Chapter 12: Water and Major Minerals

General Water Facts and Statistics

• Dietary Sources of Water: Most individuals obtain approximately $20-30\%$ of their total fluid intake from solid foods.

• Total Body Weight (TBW): Water accounts for approximately $66\%$ of a person's total body weight.

• Fluid Distribution:     * Intracellular Fluid: Approximately $65\%$ of Total Body Water is located inside the cells.     * Extracellular Fluid: Approximately $35\%$ of Total Body Water is located outside the cells.

• Water Content in Tissues and Body Types:     * Well-hydrated Muscle: Contains roughly $75\%$ water.     * Bones: Contain roughly $32\%$ water.     * Fat: Has a water content of approximately $10\%$.     * Blood: Consists of approximately $93\%$ water.     * Obese Individuals: Water weight accounts for approximately $40\%$ of total body mass.     * Athletes: Water weight accounts for approximately $70\%$ of total body mass.

Roles of Water and Body Fluid Composition

• Functional Roles of Water:     * Transports nutrients and waste products throughout the body.     * Maitains the structural integrity of large molecules.     * Actively participates in metabolic reactions.     * Acts as a universal solvent for minerals, vitamins, amino acids, glucose, and other molecules.     * Functions as a lubricant and cushion for joints, the spinal cord, and inside the eyes.     * Serves as amniotic fluid during pregnancy.     * Regulates body temperature.     * Maintains blood volume and electrolyte balance.

• Body Composition for an Average 150-Pound Male:     * Carbohydrates: <1\% (less than $1\,lb$).     * Minerals: $4\%$ ($6\,lb$).     * Fat: $15\%$ ($23\,lb$).     * Protein: $20\%$ ($30\,lb$).     * Water: $60\%$ ($90\,lb$).     * Total: $100\%$ ($150\,lb$).

• Components of Extracellular Fluid:     * Interstitial fluid.     * Plasma.

Water Intake, Output, and Requirements

• Water Requirement Formula: The general requirement is approximately $1\,ml$ per $kcal$ of energy expended.

• Factors Influencing Water Needs:     * Diet.     * Physical activity levels.     * Environmental temperature.     * Humidity levels.     * Overall state of health.

• Fluid Balance (Daily Intake and Output Example):     * Total Intake ($2350\,ml$ / ~10 cups):         * Beverages/Drink: $1000\,ml$ (4 cups).         * Water content in food: $1000\,ml$ (4 cups).         * Metabolic water (produced from metabolism): $350\,ml$ (1.5 cups).     * Total Output ($2350\,ml$ / ~10 cups):         * Urine: $1300\,ml$ (~5.5 cups).         * Skin (perspiration): $500\,ml$ (2 cups).         * Lungs (respiration): $400\,ml$ (1.7 cups).         * Feces: $150\,ml$ (0.6 cups).

• Water Content in Common Foods:     * Lettuce: $96\%$     * Asparagus: $92\%$     * Whole Milk: $87\%$     * Orange: $86\%$     * Potatoes: $80\%$     * Cottage Cheese: $79\%$     * Veal: $66\%$     * Chicken: $63\%$     * Beef: $47\%$     * Cheddar Cheese: $37\%$     * Bread: $36\%$     * Butter: $20\%$     * Dry Gelatin: $13\%$     * White Sugar: $0.5\%$

Dehydration and Hydration Indicators

• Symptoms of Dehydration Based on Body Weight Percentage Lost:     * $1-2\%$: Thirst, fatigue, weakness, vague discomfort, and loss of appetite.     * $3-4\%$: Impaired physical performance, dry mouth, reduced urine output, flushed skin, impatience, and apathy.     * $5-6\%$: Difficulty concentrating, headache, irritability, sleepiness, impaired temperature regulation, and increased respiratory rate.     * $7-10\%$: Dizziness, spastic muscles, loss of balance, delirium, exhaustion, and collapse.     * Note: Symptom severity depends on activity, fitness level, acclimation, temperature, and humidity. Uncorrected dehydration can lead to death.

