The IOM Report Fails To Detect Evidence to Support Dietary Sodium Guidelines

Abstract

The recent Institute of Medicine (IOM) report “Sodium intake in populations: Assessment of Evidence”1 has provided critical information concerning the dietary sodium guidelines currently recommended by agencies of the US government.2 The American Journal of Hypertension has assembled a set of commentaries providing the range of official and independent views addressing how the IOM report will (or should) influence dietary sodium policy and practice.3–7 Our purpose is to provide a concise and comprehensive assessment of how things stand in the immediate aftermath of the IOM report. Our hope is that these manuscripts will further inform what promises to be a lively public and scientific debate about the implications of the IOM report. The balanced review and analysis has the credibility to make this report a paradigm shifting publication. The hypothesis from which sodium guidelines emerged i.e., that because reduced sodium intake lowered blood pressure, it would inevitably prevent cardiovascular morbidity and mortality – has failed to find support in the IOM report. The Committee found that the modest blood pressure effect is not a certain surrogate for health outcomes associated with sodium intake. Instead, the Committee’s case rested upon evidence of actual health consequences associated with reducing sodium intake from the current average of 3,400 mgs/day, to 5,000 mgs) of sodium to all lower intake levels. Third, based upon the large body of mostly observational data reported over the past 8 years, it found that a possibility of harm existed at the lower (<2,300 mgs) end, and more confidently, at the higher (unspecified other than as “excessive”) end as well. This implies that a “safe” range for sodium exists. Fourth, the committee specifically declined to identify any “target” for sodium intake, or a safe range of intakes consistent with optimal human health. Fifth, the committee found insufficient evidence of either harm or benefit from sodium consumption below 2,300 mgs, and cautioned against intakes <1,500 mgs/day. Sixth, and finally, the report specifically failed to find evidence to support current guidelines promoted by both the US Centers for Disease Control and Prevention (CDC) and the New York City Department of Health. Given the prominent role played by the CDC and the New York City Department of Health in promoting current guidelines, the directors of both have been invited to respond to the IOM report.3,4 While all submissions have been subject to peer review, wide latitude has been afforded authors. Investigators who have contributed important data on both sides of the current controversy have also been invited to submit their views.5,6 In addition, a report describing sodium intake in much of the world over the past half century provides critical background for examining the sodium issue.7 And, finally, a distinguished scholar of nutrition and nutrition policy has described how nutrient guidelines have and can be reached, and describes a method, based upon pathophysiology, and consistent with clinical outcomes, for defining a safe range for sodium intake.8