WASHINGTON -- Recent studies that examine links between sodium consumption and health outcomes support recommendations to lower sodium intake from the very high levels some Americans consume now, but evidence from these studies does not support reduction in sodium intake to below 2,300 mg per day, says a new report from the Institute of Medicine.
Despite efforts over the past several decades to reduce dietary intake of sodium, a main component of table salt, the average American adult still consumes 3,400 mg or more of sodium a day – equivalent to about 1 ½ teaspoons of salt. The current Dietary Guidelines for Americans urge most people ages 14 to 50 to limit their sodium intake to 2,300 mg daily. People ages 51 or older, African Americans, and people with hypertension, diabetes, or chronic kidney disease – groups that together make up more than 50 percent of the U.S. population – are advised to follow an even stricter limit of 1,500 mg per day. These recommendations are based largely on a body of research that links higher sodium intakes to certain "surrogate markers" such as high blood pressure, an established risk factor for heart disease.
The expert committee that wrote the new report reviewed recent studies that in contrast examined how sodium consumption affects direct health outcomes like heart disease and death. "These new studies support previous findings that reducing sodium from very high intake levels to moderate levels improves health," said committee chair Brian Strom, George S. Pepper Professor of Public Health and Preventive Medicine at the University of Pennsylvania Perelman School of Medicine. "But they also suggest that lowering sodium intake too much may actually increase a person's risk of some health problems."
While cautioning that the quantity of evidence was less-than-optimal and that the studies were qualitatively limited by the methods used to measure sodium intake, the small number of patients with health outcomes of interest in some of the studies, and other methodological constraints, the committee concluded that:
- evidence supports a positive relationship between higher levels of sodium intake and risk of heart disease, which is consistent with previous research based on sodium's effects on blood pressure;
- studies on health outcomes are inconsistent in quality and insufficient in quantity to conclude that lowering sodium intake levels below 2,300 mg/day either increases or decreases the risk of heart disease, stroke, or all-cause mortality in the general U.S. population;
- evidence indicates that low sodium intake may lead to risk of adverse health effects among those with mid- to late-stage heart failure who are receiving aggressive treatment for their disease;
- there is limited evidence addressing the association between low sodium intake and health outcomes in population subgroups (i.e., those with diabetes, kidney disease, heart disease, hypertension or borderline hypertension; those 51 years of age and older; and African Americans). While studies on health outcomes provide some evidence for adverse health effects of low sodium intake (in ranges approximating 1,500 to 2,300 mg daily) among those with diabetes, kidney disease, or heart disease, the evidence on both the benefit and harm is not strong enough to indicate that these subgroups should be treated differently from the general U.S. population. Thus, the evidence on direct health outcomes does not support recommendations to lower sodium intake within these subgroups to or even below 1,500 mg daily; and
- further research is needed to shed more light on associations between lower levels of sodium (in the 1,500 to 2,300 mg/day range) and health outcomes, both in the general population and the subgroups.
The report does not establish a "healthy" intake range, both because the committee was not tasked with doing so and because variability in the methodologies used among the studies would have precluded it.
The recent studies suggest that dietary sodium intake may affect heart disease risk through pathways in addition to blood pressure. "These studies make clear that looking at sodium's effects on blood pressure is not enough to determine dietary sodium's ultimate impact on health," said Strom. "Changes in diet are more complex than simply changing a single mineral. More research is needed to understand these pathways."
The report was sponsored by the Centers for Disease Control and Prevention. Established in 1970 under the charter of the National Academy of Sciences, the Institute of Medicine provides independent, objective, evidence-based advice to policymakers, health professionals, the private sector, and the public. The National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council make up the National Academies. A committee roster follows.
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Pre-publication copies of Sodium Intake in Populations: Assessment of Evidence are available from the National Academies Press on the Internet at http://www.nap.edu or by calling. 202-334-3313 or 1-800-624-6242. Reporters may obtain a copy from the Office of News and Public Information (contacts listed above).
INSTITUTE OF MEDICINE
Food and Nutrition Board
Committee on the Consequences of Sodium Reduction in Populations
Brian Strom, M.D., M.P.H. (chair)
George S. Pepper Professor of Public Health
School of Medicine
University of Pennsylvania
Philadelphia
Cheryl A.M. Anderson, Ph.D., M.P.H.
Associate Professor
Department of Family and Preventive Medicine
University of California
San Diego
Jamy Ard, M.D.
Associate Professor
Department of Epidemiology and Prevention
Wake Forest Baptist Health
Winston-Salem, N.C.
Kirsten Bibbins-Domingo, M.D., Ph.D.
Associate Professor of Medicine and Epidemiology
University of California, and
Co-director
UCSF Center for Vulnerable Populations
San Francisco General Hospital
San Francisco
Nancy Cook, Sc.D.
Professor
Division of Preventive Medicine
Brigham and Women's Hospital
Boston
Mary Kay Fox, M.Ed.
Senior Researcher
Mathematica Policy Research Inc.
Cambridge, Mass.
Niels Graudal, M.D.
Senior Consultant
Copenhagan University Hospital, Rigshospitalet
Copenhagen, Denmark
Jiang He, M.D., Ph.D.
Joseph S. Copes Chair and Professor
School of Public Health and Tropical Medicine
Tulane University
New Orleans
Joachim Ix, M.D.
Associate Professor of Medicine
VA San Diego Healthcare System
University of California
San Diego
Stephen Kimmel, M.D.
Professor of Medicine and Epidemiology
School of Medicine
University of Pennsylvania
Philadelphia
Alice Lichtenstein, D.Sc.
Gershoff Professor of Nutrition Science and Policy
Tufts University
Boston
Myron Weinberger, M.D.
Editor-in-Chief
Journal of the American Society of Hypertension, and
Professor Emeritus
Indiana University Medical Center
Indianapolis
STAFF
Maria Oria, Ph.D.
Study Co-director
Ann L. Yaktine, Ph.D., M.S., R.D.
Study Co-director