Saturday, May 14, 2011

Salt Doesn't Cause High Blood Pressure?

The Journal of the American Medical Association reports a study that found that people who consumed the least salt had the most heart disease. But there are some issues with the details.
For over 50 years doctors have been telling patients that taking the salt shaker off the table and avoiding salty and processed foods is essential for reversing high blood pressure. The famous DASH studies took this advice a step further and found a beneficial role for increased potassium, from fruits and vegetables, along with decreased sodium from salt. Now a European study involving 3,861 people in Belgium, Bulgaria, Italy, Romania, and Russia reports that people who consume the least salt have higher blood pressure and more heart disease.

Scientists with the European Project on Genes in Hypertension measured the amount of sodium in patients' urine when they were admitted into the study and at least one more time during the course of their researcher. They assumed that higher concentrations of sodium in urine corresponded to higher amounts of salt in the diet. The researchers then tracked the health of the participants and looked for correlations between sodium excretion/salt in the diet, blood pressure, and heart disease.

In this study, the researchers found that:

  • Consuming more salt raised systolic blood pressure, but not diastolic blood pressure, and did not correlate to a diagnosis of high blood pressure.
  • The people who consumed the least salt had the most cardiovascular disease.
The 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. 

More in the low-salt group had high blood pressure, 27%, compared to the high-salt group, 25%. The difference was statistically significant although not very large.

These findings, of course, contradict most of the last 50 years of research. Is it really possible that salt is good for people?

Well, yes, it is.

However, another explanation for these findings is that people who already had high blood pressure or heart disease were put on low-salt diets, so naturally they would continue to have more high blood pressure or heart disease than healthy people.

I wouldn't stock up on salt and salty food just yet. But if you are a diabetic who has normal blood pressure, avoiding salt does not seem to be a very high priority.

Source:

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.


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