For the past century, people with weak hearts have been told to lower their salt intake, but, until now, there has been little scientific evidence behind the recommendation.
The largest randomized clinical trial to look at sodium reduction and heart failure reported results simultaneously in The Lancet and at the recent American College of Cardiology’s 71st annual scientific session, and the findings were mixed.
Though reducing salt intake did not lead to fewer emergency visits, hospitalizations, or deaths for patients with heart failure, the researchers found an improvement in symptoms such as swelling, fatigue and coughing and a better overall quality of life.
“We can no longer put a blanket recommendation across all patients and say that limiting sodium intake is going to reduce your chances of either dying or being in hospital, but I can say comfortably that it could improve people’s quality of life overall,” said lead author Justin Ezekowitz, professor in the Faculty of Medicine & Dentistry and co-director of the Canadian VIGOUR Centre.
The researchers followed 806 patients at 26 medical centres in Canada, the United States, Columbia, Chile, Mexico and New Zealand. All were suffering from heart failure, a condition in which the heart becomes too weak to pump blood effectively. Half of the study participants were randomly assigned to receive usual care, while the rest received nutritional counselling on how to reduce their dietary salt intake.
Patients in the nutritional counselling arm of the trial were given dietitian-designed menu suggestions using foods from their own region and were encouraged to cook at home without adding salt and to avoid high-salt ingredients. Most dietary sodium is hidden in processed foods or restaurant meals rather than being shaken at the table, Ezekowitz noted.
“The broad rule that I’ve learned from dietitians is that anything in a bag, a box, or a can generally has more salt in it than you would think,” said Ezekowitz, who is also a cardiologist at the Mazankowski Alberta Heart Institute and director of the U of A’s Cardiovascular Research Institute.
The target sodium intake was 1,500 mg per day – the equivalent of about two-thirds of a teaspoon of salt – which is the Health Canada recommended limit for most Canadians whether they have heart failure or not.
Before the study, patients consumed an average of 2,217 mg per day, or just under one teaspoon. After one year of study, the usual care group consumed an average of 2,072 mg of sodium daily, while those who received nutritional guidance consumed 1,658 mg per day, a reduction of a bit less than a quarter-teaspoon equivalent.
The researchers compared rates of death from any cause, cardiovascular hospitalization and cardiovascular emergency department visits in the two study groups but found no statistically significant difference.
They found consistent improvements for the low-sodium group using three different quality of life assessment tools, as well as the New York Heart Association heart failure classification, a measure of heart failure severity.
Ezekowitz said that he will continue to advise patients with heart failure to cut back on salt, but now he will be clearer about the expected benefits. He urges clinicians to recognize that dietary changes can be a useful intervention for some patients.
The team will do further research to isolate a marker in the blood of patients who benefited most from the low-sodium diet to give more targeted individual diet prescriptions in the future. The researchers will also follow up with patients in the trial at 24 months and five years to determine whether further benefits are achieved over the longer term.
“There are many challenges to eating a healthy diet, but it is achievable. It’s not some unachievable goal for patients,” Ezekowitz said. And the odd treat from time to time is fine.
“If that bowl of ice cream is really important to you, that’s great, but you shouldn’t have it every day,” he said. “It’s not about the hills and valleys; it’s all about the averages.”
The study was funded by the Canadian Institutes of Health Research, the University Hospital Foundation and the Health Research Council of New Zealand.
| By Gillian Rutherford
Gillian is a reporter with the University of Alberta’s Folio online magazine. The University of Alberta is a Troy Media Editorial Content Provider Partner.
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