Water and the Major Minerals

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Chapter 12

• Water and the Major Minerals

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I. Water and the Body Fluids

• A. Water Balance and Recommended Intake
• 1. Water intake
• a. regulation
• 1. Thirst º weakness º exhaustion º
  delirium º death
• 2. thirst mechanism
• a. lags behind actual requirement

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Regulation (cont)thirst mechanism (cont)

• b. hypothalamus senses blood concentration is
  high
• 1. Initiates drinking behavior
• c. water intoxication
• 1. rare
• 2. consuming too much water or inability
  to get rid of water (kidney problems)

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Water Balance and Recommended Intake (cont)

• 2. Water sources a. water and other
  beverages
• b. foods such as fruits, vegetables, meats,
  cheeses
• c. metabolic water
• 1. energy yielding nutrients are broken
  down to CO2 and H2O

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Water Balance and Recommended Intake (cont)

• 3. Water losses
• a. in order for the kidney to eliminate waste
  from metabolic reactions water is required
• 1. minimum amount needed (obligatory
  loss) about 500 ml
• 2. required to dilute waste
• 3. average excretion 2500 ml/day

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Water Balance
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B. Blood Volume and Blood Pressure think of
the cardiovascular system as a closed system

• 1. Hypothalamus and ADH
• a. Blood volume is low (low blood pressure)
• 1. same amount of solid particles in the
  blood so they become more concentrated
• b. Cells in the brain (hypothalamus) sense
  increase in concentration and release
  antidiuretic (ADH) hormone
• c. ADH stimulates kidneys to reabsorb H2O
• d. Blood volume goes up, concentration of
  particles decreases and ADH secretion stops

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B. Blood Volume and Blood Pressure (cont)

• 2. Liver, Lungs, Kidney and Angiotensin a.
  Blood volume is low
• b. Cells in the kidney sense low pressure and
  secrete renin
• c. Renin causes the kidneys to retain Na
• d. Renin is an enzyme that converts
  angiotensinogen to angiotensin
• e. Angiotensin is a vasoconstrictor (narrows
  blood vessels)

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B. Blood Volume and Blood Pressure (cont)

• 3. Hypothalamus, Adrenal Gland and
  Aldosterone
• a. Blood volume is low
• 1. Angiotensin stimulates release of
  aldosterone (adrenal gland)
• b. Aldosterone stimulates the kidney to
  retain Na, thus water

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Regulation of Water Balance
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C. Fluid and Electrolyte Balance

• 1. Dissociation of salt in water a. Salt
  NaCl º Na Cl-
• b. Water is also polar so electrolytes
  attract water
• 2. Extracellular and intracellular
  electrolytes
• a. K is major intracellular cation
• b. Na is major extracellular cation
• c. Transporters control electrolyte balance
  in and out of the cell, thus water balance

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Water and Electrolytes
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Electrolytes
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C. Fluid and Electrolyte Balance (cont)

• 3. Concentration
• a. Water moves from an area of low solute
  concentration to an area of high solute
  concentration
• b. So by controlling solute concentration
  water movement is controlled
• c. Kidney and intestine control solute
  concentration, thus water balance

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D. Fluid and Electrolyte Imbalance (dehydration)

• 1. Loss of electrolytes
• a. Na and Cl- most affected (extracellular)
• 1. sweating, vomiting, diarrhea, burns
• 2. Loss of fluid due to disease
• a. Diabetes (8 blood glucose º
  polyuria, polydipsia, polyphagia)
• 3. Replacing losses
• a. Water and food in most cases
• b. Severe cases IV fluids and
  electrolytes

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E. Acid-Base Balance

• 1. pH a. Acid low pH lt 7.0 (8 H) b.
  Base high pH gt 7.0 (9 H) 2. Electrolytes
  and proteins act as buffers
• a. Buffers buffer changes in pH (bind or
  release H maintaining pH within the narrow
  range
• 3. Excretion
• a. Kidneys and lungs get rid of H
• 1. 9 pH º8 breathing º 8 pH

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Sodium Bicarbonate Buffer System
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II. The Minerals

• Inorganic Elements 1. Cannot be destroyed
• Minerals in the Body (figure 12-5) 1. Can be
  toxic
• Variable Bioavailability 1. Bioavailability
  depends upon food consumed

