Electrolytes — Sodium, Potassium, and Fluid Balance

Electrolytes are minerals that carry an electrical charge in body fluids — chiefly sodium, potassium, chloride, calcium, and magnesium. They govern fluid distribution between compartments, nerve impulse transmission, and muscle contraction. During exercise, electrolytes (predominantly sodium) are lost in sweat; large or repeated losses can impair performance and, combined with overdrinking plain water, raise the risk of hyponatremia (see hyponatremia).

Sodium is the principal extracellular electrolyte. The Dietary Guidelines recommend limiting sodium to less than 2,300 mg/day for general health, because high habitual intake raises blood pressure. This dietary ceiling, however, is distinct from acute replacement during prolonged exercise: ACSM suggests including roughly 0.5–0.7 g of sodium per liter of fluid during exercise lasting over an hour to aid fluid retention, palatability, and hyponatremia prevention.

Potassium is the principal intracellular electrolyte and counterbalances sodium's effect on blood pressure; potassium-rich diets (fruits, vegetables, legumes, dairy) are encouraged, and the DASH pattern (see dash-diet) leverages high potassium, calcium, and magnesium to lower blood pressure. For everyday activity, food and water cover electrolyte needs; dedicated electrolyte products earn their place mainly in prolonged, hot, or heavy-sweat exercise (see exercise-hydration-strategy).

• Charged minerals: sodium, potassium, chloride, calcium, magnesium.
• Regulate fluid balance, nerve transmission, muscle contraction.
• Sweat loss is mostly sodium; dietary sodium limit <2,300 mg/day (DGA).
• Exercise >1 h: ~0.5–0.7 g sodium per liter of fluid (ACSM).
• Potassium counters sodium's BP effect; DASH emphasizes K, Ca, Mg.

• hydration — electrolytes work with fluid balance.
• exercise-hydration-strategy — when electrolyte replacement matters.
• hyponatremia — sodium dilution risk from overdrinking.
• dash-diet — pattern using potassium/calcium/magnesium for BP.