Strict sodium intake — with or without restrictions on fluid intake — is unlikely to confer clinical benefits on patients with heart failure, reported investigators.
Their review of studies showed sodium should only be moderately restricted because "patients are more likely to follow instructions that are not too draconian, and there is no evidence that severe sodium restriction saves lives or delays hospital admissions."
In fact, moderate daily intake of sodium (3.0-4.5 g) may improve the quality of life and functional status of these patients, even if it will not improve life expectancy or the hospitalization rate, Paolo Raggi, MD, from the University of Alberta, Edmonton, Alberta, Canada, explained in his narrative review published online in the European Journal of Clinical Investigation.
"It is always a little hard to give up long-held beliefs, and you try to find fault in the new evidence before your eyes," he said.
Raggi, who is also coeditor of Atherosclerosis, explained this work was prompted in part by the large, multicenter SODIUM-HF study, which showed that sodium restriction did not reduce the composite outcome of all-cause mortality, cardiovascular hospitalization, and cardiovascular-related emergency department visits, although it did improve quality of life and New York Heart Association class.
And "excessive fluid restriction — typically we were taught to restrict fluid intake to 1 L/d or, at the most, 1.5 L — does not reduce mortality or hospitalization rates and inflicts unnecessary strain and pain on patients," he said. "Clinicians need to get on board with this novel information."
Examining the Evidence
For the narrative review, the researchers conducted a literature search for the terms heart failure, salt, sodium, and fluid intake to identify relevant reports.
Most randomized trials were small and examined widely heterogeneous interventions. The identified trials published from 2000 to 2021 had populations that ranged from 12 to 203 participants, had inpatients and outpatients, and included people with reduced and preserved ejection fraction. Sodium interventions varied from extreme reductions (< 800 mg/d) to more moderate approaches (2-3 g/d). No study, regardless of the level of restriction, showed a reduction in mortality or hospitalization rates.
Notably, SODIUM-HF — the randomized clinical trial of sodium restriction to a target of 1.5 g/d — was stopped early after an interim analysis demonstrated the futility of the intervention, and the COVID pandemic made it difficult to continue the trial.
Although a moderate sodium intake of 3-4.5 g/d "seems prudent" for patients with recurrent hospital admissions and fluid overload, an intake of 2-3 g/d may be a more acceptable level. "A more aggressive sodium restriction may be necessary in the presence of chronic kidney disease, where the handling of sodium by the kidneys is hampered," Raggi reported.
"The debate on tight sodium restriction in heart failure continues to appear in major medical journals, yet it would seem that after many years of controversy, the time has come to close it," he said.
'One Approach Does Not Fit All'
Sodium restriction is difficult to quantify in a large cohort of patients because many studies are based on recall questionnaires and qualitative measurements, said Johanna Contreras, MD, an advanced heart failure and transplant cardiologist at the Mount Sinai Fuster Heart Hospital in New York City.
"Many patients are not aware that processed and precooked foods are very high in sodium and don't count them as sodium-rich foods," she said.
Nevertheless, heart failure has many etiologies and stages, so "one approach does not fit all," she said. For example, patients with stage C heart failure "will clearly get more decompensated when they consume sodium-rich diets, which will increase water absorption." And patients with heart failure secondary to hypertension are "particularly susceptible" and are likely to become more symptomatic and acutely congestive on diets high in sodium and water, which can increase both morbidity and mortality.
"It is important to understand the kinds of patients we are referring to, how advanced they are, and what comorbidities the patients have," she said. "We also know that there are race, ethnicity, and gender differences in sensitivity to sodium."
We should aim for a moderate sodium intake, she said, but patients with high sensitivity, multiple comorbidities, kidney disease, and certain demographic characteristics "need to be more careful."
Overall, "patients should aim to consume fresh fruits and vegetables and [be aware of] processed foods and adding salt at the table when they are eating," Contreras said.