Reducing sodium intake has been proposed as a population-level target for the prevention of cardiovascular disease (CVD) and chronic kidney disease (CKD). A recent study published in The Lancet conducted two Phase II feasibility randomized controlled trials evaluating the effects of an intensive dietary counseling intervention in a general population and another in a population with CKD.
The aim was to reduce sodium intake to levels recommended by current guidelines and compare it with usual care on biomarkers of kidney or cardiovascular disease over two years. The study hypothesized that sustained lowering of dietary sodium intake would lead to changes in cardiorenal biomarkers.
The study found that among participants with baseline moderate sodium intake, the intensive dietary counseling intervention resulted in short-term reductions in 24-hour urinary sodium and blood pressure, with an increase in direct serum renin. However, at 2 years, there was no effect of the intervention on 24-hour urine sodium, blood pressure, or cardiorenal biomarkers. The study also noted that it was unable to achieve sustained low intake despite an intensive dietary counseling intervention.
A new study called COSTICK has evaluated the effects of a dietary counseling intervention on intermediate cardiorenal outcomes in patients with mild/moderate kidney disease. The research protocol involved two randomized, two-group, parallel, open-label, controlled, single-center trials. Participants aged over 40 with stable blood pressure and willing to modify their diet were included.
They were randomized to usual care or a sodium-lowering intervention through specific counseling. In one group, the primary outcome was the change in 24-hour urinary creatinine clearance, and in the other group, the primary outcome was the change in five biomarkers.
The trial aimed to explore uncertainty about low sodium intake and cardiovascular and kidney biomarkers and help determine the feasibility of low sodium intake. The results will provide preliminary information to guide a future definitive clinical trial if indicated.
It was found that there are well-established challenges in reducing dietary sodium intake in many populations, particularly while maintaining nutrition targets. The mean achieved reductions in urinary sodium in previous clinical trials were greater than the change observed in this study.
The study suggests that there may be a floor effect in the ability to lower sodium intake and that a lower limit of sodium intake is governed physiologically. The study also found that different approaches to sodium intake measurement have implications for comparing findings from clinical trials.
It was seen that an intensive dietary counseling intervention aiming to reduce sodium intake is associated with short-term reductions in urinary sodium and blood pressure but may not be effective in achieving sustained low sodium intake in the long term. The study also highlights the challenges of reducing dietary sodium intake and the physiological limitations of lowering sodium intake beyond a certain level.