IOM, AHA at odds over sodium guidelines

Authors of a report released by the Institute of Medicine (IOM) on sodium intake by the American public failed to be persuaded that lowering daily consumption below 2,300 mg a day affected outcomes. The American Heart Association (AHA) countered the report missed the mark in its conclusions.

Committee chair Brian L. Strom, MD, a professor of public health and preventive health at the University of Pennsylvania School of Medicine in Philadelphia, and colleagues were asked to review evidence on reducing sodium intake to determine if the practice offered any benefits or risks. In particular, they focused on intake in the 1,500 mg to 2,300 mg range, noting that 2010 dietary guidelines called for daily intake below 2,300 mg, with a goal of only 1,500 mg daily for people who are 51 years old or older, African American, or have diabetes, hypertension or chronic kidney disease (CKD).   

Average daily intake in the U.S. is 3,400 mg.

“[W]hile the current literature provides some evidence for adverse health effects of low sodium intake among individuals with diabetes, CKD, or preexisting CVD [cardiovascular disease], the evidence on both benefit and harm is not strong enough to indicate that these subgroups should be treated differently from the general U.S. population,” the authors wrote. “Thus, the committee concluded that the evidence on direct health outcomes does not support recommendations to lower sodium intake within these subgroups to or even below 1,500 mg per day.”

In general, the committee deemed evidence on associations between sodium intake below 2,300 mg and CVD benefits or risks in the general population to be “insufficient and inconsistent.” They found methodological quality to be “highly variable” with a lack of consistency in data collection methods that made comparisons across studies challenging. Nonetheless, they concluded that “considered collectively, it indicates a positive relationship between higher levels of sodium intake and risk of CVD. This evidence is consistent with existing evidence on blood pressure as a surrogate indicator of CVD risk.”

The committee recommended further research on low sodium intake and the risk of adverse events in mid- to late-stage congestive heart failure patients with reduced ejection fraction who received aggressive therapeutic care. “Because these therapeutic regimes were very different than current standards of care in the United States, the results may not be generalizable,” they determined.

“[O]verall, the committee found that the available evidence on associations between sodium intake and direct health outcomes is consistent with population-based efforts to lower excessive dietary sodium intakes, but it is not consistent with previous efforts that encourage lowering of dietary sodium in the general population to 1,500 mg per day,” Strom et al wrote. Nor did it support a different approach for subgroups “except when data specifically indicates they are different.”

The AHA took the report to task, arguing that the committee fell short in their review of evidence on excessive sodium intake and hypertension. The AHA recommends that the general population limit sodium intake to 1,500 mg a day. AHA CEO Nancy Brown said in a release that the association disagreed with the IOM report’s key conclusions.

The AHA pointed out that much of the literature finding no association between reduced sodium intake and better outcomes was based on sicker patients rather than the general population. “The research that the IOM partially based their conclusions on showed inconsistencies in the relationship between sodium intake and health outcomes,” said Elliott Antman, MD, a cardiologist at Brigham and Women's Hospital, on behalf of the AHA. “Yet these studies were not designed to assess the impact of various levels of sodium intake on cardiovascular health.”

The IOM’s “Sodium Intake in Populations: Assessment of Evidence” report is available here.