Module 10 - Water & Electrolytes Student PDF

KIN275 Introduction to Nutrition Module 10 Water and Electrolytes Julia Totosy de Zepetnek, PhD Module 10 Learning Objectives 1. Describe the role of water in the body, and how body water is regulated Discuss hypo- and hyper-hydration 2. Introduce minerals and describe the key features 3. List the m...

KIN275 Introduction to Nutrition Module 10 Water and Electrolytes Julia Totosy de Zepetnek, PhD Module 10 Learning Objectives 1. Describe the role of water in the body, and how body water is regulated Discuss hypo- and hyper-hydration 2. Introduce minerals and describe the key features 3. List the major physiological functions of the major minerals – electrolytes (sodium, potassium, chloride) Where is water? Intracellular (~66%) Extracellular (~33%) – Intravascular – Intercellular (also termed interstitial) Total Body Water (TBW) = ICF + ECF Functions of Water in the Body Solvent: solutes dissolve in solvent to form solution Transport: serves as a medium for transport – Helps transport water-soluble substances within and around cells Approximate levels of water in the body § Blood = 80-90% § Muscle = 75-77% § Bone = 22-25% § Fat Tissue = 10% § *Body Mass = 45-70% *Varies with age/body composition Functions of Water in the Body Solvent: solutes dissolve in solvent to form solution Transport: serves as a medium for transport – Helps transport water-soluble substances within and around cells Osmosis: diffusion of a solvent (usually water) through a selectively permeable membrane (e.g., plasma membrane) – [substances] dissolved in water influences osmosis (e.g., sodium, glucose) Approximate levels of water in the body § Blood = 80-90% § Muscle = 75-77% § Bone = 22-25% § Fat Tissue = 10% § *Body Mass = 45-70% *Varies with age/body composition Osmosis: Movement of Water Body water is distributed between intra- and extra-cellular spaces Amount of water in blood and tissues is determined by: – Blood pressure – Force generated by osmosis Osmosis For example: electrolytes Common Electrolytes § Sodium (Na+) § Potassium (K+) § Chloride (Cl-) Regulates body fluids by controlling fluid shifts in and out of cells (osmosis) “Everywhere salt goes, water flows” Electrolytes - O2 is drawn to Na+ cation + H is drawn to Cl- anion Salts that dissolve in water Anions & cations attract water As cells move electrolytes in & out, water follows, enabled by osmotic pressure – Osmotic pressure moves water across membranes in presence of concentration gradient POP! Functions of Water in the Body Solvent: solutes dissolve in solvent to form solution Transports: serves as a medium for transport Lubricates: e.g., tears; fluid around joints; saliva Regulates body temperature: absorbs body heat from metabolic processes Chemical reactions: hydrolysis & condensation Acid-Base Balance: prevents changes in pH Approximate levels of water in the body § Blood = 80-90% § Muscle = 75-77% § Bone = 22-25% § Fat Tissue = 10% § *Body Mass = 45-70% *Varies with age/body composition How much water do you need? MYTH: Everyone should drink at least 8 cups of water per day. TRUTH: Body composition, sweat rate, and sweat electrolyte concentrations among a population varies. Fluid requirements are reflective of individual needs. There is no single, strict guideline for water intake. Individual requirements are influenced by several factors; general guidelines can be adjusted to serve individual needs How much water do you need? AI developed (not enough info for EAR / RDA) – Based on median total water intakes (from all sources) using NHANES III survey (1988-1994) – Total water intake likely to prevent deleterious, primarily acute, effects of dehydration (including metabolic & functional abnormalities) Factors Affecting Water Requirements Elderly – Likely normal hydration status in elderly Physical activity & heat strain – Substantially increase water loss through sweating Altitude & cold temperature – Increases respiratory water loss, as well as cold-induced and hypoxia-induced urine production Diabetes mellitus – Dehydration associated with