Salt affects more than just blood pressure

Researchers at the University of Delaware College of Health Sciences and Christiana Care Health System have reviewed evidence on links between dietary sodium intake and health and concluded that even in the absence of an increase in blood pressure, excess dietary sodium can adversely affect target organs, including the blood vessels, heart, kidneys and brain.

Potential effects on the arteries include reduced function of the endothelium (the inner lining of blood vessels). Endothelial cells mediate a number of processes, including coagulation, platelet adhesion and immune function. Elevated dietary sodium can also increase arterial stiffness and can lead to left ventricular hypertrophy, or enlargement of the muscle tissue that makes up the wall of the heart’s main pumping chamber. As the walls of the chamber grow thicker, they become less compliant and eventually are unable to pump as forcefully as a healthy heart.

Evidence suggests that high sodium is also associated with reduced renal function, a decline observed with only a minimal increase in blood pressure. Finally, sodium may also affect the sympathetic nervous system, which activates what is often termed the fightor-flight response. Chronically elevated dietary sodium may ‘sensitise’ sympathetic neurons in the brain, causing a greater response to a variety of stimuli, including skeletal muscle contraction. Even if blood pressure is not increased, chronically increased sympathetic outflow may have harmful effects on target organs.