Notes on Water and Major Minerals

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University of Florida
Food Science and Human Nutrition
HUN 2201

• Water and the Major Minerals o Morning cup of coffee counts towards daily water needs o Increased water intake flushes waste from the body o You NEED some sodium, shouldn’t eliminate it from the diet • Functions of water o Body temperature control  High specific heat means it is very resistant to temperature changes o Chemical reactions  Condensation and hydrolysis o Medium for metabolism o Lubrication/protection o Acid-base balance o Transport  Nutrient delivery, waste removal • Body Water o Intracellular fluid  67% body water within cells o Extracellular fluid  Intravascular • Bloodstream, 25% of body water  Interstitial fluid • Between cells, 8% of body water • Electrolytes o Sodium, potassium, chloride o Maintain osmotic pressure among cells  Electrolytes attract water • Beverages o 75-80% total water intake • Food o 20-25% • Metabolic water • Water output o Urine; 1-2 L/day o Skin: insensible losses  Sweat, expiration, lungs o GI tract, feces [low amounts] • Hormones o Control total body water content o ADH: hypothalamus and pituitary  Hypothalamus: osmoreceptor cells • Sense concentration of sodium in blood, stimulate thirst mechanism, release of pituitary hormone ADH o Kidneys produce more urine • When water level is low, ADH secretion is reduced, and resorption by the kidney is reduced o Thirst mechanism [triggered by drop in water]  Increase in plasma osmolality  Reduction in blood volume, pressure  Often unreliable; elders, exercise, illness o Renin/angiotensin: kidney [triggered by drop in bp]  Decrease in blood pressure signals:  Immediate effect: vasoconstriction [increased blood pressure]  Delayed effect: aldosterone release • Stimulates sodium retention, water follows • Recommendations for infants are higher • Dehydration o Excess sweating, vomiting, diarrhea o Groups at risk  Elderly • Poor thirst response, inadequate fluid consumption  Infants o Treatment  Fluid  Eletrolytes • Normally, losses of water are greater than losses of electrolytes, since they are usually replaced at the next meal. You only need to drink electrolytes if losses are extreme o Water intoxication  Excessive fluid consumption  Hyponatremia [low blood sodium]  Some psychiatric illnesses  Excessive fluids without electrolytes • Endurance exercise • Minerals o Major, trace [macro and micro] o Bioavailability  Absorption and utilization affected by • Body status • Dietary components  Toxicity potential: more likely than vitamins to be toxic o Functions  Regulation • Water and acid-base balance • Nervous system function • Muscle contraction • Metabolic processes [enzyme cofactors] • Structure: bones  Widely distributed in food chain o Electrolytes:  Extracellular • Sodium, chloride  Intracellular • Potassium, phosphate o Sodium: major extracellular caTion o Potassium: major intracellular caTion o Functions  Fluid balance  Muscle contraction  Conduction/transmission of nerve impulses o Chloride:  Major extracellular anion • Fluid balance • Nerve impulse  HCL production in the stomach  Immune response o Sodium/chloride food sources  75% from processed foods  cooking/table use  naturally in foods  3,000-6,000 mg/day typical intake o potassium: food sources  unprocessed foods: • fruits, vegetables, grains, legumes  processing takes out potassium, adds sodium and chloride o Sodium intake:  AI: 1500 mgday  UL: 2300 mg/day  DV: 2400 mg/day o Potassium, intake  AI: 4700 mg/day  DC: 3500 mg/day o Calcium  Bone and tooth structure • Hydroxyapatite = Ca+ P crystals • Blood clotting • Nerve impulse transmission • Muscle contraction • Metabolic reactions  Bone development • 2/3 mineral • 1/3 water ad protein o collagen • turnover constant; osteoblasts build, osteoclasts tear down  Low Blood calcium • Parathyroid hormone PTH o Kidney retention of Ca o Vitamin D activation o Osteoclast activity • Calcitriol [vitamin D] o Ca absorption  High blood calcium • Calcitonin: thyroid o Inhibits osteoclasts (prevents bone from breaking down and releasing ca into bloodstream) • PTH and calcitriol o Release decreases o Blood calcium level controlled at the expense of bone  Calcium food sources • Milk and dairy • Some greens [but low bioavailability in spinach due to presence of oxalates] • Fortified foods • Calcium-processed tofu  Factors that increase absorption • Growth hormones • Meal, stomach acid • Vitamin D • Lactose/breast milk • Optimal Ca:P ratio  Factors that decrease absorption • Aging • Low production of stomach acid • Vitamin D deficiency • High P intake • Fiber, phytate, oxalate intake • High protein/low Ca intake  Deficiency • Bone mass • Osteoporosis: bone loss • Ineffective blood clotting • Hypocalcemic tetany [muscle spasms]  Excess • Increased risk of calcium stones • Interference with absorption of other minerals [iron, zinc] o Phosphorus  Functions • Part of ATP, phospholipids, DNA, RNA • Bone structure [hydroxyapatite] • pH control [PO4 buffer system]  Food sources • Dairy, grains, meat, processed foods  Recommended intake • Average intake is higher than the recommendation, not really a nutrient of concern  Deficiency • Bone loss, weakness, lsos of appetite • Uncommon • Marginal deficiency o Premature infants, vegans, alcoholics o Chronic diarrhea, antacids  Toxicity • Bone resorption • Adequate Ca important o Magnesium  Functions • Enzyme cofactor • Activates/stabilizes ATP • Nerve, lung, cardiac function • K/Ca metabolism  bone health  Food sources • Plant foods • Hard water • Recommended intake increases with age  Deficiency • Irregular heartbeat • Weakness, muscle pain • Hypertension, heart attack • Develops slowly • Alcoholics at risk: poor diet and increased excretion  Excess • Milk of magnesia • Weakness, nausea, kidney failure • UL fro
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