For many years people with high blood pressure were told to lay off the salt as it caused an increase in fluid retention and blood volume which put harmful pressure on the blood vessels. At the same time, research going back to the 1960s and 1970s began to suspect that another mechanism may be at work.

After examining the body of hypertension studies, researchers at the Boston University School of Medicine report that salt raises blood pressure not by increasing blood volume but through its affect on the sympathetic nervous system to increase adrenalin. The adrenalin constricts arteries and causes the high blood pressure, not excess fluid volume.

In their report, the researchers point to studies in which other conditions characterized by increased blood volume do not cause a corresponding increase in blood pressure because the capillaries and veins expand to accommodate increased fluid volume.

In addition, other studies demonstrated that hypertension resulting from the excessive consumption and retention of salt stimulates the sympathetic nervous system in the brain to increase adrenaline production. The increased adrenalin being circulated throughout the body causes the arteries to constrict, which results in resistance to blood flow and a decrease in circulation.

This over-reaction of the sympathetic nervous system has been recognized as a characteristic of hypertension that accompanies kidney failure-- the most typical example of high blood pressure from excessive salt retention. Currently diuretics, which remove excess salt, are widely used to treat this type of hypertension. However, this study provides compelling evidence that the sympathetic nervous system should be the focus of new research into treatments for hypertension.

In the future, study authors believe the optimal treatment for hypertension associated with renal failure should not only include diuretics but also the use of drugs that block the central sympathetic nervous system.

To learn more - read The Truth about Salt: The Good, the Bad and the Ugly.

Sources:

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Boston University School of Medicine/