Water and the Major Minerals Chapter 12

Water and the Body Fluids Water constitutes majority of body weight Body composition Females Obese people Elderly

Water and the Body Fluids Carries nutrients and waste products Maintains structure of large molecules Participates in metabolic reactions Serves as a solvent Acts as a lubricant and cushion Aids in regulation of body temperature Maintains blood volume

Water Balance and Recommended Intake Cellular fluids Intracellular fluid Extracellular fluid Interstitial fluid Intravascular fluid

Water Balance and Recommended Intake Water intake Thirst and satiety Mouth, hypothalamus, and nerves Thirst response lags behind the body’s need for water Dehydration symptoms Water intoxication Symptoms

Signs of Dehydration

Water Balance and Recommended Intake Sources Water Beverages Foods Condensation reactions Oxidation of energy-yielding nutrients

Water Balance and Recommended Intake Losses Minimum excretion each day as urine Vapor from lungs Sweat from skin Loss in feces Recommendations Needs vary AI for total water

Water Balance and Recommended Intake Health effects Meet bodily needs Protect against urinary stones & constipation Concentration, alertness, and short-term memory Type of water Hard water Soft water

Blood Volume and Blood Pressure Kidneys are central to blood volume and pressure maintenance Antidiuretic hormone (ADH) Hypothalamus stimulates pituitary gland Water-conserving hormone Stimulates kidneys to reabsorb water Events trigger thirst

Nephron Function in the Kidney

Blood Volume and Blood Pressure Renin Enzyme released by kidney cells when blood pressure is low Kidneys reabsorb sodium Water retention Angiotensin Renin hydrolyzes angiotensinogen to angiotensin I Convert to active form – angiotensin II

Blood Volume and Blood Pressure Aldosterone Released from adrenal glands Release stimulated by angiotensin II Signals kidneys Excrete potassium Retain sodium

How the Body Regulates Blood Volume

Fluid and Electrolyte Balance Fluid balance Two-thirds inside the cells One-third outside the cells Dissociation of salt Sodium – cation Chloride – anion Conduct electricity

Fluid and Electrolyte Balance Electrolytes attract water Water molecules have net charge of zero Water follows electrolytes Electrolytes predominantly outside of cell Sodium and chloride Electrolytes predominantly inside of cell Potassium, magnesium, phosphate, sulfate Selectively permeable membranes

Water Dissolves Salts and Follows Electrolytes

A Cell and Its Electrolytes

Osmosis

A B A B A B Water can flow both ways across the divider, but has a greater tendency to move from side A to side B, where there is a greater concentration of solute. The volume of water becomes greater on side B, and the concentrations on side A and B become equal. With equal numbers of solute particles on both sides of the semipermeable membrane, the concentrations are equal, and the tendency of water to move in either direction is about the same. Now additional solute is added to side B. Solute cannot flow across the divider (in the case of a cell, its membrane). Figure 12.6: Osmosis. Water flows in the direction of the more highly concentrated solution. Stepped Art Fig. 12-6, p. 391

Fluid and Electrolyte Balance Proteins regulate fluid movement Attract water Transport proteins Passage of ions across cell membranes Sodium-potassium pump Regulation of fluid and electrolyte balance Two sites GI tract Kidneys

Fluid and Electrolyte Imbalance Causes of imbalance Prolonged vomiting or diarrhea Heavy sweating Burns Traumatic wounds Some medications An imbalance can result in a medical emergency

Fluid and Electrolyte Imbalance Solutes lost depend on why fluid is lost Vomiting or diarrhea – sodium Tumor development – potassium Replacing lost fluids and electrolytes Plain cool water and regular foods Special replacement fluids

Acid-Base Balance Regulation of acidity Concentration of hydrogen ions Narrow pH range to avoid life-threatening consequences Denaturation of proteins Concentration of hydrogen ions High hydrogen concentration – acidic Low hydrogen concentration – basic

The pH Scale

Acid-Base Balance Body defense against pH fluctuation Buffers in blood Bicarbonate Carbonic acid Respiration in lungs Excretion in kidneys

