Should you eat less salt? Public health authorities generally include cutting back on sodium as one of the important dietary steps we can all take for good health. In particular, doctors admonish people with heart failure to follow a low sodium diet. But can you go too low for heart health?
Heart Failure and a Very Low Sodium Diet:
In heart failure, the cardiac muscle struggles to pump blood efficiently. As a result, fluid may build up in the lower legs or even the lungs. For decades, doctors have warned heart failure patients to restrict their salt intake as much as possible, to help control blood pressure and to reduce edema.
A recent re-analysis of the data from a gold-standard heart failure trial, the TOPCAT trial, suggests this advice may not be helpful. Specifically, the people in the trial had a type of heart failure characterized as “preserved ejection fraction.” In this condition, the heart still pumps with vigor, but the chamber (especially the left ventricle) is stiff and doesn’t fill up with blood as it should. Most people with this type of heart failure also have high blood pressure. As a result, physicians try to do everything they can to bring blood pressure under control. High sodium intake is associated with hypertension, so it makes sense to lower sodium intake. However, new research (along with older studies) suggests that an extremely low sodium diet is not helpful.
The Data Analysis:
The researchers evaluated salt added during homemade food preparation with respect to an outcome combining cardiovascular death, heart failure hospitalization and nonfatal heart attack (Heart, July 22, 2022). People who added some salt to their food had better results than those who added none. The researchers note that non-white people, especially those under 70, were most likely to suffer poor outcomes from overly strict salt reduction.
They conclude,
“Clinicians should be prudent when giving salt restriction advice to patients with HFpEF [this type of heart failure].”
Life’s Simple 7:
The American Heart Association has a short checklist of health habits it calls Life’s Simple 7. People who follow all 7 of the suggestions are supposed to be less likely to develop heart failure. The recommendations are based on data collected on people in the Framingham Offspring Study over a 12-year period, and sound a lot like common sense: don’t smoke, lose weight, manage blood pressure, control cholesterol, exercise, eat right and control blood sugar. It is only when you delve into the “eat right” recommendations that a low sodium diet surfaces as a recommendation.
Study Data Contradict Recommendations for a Low Sodium Diet:
Despite the organization’s emphasis on keeping sodium under 1,500 mg/day to avoid heart failure, a study suggests that people who already have heart failure are at greater risk of hospitalization or death if they restrict sodium intake to less than 2,500 mg/day (JACC:Heart Failure, Jan., 2016). The study included 833 people with heart failure; out of these individuals, 145 were on a restricted sodium diet.
What the Data Show:
The statistics show that 42 percent of those keeping their sodium intake low died or were hospitalized with heart failure complications. Among those not restricting sodium, 26 percent suffered that outcome.
The scientists urge their colleagues to conduct a randomized controlled trial of sodium restriction in heart failure to determine if this apparently paradoxical finding holds up.
Not the First Time a Low Sodium Diet Has Been Questioned:
We recognize that the standard of care for patients with congestive heart failure is a low sodium diet. It is an absolute article of faith that most physicians adhere to and cardiologists preach.
The American Heart Association, the American College of Cardiology, the CDC and the World Health Organization all recommend reducing salt. That’s especially for patients with congestive heart failure.
The study in JACC Heart Failure is not the first time that we have heard that a very low sodium diet might pose problems for people in general and heart failure patients in particular.
Earlier Notes on Sodium and Heart Failure:
Here are just a few observations from the medical literature:
Current Opinion in Cardiology (online, Nov. 20, 2015):
“There has been an increasing body of evidence on the effects of sodium restriction in heart failure; however, both observational and experimental studies have shown mixed results. Recent randomized controlled trial data has even suggested that sodium restriction may have detrimental effects in patients with heart failure.”
Journal of Cardiac Failure (Dec., 2015):
“Although clinical practice guidelines support a low-sodium diet and fluid restriction, research findings have revealed that a low-sodium diet may be harmful.”
The Institute of Medicine (IOM) has the most prestigious group of health experts anywhere in the world. In May 2013 the IOM issued an “Assessment of Evidence” with regard to sodium intake.
Here are a couple of key observations:
“For population subgroups, some studies indicate that low sodium intake may lead to greater risk of adverse health effects in patients who have a diagnosis of moderate or severe congestive heart failure and are receiving certain aggressive therapeutic treatments. The committee found no evidence for benefit and some evidence suggesting risk of adverse health outcomes associated with sodium intake levels in ranges approximately 1,500 to 2,300 mg/day among those with diabetes, kidney disease, or CVD [cardiovascular disease]…”
By the way, the American Heart Association recommends that all Americans keep sodium intake below 1500 mg daily.
The American Journal of Medicine (Nov., 2013):
“…there is sound evidence that a low sodium diet leads to a worse cardiovascular prognosis in patients with systolic congestive heart failure or type 2 diabetes mellitus…Advising low sodium diets seems misguided and potentially dangerous and illustrates the problem of guidelines based on flawed studies using surrogate measures.”
What Should We Do?
People with congestive heart failure should not change their dietary sodium intake on their own. Instead, we recommend discussing the latest research with a cardiologist. Heart failure is a serious condition that requires constant and careful medical supervision. Changing dietary habits suddenly could lead to disaster!
Physicians should keep up with the latest evidence with regard to sodium and health. Accepting guidelines without reviewing the underlying data does not lead to the best patient care.