worsening control (of DM) Cystic Fibrosis – High [Na+Cl-] in sweat but no compensatory fluid osmosis (which is a trigger for thirst)… quickly become dehydrated during PA, particularly in heat Diuretics – Can cause excessive water loss What counts as water intake? Sources of Water in the USA (NHANES III) Data from 1988-1994: adults in the United States obtained total water from the following sources: – 35-54% drinking water – 49-63% other beverages (major sources: juice, carbonated drinks, milk, coffee (?!)) – 19-25% from foods (fruits, vegetables, soups, ice cream, meats) What counts as water intake? Contrary to traditional beliefs, recent scientific evidence does NOT support the belief that regular consumption of caffeinated beverages decreases total body water Therefore, caffeinated beverages can be counted towards total water intake 19 Sources of Water Beverages, food, drinking water Water Balance Water Intake Water, beverages, food, metabolic water Metabolic water: Physically inactive people ~250-350 mL/day Very active people ~500-600 mL/day Regulation of Water intake Desire to drink (thirst) stimulated by: – Amount of water in blood (sensed by thirst center in hypothalamus) – Decrease in saliva secretion (dry mouth) Water Balance Water Intake Water Loss Water, beverages, Respiratory, skin, food, metabolic water renal, GI tract In healthy people, water balance is maintained within + or - 2% of body mass Water Loss Respiratory: 200-350 mL/day for sedentary people; can increase to 500-600 mL/day for active people – Physical activity generally has a greater effect on water loss through evaporation within the lungs than do environmental factors (e.g., ambient air temp, humidity) Water Loss Skin – Insensible losses: 450 mL/day; evaporation from skin without person being aware Body size, physical activity, environmental factors (ambient air temp, humidity) – Sensible losses: sweat losses (detectable); extremely variable Hot weather: primary avenue of heat loss to defend body’s core temp Water Loss Fecal: usually small (150mL/day); 95% reabsorbed Urinary: 1-2 L/day; renal output varies depending on specific macronutrients, salt, and water loads – ↑ urine output in cold & hypoxia – ↓ urine output in exercise & heat – ↑ H2O excreted with waste products: urea and other nitrogen containing products (protein breakdown) & ketones (fat breakdown) Review: Water Balance Module 10 Learning Objectives 1. Describe the role of water in the body, and how body water is regulated Discuss hypo- and hyper-hydration 2. Introduce minerals and describe the key features 3. List the major physiological functions of the major minerals – electrolytes (sodium, potassium, chloride) Hyperhydration Hyponatremia Hypohydration ”dehydration” Hypernatremia General signs of hypohydration “dehydration” -Thirst -General Discomfort -Flushed skin - Cramps -Apathy -Dizziness -Headache -Vomiting/Nausea -Chills -Head/Neck Sensations Casa, D. J., Armstrong, L. E., Hillman, S. K., Montain, S. J., Reiff, R. V., Rich, B. S. E., & Stone, J. A. (2000). National Athletic Trainers' Association position statement: fluid replacement for athletes. Journal of athletic training, 35(2), 212. Hydration Level Indicators § Thirst § Urine Volume § Urine Color § Change in Body Mass Hydration Level Indicator: Thirst This sensation will not stimulate drinking behaviour until some degree of dehydration has already occurred. Not a very accurate indicator of water needs as some individuals are more sensitive to the sensation of thirst than others Hydration Level Indicator: Urine Volume When fluid intake is adequate, kidneys produce enough urine to maintain fluid balance – Consumption > needs; kidneys eliminate excess (body produces more urine) – Consumption < needs; kidneys produce less urine Hydration Level Indicator: Urine Color First morning urine should be comparable to pale lemonade. Use this chart to rate your fluid intake of the previous day Hydration Level Indicator: Change in Body Mass % Body Mass Change Example: 70 Kg Urine Colour Athlete Body Mass Change (kg) Well Hydrated +1 to -1 70.7 – 69.3 1 or 2 Minimal Dehydration -1 to -3 69.3 – 67.9 3 or 4 Significant Dehydration -3 to -5 67.9 – 66.5 5 or 6 < -5 < 66.5 >6 Serious Dehydration Make note of your body mass before and after your training session to estimate your losses in body fluid Dehydration (% body mass loss) Signs of hypohydration “dehydration” 1 2 3 4 5 6 7 12 Ordinary body mass fluctuations Thirst, decline in maximal aerobic power, impaired thermoregulation and cognitive function { Decrement of 20-30% in physical work capacity Further thermoregulation impairment >50% decrement in exercise performance High risk of collapse during exercise in hot/humid environment Approximate upper limit for survival, severe hypernatremia, neurologic disturbance, seizure, coma, death How does dehydration affect performance? ↓ Blood Volume ↓ Skin Blood Flow ↓ Sweat Rate ↓ Heat Dissipation ↑ Core Temperature ↑ Heart Rate ↑ Perception of Effort Can you drink too much water? No UL – Considerable ability to excrete excess water (thereby maintaining water balance) HOWEVER: acute water toxicity Hyperhydration Hyponatremia Hypohydration ”dehydration” Hypernatremia Can you drink too much water? No UL – Considerable ability to excrete excess water (thereby maintaining water balance) HOWEVER: acute water toxicity – Not as common as dehydration but more dangerous! – Water intake exceeds fluid losses – Extreme athletic endeavors with high water intake and high sweat rate – Associated with hyponatremia Hyponatremia Low levels of sodium in blood – Extreme fluid intake with high sweat rate (overwhelm kidneys) – Fluid retention – Not replenishing sodium losses after heavy sweating – Event inexperience – Other medical conditions Symptoms: – – – – – – – – Nausea & vomiting Muscle weakness, spasms, cramps Confusion Headache Loss of energy, drowsiness, fatigue Seizures Coma Death Similar to dehydration Important to distinguish between dehydration and water intoxication --> if drink more plain water, symptoms will worsen BOUNDLESS Documentary following friends/competitors Simon Donato (Calgary) and Paul “Turbo” Trebilcock (Hamilton) as they travel the world and compete in some of the most extreme events on Earth TIMES: 1:00-1:55 4:40-5:30 16:30-16:50 21:30-22:25 31:00-33:50 37:30-41:30 Season 1 - Episode 9 Cambodia: 230km 6-day ultra 47:00-End running event Module 10 Learning Objectives 1. Describe the role of water in the body, and how body water is regulated Discuss hypo- and hyper-hydration 2. Introduce minerals and describe the key features 3. List the major physiological functions of the major minerals – electrolytes (sodium, potassium, chloride) What are minerals? Inorganic elements needed in relatively small amounts – Like vitamins, they do not provide kcal … but they work with other nutrients to enable your body to function properly – Unlike vitamins they are not destroyed by heat, O2, or acid (but can leach out of food into cooking water as they are water soluble) Part of enzymes Work with your immune system Play a role in structural growth Help chemical reactions take place in cells Help muscles contract Keep heart beating Major vs. Trace Minerals Not due to relative importance – only named for amounts in diet and amounts stored in body Major minerals Trace minerals Needed in the diet in amounts greater than 100 mg/day, or Present in the body in amounts greater than 0.01% of body mass Required in the diet in amounts of 100 mg/day or less, or Present in the body in amounts of 0.01% of body mass or less Functions of Minerals Structural and regulatory roles; examples: – Ca, P, Mg, F affects structure and strength of bones – Iodine is a component of thyroid hormones (regulate metabolic rate) – Chromium plays a role in regulating blood glucose levels – Zinc plays a role in gene expression Serve as cofactors necessary for enzyme activity – Selenium is a cofactor for an antioxidant enzyme system Cofactor vs. Coenzyme? Coenzyme: organic; often bine loosely to active site of enzyme and aid in substrate recruitment Cofactor: organic or inorganic; do not bind to enzyme (they are ‘helper molecules’) Minerals as Cofactors 1. The mineral cofactor combines with the incomplete enzyme to form the active enzyme 2. The active enzyme binds to the molecule involved in the chemical reaction (compounds A & B) and accelerates their transformation into the final products (products A & B) 3. Final products are released, while enzyme remains unchanged Bioavailability Rate and extent to which a nutrient is absorbed When someone has a nutrient concern, we are looking to give them the highest source and the most absorbable Bioavailability affected by: 1. 