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Institute of Medicine: Low Salt Intake May Be Unhealthy

Health experts have long promoted one simple, consistent message when it comes to salt intake: cut back. Now, a review from the Institute of Medicine suggests that a diet too low in sodium may actually be unhealthy for those at risk for heart problems.

This conclusion was drawn by a committee designated by IOM tasked with reviewing existing research on the effects of sodium intake.

After analyzing 39 studies that fit its criteria for review, the committee found that drawing any sort of conclusion about the impact of a low-sodium diet was difficult given the wide range of methodologies used in each study.

Despite this variability, the committee said the current body of evidence still shows a positive relationship between salt intake and heart disease. And while the authors were unable to draw a conclusion about the effects of low levels of salt (less than 2,300 mg per day) on the general population, they did find convincing evidence that low sodium intake could lead to adverse effects in patients with mid- to late- stage congestive heart failure.

“The evidence on health outcomes is not consistent with efforts that encourage lowerng of dietary sodium in the general population to 1,500 mg/day,” conclude the authors. “Further research may shed more light on the association between lower—1,500 to 2,300 mg—levels of sodium and health outcomes.”

The 2010 Dietary Guidelines for Americans, issued by the federal government, recommend limiting daily sodium intake to 2,300 mg for the general population. For those at a higher risk for heart disease, including people over age 51, African Americans and those with high blood pressure, diabetes or chronic kidney disease, the Guidelines recommend consuming 1,500 mg or less per day.

But according to the IOM report, this latter recommendation is not backed up by research.

Consumer advocacy group Center for Science in the Public interest greeted the study with concern, saying it takes the focus off of the main concern for most consumers: high salt intake.

“What the committee failed to emphasize is that most Americans are deep in the red zone, consuming 3,500 to 4,000 milligrams of sodium a day,” said CSPI Nutrition Director Bonnie Liebman. “It’s clear that those excessive levels increase the risk of high blood pressure, heart attacks, and strokes.  Whether we aim for 2,300 or 1,500 milligrams a day is irrelevant until we move down out of the red zone.”

“The committee was boxed in by a narrow charge to examine only studies that looked at hard endpoints like heart attacks and strokes,” continuted Liebman. “Because of flaws in those studies, the committee did not conclude that low sodium intakes are harmful.”

The salt industry, on the other hand, praised IOM for considering the other side of the salt coin.

“We are pleased to see that the IOM report has recognized that lowering sodium intake too much may actually increase a person’s risk of some health problems, said Lori Roman, president of the Salt Institute, in a statement Tuesday. “IOM’s recommendation that more study is needed is a positive first step toward a more objective dialog about the complex effects of sodium reduction on overall health.”

There is no scientific justification for population-wide sodium reduction to such low levels and the recognition by the IOM experts that such low levels may cause harm may help steer overzealous organizations away from reckless recommendations,” said Salt Institute Vice President of Science and Research Mort Satin. 

The full report is available for download here.

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