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Water and Electrolyte Balance in Nutrition

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  • Percentage of water in lean adult male body weight

    Approximately 62% of body weight in a lean adult male is water.

  • Role of water as a solvent and solute

    Water acts as a solvent dissolving substances, while solutes are the dissolved substances; together they form a solution.

  • Functions of water in the body

    Water functions in transport (blood, urine), lubrication (tears, saliva), and temperature regulation due to its high heat capacity.

  • Difference between intracellular and extracellular fluid electrolyte concentrations

    Intracellular fluid has high potassium and low sodium; extracellular fluid has high sodium and chloride, and low potassium.

  • Sources of water intake

    Water intake comes from beverages (75-80%), food (20-25%), and metabolic water (about 10%).

  • Main routes of water loss from the body

    Water is lost via urine (1-2L/day), feces, insensible losses (skin and lungs), and sweat.

  • How kidneys regulate water balance

    Kidneys filter blood, reabsorb needed substances, and excrete unneeded substances in urine to maintain water balance.

  • Thirst mechanism triggers

    Thirst is triggered by decreased blood volume and increased solute concentration, signaling the hypothalamus.

  • Role of antidiuretic hormone (ADH) in water balance

    ADH is secreted by the pituitary gland to increase water reabsorption in kidneys, restore blood pressure, and stimulate thirst.

  • Consequences of dehydration

    Dehydration causes reduced blood volume, leading to heat exhaustion, cramps, dizziness, and potentially heat stroke.

  • What is hyponatremia and its cause

    Hyponatremia is low blood sodium caused by excessive water intake diluting sodium, leading to tissue swelling (edema).

  • Adequate Intake (AI) for water

    AI for water is 3.7 L/day for males and 2.7 L/day for females, with increased needs during activity, heat, or high salt intake.

  • Functions of electrolytes sodium, potassium, and chloride

    They regulate fluid balance, nerve conduction, muscle contraction, and blood pressure.

  • Effect of high salt intake on thirst and water balance

    High salt intake increases blood sodium, which stimulates thirst and water intake to dilute sodium levels.

  • Common dietary sources of sodium

    Processed foods contribute about 77% of sodium intake; natural sources and added salt contribute the rest.

  • Recommended sodium intake to reduce hypertension risk

    Reducing sodium intake to less than 2300 mg/day can reduce hypertension by 30% and cardiovascular disease by 13%.

  • Potassium intake recommendations and sources

    AI for potassium is 4700 mg/day for adults; best sources are fresh fruits and vegetables.

  • Symptoms of potassium deficiency and excess

    Deficiency causes muscle cramps and irregular heartbeat; excess (hyperkalemia) can cause abnormal heartbeat.

  • How electrolytes control fluid movement in cells

    Electrolytes control fluid movement by osmosis and active transport via transport proteins across cell membranes.

  • Label terms for sodium content in foods

    Labels use terms like "sodium-free" (<5 mg/serving), "low sodium" (≤140 mg/serving), and "reduced sodium" (≥25% less sodium).