Part I:Water is everywhere. Our bodies are 60-70%water. The earth's surfaceis about 71%water (https://water.usgs.gov/edu/earthhowmuch.html). Every day we lose water and must replace it (Lecture 7). Most of us are fortunate enough to have access to running water. Why is drinking water such big business these days? Let's discuss - choose one of the following topics to kick off your main post:
- Water requirements: The risks of dehydration vs. water intoxication (expand on Lecture 7)
- Vitamin Water - risky, beneficial, or neither one?
- Alkaline Water - a trend these days. Is this really beneficial?
- Electrolyte water such as Gatorade
- Which is better - tap water or bottled water
Part II: reply to the following post(in short) about 50 words is good enough.
I'll post it once part I gets done.
Bio 125 Spring 2016 Lecture 7 Janine Grant Water, Intro to Minerals, The Electrolytes 1 Bio 125 Distance Learning Lecture 7 Janine Grant Water, Intro to Minerals, The Electrolytes Learning Objectives Describe the functions of water in the body Define minerals in nutritional terms, their categories, and their functions Discuss the major minerals aka 3 major electrolytes: Sodium Potassium Chloride 2 WATER We can survive up to about 8 weeks without food but only a few days without water. Water is an essential nutrient. The healthy body maintains homeostasis of water and electrolytes. The brain, stomach receptors, adrenal glands and kidneys work to maintain correct hydration. The more we drink the more dilute the urine. We also need to drink water to compensate for sweating and other functions. Functions of water in the body: Solvent Water is a polar molecule, i.e. the oxygen is slightly negative and the hydrogen is slightly positive. Therefore water is a medium in which salts dissolve and dissociate into their anions (e.g. chloride) and cations (e.g. sodium, potassium). Intracellular fluid is high in potassium ions. Extracellular fluid is high in sodium and chloride ions. These ions are examples of electrolytes – they conduct electricity in water. Transport Blood transports oxygen and nutrients to cells and carries carbon dioxide and waste products away from cells. Urine transports waste products out of the body. Protection Lubricant, i.e. tears, synovial fluid in joints, saliva, spinal fluid Amniotic fluid 3 Body Temperature Regulation Water changes temperature slowly in response to changes in external environment. When body temperature is elevated, blood vessels dilate causing blood to flow close to surface of the body, releasing heat. When body temperature is elevated, evaporation of sweat releases heat. In a cold environment, the blood vessels constrict, restricting the flow of blood to the surface, conserving heat. Chemical Reactions – i.e. all metabolic reactions Hydrolysis – breaks bonds by adding water Condensation reactions (aka dehydration synthesis) – forms bonds Regulation of Acid/Base balance Substances dissolved in water (e.g. buffering system) help to regulate pH in the body. Chemical reactions in the body need a slightly basic environment (i.e. the pH of the blood is 7.4). 4 5 Water (H2O) is a Polar Molecule Polarity allow water to function as a solvent for charged particles (ions) and other polar molecules. Notice how the shared electrons are more strongly attracted to the oxygen (which has 8 protons) than to the hydrogen (which has 1 proton) Distribution In adults about 60% of body weight is water depending on body composition and age. Infants have the highest percentage, older adults have the lowest. Higher body fat percentage – lower water %. Blood is about 90% water, muscle is about 75% water and bone is about 25% water, fat cells about 10% water. Approximately 2/3 of body water is found in intracellular fluid (inside the cells). Approximately 1/3 is found in extracellular fluid, which includes blood plasma, lymph, gastric secretions, tears, spinal fluid, and the fluid between the cells (the interstitial fluid). Each of these compartments has varying amounts of solutes dissolved such as protein and electrolytes. 6 Water Balance Intake We cannot conserve enough to replace daily losses. It is not stored in the body and must be replaced. When water loss increases, such as in hot weather and exercise, intake must increase to maintain homeostasis. Water is absorbed from the GI tract via osmosis. Pure water increases absorption, intake of other nutrients slow absorption. Losses Urine – about 1-2 liters/day Fecal – about 200 ml/day (less than a cup) Insensible (we are unaware of it) – evaporation from skin and lungs – about 1 liter/day Sweat – differs from insensible because we are aware of it – big variations 7 Regulation of Intake Decrease in blood volume stimulates thirst. Thirst is not always a reliable, or timely, indicator of dehydration. Regulation of Water Losses Kidneys Water and solutes filtered out of blood. Amount of water and dissolved substances reabsorbed is regulated by ADH (anti diuretic hormone – secreted by posterior pituitary). Keeps level of blood solutes (dissolved substances) within normal range High protein diets increase excretion (urea must be dissolved in water). 8 8 Recommended Intake (AI) 3.7 liters/day for men, 2.7 liters/day for women, about 0.7 liters for infants up to 6 months old. (according to text) Needs are increased by: Increased physical activity Hot environment High protein intake, urea excretion Weight loss and fat breakdown – the elimination of ketone bodies High sodium intake Very high salt intake will increase the blood concentration of sodium, stimulating thirst receptors. Extra water intake dilutes the sodium and the kidneys excrete the excess sodium and water. High fiber intake (especially helps prevent supplemental fiber from forming blockages) Diuretics such as caffeine and alcohol Fever Illness resulting in diarrhea/vomiting Pregnancy 9 Water and Health Too little water = dehydration: Decreased blood volume reduces ability to deliver oxygen and nutrients, and remove waste products. Symptoms – headache, fatigue loss of appetite, dry eyes/mouth, nausea, dark colored urine, confusion. Loss of 10 – 20% of body weight in water – death Too much water = overhydration, or water intoxication: Electrolyte loss Hyponatremia (low sodium in blood) Water moves out of blood vessels, causing swelling of tissues, including brain. Symptoms are nausea, disorientation, muscle cramps. 