As the 2010 Dietary Guidelines for Americans are currently under development and regulations surrounding sodium consumption are being considered, an analysis of evidence released online today in the Clinical Journal of the American Society of Nephrology (CJASN) questions the scientific logic and feasibility of the decades-long effort to limit salt intake in humans.
After examining data from sodium intake studies worldwide and a critical body of neuroscience research on sodium appetite (innate behaviors that drive us to consume salt), researchers from the Department of Nutrition at the University of California, Davis and the Department of Anatomy and Neurobiology at Washington University found compelling evidence indicating that humans naturally regulate their salt intake within a narrowly defined physiologic range.
This new analysis, "Can Sodium Intake Be Modified by Public Policy," is timely as two expert panels convened by the U.S. government are considering nutrition policies that would lower current sodium intake recommendations and set in motion policies regulating the amount in food. The issue of whether sodium intake is a physiologic parameter which public policy cannot change has never before been considered. This study challenges the relevance of regulatory or legislative intervention by identifying evidence which must be taken into account as U.S. guidelines are being reevaluated and even more restrictive policies considered.
"If sodium intake is physiologically determined, then our national nutrition guidelines and policies must reflect that reality," said David A. McCarron, M.D., an adjunct professor with the Department of Nutrition at UC Davis and lead author. "It is unrealistic to attempt to regulate America's sodium consumption through public policy when it appears that our bodies naturally dictate how much sodium we consume to maintain a physiologically set normal range. To do otherwise will expend valuable national and personal resources against unachievable goals."
Study Analysis Finds Sodium Consumption Is Not at Extreme Levels
The researchers evaluated 24-hour urinary sodium excretion, the standard measure of daily sodium intake, from 19,151 individuals collected in 62 previously published surveys from 33 countries worldwide. In contrast to the widely held notion that salt intake has reached extreme levels in Western societies, the analysis indicates that daily sodium intake across a wide range of "food environments" tracks within a relatively narrow range: 117 mmol-212 mmol (2,700-4,900 mg). In addition, previous studies provide supportive evidence that adult humans naturally seek this range of sodium intake.
Further, the authors highlight neuroscience research in animal models demonstrating that sodium intake is tightly controlled by critical pathways in the brain to maintain optimal function of many physiologic functions.
"Decades of neuroscience research have revealed highly sophisticated brain circuits which regulate sodium appetite by facilitating communications between the brain and multiple organs throughout the body," said Joel C. Geerling, M.D., Ph.D., formerly of Washington University and a co-author of this study. "One purpose of these pathways is to ensure that the body is obtaining adequate sodium from the diet to fulfill physiologic needs." Dr. Geerling is currently a physician at New York-Presbyterian Hospital/Columbia University Medical Center.