Study Challenges Link Between Salt and Heart Disease
But, European researchers acknowledge younger, white volunteers may have skewed results
TUESDAY, May 3, 2011 (HealthDay News) -- The prevailing wisdom that high salt intake raises cardiovascular risks is being challenged by a new European study that suggests the opposite.
The Polish and Belgian researchers acknowledge that all of the study volunteers were younger and white, and that may have skewed the results.
Analyzing urine sodium tests from 3,681 participants with no previous cardiovascular disease, the scientists found that lower sodium excretion was associated with an increased risk of heart-related deaths and higher sodium excretion was not linked to increased risks for high blood pressure or complications from heart disease.
The study is published in the May 4 issue of the Journal of the American Medical Association.
Study author Dr. Katarzyna Stolarz-Skrzypek said she and her colleagues were surprised at the results, but noted they mirrored previous findings by U.S. researchers in the National Health and Nutrition Examination Surveys (NHANES).
The nearly 3,000 participants in the U.S. studies, however, had been instructed to avoid high-salt foods for four to five days before sodium excretion measurements were taken. Participants in Stolarz-Skrzypek's study were not asked to cut salt intake beforehand.
"Our findings do not support the current recommendations of a generalized and indiscriminate reduction of salt intake at the population level," said Stolarz-Skrzypek, a cardiologist at Jagiellonian University Medical College in Krakow, Poland. "We believe that the consumers should be informed about risk related to low- or high-salt diet and be free to choose the consumed food. However, our findings do not negate the blood pressure-lowering effects of a dietary salt reduction in hypertensive patients."
Over a 24-hour period, participants -- whose average age was nearly 41 -- collected their own urine in a container for testing. Over a median follow-up period of about eight years, cardiovascular deaths increased among those with the lowest amounts of sodium in their urine.
Among 2,096 participants followed for only 6.5 years, increasing sodium levels were not associated with high blood pressure, a finding that contradicts many American studies.
Dr. Suzanne Steinbaum, a preventive cardiologist at Lenox Hill Hospital in New York City, said she was "upset" by the research and feels its limitations should prevent it from being taken seriously in the United States.
"The results are just so shocking," Steinbaum said. But, "this was a strictly European population, not our melting-pot-of-America mix. So this isn't exactly pertaining to our population."
Stolarz-Skrzypek conceded that the number of cardiovascular events among such a young study population might be small regardless of salt intake and that a single 24-hour collection of urine might be insufficient to characterize an individual's habitual salt use.
"Our study included only white Europeans, and its findings therefore cannot be extrapolated to Asian or, in particular, black individuals, who might be more salt-sensitive than white people," she said.
A January advisory issued by American Heart Association President Dr. Ralph Sacco noted that the health advantages of lower salt intake have been proven in an ever-expanding amount of research.
"A compelling and still-increasing body of evidence supports the imperative for population-wide sodium reduction as an integral component of public health efforts to prevent [cardiovascular disease], stroke and kidney disease," said Sacco, who is also chairman of neurology at the University of Miami. "The potential public health benefits are enormous and extend to virtually all Americans."
Harvard Health has more on salt intake and health risks.