2. 3. 4. 5. Digestive efficiency Nutrition status Concurrent intake of inhibitors/promotors Food preparation Nutrient source (supplement vs. whole food) Bioavailability of Minerals (examples) Almost 100% Na absorbed vs. ~5% Fe vs. ~25% Ca (but absorption higher at certain stages of life [pregnancy, infancy]) For some, absorption depends on am’t mineral consumed… for others consumption of other minerals carrying the same charge affects absorption – Ca, Mg, Zn, Cu, Fe all carry 2+ charge; high intake of one may reduce absorption of others Sources of Minerals Compared to plant foods, animal foods more reliable sources of minerals (e.g., iron, calcium) – Animal products have [higher] Plant foods may contain phytic acid or oxalic acid (naturally occurring molecules that interfere with mineral absorption) – Phytic acid is in whole grains and certain seeds – Oxalic acid is in spinach, collard greens, sweet potatoes Tap water may be a source – “hard” water naturally contains a variety of minerals: calcium, magnesium, sulfur, iron, zinc Natural Sources In some foods, am’t minerals are predictable Might vary depending on mineral concentration in soil/water at foods source Modern transportation systems make foods produced in many locations possible Processed Foods Processing/refining can cause losses or can add minerals Minerals can enter food supply inadvertently through contamination Supplements Daily multivitamin-multimineral supplement generally safe for healthy people (but be careful of single-mineral supp) Understanding Mineral Needs Maintenance of health: diet must contain all minerals in correct proportions – Short-term vs. long-term health consequences Deficiencies in iron, iodine, calcium are world health problems Deficiencies in other minerals are rare Toxicities occur most often due to environmental pollution or excessive use of supplements – e.g., lead, mercury Module 10 Learning Objectives 1. Describe the role of water in the body, and how body water is regulated Discuss hypo- and hyper-hydration 2. Introduce minerals and describe the key features 3. List the major physiological functions of the major minerals – electrolytes (sodium, potassium, chloride) Serum Electrolytes Common Electrolytes (reference range) § Sodium (Na+) (135-145 mEq/L) § Potassium (K+) (3.5-5.0 mEq/L) § Chloride (Cl-) (95-105 mEq/L) Other electrolytes: Magnesium (Mg+) Calcium (Ca+) Phosphate (P-) Bicarbonate (HCO3-) Cells use electrolytes to conduct electrical charges Na+Cl- (salt) is neutral; when dissolved in water Na+ and Cl- split apart; electricity can jump between them Most basic level: electrolytes help body maintain balance Electrolytes (Na+, Cl-, K+) Cations (+) and anions (-) are balanced Intracellular fluid (within cells) K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ Extracellular fluid (between cells & within plasma) Cl- Na+ Na+ ClNa+ Cl- Cl- Body fluids are neutral in charge – Cations (+) and anions (-) are balanced Na+ and K+ can ‘leak’; high K and low Na in intracellular fluid are maintained by Na-K pumps (supplied by ATP) Sodium and Chloride + (Na and Cl ) Sodium and Chloride Sodium Chloride (NaCl) Sodium is main extracellular cation (+) Cl Na Chloride is main extracellular anion (-) Sodium roles in body: Maintains fluid & electrolyte balance Nerve transmission Muscle contraction Regulates acid/base balance Chloride roles in body: Maintains fluid & electrolyte balance Nerve transmission Role in digestion (HCl in stomach) Regulates acid/base balance NaCl (table salt): 40% is Na+ and 60% is Cl