Which statement about sodium intake is true?

• A. Sodium is not an electrolyte and does not affect water balance.
• B. Sodium has no role in hydration.
• C. Sodium should be consumed only in tiny amounts.
• D. Sodium is an electrolyte and is key for your body to retain water.

Answer: (D)

Sodium is an essential electrolyte that sits mostly outside cells and helps regulate the volume and osmolality of the extracellular fluid. Water follows sodium osmotically, so when sodium is present and retained, water is retained as well, which affects hydration and blood volume. This is why the statement that sodium is an electrolyte and is key for your body to retain water is true. The other ideas—sodium not being an electrolyte or having no role in hydration—conflict with basic physiology; and while we monitor sodium intake to stay within healthy limits, sodium is necessary in appropriate amounts for fluid balance, nerve function, and muscle activity.