10 MINERALS Inorganic elements required by the body. Unlike vitamins, minerals are not destroyed by heat, oxygen or acid. They retain their chemical identity in the body. Functions: Co-factors (similar to coenzymes) for many enzymes Structural components (e.g. bones) Regulators of body processes such as: Oxygen transport (iron/hemoglobin) Regulation of metabolism (iodide/thyroid hormone) Osmotic pressure, fluid/electrolyte balance Transmission of nerve impulses – electrolytes Muscle contraction – calcium/magnesium pH balance 11 MAJOR MINERALS (macrominerals) Requirements of greater than 100 mg. per day MagnesiumSodium PhosphorusPotassium CalciumChloride Sulfur (usually from amino acids) TRACE MINERALS (microminerals) Requirements of less than 100 mg. per day IronManganeseGermanium ZincFluorideTin CopperMolybdenumSilicon ChromiumNickelColbalt SeleniumLithiumVanadium IodideBoron 12 MINERALS IN THE DIET Minerals come from plant and animal sources. Mineral content depends on soil in which it is grown. Processed foods lose most of their minerals, however these foods are usually high in added sodium. MINERALS IN THE DIGESTIVE TRACT Mineral absorption and bioavailability depends on: Amount consumed Requirements - low levels in the body enhance absorption. Organic acids present in some plant foods that can act as antinutrients: Phytates - organic compounds found in whole grains, bran and soy products that bind zinc, calcium, magnesium, iron. Tannins - organic compounds found in tea, wine and some grains, that may interfere with iron absorption. Oxalates - organic compounds found in spinach, rhubarb, beet greens, and chocolate, that may interfere with calcium and iron absorption. Acidic foods and vitamin C enhance absorption of iron POST ABSORPTION Minerals are transported in the blood bound to transport proteins. 13 13 14 ELECTROLYTES: (3 of the Major Minerals) Electrolytes conduct electricity when dissolved in water. The main electrolytes in body fluid are sodium, potassium and chloride. The modern diet is low in potassium and high in sodium and chloride (table salt) because it incorporates a lot of processed foods. Functions of Electrolytes: Regulation of Fluid Balance High concentration of electrolytes attracts water via osmosis to dilute their concentration. Nerve conduction Muscle contraction OVERVIEW OF THE MAIN ELECTROLYTES: Sodium and Potassium: Both positively charged (cations). Sodium and potassium maintain fluid balance in the tissues, pH balance (keeps heartbeat regular). Sodium and potassium work together with nerve impulse transmission, muscle contraction and cardiac function. Sodium concentration is high outside the cell; potassium concentration is highest inside. Stimulation of nerve cell by neurotransmitters causes sodium to rush inside the cell, reversing or depolarizing the charge of the cell membrane. Then the original membrane potential is restored via the sodium-potassium pump. Chloride: Principal extracellular anion (negatively charged). 15 SODIUM Major extracellular cation (e.g. blood) Absorption and Metabolism Easily absorbed, mostly in small intestine. 90-98% of dietary sodium is absorbed. Kidneys filter excess sodium from blood. Aldosterone (hormone from adrenal glands) maintains correct level in blood. If sodium levels drop too low, aldosterone promotes sodium retention and potassium excretion. If blood levels are too high, thirst encourages extra water intake to keep ratio of sodium to water constant. Functions Maintains extracellular fluid balance (e.g. in blood) by attracting water. Blood pressure regulation. Nerve impulse transmissions, including to heart muscle. Acid/Base (pH) balance. 16 RDAs for Adults No RDA. Minimum recommended intake 500 mg. AI 1500 mg day (from 3800 mg table salt - NaCl) Daily Value (DV) no more than 2300 mg Deficiency (Hyponatremia) Muscle cramps, nausea, vomiting, dizziness. In severe depletion, coma. Deficiency is uncommon. When levels in body are low, desire for salt increases. Toxicity Hypertension due to an increase in blood volume in salt sensitive individuals. Toxicity uncommon when kidneys are functioning. High sodium intake has been associated with increased calcium excretion – unproven. Good Food Sources Table salt (sodium chloride), soy sauce, processed foods are major sources. 17 POTASSIUM Major intracellular cation (electrolyte) Absorption and Metabolism Easily absorbed; at least 90% of dietary potassium is absorbed from the small intestine. Most diuretics deplete potassium. Fasting also depletes. Functions Many overlapping functions as sodium (the two minerals work together) Fluid balance within the cell Blood pressure Nerve impulses Muscle contractions, including the heart pH balance 18 RDAs for Adults No RDA. Minimum recommended intake 1,600 to 2,000 mg/day AI - 4700 mg/day Daily Value (DV) – at least 3,500 mg/day Deficiency (Hypokalemia) Muscle weakness, muscle cramps, fatigue, confusion, irritability Heart rhythm disturbance Hypertension Excessive sweating, diarrhea, fasting. Very low dietary intake of fresh fruits and vegetables. Diuretics - most deplete potassium Magnesium depletion correlated with potassium loss Black licorice depletes potassium 19 Toxicity Can result from oral supplemental intake: Vomiting, muscle weakness, possibly fatal irregular heartbeat. Can result from impaired kidney function. Toxicity from extremely high IV intake can stop the heart. Good Food Sources Fresh fruits and vegetables, dairy, meat, nuts 20 CHLORIDE Major extracellular anion (negatively charged) Absorption and Metabolism Easily absorbed, along with dietary sodium, i.e. as sodium chloride. Free chlorine is a toxic gas, it exists in the body as the chloride ion, which is not toxic and essential to health. Functions Major negatively