Water and The Major Minerals

Water

• 50-70% of body weight (10 gallons or 40 liters)
• Lean muscle contains 73% water
• Adipose is about 20%
• Survive only few days without water.....WHY?
  
• Polar compound with two partial positive hydrogen molecules and one partial negative oxygen molecule
• Polarity give water the property to dissolve many substances.... WHY?
  

Water in the Body

• Intracellular fluid  - fluid contained within a cell
• Extracellular fluid – fluid present outside the cell
• Intravascular fliud – fluid within the blood stream
• Interstitial fluid – fluid in between cells
• Water shifts freely in and out of cells
• Osmosis – the movement of water through a membrane from an area of higher concentration to a lower concentration
• Osmolality – a measure of total concentration of a solution
• Osmotic pressure – the exerted pressure needed to keep particles in solution from drawing liquid toward them across a semi-permiable membrane
• Shifts in water influenced by concentration of ions (anions and cations) inside and outside of cells

Functions of Water

• Serves as a solvent and helps to form a solution
• Regulates temperatures because of its high heat capacity (specific heat)
• Helps remove wastes (ex: 1-2 liters of urine per day)
• Helps form lubricants found in knees and other joints
• Water volume directly involved in the regulation Blood and Blood Pressure!
• It is basis for saliva, bile, and amniotic fluid

Water Needs

• Need 1ml of water per kcal expended
• Consume about 1 liter a day (in various forms of liquids)
• Foods provide another liter of water
• Water as a by-product of metabolism provides 350 ml of additional water
• Therefore water supplies around 2400 milliliters per day for a 2400 kcal diet
• Of the 2400, 1400 are used to produce urine
• Insensible losses of water -  the lungs (400ml), feces (150 ml), and skin (500 ml)
• Water Deficiency:
  • Thirst – mechanism occurs but imperfect indicator of how much water is really needed
  • Water loss is common in athletes infants, elderly, sickness
  • Regulation of water
    • Hormones compensate for imperfect thirst mechanism
      • Antidiuretic hormone (ADH) - synthesized in hypothalamus, stored in and released by pituitary; causes reabsorption of water in kidney
      • Renin-Angiotensin mechanism
        • If blood volume decreases, the enzyme renin (produced in kindey)
        • Renin then cleaves angiotensinogen (produced by liver) into angiotensin I
        • Angiotensin I is then converted (via an enzyme called ACE made in lungs) into Angiotensin II
        • Angiotensin II then causes 1) vasoconstriction of blood vessels, 2) release of Aldosterone, and 3) release of ADH
      • Aldosterone - hormone that prevents the loss of sodium in the kidneys, thus decreasing the loss of water
• Water in foods – fruits and veggies!
• Water safety
  • Monitored by EPA
  • Cryptosporidium
• Water toxicity
  • Water intake without sufficient electrolyte intake
  • Many liters beyond need (hyperhydration)
  • May cause death

Minerals

• Major (requiring 100mg or more/day) and trace mineral
• Many minerals have similar molecular weights and charges
  • Causes competition for absorption
  • Affects bioavailability
• Bioavailability also affected by non mineral substances
  • Fiber (regulates motility of intestine thereby regulates mineral absorption)
    
  • Oxalic acid (decreases mineral absorption by reacting and combining with minerals)
    
• Excess minerals are primarily excreted though urine
• Functions
  • Cofactors
  • Components of body compounds
  • Transmission of nerve impulses
  • Body growth
  • Water balance
• Food sources – plant and animal sources
• Risk of mineral deficiencies in North Americans – calcium for major and zinc and iron for trace minerals

Sodium (Na)

• Sodium found in sodium chloride (NaCl) – 40% sodium 60% chloride
• 95% sodium is absorbed in the small intestine
• Transported in blood stream
• Excreted via the kidneys when in excess
  • Regulated by rennin-angiotensin and catecholamines
• 10% of sodium consumed is needed by the body
• The rest is eliminated via kidneys, skin, and GI tract
• Functions:
  • Positive cation of extracellular fluid therefore helps maintain fluid balance
  • Involved in nerve transmission
• Deficiency (or depletion): causes muscle cramps, nausea, vomiting, dizziness, and shock
• Sources: table salt and processed foods
• RDA: 500 mg
• Toxicity: causes hypertension and calcium loss

Potassium (K)

• 90% of potassium absorbed in the small intestine
• Transported in the blood stream
• Excreted via kidneys
• Levels in the body regulated by kidneys and aldosterone
• Functions:
  • Positive cation of intracellular fluid therefore helps maintain fluid balance
  • Involved in nerve transmission
• Deficiency:
  • Caused by use of diuretics
  • Irregular heart beat, loss of appetite, muscle cramps
• Sources: fresh fruits and vegetables
• RDA: 2000 mg
• Toxicity: hyperkalemia, slowed heart rate

Chloride (Cl)

• All is absorbed in the small intestine and colon
• Excreted through kidneys, skin, and GI tract
• Functions:
  • Anion of extracellular fluid
  • Aids in the production of stomach acid (hydrochloric acid)
• Deficiency: convulsions seen in infants
• Sources: table salt, seaweed, olives, rye, lettuce, vegetables
• RDA: 700-750 mg
• Toxicity: linked to hypertension

Calcium (Ca)

• 99% of calcium in body is used as a component of bone
• represents 40% of all minerals present in the body – 2.5 pounds
• 25% of calcium is absorbed from the diet
• Absorption occurs in the duodenum of small intestine
• Absorption requirements:
  • A ph below 6 and presence of vitamin D
  • Parathyroid hormone
  • Presence of glucose and lactose
  • Normal intestinal flow
• Absorption limiting factors:
  • Phytic acid in dietary fiber
  • Vitamin D deficiency
  • Increased intestinal flow (diarrhea)
• Functions:
  • Bone and tooth strength
    • Parathyroid hormone (PTH) and calcitonin regulates calcium levels and thus calcium's involvement in bone remolding and repair
    • Bone mass fluctuates dependent upon calcium levels
      
  • Blood clotting
    • Involved in the conversion of prothrombin to thrombin
  • Nerve transmission
  • Muscle contractions
• Deficiency:
  • Osteopenia (low bone density)
    
  • Osteoporosis (process of bone loss)
• Sources: dairy products, leafy vegetables, canned fish
• RDA: 1000-1200 mg (1300 ages 9-18)
• Toxicity: kidney stones and poor mineral absorption

Phosphorus (P)

• 70% of dietary phosphorus absorbed
• Vitamin D enhances absorption
• Excreted by kidneys
• Functions: used in bone (calcium phosphate), used in many compounds (ex: ATP), used in acid-base balance
• Deficiency: bone loss
• Sources: diary products and processed cheese
• RDA:  700 mg (1250 ages 9-18)
• Toxicity: poor bone mineralization

Magnesium (Mg)

• 40-60% of dietary Magnesium absorbed in the small intestine
• Vitamin D enhances absorption
• Excreted by kidneys but some stored in bone and muscle
• Functions: used in enzyme catalyzed reactions, activation of ATP, DNA and RNA synthesis, prevents heart rhythm abnormalities
• Deficiency: rapid heart beat, weakness, muscle spasm, disorientation, nausea and vomiting
• Sources: wheat bran, green vegetables, nuts, chocolate, legumes
• RDA: 400-420 mg for men 310-320 mg for women
• Toxicity: from use of antacids and laxatives; may cause diarrhea, weakness

Sulfur (S)

• Element used in amino acid synthesis; found in wide variety of foods
• No deficiencies, no RDA, no toxicities

Minerals and Hypertension

Question: How water and minerals involved in the regulation of blood pressure and blood volume?