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Minerals in a 60 kg Person
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A. Sodium

• 1. Roles in the body a. major extracellular
  cation b. regulates volume of extracellular
  fluid
• c. maintains acid-base balance (kidney)
• d. essential to cell (nerve, muscle) function
  2. Sodium recommendations
• a. minimum requirement 500 mg/day
• b. suggested intake lt 3000 mg/day
• c. persons with hypertension lt 2000 mg/day
• 1. salt sensitive individuals (15)
• 2. lower intake º lower blood pressure

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Sodium (cont)

• 3. Sodium intakes
• a. salt is 40 sodium
• b. 5 grams salt 1 teaspoon
• c. vary widely º US average male- 3300 mg
  Na/day or about 8 g salt/day, average
  Asian male around 30 g salt/day

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Sodium (cont)

• 4. Sodium in foods
• a. 85 from foods (90 during processing),
  15 from cooking and table
• b. high in processed foods (table 11-4)
• c. canned or instant soups
• d. Cheese
• e. condiments
• f. salted of smoked meats or fish
• g. Read food labels

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Sodium (cont)

• 5. Restricting sodium
• a. avoid highly salted foods
• b. do not add salt in cooking
• c. do not add salt from saltshaker
• d. read food labels
• e. avoid fast foods
• f. use sodium-free seasonings
• 1. Potassium chloride (KCl)
• g. adapt to using less salt slowly
• 1. wean yourself from Na

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Sodium (cont)

• 6. Sodium toxicity
• a. Edema
• 1. Na is major extracellular cation
• b. hypertension (high blood pressure)
• 1. habitual high sodium diet
• 2. 15 of people retain sodium
• a. causes water retention º blood
  pressure

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Sodium (cont)hypertension (cont)

• 3. Treatment
• a. low salt diets
• b. no discretionary salt (table/cooking)
• c. sometimes difficult to maintain
• 1. diuretics (increase fluid loss)
• 2. beta-blockers
• 3. ACE inhibitors (inhibit synthesis of
  angiotensin)

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B. Chloride (Cl-)

• 1. Roles in the body
• a. Major extracellular anion
• b. Maintains fluid and electrolyte balance
• c. Forms part of HCl (acid in the stomach)
• 2. Recommendations and intakes
• a. No RDA
• b. Associated with NaCl
• 1. 60 of salt is Cl-
• 3. Deficiency and toxicity
• a. Unlikely

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C. Potassium (K)

• 1. Roles in the body
• a. maintains blood pressure
• 1. maintain fluid and electrolyte balance
• b. nerve transmission
• c. muscle contraction
• 1. Deficiencies (hypokalemia) º sore
  muscles and cramps
• 2. Excess (hyperkalemia) associated with
  disease º irregular muscle contraction
  (heart)

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Potassium (K) (cont)

• 2. Recommendations and food sources
• a. 2000 mg/day
• b. fresh fruits, vegetables and legumes
• c. Processed foods low in K as opposed to
  being high in Na

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Potassium (K) (cont)

• 3. Potassium deficiency
• a. unlikely but possible
• b. most likely due to excessive losses
• 1. Sweating
• 2. Vomiting
• 3. Diarrhea
• 4. Drugs
• a. weight loss pills
• b. Diuretics
• 5. Potassium toxicity
• a. Unlikely

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Potassium in Foods
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Na and K in Processed Foods
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D. Calcium (Ca)

• 1. Roles of Calcium in the body
• a. calcium in bones/teeth
• 1. 99 of body calcium
• a. bone structure
• b. calcium bank
• b. calcium in fluids and soft tissue
• 1. blood clotting
• 2. nerve conduction
• 3. muscle contraction

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Bone Tissue
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Calcium (Ca) (cont)

• 2. Calcium regulation
• a. blood levels drop
• 1. parathyroid hormone (PTH) is secreted
  from the parathyroid gland
• a. PTH increases the amount of active
  vitamin D
• 1. increase intestinal absorption of
  Ca
• 2. decrease urinary calcium
• 3. move calcium from bone to blood
  (activates osteoclast cells that cause
  bone breakdown)

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Calcium (Ca) (cont)

• b. blood levels rise
• 1. calcitonin is secreted from the thyroid
  gland
• a. Shuts off PTH release
• 1. So active vitamin D declines as do
  the effects of vitamin D
• b. Activates osteoblasts which build bone

