Study Notes: Minerals and Water Balance

Water as the Most Abundant Substance in the Body
- Average healthy adult is approximately 60% water.
- Muscle tissue is 75% water; fat tissue is about 20% water.
- Humans can survive only a few days without water.
Fluid Compartments
- Intracellular fluids: fluids within cells.
- Extracellular fluids: consists of interstitial fluid between cells and fluid present in blood.
Electrolytes
- Define electrolytes: minerals that help regulate fluid balance in the body.

Water acts as a universal solvent and a transport medium.
- It facilitates chemical reactions in the body.
- In blood, it transports oxygen, nutrients, and hormones to cells.
- In interstitial fluid, it helps carry waste products away from cells for excretion.
Maintains body temperature.
Serves as a lubricant for joints and eyes; part of mucus and saliva.
Acts as a protective cushion for vital organs, the brain, and fetuses.

Definition of Water Balance: Water consumed equals water lost.
Water Intake Sources: Beverages and food.
Water Loss Sources:
- Through kidneys (urine), large intestine, lungs, and skin.
- Insensible water loss: evaporation from skin, exhalation.
- Sensible water loss: through urine, feces, and sweat.

Losing too much water can lead to dehydration.
- Causes include inadequate intake, diarrhea, vomiting, fever, and diuretics.
- Thirst Mechanism: Signals dehydration when mouth becomes dry (indicates high electrolyte concentration in blood) and decreases blood volume triggers antidiuretic hormone (ADH) release to reduce urine output.

Symptoms of Dehydration

Cornerstone method: Weighing body before and after exercise; weight loss indicates water loss.
Urine color: Darker color indicates higher concentration, suggesting dehydration.

Define hyponatremia: Condition of low sodium in the blood.
Water toxicity is rare in healthy individuals but can occur in specific populations (e.g., soldiers, athletes).

Water needs vary depending on physical activity, environment, and diet.
- Recommended Intakes:
- Men: 16 cups (approx. 13 cups from beverages)
- Women: 12 cups (approx. 9 cups from beverages)
- Approximately 80% from beverages, 20% from food.

High-water content foods:
- Vegetables: Potatoes, lettuce, tomatoes, etc.
- Fruits: Peaches, pears, oranges, grapes, watermelon.
- Dairy & Grains: Yogurt, rice, etc.

Common misconceptions about bottled water being purer than tap water.
Tap water is monitored by the Environmental Protection Agency (EPA) and typically contains fluoride.
Bottled water can sometimes be tap water and is costlier.

Mineral Water: Contains naturally occurring minerals; cannot add minerals post-bottling.
Spring Water: Flows naturally from springs and collected directly.
Sparkling Water: Carbonated water; considered a soft drink.
Distilled Water: Boiled to remove contaminants but still may contain some.
Flavored Waters: Added flavors and sugars.

Minerals: Inorganic elements needed in small amounts with biological importance.
Absorption Factors: Depends on bioavailability, competition among minerals, and binding substances.
- Example: Excess zinc may inhibit copper absorption.

Major Minerals (Macrominerals): Required in amounts >100 mg/day
Trace Minerals (Microminerals): Required in amounts <15 mg/day
Major minerals play critical roles in fluid balance, bone health, and cell function.

Sodium: 1,500 mg/day. Major electrolyte, regulates body water and blood pressure. Major food sources include processed foods, table salt, meat, and dairy. Toxic levels (>2,300 mg) can cause hypertension.
Potassium: 4,700 mg/day. Important for muscle contraction and regulating blood pressure. Food sources include fruits, vegetables, and meat. Toxicity: hyperkalemia, deficiency: hypokalemia.
Calcium: 1,000 mg/day. Key for bone health and muscle function. Sources: dairy products, leafy greens, and fish. Toxicity: hypercalcemia, deficiency: osteoporosis.
Phosphorus: 700 mg/day. Involved in bone and teeth formation. Major sources: meats, fish, poultry. Toxic levels (>4,000 mg) can lead to muscle weakness, confusion, or death.
Magnesium: 310-420 mg/day for adults. Vital for enzyme function; sources include whole grains and green vegetables. Toxicity from supplements can cause diarrhea.
Chloride: 2,300 mg/day; maintains fluid balance. Sources: table salt; toxicity and deficiency are rare.
Sulfur: No specific dietary recommendations; aids in amino acid function.

Iron: 8-18 mg/day. Essential for oxygen transport and brain function. Main sources: meats and fortified grains. Toxicity affects organs; deficiency leads to anemia.
Copper: 900 µg/day essential for iron transfer and immune function; sources include organ meats and nuts; toxicity can cause liver damage.
Zinc: 8-11 mg/day; key for immune health and wound healing. Predominantly from animal sources; excess impairs copper absorption.
Selenium: 55 µg/day; antioxidant role. Ideal sources: meats and nuts. Toxicity can lead to selenosis.
Fluoride: 3-4 mg/day; primarily protects dental health. Sources: fluoridated water; excess can cause fluorosis.
Chromium: 20-35 µg/day; aids insulin function. Rare deficiency.
Iodine: 150 µg/day; essential for thyroid function. Found in iodized salt and seafood.
Manganese: 1.8-2.3 mg/day; aids in metabolism; found in whole grains and nuts.
Molybdenum: 45 µg/day; functions in enzyme activity; food sources include legumes.

Trace minerals support vital physiological functions, and their presence is crucial even in small amounts. Deficiencies or toxicities can significantly impact health.