• Hydration Status by Urine Color:     * Good: Clear or Light (Well Hydrated).     * Fair: Yellow (Need to drink more fluids).     * Poor: Dark Yellow/Amber (Seek medical staff or athletic trainer).

Physiological Regulation of Blood Volume and Pressure

• Hormonal Control Mechanisms:     * Thirst: A primary signal for fluid intake.     * Renin-Angiotensin-Aldosterone System:         1. Reduced blood flow triggers the Kidneys to release the enzyme Renin.         2. Renin activates the protein Angiotensinogen to Angiotensin.         3. Angiotensin causes vasoconstriction (narrowing of blood vessels) to raise blood pressure.         4. Angiotensin signals the Adrenal Glands to secrete Aldosterone.         5. Aldosterone signals the kidneys to retain sodium, which leads to water retention.     * Antidiuretic Hormone (ADH) / Vasopressin:         1. The Hypothalamus detects high salt concentrations and stimulates the Pituitary Gland.         2. The pituitary gland releases ADH.         3. ADH signals the kidneys to reabsorb water, preventing loss and increasing blood volume.

Electrolytes and Fluid Balance

• Definition: Minerals capable of carrying an electrical current are called electrolytes or ions.     * Cations: Positively charged ions.     * Anions: Negatively charged ions.

• Concentrations of Major Electrolytes ($mEq/L$):     * Cations:         * Sodium ($Na^+$): Intracellular ($10$); Extracellular ($142$).         * Potassium ($K^+$): Intracellular ($150$); Extracellular ($5$).         * Calcium ($Ca^{++}$): Intracellular ($2$); Extracellular ($5$).         * Magnesium ($Mg^{++}$): Intracellular ($40$); Extracellular ($3$).     * Anions:         * Chloride ($Cl^-$): Intracellular ($2$); Extracellular ($103$).         * Bicarbonate ($HCO_3^-$): Intracellular ($10$); Extracellular ($27$).         * Phosphate ($HPO_4^{--}$): Intracellular ($103$); Extracellular ($2$).         * Sulfate ($SO_4^{--}$): Intracellular ($20$); Extracellular ($1$).         * Proteins: Intracellular ($57$); Extracellular ($16$).

• Electrical Neutrality: Total cation charges equal total anion charges in a fluid (e.g., $155\,mEq/L$ in extracellular fluid).

Overview of Minerals

• Classification:     * Major Minerals: Present in the body in amounts larger than $5\,g$ (about a teaspoon). This includes Calcium, Phosphorus, Potassium, Sulfur, Sodium, Chloride, and Magnesium. Only calcium and phosphorus are present in amounts exceeding a pound ($454\,g$).     * Trace Minerals: More than a dozen exist, but key ones include Iron ($2.4\,g$), Zinc ($2.0\,g$), Copper ($0.09\,g$), Manganese ($0.02\,g$), Iodine ($0.02\,g$), and Selenium ($0.02\,g$).

• Handling and Bioavailability:     * Some minerals act like water-soluble vitamins, others like fat-soluble vitamins.     * Excessive intake can be toxic.     * Binders: Foods containing phytates (legumes/grains) or oxalates (spinach/rhubarb) can chemically combine with minerals and inhibit absorption in the intestine.

Sodium ($Na^+$)

• Functions: Fluid balance maintenance (as an electrolyte), acid-base balance maintenance, nerve impulse transmission, and muscle contraction.

• Requirements:     * Adequate Intake (AI): $1500\,mg/day$.     * Minimum Adult Requirement: $500\,mg/day$.     * Upper Intake Level (UL): $2300\,mg/day$.     * Composition of Salt: $1\,tsp$ of salt contains approximately $2300\,mg$ of sodium. Salt is $40\%$ sodium and $60\%$ chloride.

• Sources of Sodium:     * Processed and prepared foods: $77\%$.     * Natural sources: $12\%$.     * Added while eating: $6\%$.     * Added while cooking: $5\%$.

• Comparison (Unprocessed vs. Processed): Processed items like instant chocolate pudding, chipped beef, canned cream corn, peach pie, and oat cereal have significantly higher sodium and lower potassium than their fresh counterparts.