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Calcium Metabolism
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Calcium Metabolism
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Calcium (Ca) (cont)

• 3. Calcium absorption
• a. about 30 in adults
• b. about 50-60 during growth
• c. about 50 during pregnancy/lactation
• d. controlled by Vitamin D
• 1. increase calcium binding protein in
  intestinal cell (calbindin)
• 2. changes to intestinal cell

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Calcium (Ca) (cont)

• e. increased bioavailability
• 1. stomach acidity
• 2. vitamin D
• 3. Lactose
• 4. Exercise
• 5. proper calcium/phosphorous ratio
• f. decreased absorption
• 1. aging - lower stomach acid
• 2. high fiber diets
• a. Oxalates
• b. phytates

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Calcium Absorption
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Calcium (Ca) (cont)

• 4. Calcium recommendations
• a. 800 mg/day adults over age 24
• b. 1200 mg/day adults 19-24 years
• c. (1200 - 1500 mg/day post-menopause women,
  supplements may be required)
• 5. Osteoporosis and calcium
• a. 1/3 of all women over age 65 suffer spinal
  fractures
• b. over 1 million per year have fractures

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Calcium (Ca) (cont)Osteoporosis (cont)

• c. 250,000 plus hip fractures/year
• 1. do women fall and break their hip or dose
  their hip break and then they fall?
• d. occurs with loss of trabecular bone
• 1. spongy bone
• a. spinal vertebrae
• b. heads of long bones
• c. pelvis (hip)

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Osteoporosis and Trabecular Bone
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Calcium (Ca) (cont)Osteoporosis (cont)

• e. Age
• 1. bones lose density after age 30
• a. See Ca requirements
• 2. bones are strongest and densest in young
  adulthood
• f. gender
• 1. faster calcium loss in women with ageing
• 2. a large increase in urinary calcium is
  associated with menopause

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Loss of Bone and Height
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Calcium (Ca) (cont)Osteoporosis (cont)

• g. Genetics
• 1. bones more dense in blacks
• 2. less dense in Asians, and Hispanics
• h. physical Activity
• 1. weight bearing exercises increases bone
  density
• i. smoking and Alcohol
• 1. smoking increases risk
• a. 5-10 less bone mass in adult smokers
• b. increased urinary calcium
• 2. moderate alcohol suspected risk
• 3. alcoholism high risk

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Calcium (Ca) (cont)

• 6. Calcium and nutrition
• a. bone stores important in maintaining Ca
  balance
• 1. maximize input (RDA) during bone
  formative years (lt30)
• 2. calcium intake as adult controversial
• a. some research shows that bone loss
  not related to intake
• b. loss most important
• 1. Insufficient intake
• 2. Inactivity
• b. excess dietary protein intake causes loss
  of calcium in urine

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Calcium and Osteoporosis
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Calcium (Ca) (cont)

• 7. Recommendations
• a. RDA for calcium
• b. physical activity
• c. limit alcohol/smoking
• d. estrogen and calcium supplementation after
  menopause

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Calcium in Foods
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Absorption of Calcium
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E. Phosphorous (P)

• 1. Roles in the body
• a. functions with Ca in bone mineralization
• b. functions in buffering systems
• c. part of DNA, RNA
• d. part of cell membrane
• 1. Phospholipid (polar and non-polar)
• e. ATP (adenosine tri-phosphate)

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E. Phosphorous (P) (cont)

• 2. Recommendations
• a. same as that for Ca
• 3. Intakes
• a. widely available in diet
• b. deficiency unknown

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F. Magnesium (Mg)

• 1. Roles in the body
• a. Functions as a necessary cofactor in
  hundreds of enzyme systems
• 1. DNA synthesis
• 2. ATP synthesis
• 3. Opposes Ca in muscle contraction and
  blood clotting
• 2. Intakes
• a. RDA for men 350 mg, women 280 mg
• b. Food supplies about 75, amount in water
  varies throughout the country

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F. Magnesium (Mg)

• 3. Deficiency
• a. Associated with disease
• 1. Muscle tetany (muscle spasms)
• 2. Alcoholism, prolonged vomiting or
  diarrhea
• 4. Hypertension
• a. Vasculature undergoes changes and
  becomes less elastic with Mg deficiency