Most sodium and chloride in diet comes from processed foods Na Cl Na Cl Cl Sodium and Chloride Sodium Sodium “healthy” foods Adults need... only 1500mg/day 480 x 6 = 2,880mg Sodium Sodium UL: Upper Limit CDRR: Chronic Disease Risk Reduction Intake 2300 mg/day Sodium Sodium Sodium Toxicity (hypernatremia) Increased plasma Na+ caused by: – Water loss (lack of thirst, unable to drink, vomiting, diarrhea, excess sweat, renal losses) OR – Gain in sodium (dietary or renal) Symptoms: edema, hypertension Sodium Aldosterone ↑ Na+ reabsorption by kidneys Water follows Na+, helping to maintain blood volume and BP ↓BP triggers ↓ kidney to release renin Ang II stim release aldosterone from adrenal gland ReninAngiotensinAldosterone System Renin converts angiotensinogen into angiotensin I, which is activated to angiotensin II Ang II ↑BP by constricting walls of blood vessels Sodium Sodium Toxicity (hypernatremia) Increased plasma Na+ caused by: – Water loss (lack of thirst, unable to drink, vomiting, diarrhea, excess sweat, renal losses) OR – Gain in sodium (dietary or renal) Symptoms: edema, hypertension A person who is sodium-sensitive more likely to develop hypertension from high-sodium diet – Kidneys may be unable to eliminate excess sodium as effectively … excess causes body to retain water and blood volume and BP to increase Sodium Sodium Prevalence of Hypertension in Canada Sodium HYPERTENSION Hemorrhage, Stroke Retinopathy LV hypertrophy, CAD, CHF Peripheral Vascular Disease Renal Failure Sodium Sodium Sodium Deficiency (hyponatremia) Nausea & vomiting Muscle weakness, spasms, cramps Confusion Headache Without hyponatremia Loss of energy, drowsiness, fatigue Balanced water and sodium Seizures Coma Death ? r e b m Reme With hyponatremia Imbalanced water and sodium Chloride Sources of Chloride Most chloride consumed is in table or sea salt (sodium chloride) Salt substitutes (potassium chloride) Many vegetables contain chloride Seaweed, rye, tomatoes, celery, olives are excellent sources Chloride Chloride Toxicity: – Rare (special case of impaired metabolism) – Can contribute to hypertension – Severe dehydration can lead to abnormally elevated blood chloride levels Deficiency: – Rare – Associated with chronic vomiting & diarrhea (GI bug), sweating, diuretic use – Symptoms: fatigue and loss of appetite Quick Review: NaCl Na is main extracellular cation (+) Cl is main extracellular anion (-) NaCl (table salt): 40% Na+ & 60% Cl As a society we consume WAY TOO much Na+ – Contributes to the high prevalence of hypertension in Canada K+ acts to lower BP! But we don’t take in enough … Potassium + (K ) Potassium Potassium Main intracellular cation (+) Roles in the body: – Lowers high BP – Fluid and electrolyte balance – Nerve transmission – Muscle contraction (incl heart) Potential Mechanisms for ↓ BP? High K intake has no effect on BP in normotensive individuals, but lowers BP in those with hypertension Mechanisms? – remember RAAS ! – Decrease in plasma renin activity – Decreased responsiveness to pressor effects of angiotensin II Increased prostaglandin production, receptor occupancy, decrease in angiotensin II receptor affinity – Decrease in aldosterone levels – Effects on resistance vessels K ↓ Aldosterone (and ∴ ↓ Na reabsorption) Aldosterone ↑ Na+ reabsorption by kidneys ↓BP triggers ↓ kidney to release renin K ↓ renin ber? m e Rem Water follows Na+, helping to maintain blood volume and BP DECREASE IN BLOOD PRESSURE Ang II stim release aldosterone from adrenal gland K ↓ Ang II Role of K in Renindecreasing BP Angiotensin(for those Aldosterone with System hypertension? Renin converts angiotensinogen into angiotensin I, which is activated to angiotensin II Ang II ↑BP by constricting walls of blood vessels DECREASE IN BLOOD PRESSURE Potassium Potassium Potassium Potassium Potassium Potassium Potassium Deficiency (hypokalemia) For the healthy person, K deficiencies are rare – Diets low in K and high in Na can lead to increased risk of heart disease Usually due to high losses --> dehydration, vomiting, diarrhea, K-wasting drugs (antibiotics, diuretics), steroid