High-salt diets affect organs even in normal BP

Normal blood pressure offers you no license to eat all the salty snacks and convenience foods you want, says a study that shows that high blood pressure is not the only risk that too much salt in your diet can increase.

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, said the researchers from the University of Delaware.

"Blood pressure responses to alterations in dietary sodium vary widely, which has led to the concept of 'salt-sensitive' blood pressure," said one of the study authors William Farquhar.

"If blood pressure increases during a period of high dietary sodium or decreases during a low-sodium period, the person is considered salt sensitive. If there is no change in blood pressure with sodium restriction, an individual is considered salt resistant," Farquhar noted.

However, the new research points to evidence of adverse effects on multiple target organs and tissues, even for people who are salt resistant.

Potential effects on the arteries include reduced function of the endothelium, which is 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, the researchers noted.

"High dietary sodium can also lead to left ventricular hypertrophy, or enlargement of the muscle tissue that makes up the wall of the heart's main pumping chamber," co-author of the review paper David Edwards noted.

"As the walls of the chamber grow thicker, they become less compliant and eventually are unable to pump as forcefully as a healthy heart," Edwards pointed out.

Regarding the kidneys, high sodium is associated with reduced renal function, a decline observed with only a minimal increase in blood pressure, the researchers noted.

Finally, sodium may also affect the sympathetic nervous system, which activates what is often termed the fight-or-flight response.

"Chronically elevated dietary sodium may 'sensitize' sympathetic neurons in the brain, causing a greater response to a variety of stimuli, including skeletal muscle contraction," Farquhar noted.

The study was published in the Journal of the American College of Cardiology.