Sodium has a positive association with your blood pressure (BP). The higher the sodium level in your blood, the higher is your BP. This effect of sodium on BP is more pronounced as your age advances. In general, increased sodium intake, by increasing your blood pressure, has a negative impact on your health.
The Sodium and Water Balance in the Body
Your body needs sodium and potassium to maintain its water balance. Both of these minerals (or electrolytes) are capable of holding water. Potassium retains water inside the cells (intracellular compartment). Sodium functions to keep hold of water outside the cells - in the space around the cells and in the blood (extracellular compartment). Thus both these minerals work together to maintain the water level in their respective compartments.
In order to maintain the water balance, it is necessary that the levels of these electrolytes are also in balance. If the relative concentration of one of the two electrolytes rises, water gets attracted to one particular compartment resulting in water retention in that compartment. In this way, if the level of sodium in blood increases, it results in fluid retention in the extracellular compartment. This increases blood volume.
Normally, the kidneys maintain the levels of these minerals in our body. When there is too much of sodium in the blood, the kidneys filter the excess sodium ions and pass them into the urine. But when the sodium levels are too high to be handled by the kidneys, more water is retained in the blood. This increases the blood volume and raises the blood pressure.
How Sodium Affects Your Blood Pressure?
The arteries carry blood from the heart to various parts of the body. The heart beats in a rhythmic fashion and during every beat it pumps blood into the arteries. The amount of blood the heart pumps out every minute is called cardiac output. Blood pressure is the pressure exerted by the blood on the arterial walls. The cardiac output determines the level of the pressure exerted on the walls of the arteries. When the water content of your blood is high, this naturally increases your cardiac output and persuades your heart to pump with more force. This translates into higher pressure over the arterial walls. Thus, an increase in the sodium content of your blood leads to high BP.
The mechanism by which sodium influences blood pressure seems very simple. But in reality, there are so many physiological systems in your body that interact in a complex fashion to influence blood pressure. Nonetheless, a low-salt diet can help reduce your BP. Apart from this, a low-salt diet also ensures protection against heart attack and stroke.