use, laxative abuse Associated with metabolic disorders, medical conditions or prescription drugs Symptoms: muscle weakness (problem with older population – falling), fatigue, heart complications, paralysis 100 Potassium Potassium Toxicity (hyperkalemia) Very rarely dietary (but can occur from supplements) Most often seen with medical conditions (heart disease; impaired kidneys), prescription drugs, severe dehydration, renal disease, immunosuppressants, supplemental overdose – Symptoms: arrhythmias, cardiac arrest No UL – not a problem in healthy adults 101 Electrolytes (Na+, Cl-, K+) Electrolytes Common Electrolytes § Sodium (Na+) § Potassium (K+) § Chloride (Cl-) The common diet is high in Na+, Cl-, and low in K+ Regulate body fluids by controlling fluid shifts in and out of cells (osmosis) Maintain blood pH Electrolytes act as buffers to maintain acid-base balance pH maintained 7.35-7.45 … by buffers! plasma proteins, bicarbonate, phosphate – Bicarbonate (HCO3-) is a neg. charged ion (electrolyte) that works with other charged electrolytes (Na+, K+, Cl-) to help maintain acid-base balance Bicarbonate-Carbonic Acid Buffer NaHCO3 + HCl → H2CO3 + NaCl (sodium bicarbonate) + (strong acid) → (weak acid) + (a salt) H2CO3 + NaOH→ NaHCO3 + H2O (weak acid) + (strong base) → (sodium bicarbonate) + (water) Bicarbonate ions (HCO3) and carbonic acid (H2CO3) are present in blood in 20:1 ratio if blood pH is in normal range – ∴ most efficient at buffering acids (helpful since lactic acid, ketone bodies are acids…) Carbonic acid levels controlled via expiration (CO2) Bicarbonate levels controlled via renal system (passed back into blood) Phosphate Buffers HCl + Na2HPO4→NaH2PO4 + NaCl (strong acid) + (weak base) → (weak acid) + (a salt) NaOH + NaH2PO4→Na2HPO4 + H2O (strong base) + (weak acid) → (weak base) + (water) Electrolytes and pH balance When electrolytes are out of balance due to dehydration, pH levels decrease (metabolic acidosis) – Symptoms: confusion, fatigue, headache, increased heart rate When electrolytes are out of balance due to hyperhydration, pH levels increase (metabolic alkalosis) – Symptoms: confusion, hand tremor, lightheadedness, muscle spasms, nausea Electrolytes (Na+, Cl-, K+) Electrolytes Common Electrolytes § Sodium (Na+) § Potassium (K+) § Chloride (Cl-) The common diet is high in Na+, Cl-, and low in K+ Regulate body fluids by controlling fluid shifts in and out of cells (osmosis) Help maintain blood pH Vital role in muscle contractions and neural impulses necessary for physical activity (Ca+, K+, Na+) Electrolytes (Na+, Cl-, K+) Summary: Water Functions: transports, lubricates, regulates body temperature Adult human is ~60% H2O distributed between intra- and extracellular components Water regulated via solute (electrolyte) and solvent (water) concentrations in body compartments… via osmosis Water IN: water, beverages, food – AI for water: 2.7L females; 3.7L males (no UL) Water OUT: urine, feces, respiratory, sweat Water needs vary based on environmental conditions, activity levels Summary: What are minerals Elements needed by the body to regulate chemical reactions and provide structure (found in both plant and animal foods) Sources: added to some foods through fortification; get into some foods by contamination; supplements Bioavailability affected by body needs, interactions with other minerals, vitamins, dietary components Water Imbalance Electrolytes Hypohydration/dehydration (or Na+, Cl-, and K+ important in hypernatremia) vs. maintenance of fluid balance hyperhydration (or & formation of membrane hyponatremia) are conditions potentials (essential for related to lack of water nerve transmission & muscle homeostasis contraction) Hypohydration most common, + and Cl Diet abundant in Na can be monitored by: thirst, urine from processed foods and volume & color, body mass + table salt; generally low in K change, sweat rate Hyperhydration is associated with hyponatremia – dangerously low levels of sodium that can lead to death END Water and Electrolytes! 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