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How much salt is too much? (iStockphoto.com)

Study Muddies Water On Health Effects Of Salt

by Scott Hensley
May 4, 2011

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Might be time to dust off Woody Allen's Sleeper, the 1973 movie that, among other zany things, told us all the foods that we thought were bad for us (think steak and hot fudge) were found by future generations to be good.

A provocative study in the latest issue of JAMA suggests that moderate salt intake might be no problem and that for many people diets very low in salt could be a recipe for trouble.

European researchers studying nearly 4,000 people as they aged found increases in systolic blood pressure were associated with increases in salt measured in the urine. (Sorry, that's how the researchers could accurately quantify how much salt people had in their systems.)

Changes in diastolic blood pressure (the bottom number in blood pressure readings) didn't show a relationship with salt.

And, perhaps most interesting of all, the increases in salt and diastolic pressure were not associated with an increase in deaths from cardiovascular disease, such as heart attacks and strokes. Indeed, people with less salt in their urine were more likely to die from cardiovascular causes.

Surprising, right? Previous research has predicted, for instance, that lowering salt intake just a little — a half-teaspoon a day — would save the lives of at least 44,000 Americans a year.

Well, it wasn't surprising to Dr. Jan A. Staessen, a hypertension researcher at the University of Leuven, who is the senior author on the paper. He told the news@JAMA blog:

We started this research more than 25 years ago, and in all our studies, it was almost impossible to find an association between blood pressure and 24-hour sodium excretion. We were a bit surprised to see an inverse relationship between sodium intake and cardiovascular death.

He acknowledges that limitations of the study don't make it easy to explain exactly what's going only. Staessen theorized that cutting way back on salt can "activate some of the systems that conserve sodium and they are known to have a negative influence on cardiovascular outcomes." In any case, he said, the findings should give pause to people making population-wide recommendations to cut salt intake.

The Centers for Disease Control and Prevention, one of the big proponents of lower salt consumption, isn't so sure about that. In an interview with the New York Times, CDC's Dr. Peter Briss faulted the study, saying it was small, included relatively young subjects and had relatively few cardiovascular deaths.

Among the people in the the study, there were 84 deaths due to cardiovascular disease. The majority of those — 54 — occurred in the third of people who happened to have the lowest salt consumption.

The limitations, Briss said, make it hard to draw conclusions that would overturn the previous work that has link increased salt intake and bad health outcomes. "At the moment, this study might need to be taken with a grain of salt," Briss told the Times.

The European researchers had no financial conflicts of interest to report. They received funding from a bunch of governments.

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