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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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Dr Reed Berger

Nutrition Course Director

Visiting Clinical Professor GI/Nutrition

general lecture format
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!!
  • 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

-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

skeletal calcium
Skeletal Calcium

-if there is no reserve, calcium is drawn from bone—leading to deficiency

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
-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
  • -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
  • -***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
factors that increase calcium absorption
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
factors that decrease absorption
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
maintenance of serum level
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
maintenance of serum level cont d
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
causes of hypocalcemia
Causes of hypocalcemia


-small bowel bypass, short bowel

-vit D deficiency


-***chronic renal insufficiency

-***diuretic therapy

causes of hypocalcemia cont d
Causes of hypocalcemia cont’d





-calcitonin secretion with medullary carcinoma of the thyroid

causes of hypocalcemia cont d1
Causes of hypocalcemia cont’d

-***associated with low serum albumin (ionized calcium will be wnl)

-decreased end organ response to vit D


-***aminoglycosides, plicamycin, loop diuretics, foscarnet

causes of hypercalcemia
Causes of hypercalcemia

-milk-alkali syndrome

-vit D or vit A excess

-primary hyperparathyroidism

-secondary hyperparathyroidism (renal insuff, malabsorption)


-adrenal insufficiency

causes of hypercalcemia cont d
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

causes of hypercalcemia cont d1
Causes of hypercalcemia cont’d

-***thiazide diuretic


-paget’s disease of bone


-familial hypocalciuric hypercalcemia

-complications of renal transplant


  • -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
  • -see handout
  • 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
  • -***polyuria, constipation, bone pain, azotemia, coma
  • -”stones, bones(bone pain), groans, psychiatric overtones”
  • Levels maintained by parathyroid gland
  • -structure of teeth and bones
  • -essential component in cell membranes, nucleic acids, phospholipids
  • -phosphorylation of glucose
  • -buffer system in ICF and kidney

-best occurs when calcium and phos are ingested in equal amts (milk)

-vit D also increases absorption

  • -see table (and for all RDA’s)

***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
causes of hypophosphatemia
Causes of hypophosphatemia


-TPN with inadequate phos content

-malabsorption, small bowel bypass

-vit D deficient and vit D resistant osteomalacia

causes of hypophosphatemia cont d
Causes of hypophosphatemia cont’d

-phosphaturic drugs: theophylline, diuretics, bronchodilators, corticosteroids

-hyperparathyoidism (primary or secondary)


-renal tubular defects

-hypokalemic nephropathy

-inadequately controlled DM


causes of hypophosphatemia cont d1
Causes of hypophosphatemia cont’d

Intracellular shift of phosphorus

-administration of glucose

-anabolic steroids, estrogen, OCP

-respiratory alkalosis

-salicylate poisoning

Electrolyte abnormalities



-metabolic alkalosis

causes of hypophosphatemia cont d2
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

causes of hyperphosphatemia
Causes of hyperphosphatemia

-excessive growth hormone (acromegaly)

-hypoparathyroidism assoc with low Ca

-pseudohypoparathyroidism assoc with low Ca

-***chronic renal insufficiency

-acute renal failure

causes of hyperphosphatemia cont d
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

  • -fatal
  • -usually rare with food intake
  • -***respiratory muscle collapse
  • -heart failure
  • -muscle aches, bone pain, and fracture
  • -symptoms of the primary disorder

-bone, muscle contractility, nerve excitability

-antagonistic to calcium

--in a muscle contraction, Mg relaxes, and calcium contracts

--low Mg can cause pregnancy induced HTN

absorption excretion
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
  • -seeds, nuts, legumes, unmilled cereal grains, dark greens
  • -fish, meat, milk, fruits
  • -lost during refining of flour, rice, vinegar
causes of hypomagnesemia
Causes of hypomagnesemia