• Deficiency: Rapid loss via vomiting, diarrhea, or heavy sweating. Symptoms include muscle cramps, mental apathy, and loss of appetite.

• Toxicity: Can lead to edema and acute hypertension. Prolonged high intake contributes to hypertension.

Chloride ($Cl^-$)

• Roles: Essential nutrient for fluid balance; component of hydrochloric acid ($HCl$) in the stomach required for digestion.

• Recommendations:     * Adequate Intake (19-50 years): $2300\,mg/day$.     * Upper Intake Level (UL): $3600\,mg/day$.

• Deficiency and Toxicity: Deficiency is rare but can occur with vomiting, diarrhea, or heavy sweating. Dehydration can lead to high concentrations of chloride in the body.

Potassium ($K^+$)

• Roles: Maintenance of fluid and electrolyte balance, support of cell integrity, assistance in nerve impulse transmission, muscle contraction, and maintaining the heartbeat.

• Recommendations:     * Adequate Intake (AI): $2600\,mg/day$ for females; $3400\,mg/day$ for males.     * General AI Goal: Often cited as $4700\,mg/day$ (from chart).

• Sources: Abundant in fresh foods (fruits, vegetables, legumes, meats). Processed foods are typically lower in potassium.

• Deficiency: Symptoms include muscular weakness, paralysis, confusion, increased blood pressure, salt sensitivity, kidney stones, irregular heartbeats, and glucose intolerance.

• Toxicity: Results from supplements or overconsumption of potassium salts. Symptoms include muscular weakness and vomiting.

Calcium

• Distribution: $99\%$ of calcium is stored in bones; $1\%$ is in the blood.

• Blood Calcium Functions: Blood clotting, hormone secretion, enzyme activation, nerve transmission, and muscle contraction.

• Recommendations:     * RDA (19-50 years): $1000\,mg/day$.     * Upper Level (UL): $2500\,mg/day$.

• Bioavailability Factors:     * Enhancers: Stomach acid, Vitamin D, Lactose, and Growth Hormones.     * Inhibitors: Lack of stomach acid, Vitamin D deficiency, high phosphorus intake, high-fiber diet, phytates (seeds, nuts, grains), and oxalates (beet greens, rhubarb, spinach).

• Absorption Rate: Adults generally absorb about $25\%$ of consumed calcium.

• Food Absorption Rates:     * $\ge 50\%$ absorbed: Broccoli, bok choy, cauliflower, brussels sprouts, kale, mustard/turnip greens.     * $\approx 30\%$ absorbed: Milk, fortified soy milk, calcium-set tofu, cheese, yogurt.     * $\approx 20\%$ absorbed: Almonds, sesame seeds, pinto beans, sweet potatoes.     * $\le 5\%$ absorbed: Spinach, rhubarb, Swiss chard.

• Deficiency and Toxicity:     * Deficiency: Stunted growth in children; bone loss (osteoporosis) in adults.     * Toxicity: Risk of urinary stone formation, kidney dysfunction, and interference with other mineral absorption.

Phosphorus

• Roles: Mineralization of bones and teeth, genetic material (DNA and RNA), structural part of phospholipids, buffer systems for acid-base balance, and energy transfer.

• Recommendations:     * RDA (19-70 years): $700\,mg/day$.     * Upper Intake Level (UL): $4000\,mg/day$.

• Sources: Protein-rich foods like milk, meats, and legumes.

• Toxicity: calcification of nonskeletal tissues, particularly the kidneys.

Magnesium

• Roles: Enzyme action, muscle contraction, nerve impulse transmission, immune system function, and blood clotting.

• Recommendations:     * RDA: $320\,mg/day$ for females; $420\,mg/day$ for males.     * Upper Intake Level (UL): $350\,mg/day$ from supplemental magnesium only.

• Deficiency: Rare, but can develop from alcohol abuse, protein malnutrition, kidney disorders, or prolonged vomiting/diarrhea. Symptoms include weakness, confusion, convulsions, hallucinations, swallowing difficulties, and growth failure in children.

• Toxicity: Symptoms include diarrhea, alkalosis, and dehydration.