From niddk.nih.gov

Sunday Sep 21, 2008 (foodconsumer.org) – A study presented at the American Heart Association's Fall Conference of the Council for High Blood Pressure Research, in Atlanta shows too much dietary salt can contribute to resistant high blood pressure.

Another study also presented at the same conference showed that vitamin C intravenously delivered can lower blood pressure by acting on an overactive central nervous system. Read Vitamin C lowers blood pressure for details.

Resistant hypertension refers to a condition where blood pressure remains above the target level even when three medications are used in an effort to lower it.   High blood pressure is also called resistant to treatment if the condition can only get controlled by taking four or more medications.

The study led by the University of Alabama researchers involved 13 patients with resistant high blood pressure. Participants were assigned to a high or low salt diet and all of them were taking at least three blood pressure medications.

The researchers found those assigned the low-salt diet reduced their systolic blood pressure by 22.6 percent and diastolic blood pressure by 9.2 percent compared to those who were assigned to the high-salt diet.

A Japanese study also presented at the conference showed that high salt diet can exacerbate hypertension via an increase in oxidative stress.

"Excess sodium intake, above 2,300 milligrams daily, should be avoided in all patients with hypertension, and among those patients with medically resistant hypertension, a closely monitored low-salt diet [1,500 milligrams daily] should be considered," Dr. Gregg C. Fonarow, a professor of cardiology at the University of California, Los Angeles was quoted by healthday.com as saying.

A study led by Ostchega Y and colleagues at the centers for Disease Control and Prevent and published in the July 2007 issue of Journal of the American Geriatrics Society showed that in the US, 67 percent adults aged 60 or older were hypertensive in 1999 to 2004, an increase of 10 percent from the prevalence for the period of 1988-1994.

Low salt diet is believed to help maintain normal blood pressure.   For average people, 3,000 milligrams of sodium per day will be enough.   To limit salt intake, people may want to pay attention to salt-rich foods such as products containing baking soda, baking powder, soy sauce, as canned food.

However, the claim on the association between high salt and high blood pressure has been questioned by DAVID A. FREEDMAN University of California - Berkeley and DIANA B. PETITTI Kaiser Permanente Southern California who published a review on the issue.   They say in their report:

The “salt hypothesis” is that higher levels of salt in the diet lead to higher levels of blood pressure, increasing the risk of cardiovascular disease. Intersalt, a crosssectional study of salt levels and blood pressures in 52 populations, is often cited to support the salt hypothesis, but the data are somewhat contradictory. Four of the populations (Kenya, Papua, and two Indian tribes in Brazil) do have low levels of salt and blood pressure. Across the other 48 populations, however, blood pressures go down as salt levels go up—contradicting the hypothesis. Experimental evidence suggests that the effect of a large reduction in salt intake on blood pressure is modest, and health consequences remain to be determined. Funding agencies and medical journals have taken a stronger position favoring the salt hypothesis than is warranted, raising questions about the interaction between the policy process and science.

Editor’s note: Does that mean salt may serve as a scapegoat for the widespread condition? We don’t know.   But if that is the case, it should not be a surprise because salt is a minor ingredient for a food. And if something needs to be blamed, this little guy could be a perfect target.  The salt industry has been fighting against the claim on the association between salt and high blood pressure.