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Lecture 6

Water (week 6).docx

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Health Studies
HLTH 230
Jeffery Lalonde

Water  Most essential nutrient o More important than any other nutrient  Needed in large quantities o Can only survive without water for a few days  Aprox. 60% of adults body is water o Makes ¾ of weight of tissue o ¼ of the weight of fat  Percentage of water is lower in females, elderly and obese people Roles of Water in Body Fluids  Carries waste products and nutrients  Maintains structure of large molecules o Protein o Glycogen  Participates in metabolic reactions o Hydrolysis  Serves as a solvent for vitamins and minerals, amino acids, glucose o Allows them to participate in metabolic reactions  Acts as a lubricant and cushion for joints o Inside eyes, spine  Aids in regulation of body temperature  Maintains blood volume o Body must maintain all water balance to support all of these vital functions Water Balance  Water intake and excretion is adjusted to ensure intracellular fluid and interstitial fluid is maintained o Within and in between cells  Intracellular Fluid – Within o 2/3 of body’s water o High in potassium and phosphate  Intravascular  Inside blood cells  Interstitial Fluid – Between o Largest component of extracellular fluid  Outside of the cell o High in sodium and chloride Water Intake  Thirst o Conscious desire to drink o Thirst is only second behind the body’s actual need for it  Body’s need comes first, thirst comes after o Beginning of dehydration  Influenced by response to changes o Sensed by the mouth o Hypothalamus  Blood becomes concentrated  Mouth becomes dry o Nerves  Excessive water o Stopped by stretch receptors in the stomach o Volume receptors in heart signal drinking to stop Dehydration  Water output exceed water input o Thirst, dry mouth o Dry skin and mucous membranes o Weakness, exhaustion o Rapid heart beat o Low blood pressure  Symptoms o Thirst, fatigue, weakness  1-2% body weight lost o Impaired physically performance, dry mouth, reduction in urine, flushed skin, impatience  3-4% body weight lost o Difficult in concentrating, headache, sleepiness, impaired temperature, increased breathing  5-6% body weight lost o Dizziness, loss of balance, delirium, exhaustion, collapse  7-10% body weight lost Water Intoxication  Body’s water content are too high in all body fluid compartments o Occurs with excessive water consumption o 10-20 litres in a few hours  Can lead to hyponatremia  Decreased sodium in the blood  Kidney disorders  Reduce urine production  Confusion  Convulsion  Death Water Sournces  Water + beverages o 80-100% water  Fruits and vegetables o 70-99% water  Meats and cheese o 30-69% water  Butters and Oils o 0-20%  Generated in metabolism o 200-300ml a day  Energy yielding nutrients producing carbon dioxide and water in their breakdown Water Losses  Body must excrete at least 500 ml of urine per day to carry out waste products o More is usually excreted to adjust for intake  Water is lost in urine  Lungs as vapour (breath) o 350ml  Skin as sweat o 450-900ml  Gi tract as feces o 150ml  Food Sources o 700-1000ml  Metabolism o 200-300ml  Insensible water loss (unnoticeable)  Lungs and skin  Half of daily water loss Water Recommendations  Adequate Intake o 3.7L for men o 2.7L for women  DRI committee o Total water intake includes  Food  Caffeinated and non caffeinated beverages  Reccomendations o 1 – 1.5ml for every kcal energy expended for adults o 1.5ml for every kcal energy expended athletes and infants  Beverages ccount for more than 20% of energy intake o Any beverage can meet water needs o With or without energy  Water is the best choice  Caffeine free way to quench thirst  Situations in which water needs exceed norm o Sickness o Blood donation, surgery o Exercise  Lost during skin as sweat  Breathing as vapour o Pregnancy o Breastfeeding o Environmental conditions  Extreme heat Health Effects of Water  Water intakes have health benefits o Can protect against stones and constipation o Dehydration can affect physical and mental performance  Hard Water o Contains calcium and magnesium  Soft Water o High sodium or potassium o Prevents rings in bath tubs o More easily dissolves contaminants such as lead  Toxic Blood Volume and Blood Pressure  Fluid maintains blood volume o Blood pressure  Kidneys regulate blood volume and blood pressure o Filters that reabsorb needed nutrients o Excrete waste products  Amount of urine and concentration is caused by the kidneys  Based on food and beverage intake  Instructions on releasing or retaining substances come from o ADH (Antidiuretic Hormone)  Water retention  Hypothalamus signals pituitary gland to release ADH  When blood volume or blood pressure drops low  Extracellular fluid becomes concentrated  ADH stimulates kidneys to reabsorb water  Thirst is then triggered  Drinking water and retaining fluids restores blood volume  ADH is water conserving  The more water you need  The less water kidneys excrete o Renin  Sodium retention  Blood Pressure is low  Causes sodium reabsorption in the kidneys  Causes water retention  Water rentension increases blood pressure and blood volume  Angiotensin  Inactive until converted into angiotension 2  Narrows blood vessels  Increases blood pressure  The smaller, the more pressure  Stimulates Aldosterone  Adrenal glands  Signals kidneys to retain more sodium and more water  Regulates electrolytes o Potassium, Sodium, Chloride and other minerals o Rehydration  Fluid maintains body temperature o 2 factors on how water keeps us cool  Body has a high heat capacity  it takes a lot to actually make us hot  takes a large amount of heat to heat water  Body fluids cool body  Increases blood flow to area to cool under the skin  Secrete more sweat when we are hot  Evaporates which releases heat  Fluid protects and Lubricates Other Tissues o Water protects tissues and organs form injury  Saliva  Amniotic fluid  Synovial fluid  Joints  Tears  Spinal fluid  Fluid balance and electrolyte balance o Balance of water inside and outside cells is essential  2/3 of body’s water is inside the cells  1/3 outside the cells o Movement in minerals has role in maintaining balance  Mineral salt  Creates positive and negative ions  Ca
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