Week 30. Water Balance and Minerals

Transcription

1 Week 30 Water Balance and Minerals

2 Water: more vital to life than food involved in almost every body function is not stored--excreted daily largest single constituent of the human body, averaging 60% of total body weight although most people can survive 6 weeks or longer without food, death occurs in a matter of days without water occupies essentially every space within and between body cells and is involved in virtually every body function

3 Basic Principles Body water compartments Intracellular Extracellular Intravascular Interstitial Membranes separate water compartments Particles in solution Homeostasis

4 Functions of Water in the Body

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6 Water Under normal conditions, water intake equals water output to maintain water balance In most healthy people, thirst is a reliable indicator of need The body s need for water is influenced by many variables A general guideline is to consume 1.0 ml of fluid per calorie consumed, with a minimum of 1500 ml/day to meet metabolic needs

7 Water: an essential nutrient Water is an essential nutrient because the body cannot produce as much water as it needs On average, adults lose approximately 1450 to 2800 ml of water daily

8 Insensible water loss--immeasurable Insensible water losses from the skin and expirations account for approximately half of the total water lost daily Extreme environmental temperatures (very hot or very cold), high altitude, low humidity, and strenuous exercise increase insensible losses Water evaporation from the skin is also increased by prolonged exposure to heated or recirculated air such as during long airplane flights

9 Sensible water loss--measurable Sensible water losses from urine and feces make up the remaining water loss Because the body needs to excrete a minimum of 500 ml of urine daily to rid itself of metabolic wastes, the minimum daily total fluid output is approximately 1500 ml To maintain water balance, intake should approximate output

10 Sources and average amounts of daily water loss Source of Water Average Amount Loss Lost (ml/d) Perspiration 450 to 900 Exhalations 350 Urine 500 to 1400 Feces 150 Total 1450 to 2800

11 Electrolytes Small, inorganic substances When they dissociate they carry a charge Cation Na+, K+, Ca++, Mg++ Anion Cl-, HCO3-, PO4-, so4 Balanced Measured in milliequivalents

12 Plasma Proteins Albumin Globulin Large molecules

13 Small Organic Compounds Dissolved in water Usually small concentrations Do not ordinarily influence water movement in the body

14 Membranes Capillary membranes Cell membranes

15 Movement of Water in the Body Osmosis Diffusion Facilitated diffusion Filtration Active transport Pinocytosis

16 Hormonal Control Antidiuretic hormone AKA vasopressin Aldosterone

17 Minerals Minerals are inorganic substances that cannot be broken down and rearranged in the body 117 known elements 25 essential to life and perform a variety of metabolic functions 7 major and 18 minor minerals

18 Mineral Metabolism Digestion Absorbed as ions Do not require mechanical or chemical digestion Absorption Transport Tissue Uptake

19 Functions of Minerals Structure Fluid balance Acid---base balance Nerve cell transmission and muscle contraction Vitamin, enzyme, and hormone activity

20 Mineral toxicities are not likely to occur from diet alone are most often related to excessive use of mineral supplements environmental exposure alterations in metabolism

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22 Mineral balance Depending on the mineral involved, the body can maintain mineral balance by altering the rate of absorption altering the rate of excretion releasing minerals from storage when needed The absorption of many minerals is influenced by mineral-mineral interactions Too much of one mineral may promote a deficiency of another mineral

23 Sodium One of the most plentiful minerals in the body Function Maintain water balance Muscle action Nutrient absorption Deficiency: rare

24 Sodium and the American diet As much as 75% of sodium consumed in the average American diet is from processed food Americans are urged to reduce their intake of sodium because of its potential role in the development of hypertension

25 Sodium National Academy of Science s Institute of Medicine Healthy Adult mg Less if >50 or have HTN Average Adult Male: 3300mg/d

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27 Descriptors of Sodium Content If the label says... 1 serving contains... Sodium free <5 mg Very low sodium <35 mg Low sodium <140 mg Reduced or less sodium 25% less sodium Light in sodium 50% less sodium Salt free <5 mg Unsalted or no added saltno salt added during processing

28 Calcium Many American adults consume less than optimal amounts of calcium, placing them at risk of osteoporosis and possibly hypertension Milk and yogurt are the richest sources of calcium, and their vitamin D and lactose content promote its absorption The National Academy of Science recommends American adults consume mg of calcium daily

29 Calcium Deficiency and Toxicity Rickets Related to inadequate vitamin D Tetany Osteoporosis Toxicity unlikely from food sources Kidney stones Decreased absorption of other minerals

30 Calcium Supplements TUMS is made of calcium carbonate--it is 40% elemental calcium and is generally the least inexpensive calcium supplement Calcium carbonate supplements can cause constipation-- encourage an adequate fluid intake and a high fiber diet as needed Calcium citrate is less likely to cause constipation than calcium carbonate Calcium from supplements is absorbed best in doses of 500 mg or less--tablets should be spread out over the day

31 Phosphorus Functions Bone and tooth formation Energy Metabolism Acid-base balance Sources Found in all plant and animal cells Deficiency and toxicity: rare

32 Potassium Functions Water balance Metabolic reactions Muscle action Insulin release Blood pressure AI =4.7g/day for all adults Deficiency and Toxicity Sources

33 Chloride Major extracellular anion One of the elements in HCl Acid-base balance Deficiency and toxicity

34 Magnesium Mostly in bone A cofactor for more than 300 enzymes Magnesium intake is 80% of recommended Large doses of supplemental magnesium may cause diarrhea, nausea, cramping Food sources

35 Sulfur Essential part of protein structure: hair, skin and nails, necessary for collagen formation Supplied by protein foods Deficiency and toxicity unseen

36 Iron Essential but toxic in excess 70% of body s iron is in hemoglobin Necessary for glucose metabolism, antibody production, drug detoxification, conversion of beta carotene to vitamin A Deficiency and toxicity Food sources

37 Iodine Component of T4 (thyroxine) Deficiency Goiter Cretinism Hypothyroidism Hyperthyroidism Toxicity Food sources Food sources dependent on iodine in the soil Major reliable source: iodized salt

38 Fluoride Binds with calcium Strengthens tooth enamel

39 Zinc Functions Enzyme constituent Immune system Prohormone Deficiency and Toxicity Food sources

40 Encourage healthy beverage choices: Replace soft drinks with calorie-free versions such as diet soda or sparkling water Use bottled water, if the taste of tap water is objectionable Refrigeration usually improves the taste of tap water Drink a glass of water before each meal, especially if weight control is a concern Eat enough fruits and vegetables