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Lecture 6

Lecture 6 - Water and Water Soluble Vitamins.doc

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Health Studies
HLTH 230
Jeffery Lalonde

Lecture 6 - Water and Water Soluble Vitamins • an essential nutrient - more important than any other nutrient • needed in larger quantity/day than any other nutrient survival without water is only a few days compared to weeks, months, years for other nutrients • Water and the body fluids -approximately 60% of an adult’s body weight is water -water makes up: -approx. 3/4 of the weight of lean tissue -less than 1/4 the weight of fat -> generally percentage of water is lower in females, elderly, and obese people athletic/muscular people = lots of water Roles of water in body fluids • carries waste products and nutrients maintains structure of large molecules such as proteins and glycogen • • participates in metabolic reactions -condensation and hydrolysis reactions • serves as a solvent for vitamins, minerals, a.a., glucose to participate in metabolic rxns • acts as a lubricant and cushion around joints, inside the eyes, spine • aids in regulation of body temperature • maintains blood volume • body must actively maintain an appropriate water balance to support all vital functions Water Balance • water intake and excretion quickly adjusted to ensure composition of intracellular fluid and interstitial fluid is maintained intracellular fluid (fluid within the cells) -accounts for 2/3 of body’s water -usually high in potassium and phosphate interstitial fluid (between the cells) -largest component of extracellular fluid -usually high in sodium and chloride -> interstitial (between cells) -> intravascular (inside blood vessels) Water Intake thirst: a conscious desire to drink • thirst lags behind the body’s need -if you feel thirsty, you are already dehydrated! • influences water intake in response to changes sensed by mouth, hypothalamus, and nerves hypothalamus initiates drinking when: • -blood becomes concentrated -mouth becomes dry • excessive water intake stopped by: (signal you to stop drinking) Lecture 6 - Water and Water Soluble Vitamins -stretch receptors in stomach and volume receptors in heart dehydration: the condition in which body water output exceeds water input • symptoms: -thirst, dry mouth -dry skin and mucous membranes -weakness -rapid heart beat -low blood pressure -exhaustion, delirium, death Body Weight Lost (%) Symptoms 1-2 thirst, fatigue, weakness, vague discomfort, loss of appetite 3-4 impaired physical performance, dry mouth, reduction in urine, flushed skin, impatience, apathy 5-6 difficulty in concentrating, headache, irritability, sleepiness, impaired temperature regulation, increased respiratory rate 7-10 dizziness, spastic muscles, loss of balance, delirium, exhaustion collapse 1L of water = 2.2 lbs ex. someone weighs 200 lbs, losing 1L of water is 1-2% of body weight water intoxication: body water contents are too high in all the body fluid compartments • is rare, but may occur with: -excessive water consumption (10-20L in a few hours) -ex. trying to flush out toxins, recreational drugs -can lead to hyponatremia - a decreased Na+ conc. in blood -ex. endurance athletes lose a lot of sodium from sweat, end up with low blood sodium, taking in water after a race will dilute symptoms -> confusion, convulsions (only in intoxication, not dehydration!), death Water Sources & Percentage of Water water • • beverages = 80-100% water • fruit and vegetables = 70-99% water • meats and cheese = 30-69% water butter and oils = 0-20% water (fats are low in water) • • we also produce water during metabolism = 200-300ml/day -energy yielding nutrients producing CO2 and H20 with their breakdown (condens.rxn) Lecture 6 - Water and Water Soluble Vitamins Water Losses • body must excrete at least 500ml of urine/day to carry away waste products more usually excreted to adjust for intake (drinking water) • • water lost in urine, lungs as vapour (breath), skin as sweat, GI tract with feces • insensible water loss - via lungs and skin make up for about half the daily water loss -> foods and beverages provide the most water TABLE 12-3 - THIS IS IMPORTANT! -in order to balance this, kidneys produce urine, skin sweats, lungs excrete from breathing, GI tract loses water from feces -> liquids and foods are the main water sources! -> kidneys and skin are the main causes of water losses! Water Recommendations • 1.0 -1.5ml/kcal of energy expended for adults • 1.5ml/kcal of energy expended for infants and athletes • AI total water -3.7L/day for men -2.7L/day for women *according to DRI committee, total water intake includes caffeinated and non caffeinated beverages and food! What beverages are best? • beverages account for more than 20% of energy intake in US • obesity is a major concern - drink more water (no calories) • any beverage