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"No one should run out and buy a salt shaker to try to improve their cardiovascular health. But we think it's reasonable to say that different people have different needs," said study author Dr. Hillel W. Cohen, an associate professor of epidemiology and population health at Albert Einstein College of Medicine of Yeshiva University.
The study, published online in the Journal of General Internal Medicine, doesn't confirm that a low-salt diet itself is bad for the heart. But it does say that people who eat the least salt suffer from the highest rates of death from cardiac disease.
"Our findings suggest that one cannot simply assume, without evidence, that lower salt diets 'can't hurt,' " Cohen said.
Cohen and his colleagues looked at a federal health survey of about 8,700 Americans between 1988 and 1994. All were over 30, and none were on special low-salt diets.
The researchers then checked to see what happened to the volunteers by the year 2000.
Even after the researchers adjusted their statistics to account for the effect of cardiac risk factors like smoking and diabetes, the 25 percent of the population who ate the least salt were 80 percent more likely to die of cardiac disease than the 25 percent who ate the most salt.
Cohen doesn't discount that salt could be bad for some people. However, "the main argument for reducing salt in prevention of heart disease has been that there's a relationship between higher sodium and higher blood pressure," he said. "There have been many studies of this relationship, but when one actually looks at the numbers, the average blood pressure difference associated with quite a bit of sodium intake is very modest."
He questions telling healthy people to cut down on salt, especially when modest changes may have no effect. "For most people, especially those whose blood pressure is normal, why are you telling them they shouldn't have salt?"
The study was not designed to detect a direct cause-and-effect relationship between consumption of salt and cardiac death. Instead, it only looked at a potential link. It's possible that salt consumption could reflect some other factor that's playing a greater role, although Cohen said the researchers tried to account for that possibility.
Existing disease could be a hidden factor, said Howard Sesso, an assistant professor of medicine at Brigham and Women's Hospital in Boston. According to him, the study authors may not have been able to account for every survey participant who reduced salt intake because of heart disease, high blood pressure or diabetes.
Overall, Sesso said, research about the hazards of salt remains mixed. "Patients with normal blood pressure can continue to consume salt, but in moderation and keeping in mind that it is the entire dietary portfolio that matters most."
SOURCES: Hillel W. Cohen, M.D., associate professor, epidemiology and population health, Albert Einstein College of Medicine of Yeshiva University, New York City; Howard D. Sesso, Sc.D., M.P.H., assistant professor, medicine, Division of Preventive Medicine, Brigham and Women's Hospital, Boston; May 15, 2008, Journal of General Internal Medicine, online
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