Overly restrictive salt intake may worsen outcomes for common form of heart failure

Restricting salt intake is considered a key component of heart failure treatment, but restricting it too much may actually worsen the outcomes for people with a common form of the condition, suggests research published online in the journal Heart. Younger people and those of black and other ethnicities seem to be most at risk, the findings indicate.

A phase III, randomised, double-blind, placebo-controlled study, this trial was designed to find out if the drug spironolactone could effectively treat symptomatic heart failure with preserved ejection fraction.

Participants were asked how much salt they routinely added to the cooking of staples, such as rice, pasta, and potatoes; soup; meat; and vegetables, and this was scored as: 0 points (none); 1 (⅛ tsp); 2 (¼ tsp); and 3 (½+tsp).

Around half the participants (816) had a cooking salt score of zero: more than half of them were men (56%) and most were of white ethnicity (81%). They weighed significantly more and had a lower diastolic blood pressure (70 mm Hg) than those with a cooking salt score above zero (897).

They had also been admitted to hospital more often for heart failure, were more likely to have type 2 diabetes, poorer kidney function, to be taking meds to control their heart failure, and to have a reduced left ventricular ejection fraction (lower cardiac output).

Participants with a cooking salt score above zero were at significantly lower risk of the primary endpoint than those whose score was zero, mainly driven by the fact that they were less likely to be admitted to hospital for heart failure. But they were no less likely to die from any cause or from cardiovascular disease than those whose cooking salt score was zero.

Those aged 70 or younger were significantly more likely to benefit from adding salt to their cooking than were those older than 70 in terms of the primary endpoint and admission to hospital for heart failure.

But their study findings show that the volume of plasma in the blood—an indicator of congestion----wasn't significantly associated with cooking salt score, suggesting that low sodium intake didn't ease fluid retention in people with heart failure with preserved ejection fraction, point out the researchers.

References: "Overly restrictive salt intake may worsen outcomes for common form of heart failure"; BMJ JOURNAL Heart; DOI:10.1136/heartjnl-2022-321167.