Salty Science

You’ve heard it for years: Cut down on sodium. More salt in your diet may contribute to more problems for your body. However, recent media reports question the validity of the science that supports sodium reduction. The American Heart Association feels strongly that the majority of science supports reduction, and that studies that challenge reduction have methodological flaws. Since March 19-23 is World Salt Awareness week, we thought it was a good time to address this issue.

Extensive research has shown that too much sodium can cause high blood pressure, a primary cause of heart disease and stroke, the two leading causes of death in the world. Interestingly, the salt shaker is not the culprit. About three-quarters of the sodium Americans consume comes from packaged, prepared and restaurant foods. This means that we do not get to choose how much sodium we eat; rather, that decision is made for us by food manufacturers and the restaurant industry. “Sodium serves many different functions in food, including food safety and enhancement of thickness, and strength of flavor,” said Penny Kris-Etherton, Ph.D., R.D., Distinguished Professor of Nutrition, Department of Nutritional Sciences at Pennsylvania State University.

Extra sodium in the bloodstream pulls water into the blood vessels, increasing the amount of blood inside, which increases blood pressure. “It’s like turning up the water supply to a garden hose — the pressure increases as more water is blasted through,” Kris-Etherton said. “Over time, this pressure may overstretch or injure the blood vessel walls and speed the build-up of gunky plaque that can block blood flow. The added pressure also tires out the heart by forcing it to work harder.”

The studies are clear, and the outcomes are imperative for Americans, who have high rates of heart disease and high blood pressure. One study estimated that lowering sodium in the food supply could eliminate about 1.5 million cases of uncontrolled hypertension and save billions of dollars in healthcare costs.

The American Heart Association’s lifestyle guidelines on sodium reduction were developed after a review of 30 studies about sodium. These guidelines were endorsed by the following organizations:

American Association of Cardiovascular and Pulmonary Rehabilitation

American Pharmacists Association

American Society for Nutrition

American Society for Preventive Cardiology

American Society of Hypertension

Association of Black Cardiologists

National Lipid Association

Preventive Cardiovascular Nurses Association

Women Heart: The National Coalition for Women with Heart Disease.

“There is strong evidence, including a recent analysis of more than 100 randomized clinical trials, that sodium reduction reduces blood pressure in adults,” said Tom Frieden, former director of the Centers for Disease Control and Prevention.

Public health recommendations are made after weighing all the evidence. A vast body of diverse research indicates that lowering sodium intake lowers blood pressure, a major risk factor for heart disease, stroke and other major health problems.

About Studies That Challenge Sodium Reduction

There have been scientific flaws in studies suggesting that too little salt could cause risk for death and disease. These flaws range from inadequate controls in the collection of data (urine collection or dietary surveys) to recruiting participants who already had advanced heart disease to a variety of problems with statistical analysis. A thorough analysis of these studies was published in Circulation in 2014. The analysis pointed out four potential issues with the way studies are conducted that produce unreliable results. These include:

  • systematic error — using unreliable measures for sodium intake
  • reverse causality — including sick people who might have reduced sodium to address their disease
  • residual confounding — not considering factors that may influence the outcome
  • inadequate follow-up — only including people who follow up with the study on their own instead of researchers actively following up

It is important to measure sodium intake accurately in order to identify how it impacts risk of heart disease. Some studies look at large numbers of people but use imprecise ways to estimate sodium intake — and that can lead to inaccurate results. Studies like this may delay effective action to reduce blood pressure and save lives.

“Reducing sodium is a tried and true way to keep your pressure in the healthy range,” Kris-Etherton said. “This is so important because by one estimate, 90 percent of us will have high blood pressure at some point in our lives.”

What You Can Do

Take control of the food you eat. Join thousands of others by taking the pledge to eat healthier and reduce the sodium you eat.

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