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If your blood pressure readings are running a little high, the first thing your doctor is likely to tell you is to do is to cut back on salt. Now a study tells us that cutting back on salt actually raises the risk of heart and blood vessel diseases.

Latest Study Findings Contradict Decades-Old Recommendation to Cut Out Salt

Dr. Jan Staessen at the University of Leuven in Belgium and colleagues at research institutions all over Europe participating in the European Project on Genes in Hypertension took urine samples from 3,700 patients to measure sodium excretion. They divided the patients into the three groups on the basis of the amount of excess sodium, presumably from dietary salt, in the sample. One group had unusually low sodium spillover reflecting low consumption of dietary salt, another had unusually high sodium spillover reflecting high consumption of dietary salt, and the third group was in the middle of salt and sodium values. Staessen and coworkers then followed the patient's health for nearly eight years.

salt.jpgThe group that had the lowest consumption of salt had 50 deaths from cardiovascular disease. The group that had "average" consumption of salt had 24 deaths from cardiovascular disease. The group that had the highest consumption of salt had just 10 deaths from cardiovascular disease, less than 20% as many heart and stroke deaths as among those who ate the least salt.  

Given years of research studies telling us to expect the exact opposite result, how could this be?

One possibility, of course, is that the patients who consumed the lowest amount of salt were already sick, reducing salt restriction on doctor's advice. Those who ate the most salt possibly were healthy and seldom saw a doctor, so they were never told to cut back.

Another possibility is that salt raises systolic blood pressure (the first number) but not diastolic blood pressure (the second number). The European investigators observed that each additional 0.01 gram of sodium in a 100 ml urine sample resulted in a 1 mm Hg (1 "point") increase systolic blood pressure, but not in diastolic blood pressure.

The patients who consumed the most salt had higher systolic blood pressure, but not higher diastolic blood pressure. Their cardiovascular systems still got an opportunity to "rest" between beats, which may have protected them against the ill effects of high blood pressure even though systolic pressures went up.

Again, it is possible that the study participants who were consuming the least salt were also taking drugs for high blood pressure, and their pre-existing condition explained the results. The scientists conducting this study do not advise anyone who already has high blood pressure or heart disease to start eating more salt. But the role of salt in developing high blood pressure and heart disease may be different from what the last 30 years of studies have led us to believe.
  • Katarzyna Stolarz-Skrzypek, Tatiana Kuznetsova, Lutgarde Thijs, Jan A. Staessen, et al. for the European Project on Genes in Hypertension (EPOGH) Investigators. Fatal and Nonfatal Outcomes, Incidence of Hypertension, and Blood Pressure Changes in Relation to Urinary Sodium Excretion. JAMA. 4 May 2011, 305(17):1777-1785.