Salt, hypertension link clarified

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BOSTON, Jan. 12 (UPI) -- A U.S. review of studies refutes a widely held belief that high blood pressure results from excess salt causing an increase in blood volume, researchers say.

Study leaders Dr. Irene Gavras and Dr. Haralambos Gavras, both professors of medicine at Boston University School of Medicine, said the term "volume-expanded hypertension" implies that excess salt leads to the retention of extra fluid within the arterial circulatory system, causing an increase in blood volume and added pressure on the arterial walls.

However, the research showed conditions characterized by the expansion of blood volume from other causes, such as the secretion of anti-diuretic hormone or the excessive elevation of blood sugar, do not cause a rise in blood pressure because the extra fluid is accommodated by the distention -- state of being stretched beyond normal dimensions -- of capillaries and veins.

"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," said Irene Gavras, who is also a physician in Boston Medical Center's hypertension practice. "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."

The review, published in the Journal of Hypertension, demonstrated that excess salt stimulates the sympathetic nervous system to produce adrenalin, causing artery constriction and hypertension.