Extreme Sodium Reduction May Cause Harm, Institute of Medicine Report Says

Lowering sodium intake too much could increase some people’s risk of health problems, says a report released today by the U.S. Institute of Medicine (IOM). The report, “Sodium Intake in Populations: Assessment of Evidence,” examined the latest research on sodium reduction among the U.S. population.

The U.S. Centers for Disease Control and Prevention (CDC) commissioned the report, asking the IOM to review the latest evidence in response to questions of whether sodium reduction may lead to risk of adverse health outcomes in some of the population.

The current 2010 Dietary Guidelines for Americans advise that African Americans; people with hypertension, diabetes, or chronic kidney disease; and individuals aged 51 and older reduce sodium intake to 1500 mg/day because these groups may be more sensitive to the blood pressure–raising effects of sodium. However, in this new report, the IOM committee said it found “no evidence for benefit and some evidence” that sodium intake levels between 1500 to 2300 mg/day may increase risk of adverse health outcomes in those with diabetes, kidney disease, or cardiovascular disease. As such, “the evidence on both the benefit and harm is not strong enough to indicate that these subgroups should be treated differently than the general U.S. population,” the report said, meaning that the Dietary Guidelines for Americans recommending a sodium intake of 2300 mg/day or less for the general U.S. population should also apply to these subgroups.

The report further stated that “the evidence on direct health outcomes does not support recommendations to lower sodium intake within these subgroups to or even below 1500 mg/day” and that the committee’s new findings are “not consistent with efforts that encourage lowering of dietary sodium in the general population to 1500 mg/day.”

It is unclear how this report will impact sodium recommendations in the updated version of the Dietary Guidelines for Americans, due in 2015.

Those subgroups aside, however, the IOM report found that most in the U.S. still consume an average of 3400 mg/day sodium (equivalent to 1.5 tsp salt)-well over the generally recommended 2,300 mg/day sodium intake level. IOM said the new studies it examined did overall support previous findings that reducing very high sodium intake levels does improve health.

But IOM noted that the studies it used still had a number of limitations, including the fact that many were not consistent in how they measured sodium intake. IOM said that, in the future, more randomized controlled studies should be done and that studies need to standardize methodological approaches for measuring sodium intake.

IOM is releasing its latest findings about adverse effects of too-low sodium intake despite these study limitations. It concluded that “studies on health outcomes are inconsistent in quality and insufficient in quantity to conclude that lowering sodium intake levels below 2300 mg/day either increases or decreases the risk of heart disease, stroke, or all-cause mortality in the general U.S. population.”

The report did not establish an official healthy sodium intake range because the IOM committee says it was not asked to do so and because “variability in the methodologies used among the studies would have precluded it.”