Sodium Intake Alone May Not Affect Risk of Chronic Kidney Disease, Study Finds

Dietary recommendations for chronic kidney disease (CKD) risk reduction include decreasing sodium intake, but the role of potassium and the ratio of sodium to potassium in CKD are not well-understood. A recent study published in BMC Nephrology aimed to clarify the associations between sodium, potassium, and the sodium-to-potassium ratio with incident CKD in a cohort of Hispanic/Latino people living in the United States.

“The benefits of a low sodium diet in those with kidney impairment remain somewhat controversial, and recommendations are not based on directly established relationships between high sodium and CKD,” study authors wrote.

This study is the first to the authors’ knowledge to examine CKD and the role of dietary potassium in a diverse Hispanic/Latino population—a group with a higher prevalence of CKD and unfavorable sodium and potassium profiles than the overall US population.

A total of 9778 participants of the Hispanic Community Health Study/Study of Latinos (HCHS/SOL) with a mean age of 41 years were studied. All participants had no CDK at baseline between 2008 and 2011, and they were examined again between 2014 and 2017. Dietary intakes of sodium, potassium, and the ratio of sodium to potassium were measured by a pair of 24-hour dietary recalls at baseline.

An estimated glomerular filtration rate (eGFR) decline of 1 unit per year and eGFR under 60 ml/min/1.73m2 or an albumin to creatinine ratio at or above 30 mg/g at the follow-up visit were both classified as incident CKD in the study. A multivariable survey weighted Poisson regression estimated adjusted incident rates of CKD at an average follow-up of 6.2 years.

The mean sodium intake per day was 3203 mg of sodium and 2433 mg of potassium. The mean molar ratio was 2.4 for sodium-to-potassium ratio. The age- and sex-adjusted CKD incidence was 10.2 per 1000 person-years (PY), and incidence rate (IR) did not significantly differ between tertiles of sodium intake.

Participants in the highest tertile of potassium intake (2662-11,550 mg/day), however, had a significantly lower IR compared with participants in the medium (1904-2662 mg/day) and low (273-1903 mg/day) tertiles. Those in the highest tertile showed an IR of 8.6 per 1000 PY, the medium tertile IR was 11.2 per 1000 PY, and the low tertile IR was 11 per 1000 PY.

In the highest tertile of sodium-to-potassium ratio (2.85-10.9) the IR rate was 11 per 1000 PY, and the medium tertile (1.75-2.5) had an IR of 9.4 per 1000 PY. But in the lowest tertile for sodium-to-potassium ratio (0.14-1.72), the IR was 10.2 per 1000 PY.

While fully adjusted models showed no significant associations between sodium intake and CKD, there was an 11% increased risk of incident CKD with each 500 mg decrease in potassium intake. There was also a 21% increase in CKD risk with each molar increment in sodium-to-potassium ratio. Specifically in patients with diabetes, each 500 mg/day increment in sodium was associated with a 9% greater risk of CKD.

Study limitations included relying on 24-hour dietary recalls, which are not as accurate as 24-hour urine collection for dietary sodium assessment; and the relatively short follow-up period, given CKD develops over decades and diet can vary over time. But it also has strengths, being the first to explore the target associations in a large group of Hispanics/Latinos, who are an understudied ethnic minority.

Overall, the data suggest that lower potassium and higher sodium-to-potassium ratios may be associated with an increased CKD risk in Hispanic/Latino populations in the United States. Despite its limitations, the findings are consistent with previous studies suggesting sodium alone is not a significant predictor of incident CKD in otherwise healthy individuals.

“Our findings support dietary approaches to the prevention of CKD that focus simultaneously on limiting sodium and increasing potassium intake, rather than more simplistic approaches focused on individual nutrients,” study authors concluded. “Potassium is a known marker of diets high in fruits and vegetables, so we believe our results further underscore the importance of diets high in fruits and vegetables in the prevention of chronic disease.”

Reference

Swift SL, Drexler Y, Sotres-Alvarez D, et al. Associations of sodium and potassium intake with chronic kidney disease in a prospective cohort study: findings from the Hispanic Community Health Study/Study of Latinos, 2008-2017. BMC Nephrol. Published online April 6, 2022. doi:10.1186/s12882-022-02754-2