Laura Coronado Laney College1 Chapter 8 Water and Electrolytes: Striking a Balance

A Water Molecule Inorganic (no carbon) Laura Coronado Laney College2

Water’s Charge Distribution Laura Coronado Laney College3

A Water Molecule Water has unique bonding properties than in other substances. – Hydrogen side has a slight positive charge – Oxygen has a slight negative charge – Because of this unique polarity in charge, other substances that are charged, such as table salt, can dissolve in water. Laura Coronado Laney College4

Distribution of Water in the Body Laura Coronado Laney College5

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Distribution of Water in the Body The adult human body is 56 to 64 percent water: Found inside the cells (intracellular), 60% (muscle cells) Found outside the cells (extracellular), 40%  Water between cells (interstitial)  Connective tissue, joints, spinal fluid, mucus Men have higher percentages than do women. Laura Coronado Laney College7

Is Bottled Water Better? Despite lack of scientific research, consumers believe that bottled water is better for them. It may be safer for health. But is it “safer” for the environment? Laura Coronado Laney College8

Bottled Water FDA regulates bottled water if it crosses state lines 25% bottled water comes from tap water Spring water comes from an underground source, must maintain the composition found at the source, and must contain less than 250 ppm solids Mineral water is the same as spring water except it has greater than 250 ppm solids and no minerals can be added Sparkling water is similar to spring water but must have dissolved carbon dioxide present at its source Laura Coronado Laney College9

Water Balance Highest fluctuating nutrient must balance water depletion with ingestion Water has no storage mechanism Water loss depends on – Environmental temperature, age, activity level Water is loss in respiration (lungs), urine & feces Infants lose more relative to weight Remember, the main function of water is to cool the body Laura Coronado Laney College10

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Hydration: Water Intake and Retention Thirst is controlled by the hypothalamus Thirst not best indicator of hydration may lag behind actual body’s needs Antidiuretic hormone secreted by pituitary gland – Signals kidneys to retain water Aldosterone secreted by adrenal glands – Signals kidneys to retain sodium resulting in holding onto water Laura Coronado Laney College12

How Much Water Should We Drink? 1.5 mL/kcal or 8–12 cups per day (including beverages and water in food) May need more if: – Pregnant – Breast feeding – Exercising ¾–1.5 cups for every 15 minutes – On a high-protein diet to remove amines & ketone bodies Laura Coronado Laney College13

Staying Hydrated During Exercise Drink before, during, and after exercise Drink early, drink often Before: 1.5–2.5 cups of fluid every 2–3 hours During: ¾ to 1.5 cups every 15–20 min After: 2–3 cups first 30 minutes after exercise; 4 – 4.5 cups every 1–2 hours until body weight is back to pre-exercise level Do not drink just plain water need to replace electrolytes, especially sodium Select foods high in water Laura Coronado Laney College14

Dangers of Dehydration Decrease in extracellular water concentration will result in water be taken from the cell (intracellular water) causing dehydration 1 - 2% can cause lack of concentration, mild fatigue, and impaired athletic performance 5% can lead to cramping and heat exhaustion 7 – 10% causes hallucinations and heat stroke Occurs with diarrhea & vomiting Laura Coronado Laney College15

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Dehydration in Infancy Increased ratio of surface area to body volume = greater water loss – Greater requirement relative to weight – Greater metabolic rate Diarrhea and vomiting increase chances of dehydration Infants need 2 oz. of fluid/day per pound of weight – Easily met by breast milk or formula Oral rehydration solution – Pedialyte With hotter weather need to increase fluids Laura Coronado Laney College17

Signs of Dehydration in Infants Dry mouth and tongue No tears even when crying Irritability No wet diapers for three hours or more (five to six wet diapers are normal) Sunken eyes and cheeks Inactivity or sleepiness Sunken soft spot on the head Laura Coronado Laney College18

Role of Kidneys & Urine in Water Balance Laura Coronado Laney College19

Role of Kidneys in Water Balance Nephrons in your kidneys control the composition of urine and blood; they filter the blood Hormonal signals tightly control what is filtered and what is excreted as urine Water and electrolytes are reabsorbed based on your body’s needs and hydration level At rest 1 liter of blood is filter per minute Laura Coronado Laney College20