can meet water needs, with or without energy • water is best choice for most people • Canada’s Food Guide: “Satisfy your thirst with water!” -“Drink water regularly. It’s a calorie-free way to quench your thirst” Lecture 6 - Water and Water Soluble Vitamins Situations where water needs above the norm • fever, diarrhea, vomiting, runny nose • blood donation, surgery • exercise - increased loss via skin and respiration • pregnancy, breastfeeding • environmental conditions (extreme heat) Health Effects of Water • not only do fluid needs have to be met, but water intake can have health benefits -may protect against urinary stones and constipation -even mild dehydration can interfere with physical and mental performance hard water -high concentrations of calcium and magnesium -water that leaves dark rings around sinks -some people have water softners where you add sodium/potassium soft water -high sodium or potassium -generally sodium is added to water -prevent rings in the bathtub, toilet, and laundry tub -produces more bubbles when soap is added -more easily dissolves contaminants like cadmium and lead Blood Volume and Blood Pressure • fluid maintains blood volume -> directly related to blood pressure • kidneys play a major role in regulating blood pressure and blood volume -are filters that reabsorb needed nutrients and excrete waste products • volume concentration of urine is adapted by kidneys based on food and beverage intake • instructions on whether to retain/release substances come from: -ADH, renin, angiotensin, aldosterone ADH (Antidiuretic hormone) and water retention • hypothalamus signals pituitary gland to release ADH when: -BV or BP drops low -extracellular fluid becomes too concentrated • ADH stimulates kidneys to reabsorb water • thirst is triggered - drinking water and retaining fluids help restore blood volume *ADH is a water conserving hormone -consequently, the more water you need, the less water your kidneys would excrete Renin and Sodium Retention • renin released by kidney cells when BP is low Lecture 6 - Water and Water Soluble Vitamins • release of renin -> chain of events -> Na+ reabsorption by kidneys -> H20 reabsorption -> increase in blood pressure and volume Angiotensin and blood vessel constriction • renin also initiates activation of angiotensinogen -> angiotensin I • Angiotensin I is inactive until converted to angiotensin II • Angiotensin II: vasoconstrictor (narrows blood vessels => increase blood pressure) Aldosterone and Na+ retention • Angiotensin II also stimulates release of hormone aldosterone from adrenal glands • aldosterone signals kidneys to retain more Na+ -> more water FIGURE 12-3 IN TEXT Fluids help maintain body temperature -water can help us keep cool through 2 factors: 1) Water has a high heat capacity -takes a lot of heat to raise the temperature of water 2) Body fluids are our primary coolant -too cool: increase blood flow to vessels just under the skin -too hot: secrete more sweat, evaporates and releases heat Fluids protect and lubricate other tissues -water protects tissues and organs from injury -cerebrospinal fluid -amniotic fluid -synovial fluid -tears -saliva Fluid and Electrolyte Balance • balance of water inside and outside cell is essential -approx. 2/3rd of body water is inside cell -1/3rd outside the cells -movement of major minerals plays essential role in maintaining this balance -ex. water follows salt! dissociation of salt in water -mineral salt dissociates into positively and negatively charged particles (Na+ and Cl-) -Cations - positively charged (ex. Na+) -Anions - negatively charged (ex. Cl-) -pure water => poor conductor of electricity -ions dissolved in water => carry electric current -(+) and (-) charges inside and outside cells are perfectly balanced even though numbers of different kinds of ions may be different Lecture 6 - Water and Water Soluble Vitamins -ex. if there are 1000 (-) charges, there must also be 1000 (+) charges -when an Na+ leaves the cell, a K+ is entering electrolytes attract water -water molecules each have a net charge of zero -O side: (-) slightly negative -H side: (+) slightly positive -this attraction dissolves salts in water and enables body fluids to move into appropriate compartments water follows electrolytes -sodium and chloride are typically outside the cell -potassium, magnesium, phosphate, and sulphate are typically inside cell -cell membranes are selectively permeable -whenever electrolytes move across the membranes, water follows -osmosis: movement of water towards the more concentrated solute water moves to make sure concentration is the same so concentration in both sides is the same Lecture 6 - Water and Water Soluble Vitamins proteins regulate flow of fluids and ions -protein can act as a pump regulating crossing of a membrane -ex. Na/K pump (exchanges sodium for potassium) uses ATP for energy regulation of fluid and