-malabsorption, chronic diarrhea, laxative abuse

-prolonged GI suction

-small bowel bypass




-TPN with inadequate Mg

causes of hypomagnesemia cont d
Causes of hypomagnesemia cont’d



-hyperaldosteronism, Barrter’s syndrome


-renal Mg wasting



-vit D therapy

-aminoglycosides, ***cisplatin, ampho B

causes of hypermagnesemia
Causes of hypermagnesemia

Decreased renal fxn

***Increased intake—abuse of Mg containing antacids (MOM) and laxatives in renal insufficiency

  • -anorexia, growth failure, cardiac and neuromuscular changes—weakness, irritability, mental derangement
  • -tetany, muscle cramps
  • -respiratory—depression, apnea
  • -CV—hypotension, cardiac arrest, EKG (prolonged QRS and QT, heart block, peaked T waves)
  • -GI—N/V
  • -neuromuscular—paresthesias, somnolence, confusion, coma, hyporeflexia, paralysis, apnea
  • -respiratory transport of O2 and CO2
  • -immune system
  • -cognitive performance
  • -found in Hgb (in RBC’s) and myoglobin (in muscles)
  • -cytochrome p450 system
absorption and transport
Absorption and transport
  • -dietary iron exists in heme (Hgb and myoglobin) and non-heme
  • -***heme Fe is absorbed better
  • -non-heme Fe has to be present in the duodenum or upper jejunum in soluble form if it is to be absorbed
  • -in Fe deficiency, 50% can be absorbed
  • -***2-10% of Fe from veggies is absorbed and 10-30% is absorbed from animal protein
factors affecting absorption
Factors affecting absorption
  • -***ascorbic acid is the most potent enhancer
  • -animal proteins (beef, pork, veal, lamb, liver, fish, chicken) enhance
  • -but, proteins from cow’s milk, cheese, eggs, don’t
  • -gastric acidity enhances absorption (antacids interfere)
  • -pregnancy, increased growth, Fe defic all increase deficiency
-phytate and tannins decrease abs
  • -Fe used for enrichment are less absorbed than elemental Fe
  • -increased intestinal motility decreases absorption because it decreases contact time for absorption
  • -stored as ferritin and hemosiderin
  • -long term high Fe ingestion or frequent blood transfusions can lead to accumulation of Fe in the liver
  • -***hemosiderosis develops in individuals who consume a lot of Fe or have a genetic defect resulting in increased Fe absorption
  • -in associated with tissue damage, it is called hemochromatosis
  • -lost thru bleeding, feces, sweat, exfoliation of hair and skin
  • -none in urine
sources and intakes
Sources and Intakes
  • -best source is liver
  • -oysters, shellfish, kidney, lean meat, poultry, fish
  • -dried beans, veggies, dark molasses
  • -egg yolks, dried fruit, enriched breads,
  • -requirements are highest in infancy and adolescence
  • -females stay high because of menstruation
  • -decrease with menopause and increased with pregnancy
  • -most common deficiency
  • -most at risk: <2 yrs old, teens, pregnancy, elderly
  • -***anemia (hypochromic, microcytic)
  • -tx: diets high in absorbable Fe and/or Fe supplements (ferrous sulfate, ferrous gluconate)
  • -can be caused by injury, hemorrhage, illness, poor diet
  • -involved in synthesis or degradation of CHO, proteins, lipids, nucleic acids
  • -stabilizes RNA and DNA
  • involved in transcription and replication
  • -needed for bone enzymes and osteoblastic activity
  • Impaired absorption in Crohn’s or pancreatic insufficiency
  • -plasma zinc levels act as acute phase reactants and fall by 50% with injury (like platelets)
inhibiting factors
Inhibiting Factors
  • -fiber, phytate
  • -high doses of copper
  • -Fe competes with zinc for absorption
enhancing factors
Enhancing Factors
  • -glucose, lactose, and soy protein
  • -red wine
  • -human milk
  • -feces—almost entirely
  • -***in urine with starvation, nephrosis, DM, alcoholism, hepatic cirrhosis (zinc supplementation in encephalopathy), porphyria
sources and intakes1
Sources and Intakes
  • -meat, fish, poultry, milk
  • -oysters, shellfish, meat, liver, cheese, whole grains, dry beans, nuts
  • -short stature, hypogonadism, anemia
  • -with diets high in unrefined cereal and unleavened bread
  • -delayed wound healing, alopecia
  • ***-acrodermatitis enteropathica=AR dz with zinc malabsorption
  • -eczematoid skin lesions, alopecia, diarrhea, bacterial and yeast infections, death
causes of deficiency
***Causes of deficiency
  • Anorexia Nervosa
  • TPN without zinc (diarrhea, small bowel fistulas)
  • High intake of phytate, tannins, binding drugs (EDTA), oxalate
  • High iron intake
  • Malabsorption syndromes
  • Acrodermatitis enteropathica
  • Diarrhea
  • Pancreatico-cutaneous fistula
  • Proximal entero-cutaneous fistulas
  • Hemolytic anemias (sickle cell anemia)
  • Renal failure patients on dialysis
zinc deficiency
***Zinc Deficiency

42 yo female with chronic uremia on dialysis. Recently started on iron supplement for anemia. Presents with rash, hypogeusia, hyposmia and poor dark adaptation.

acrodermatitis enteropathica
Acrodermatitis Enteropathica
  • Autosomal recessive disease associated with a defect causing a reduction in zinc absorption
  • Can be treated by pharmacologic doses of oral zinc
  • ->100-300 mg/d
  • -rare
  • -interferes with copper absorption
  • -decrease in HDL
  • -GI irritation, vomiting
  • -tooth enamel
  • -resistance to dental caries
  • -fluoridation of h20 has decreased caries by half
  • -found in drinking h20, teflon pots and pans (cooked in these)
  • -toxicity at doses >0.1 mg/kg/d
prevention of dental caries
Prevention of dental caries
  • ***Incidence of dental fluorosis (mottled teeth) occurs with increased intake above 1-2 ppm.
  • Intervention studies have demonstrated water supplementation reduces prevalence of caries
  • -found in many enzymes
  • -connective and bony tissue formation
  • -growth and reproduction
  • -CHO and lipid metabolism
absorption and excretion
Absorption and Excretion
  • -after absorption, it appears rapidly in the bile and is excreted in the feces
  • -concentrated in liver and increases with liver disease
sources and intakes2
Sources and Intakes
  • -whole grains, legumes, nuts, teas, fruit, veggies, instant coffee, and tea
  • -wt loss, ataxia, dermatitis, N/V, decreased hair growth, impaired reproductive activity, decreased pancreatic function and CHO metabolism
  • -accumulates in liver and CNS—parkinsonian sx