What happens to sodium in the body?

The body needs some sodium to work well. Sodium plays a role in:

• The balance of fluids in the body.
• The way nerves and muscles work.

The kidneys balance the amount of sodium in the body. When sodium is low, the kidneys hold on to it. When sodium is high, the kidneys release some in urine.

If the kidneys can't remove enough sodium, it builds up in the blood. Sodium attracts and holds water, so the blood volume rises. The heart must work harder to pump blood, and that increases pressure in the arteries. Over time, this can raise the risk of heart disease, stroke and kidney disease.

Some people are more sensitive to the effects of sodium than are others. That means they hold onto sodium more easily. As a result, more fluid stays in the body and blood pressure rises.