How Much Salt Is Best for the Heart?

New study shows fine balance: too much or too little raises death, hospitalization risk

By Amanda Gardner
HealthDay Reporter

TUESDAY, Nov. 22 (HealthDay News) -- For people with heart disease or diabetes, too little salt may harbor almost as much danger as too much salt, researchers report.

Reducing salt is still very important in people consuming more than 6,000 or 7,000 milligrams of sodium per day, said Dr. Martin O'Donnell, lead author of a study in the Nov. 23/30 issue of the Journal of the American Medical Association.

But people who already consume moderate or average amounts of salt may not need to reduce their intake further, added O'Donnell, an associate clinical professor at McMaster University in Hamilton, Ontario, in Canada.

"We're seeing more and more that there may be an optimal moderate amount of salt that people should be eating," said Dr. John Bisognano, professor of medicine and director of outpatient cardiology at the University of Rochester Medical Center, in New York. "This is reassuring for people who eat a diet that is moderate in salt."

Bisognano was not involved with the study, which was funded by pharmaceutical company Boehringer Ingelheim.

After years of seemingly happy agreement that people should lower their salt intake, experts recently have begun debating whether or not lower salt intake is actually good for everyone.

One recent study found that although cutting back on salt does lower blood pressure, it may also increase levels of cholesterol, triglycerides and other risk factors for heart disease.

Another study found that lower sodium excretion (sodium excretion is a way to measure how much salt is consumed) was associated with an increased risk of heart-related deaths, while higher sodium excretion was not linked with increased risks for blood pressure or complications from heart disease in healthy people.

However, in the latest study, results were somewhat different.

These authors looked at how much sodium and potassium were excreted in urine in a group of about 30,000 men and women with heart disease or at high risk for heart disease. Participants were followed for an average of more than four years.

In this study, sodium excretion levels that were either higher or lower than the moderate range were each associated with increased risk.

For example, people who excreted higher levels of sodium than those with mid-range values had a greater risk of dying from heart disease, heart attack, stroke and hospitalization for heart failure, the report found.

On the other hand, people who excreted lower levels than mid-range were at a raised risk of dying from heart disease or being hospitalized for heart failure.

When the researchers assessed potassium levels, they found that a higher level of excretion of the nutrient was associated with a lower risk of stroke.

"The importance of potassium intake needs to be emphasized, a finding that may be lost in the discussion on sodium," said O'Donnell, who is also an associate professor of translational medicine, at the National University of Ireland in Galway. "Diets rich in fruit and vegetables are also rich in potassium intake."

It's not clear if these findings -- which came from a population already at high risk for heart trouble -- may also apply to lower-risk populations.

"They're really looking at the sickest of the sick. How does that apply to all of us?" said Dr. Daniel Anderson, an assistant professor of medicine at the University of Nebraska Medical Center. "I think the difficulty is it probably doesn't. I worry that we're going to misinterpret this as meaning that too little sodium is a bad thing."

Bisognano agreed. "We don't want to give people the message that they should salt their pizza from this point forward," said Bisognano.

But consuming the right amount of sodium is only one aspect of heart health, said Karen Congro, director of the Wellness for Life Program at the Brooklyn Hospital Center in New York City.

"It's not the be all and end all. You have to do other lifestyle interventions," she said.

New U.S. dietary guidelines now recommend that people aged 2 years and older limit daily sodium intake to less than 2,300 milligrams (mg).

People aged 51 and older, blacks and anyone with high blood pressure, diabetes or chronic kidney disease should consider going down to 1,500 mg per day, many experts say.

It's estimated that the average American consumes 3,400 milligrams of sodium a day.

More information

Find out more about the new dietary guidelines for Americans from the U.S. Department of Agriculture.

SOURCES: Martin J. O'Donnell, M.B., Ph.D., associate clinical professor, McMaster University, Hamilton, Ontario, Canada, and associate professor, translational medicine, National University of Ireland, Galway; John Bisognano, M.D., Ph.D., professor of medicine and director, outpatient cardiology, University of Rochester Medical Center, New York; Karen Congro, R.D., director, Wellness for Life Program, Brooklyn Hospital Center, New York City; Daniel R. Anderson, M.D., Ph.D., associate professor of medicine, University of Nebraska Medical Center, Omaha; November 23/30, 2011 Journal of the American Medical Association

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