Salt increases blood pressure by adrenalin, not volume expansion

Published online in the Journal of Hypertension​​, the new study was led by Dr. Irene Gavras and Dr. Haralambos Gavras, both professors of medicine at the university. Since the 1960s and 1970s, researchers have questioned the theory that increased blood volume puts pressure on the arterial walls, they wrote.

"The body's circulatory system is a highly flexible vascular system with the capacity to open up new capillaries and distend veins in order to accommodate increased fluid volume,"​ said Irene Gavras. "…The purpose of this paper is to correct an erroneous concept that has prevailed for many years, even though scientific evidence has mounted against it.”​

The idea of ‘volume-expanded hypertension’ implies that excess sodium leads to the retention of extra fluid within the arteries, and this causes an increase in blood volume, resulting in added pressure on arterial walls. However, research has shown that conditions characterized by the expansion of blood volume from other causes, such as the excessive elevation of blood sugar, do not cause a rise in blood pressure because the extra fluid is accommodated by the expansion of capillaries and veins, a university statement said.

Instead of increasing blood volume, the review’s authors claim there is a strong body of evidence to suggest that sodium stimulates the sympathetic nervous system to produce adrenalin, and the excess adrenalin constricts the arteries and causes high blood pressure.

This could have implications for the treatment of high blood pressure, and future treatments should focus on the nervous system, they wrote.