Bicarbonate-Carbonic Acid Buffer System

The Minerals – An Overview Major vs. trace minerals Variation in amounts needed Inorganic elements Always retain chemical identity Cannot be destroyed by heat, air, acid, or mixing Body’s absorption and handling Freely or with carriers

The Minerals – An Overview Bioavailability Varies Food binders Nutrient interactions Presence of other minerals Absorption, metabolism, and excretion Varied roles

Sodium Roles in body Sodium travels freely in the blood Principal cation of extracellular fluid Primary regulator of volume Acid-base balance Nerve impulse transmission Muscle contraction Sodium travels freely in the blood Kidneys: filter out and return what is needed

Sodium Recommendations Hypertension Diets rarely lack sodium UL for adults Average intake in U.S. exceeds the UL Hypertension Salt vs. sodium or chloride alone Salt intake DASH diet

Sodium Bone Loss (osteoporosis) Food sources High salt intake is associated with increased calcium excretion Potassium as protective factor DASH diet recommendation Food sources Processed foods More sodium Less potassium

Sodium Deficiency Toxicity Conditions causing a deficiency Acute Hyponatremia Toxicity Acute Edema and high blood pressure Chronic Hypertension

Chloride Essential nutrient Roles in the body Major anion of extracellular fluids Moves passively across membranes Associates with sodium and potassium Helps maintain fluid and electrolyte balance Part of hydrochloric acid

Chloride Recommendations and intakes Deficiency and toxicity Abundant in processed foods Recommendations are slightly higher, but still equivalent to those of sodium Deficiency and toxicity Diets rarely lack chloride Conditions leading to deficiency Toxicity – due to water deficiency

Potassium Principal intracellular cation Roles in the body Helps maintain fluid and electrolyte balance Helps maintain cell integrity Aids in nerve impulse transmission and muscle contraction

Potassium Recommendations and intakes Hypertension Fresh foods are richest sources AI for potassium Increase fruit and vegetable consumption Hypertension Diets low in potassium Diets high in potassium Risk of stroke

Potassium Deficiency Toxicity Increase in blood pressure Salt sensitivity Kidney stones Bone turnover Irregular heartbeats Muscle weakness Glucose intolerance Toxicity No UL Overconsumption of potassium salts or supplements Certain diseases or treatments Kidneys accelerate excretion

Calcium Most abundant mineral in the body Adequate intake Grows a healthy skeleton in early life Helps minimize bone loss in later life Majority of body’s calcium is in bones and teeth Part of bone structure Calcium bank

Calcium In bones In teeth Calcium salts form crystals Hydroxyapatite Strength and rigidity to maturing bones Bone remodeling In teeth Fluoride stabilizes calcium crystals in teeth

Calcium In body fluids Helps to maintain normal blood pressure Extracellular calcium Participates in blood clotting Intracellular calcium Regulation of muscle contraction Transmission of nerve impulses Secretion of hormones Activation of some enzyme reactions

Calcium Disease prevention Obesity Hypertension Blood cholesterol Diabetes Colon cancer Obesity May help maintain healthy body weight Inverse relationship with food sources

Calcium Calcium balance Involves system of hormones and vitamin D Parathyroid hormone & calcitonin Organ system response Intestines Bones Kidneys Calcium rigor Calcium tetany

Calcium Balance

Calcium Absorption Adults absorb about 30% of the calcium ingested Stomach’s acidity – calcium soluble Vitamin D – calcium-binding protein Efficiency and inadequate intakes Factors that enhance calcium absorption Factors that inhibit calcium absorption

Calcium Recommendations Based on amount needed to retain calcium in bones Peak bone mass Set high enough to accommodate 30% absorption rate UL has been established Adverse effects from supplements

Maintaining Blood Calcium

Calcium Milk products Other foods Calcium and iron Calcium is most abundant in milk products Conceal milk products in foods Consequences of drinking too little milk Other foods Bioavailability Fortified juices and foods Calcium and iron