Role of Urine in Water Balance Major source of water loss You produce 4–8 cups of urine per day Water, electrolytes, urea, creatinine Urea is a waste product of protein and muscle metabolism Laura Coronado Laney College21

Electrolytes: Sodium (Na⁺), Potassium (K⁺) & Chloride (Cl¯) Electrolytes = minerals that when placed in water become charged particles Cations - Positively charged (sodium extracellular and potassium intracellular) Anions - Negatively charged (chloride) associated with sodium (extracellular) Laura Coronado Laney College22

Should someone who does not exercise be concerned about electrolytes? It depends on which electrolyte. Sodium: No – DRI for sodium = 1,500 mg – Table salt is 40 percent sodium. – The average American consumes eight to twelve times the estimated daily requirement. Potassium: Yes – DRI 5,700 mg; many people do not get this amount. – One banana = 450 mg Chloride: No – 2,300 mg/day consumed with sodium Laura Coronado Laney College23

Dietary Sodium DRI – 1500 mg/day Most sodium consumed is from processed foods, not table salt % of sodium in the American diet is added to food by manufacturers Laura Coronado Laney College24

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Chloride in Food Natural Cl¯ content in most food is low 1 g sodium chloride or table salt is 600 mg chloride (60%) Most Americans consume 10 to 15 g of salt during cooking or adding at table Easy to exceed the DRI of 2,300 mg Laura Coronado Laney College26

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Potassium DRI mg/day Not usually added to foods Good sources are fresh fruits and vegetables – Tomatoes, carrots, potatoes, beans, peaches, pears, squash, oranges, bananas Laura Coronado Laney College28

Sodium and Hypertension A diet high in sodium may increase risk for high blood pressure 25% of Americans have high blood pressure known risk factor for coronary heart disease & stroke Essential hypertension – high blood pressure with no known cause (most cases) Most treatable Laura Coronado Laney College29

High Blood Pressure High blood pressure 140/90 Systolic, top number Diastolic, bottom number To treat – Lose weight – Reduce sodium in some people – Consume adequate potassium Laura Coronado Laney College30

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High Blood Pressure Salt sensitive – some people will have an increase in blood pressure on a high Na⁺ diet Low Na⁺ diets are often recommended for people with high blood pressure Potassium seems to provide an antihypertensive effect by relaxing blood vessels – maintain a balance between K⁺ and Na⁺ A lack of magnesium and calcium may also contribute to high blood pressure Laura Coronado Laney College32

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Absorption and Function of Electrolytes Sodium is absorbed by several mechanisms in the small intestine and colon along with chloride. – Helps absorption of amino acids, glucose, and some B vitamins Potassium absorption occurs along the length of the intestines, especially the colon. – Necessary for the movement of sodium across the small intestine & colon Laura Coronado Laney College34

Physiological Functions The movement of water and electrolytes across cells is important for the maintenance of health and normal functions Water and electrolytes move across cells by two processes – Osmosis – Diffusion Laura Coronado Laney College35

Physiological Functions Osmosis is the movement of water across a membrane from an area where there are fewer particles to an area where there are more particles in order to equalize the concentration in both cells – Membrane is permeable to the water but not to the salt in this example Laura Coronado Laney College36

Physiological Functions Diffusion is the movement of electrolytes from an area of greater concentration to an area of lesser concentration Laura Coronado Laney College37

Sodium and Potassium and Nerve Transmission Laura Coronado Laney College38

Physiological Functions Chloride is part of stomach acid (HCl) Electrolytes buffer body fluids Electrolytes enhance water absorption Laura Coronado Laney College39

Deficiencies Sodium deficiency is rare. – Hyponatremia – occurs with dehydration or if water is replaced with no sodium Potassium deficiency – hypokalemia – Use of laxatives and diuretics – Excessive vomiting and/or diarrhea – Kidney disease – Extreme weight loss Laura Coronado Laney College40

Sports Drinks Enhance water absorption and replace lost electrolytes Not needed in events less than one hour 6% glucose ideal 2.5 cups per pound of weight lost Help replace sodium and potassium Laura Coronado Laney College41