Contrary to what medical experts have been saying for years, a new study suggests salt may not be as bad for the heart as commonly believed.
Researchers from the Universities of Exeter and Plymouth in Exeter, U.K. reviewed data from seven studies with nearly 6,500 participants who reduced their salt intake and found that while eating less salt did lower blood pressure, it did not reduce the risk of dying or of having heart disease.
But this finding doesn't mean people can eat as much salt as they want. The authors caution that they don't have enough data to come to any firm conclusions about salt intake and heart disease.
"We would require some 2,500 cardiovascular events in over 18,000 trial participants to detect a small reduction in relative risk," they wrote. They also said that the study subjects only moderately lowered their sodium intake, so the effect on blood pressure and heart disease was small.
Numerous experts who were not involved with this research weighed in on the findings, and their opinions are mixed. They agree more data are needed to provide a better explanation of the findings and that there are other limitations to the study design, but debate how big a role sodium plays in the development of heart disease.
"I had been long concerned that the bold and strident public health recommendations of trying to reduce salt intake in Western societies was not based on robust data and may be premature," said Dr. Salim Yusuf, professor of medicine at McMaster University in Hamilton, Ontario, Canada. The studies reviewed by the authors, he said, suggest the relationship between salt consumption and cardiovascular disease is complex and requires more research. This research should be a priority, he added.
"I have always viewed the data for salt shortening life as being very weak," said Dr. Ken Fujioka, director of the Nutrition and Metabolic Research Center at Scripps Health in San Diego.
But other experts say salt does contribute to heart disease and other life-threatening conditions, which can lead to an untimely death in the long term.
"There is extensive evidence that excessive salt intake places many individuals at risk for hypertension and cardiovascular disease. These long term effects may not result in death for many years," said Dr. Pascal Imperato, dean of SUNY Downstate Medical Center's School of Public Health in Brooklyn, N.Y.
"[R]educing blood pressure does reduce the risk of cardiovascular disease and related mortality," said Dr. Redford Williams, director of the Behavioral Medicine Research Center at Duke University in Durham, N.C.
"We do know that high blood pressure, while associated with all forms of cardiovascular disease, is particularly associated with risk for stroke," said Dr. Merle Myerson, director of the Cardiovascular Disease Prevention Program at St. Luke's-Roosevelt Hospital in New York.
Dr. Clyde Yancy, chief of the Division of Cardiology at Northwestern University's Feinberg School of Medicine, said prior research does support the conclusion that restricting sodium can lead to "fewer deaths and much less money spent on health care for blood pressure-related diseases."