Which mineral is primarily responsible for electrolyte balance?

• A. Calcium
• B. Potassium
• C. Sodium
• D. Magnesium

Answer: (C)

Electrolyte balance is governed largely by the concentration of sodium in body fluids. Sodium is the main positively charged ion outside cells, so it sets the osmotic pressure of extracellular fluid and determines water distribution between blood, tissues, and cells. This controls blood volume and blood pressure, with the kidneys adjusting sodium levels through reabsorption or excretion under hormonal control. While other minerals like potassium, calcium, and magnesium are important for nerve function, muscle contraction, and bone health, they do not regulate extracellular fluid balance to the same extent. Therefore, sodium is the mineral most responsible for electrolyte balance.