electrolyte balance -amounts of various minerals in the body must remain constant -steady state maintained by: -GI tract -minerals in digestive juices and food are reabsorbed in large intestine as needed -kidneys -control body water with ADH -electrolyte content is regulated by aldosterone Fluid and Electrolyte Imbalance • ex. prolonged diarrhea, vomiting, heavy sweating, burns, medications -ex. potassium wasting diuretics sodium and chloride most easily lost -principle extracellular cation and anion in the body, they are lost via sweater, blood, or excretion -easier to lose because they are outside the cell different solutes lost by different routes -vomiting and diarrhea causes sodium to be lost indiscriminately -too much K+ may be excreted if tumor develops, causing adrenal glands to secrete too much aldosterone -person with uncontrolled diabetes may lose glucose in urine -dehydration may occur in all situations, but water alone will not restore electrolyte balance -electrolytes are lost too, need electrolytes as well as water replacing fluid and electrolyte loss -drinking water and eating regular food -medical attention (ex. IVs) sometimes required Lecture 6 - Water and Water Soluble Vitamins Acid-Base Balance • body must maintain blood pH between 7.35 and 7.45 • wrong pH can denature proteins -prevents enzymes from working -> stops reactions -> serious consequences • pH primarily regulated by -Buffers -bicarbonate (base) and carbonic acid (acid) found in body fluids protect body against changes in acidity by neutralizing acids and bases -some proteins act as buffers -Lungs -control concentration of carbonic acid by changing respiration rate -if carbonic acids build up -> respiration rate increases -> increase in CO2 exhaled -Kidneys -role in long term acid base balance -> selecting ions to retain and secrete -urine acidity fluctuates to help body pH remain constant Sodium AI: 1500mg UL: 2300mg 1 teaspoon of salt = approx. 2300mg Na very common in processed foods reducing sodium in the diet has been linked to reduced blood pressure WATER - SOLUBLE VITAMINS • vitamins -> powerful substances discovered in early 1900s • vitamins can fight certain diseases, absence can cause dreadful conditions like scurvy, blindness, dementia support nutritional health but do not cure all • • supplements do not offer many benefits of vitamin-rich foods • are “organic, essential nutrients required in small amounts by body for health. they regulate processes that support and maintain life.” • “vita” - life “amin” - nitrogen containing Vitamins differ from carbs, protein, and fat in 3 main ways: Structure -vitamins are individual units (not linked together) where as carbs and proteins generally are Function -vitamins DO NOT YIELD USABLE ENERGY!!!! -often play an important role in metabolism Food Contents -measured in micrograms and milligrams, not grams • similar to energy yielding nutrients in the way that they are essential to life, organic and available from foods Bioavailability Lecture 6 - Water and Water Soluble Vitamins bioavailability: rate and extent to which a nutrient is absorbed and used • amount of vitamins available from food is dependent on: 1) amount in the food (quantity) 2) amount that can be absorbed and used by the body • food may be high in a particular vitamin but amount absorbed and used be very little bioavailability depends on: -efficacy of digestion and time of transit through GI tract -previous nutrient intake and nutritional status -other foods consumed at the same time -ex. vitamin C assists absorption of iron phytates assists absorption of calcium -method of food preparation (raw, cooked, processed) -source of nutrient (synthetic, fortified, naturally occurring) • provitamin is a precursor of a vitamin -ex. some vitamins in food are in their inactive form and are converted to active form within body (ex. beta carotene is converted to vitamin A in the body) • vitamins are organic and can be destroyed during handling and cooking -ex. oxygen destroys vitamin C, prolonged heating may destroy thiamin, UV light can destroy riboflavin Minimizing nutrient losses 10-1 • refrigerate most fruits and veg • store fruits and vegetables (that have been cut) in airtight containers (limit oxidation) • to prevent losses during washing, cut fruits and vegetables after washing • to minimize losses during cooking: -use microwave or steam vegetables in small amount of water -put vegetables in soup after water is boiling -avoid high temp and long cooking times *less cooking time = more nutrients! Solubility -hydrophilic vitamins referred to as water soluble vitamins -these 9 vitamins are dissolvable in water -water soluble vitamins include -Thiamin -Riboflavin -Niacin -Biotin -Vitamin B12 -Pantothenic Acid -Vitamin B6 -Folate -Vitamin C water soluble vitamins generally found in watery compo
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