Which mineral is crucial for maintaining fluid balance in the body?

Sodium is crucial for maintaining fluid balance in the body because it plays a key role in regulating the movement of fluids in and out of cells and tissues. It is one of the primary electrolytes found in extracellular fluid, which means it helps to maintain osmotic pressure, influencing how much water is retained or excreted by the kidneys. Sodium helps to draw water into the bloodstream, affecting blood volume and pressure. It is especially important in conjunction with potassium, as these two minerals work together to maintain a healthy balance of fluids within the cells and the extracellular space.

In contrast, while calcium is important for bone health and muscle function and supports various physiological processes in the body, it does not primarily regulate fluid balance. Iron is essential for oxygen transport in the blood and does not have a direct role in fluid regulation. Potassium is important for fluid balance as well and is involved in maintaining cellular function, but sodium is the dominant electrolyte responsible for the overall control of extracellular fluid volume.