Doctors have long encouraged patients to slash their salt intake for good heart health.
The American Heart Association advises people to consume no more than 1,500 milligrams a day of sodium to reduce their risk of high blood pressure, heart attacks, stroke and kidney disease. This is less than half of what people consume now.
One reason for this advice: Elevated blood pressure is a major public health problem. About 90 percent of all Americans will develop hypertension over their lifetime, the heart association says.
But a European study coordinated in Belgium raises questions about sodium's effect on the heart.
Researchers followed 3,681 people, average age 40, for about eight years, testing sodium excretion in the urine. They found that systolic blood pressure (top number) was slightly lower in those who excreted less sodium, but that didn't translate into a lower risk of cardiovascular death. In fact, those with lower sodium excretion had an increased risk of cardiovascular death. The findings were consistent in participants younger and older than 60.
Jan Staessen, a professor of medicine at the University of Leuven in Belgium and one of the authors of the report in Wednesday's Journal of the American Medical Association, says the study does not support the recommendation of a general reduction of salt intake for everyone, although salt reduction could be beneficial in lowering the blood pressure of people with hypertension. Reducing salt "is recommended for people with high blood pressure and people with heart failure, but recommending it to the population as a whole, I wouldn't do without proving it's completely safe," he says.
"If one lowers sodium intake to lower blood pressure, this change in sodium activates several systems that conserve sodium, and those systems are implicated in disease processes such as damaging the arterial wall and kidneys."
The findings may apply to Americans of white European descent but might be less applicable to blacks because they are believed to be more salt-sensitive, he says.
The research is drawing fire from medical experts here. Ralph Sacco, president of the American Heart Association and chairman of neurology at the University of Miami, says this is only one study of a relatively young, mostly white population-and blood pressure tends to rise with age and affect African Americans disproportionately.
"We have based our recommendations on the many scientific studies which show a strong relationship between reduced sodium consumption and a lower risk of heart attacks, congestive heart failure and stroke," he says. "There are good randomized, controlled studies-the gold standard of scientific studies-that show a lower sodium diet has a meaningful effect on blood pressure."
Atlanta cardiologist Gina Lundberg supports the 1,500-milligram limit: "We're all eating too much sodium too many prepared, processed foods."
Leaders in the salt industry applaud the new research. "This study basically says that salt reduction to reduce cardiovascular disease is a strategy that is not going to work," says Morton Satin of the Salt Institute, an industry group.
Explore further: Study evaluates relationship of urinary sodium with health outcomes