemia cont’d -phosphaturic drugs: theophylline, diuretics, bronchodilators, corticosteroids -hyperparathyoidism (primary or secondary) -hyperthyroidism -renal tubular defects -hypokalemic nephropathy -inadequately controlled DM -***alcoholism

  35. Causes of hypophosphatemia cont’d Intracellular shift of phosphorus -administration of glucose -anabolic steroids, estrogen, OCP -respiratory alkalosis -salicylate poisoning Electrolyte abnormalities -hypercalcemia -hypomagnesemia -metabolic alkalosis

  36. Causes of hypophosphatemia cont’d Abnormal losses followed by inadequate repletion -***DM with acidosis—with aggressive therapy -***recovery from starvation or prolonged catabolic state—refeeding syndrome -***chronic alcoholism, especially with nutritional repletion, assoc with hypomagnesemia—” -recovery from severe burns

  37. Causes of hyperphosphatemia -excessive growth hormone (acromegaly) -hypoparathyroidism assoc with low Ca -pseudohypoparathyroidism assoc with low Ca -***chronic renal insufficiency -acute renal failure

  38. Causes of hyperphosphatemia cont’d Catabolic states, tissue destruction -stress or injury, rhabdomyolysis (esp with renal insufficiency) -chemotherapy of malignant disease, particularly lymphoproliferative disease Excessive intake or absorption -laxatives or enemas containing phosphate -hypervitaminosis D

  39. Deficiency • -fatal • -usually rare with food intake • -***respiratory muscle collapse • -heart failure • -muscle aches, bone pain, and fracture

  40. Toxicity • -symptoms of the primary disorder

  41. Magnesium

  42. Function -bone, muscle contractility, nerve excitability -antagonistic to calcium --in a muscle contraction, Mg relaxes, and calcium contracts --low Mg can cause pregnancy induced HTN

  43. Absorption / Excretion • -absorption varies • -similar to calcium (low pH, upper GI), however, no Vit D required-kidney conserves Mg when intake of Mg is low • -large losses with vomiting because of high levels of gastic juice

  44. sources

  45. Sources • -seeds, nuts, legumes, unmilled cereal grains, dark greens • -fish, meat, milk, fruits • -lost during refining of flour, rice, vinegar

  46. Causes of hypomagnesemia -malabsorption, chronic diarrhea, laxative abuse -prolonged GI suction -small bowel bypass -malnutrition -***alcoholism -refeeding -TPN with inadequate Mg

  47. Causes of hypomagnesemia cont’d -DKA -diuretics -hyperaldosteronism, Barrter’s syndrome -hypercalcuria -renal Mg wasting -hyperparathyroidism -postparathyroidectomy -vit D therapy -aminoglycosides, ***cisplatin, ampho B

  48. Causes of hypermagnesemia Decreased renal fxn ***Increased intake—abuse of Mg containing antacids (MOM) and laxatives in renal insufficiency

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