Bioavailability of Calcium from Selected Foods

Almonds, sesame seeds, pinto beans, sweet potatoes Cauliflower, watercress, brussels sprouts, rutabaga, kale, mustard greens, bok choy, broccoli, turnip greens ≥ 50% absorbed ≈ 30% absorbed Milk, calcium-fortified soy milk, calcium-set tofu, cheese, yogurt, calcium- fortified foods and beverages Figure 12.15: Bioavailability of Calcium from Selected Foods. ≈ 20% absorbed Almonds, sesame seeds, pinto beans, sweet potatoes ≤ 5% absorbed Spinach, rhubarb, Swiss chard Stepped Art Fig. 12-15, p. 404

Calcium Deficiency Peak bone mass by late 20s All adults lose bone with age Begins between 30 and 40 years of age Osteopenia Osteoporosis Silent disease Blood samples offer no clues

Phases of Bone Development Throughout Life

Phosphorus Second most abundant mineral in body Roles in body Hydroxyapatite crystals of bone and teeth Roles in body Part of major buffer system Part of DNA and RNA Assists in energy metabolism Helps transport lipids in the blood Structural component of cell membranes

Phosphorus Recommendations and intakes Deficiencies are unlikely Best sources Foods rich in proteins Phosphoric acid intake and bone density UL has been established

Magnesium Body locations More than half is found in the bones Reservoir Muscles and soft tissues Extracellular fluid

Magnesium Roles in body Maintains bone health Part of protein making machinery Necessary for energy metabolism Participates in enzyme systems Catalyst in ATP production Muscle contraction and blood clotting Supports normal function of immune system

Magnesium Intakes Sources Average dietary intake for U.S. adults is below recommendations Hard water contributions Sources Legumes, seeds, and nuts Leafy green vegetables

Magnesium Deficiency Hypertension Toxicity Rarely occurs Occurs with diseases Causes tetany and impair central nervous system activity Hypertension Protective factor Toxicity

Sulfate Sources of sulfate No recommended intake Food and beverages Amino acids Methionine Cysteine No recommended intake Normal protein intake

Osteoporosis and Calcium Highlight 12 Osteoporosis and Calcium

Introduction Osteoporosis becomes apparent in the later years Develops earlier without warning Osteoporosis is one of the most prevalent diseases in U.S. Burden of disease

Bone development and Disintegration Cortical bone Hard outer shell Gives up calcium to blood Slow and steady rate Trabecular bone Lacy matrix Give up calcium when diet runs short Impacted by day-to-day intake and need for calcium

Healthy and Osteoporotic Trabecular Bone

Bone development and Disintegration Types of osteoporosis Type I Trabecular bone loss Women are more likely victims Type II Cortical and trabecular bone losses Dowager’s hump DEXA scan Risk factors and protective factors

Loss of Height in a Woman Caused by Osteoporosis

Types of Osteoporosis Compared

Risk Factors and Protective Factors for Osteoporosis

Age and Bone Calcium Two major stages of life Maximizing bone mass Childhood and adolescence Bone-acquiring stage Late adulthood Bone-losing decades Maximizing bone mass Minimizing bone loss Calcium and vitamin D status

Gender and Hormones Men have greater bone density and smaller losses later in life Women and menopause Estrogen Up to 20% bone loss in 6 to 8 years after menopause Drugs Antiresorptive agents Anabolic agents

Genetics and Ethnicity Osteoporosis may, in part, be hereditary Exact role of genetics is unclear Ethnicity Groups at high risk Environmental factors influence gene expression

Physical Activity and Body Weight Important factor supporting bone growth during adolescence Muscle strength and bone strength work together Weight training or weight-bearing endurance activities Being overweight may protect bones Risks vs. benefits of being overweight

Smoking and Alcohol Smoking decreases bone density Can be reversed with smoking cessation Benefits seen in 6 weeks Alcohol abuse and osteoporosis Increased level of fractures Moderate alcohol consumption May increase bone mineral density

Dietary Nutrients Calcium Protein Vitamins D and K Vitamins C and A Adequate levels during growing year Recommended levels Protein Vitamins D and K Vitamins C and A Salt Omega-3 fatty acids

Supplements Lack of calcium-rich foods Calcium supplement with vitamin D May increase risk of heart attacks Calcium supplement forms Natural products and lead content Questions How much calcium provided? How body absorbs and uses the calcium?