Salt Is OK for People With Heart Failure: Review

According to the review author, some of the papers analyzed even suggested extreme salt restrictions could be harmful.

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Salt restriction, a long-standing recommendation for patients with heart failure, has no proven clinical benefits, according to a review published on June 26 in the European Journal of Clinical Investigation.

While some studies reported possible improvements in quality of life and functionality, the review author, Dr. Paolo Raggi from the University of Alberta, wrote that there is no evidence that severe sodium restriction reduces mortality and hospitalization in patients with heart failure.

The review evaluated randomized controlled trials conducted from 2000 to 2023. Most were small, and a single large trial concluded early due to futility.

“Doctors often resist making changes to age-old tenets that have no true scientific basis; however, when new good evidence surfaces, we should make an effort to embrace it,” Dr. Raggi said in a statement.

How Does Salt Affect the Heart?

Heart failure is a chronic condition that occurs when the heart muscles cannot pump enough blood to meet the body’s needs for blood and oxygen.

Reduction in salt intake is recommended for heart failure because salt draws water. More salt in the blood can increase blood volume, thereby increasing blood pressure, which can then cause further damage to blood vessels and the heart.

Severe reductions in salt intake can also cause a drastic decrease in blood volume, which can be harmful.

Scientists cannot agree on how much salt should be reduced, and this discrepancy is due to differences in data interpretation, Dr. Raggi wrote.

It has also been difficult to conduct a proper study evaluating the long-term effects of salt restriction since low-salt diets are challenging for patients to adhere to, and salt intake is hard to measure.

Several prominent health organizations, including the American Heart Association (AHA), recommend that patients with heart failure consume under 2 grams (about half a teaspoon) of salt daily. The author said that this recommendation likely arose from the conclusions of several trials, including the famous DASH-sodium trial, which found that people who consumed less than 1 1/2 grams of salt daily had lower blood pressure.

While proponents of the DASH-sodium trial support its findings and recommendations, dissidents argue it was too short and that such salt restrictions are unlikely to be sustainable.

Dr. Raggi wrote that moderating salt intake would benefit people consuming high levels of salt. However, just how much salt should be reduced is unknown. Quality of life does improve with lower salt intake; however, there is no clinical evidence that it results in fewer cardiovascular events and deaths.

While salt restriction clearly lowers blood pressure, especially in hypertension patients, the effect appears to wane with time.

“It has been estimated that tens of thousands of patients (the numbers varying depending on the baseline risk profile of the population enrolled) would have to be followed for 5 to 10years [sic] to prove that a strict sodium intake is associated with a 15% reduction in cardiovascular events. Such a proposition seems unlikely to materialize,” the author wrote.

Even the Cochrane review, seen as the gold standard in research, yielded an inconclusive result.

“The Cochrane review concluded that there was insufficient power to show an effect on mortality, although there might be a reduction in cardiovascular events with sodium restriction,” Dr. Raggi wrote.

He noted that none of the studies included in the Cochrane review and the many studies before it advised that salt intake should be as low as authorities such as the AHA suggested. Therefore, he concluded that questions about appropriate salt intake remain unanswered.

A Reduction in Fluids?

Instead of focusing on sodium intake, Dr. Raggi said monitoring fluid intake could help treat people with heart failure. In heart failure, the blood vessels expand, and swelling occurs under the skin. As it progresses, total body volume also increases. Therefore, he reasoned, it may be sensible to restrict fluids to reduce further swelling.

While some research has put this theory to the test, sample sizes have been relatively small, and evidence demonstrating noteworthy benefits has been limited.