In a sure-to-be-controversial new study, Belgian researchers have challenged the conventional wisdom that cutting back on salt reduces the risk of developing high blood pressure and dying from cardiovascular causes.
Katarzyna Stolarz-Skrzypek, MD, PhD, of the University of Leuven, and colleagues noted, The assumption that lower salt intake would in the long run lower blood pressure, to our knowledge, has not yet been confirmed in longitudinal population-based studies. So they examined the incidence of death, illness and hypertension in relation to urinary sodium excretion, used as a marker of salt intake. Their study included 3,681 participants initially without cardiovascular disease; 2,096 had normal blood pressure at the start.
Over nearly eight years, the one-third of participants with the highest sodium levels actually recorded the fewest deaths from cardiovascular disease. Among participants initially without high blood pressure, there was no association between sodium levels and risk of developing the condition. The expected link between sodium and increasing blood pressure was found only among a cohort of 1,499 people who were not on any hypertension medication, and then only for systolic pressure.
Taken together, our current findings refute the estimates of computer models of lives saved and health care costs reduced with lower salt intake, the researchers concluded. They do also not support the current recommendations of a generalized and indiscriminate reduction of salt intake at the population level.
Response to the unconventional findings was swift and negative. Peter Briss, MD, of the US Centers for Disease Control and Prevention (CDC) criticized the study in an interview. Dr. Briss said because the subjects were relatively young (initially average age about 40) and the number of cardiovascular events (including 84 deaths) was small, this study might need to be taken with a grain of salt.
Ralph Sacco, MD, president of the American Heart Association, said that while the study raises some interesting questions, the bulk of the evidence supports the view that reducing sodium intake helps lower blood pressure and reduce the risk of heart disease. The Heart Association, he said, would stand by its recently updated advice to limit daily sodium intake to 1,500 milligrams.
The 2010 federal Dietary Guidelines for Americans recommend limiting sodium to 2,300 milligrams daily. A lower, 1,500-milligram ceiling is advised, however, for all African-Americans and people older than 51, as well as those with hypertension, diabetes and chronic kidney disease.
This study doesnt really shake up those recommendations, says Irwin R. Rosenberg, MD, editor of the Tufts Health & Nutrition Letter. The real message is that all along, the evidence about the health effects of salt has been a seesaw.
TO LEARN MORE: JAMA, May 4, 2011; abstract at jama.ama-assn.org/content/305/17/1777.abstract.