Association Between Hyperkalemia, Dietary Potassium With NDD-CKD

Hyperkalemia is a serious complication of chronic kidney disease (CKD) that is associated with an increased risk of cardiovascular events and all-cause mortality. Dietary restriction of potassium, including from fruits and vegetables, is a longstanding aspect of hyperkalemia management supported by clinical guidelines. However, recent research has begun to question such dietary recommendations, and evidence on the association between hyperkalemia and dietary potassium is inconsistent.

Nobuhisa Morimoto, PhD, and others decided to study the association between potassium intake from different food sources and hyperkalemia in patients with non–dialysis-dependent CKD (NDD-CKD). Their findings were published in the Journal of Renal Nutrition.

Morimoto et al recruited 285 patients (median age, 72 years; 33% female) with NDD-CKD from three hospitals in Tokyo who were admitted between April 1, 2022, and March 31, 2023. CKD was defined as having an estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m², a history of nephrotic syndrome or glomerulonephritis that had been treated, or persistent proteinuria or hematuria for at least 3 months.

The researchers estimated patients’ dietary potassium intake based on responses to a validated diet history questionnaire. Patients also answered questions about their lifestyle, including smoking, alcohol consumption, and bowel movements. Blood and urine samples were collected from most (>80%) patients within 1 month before or after they completed the questionnaire. Data on comorbidities, medical history, and medication use came from the three hospitals’ electronic medical records.

The primary outcomes were serum potassium level (a continuous variable) and hyperkalemia, defined as serum potassium level ≥5.0 mEq/L. Patients with CKD stages 3b and 4 comprised approximately 60% of the study population. The median patient eGFR was 31.2 mL/min/1.73 m². The mean serum potassium level was 4.4 ± 0.5 mEq/L. Prevalence of hyperkalemia was 13.3%, and 14.0% of participants used potassium binders.

The research team used multivariable linear regression to examine associations of potassium intake from all foods and individual food groups with serum potassium among potassium binder nonusers. They used multivariable logistic regression to study the association between tertile groups of potassium intake and hyperkalemia.

Among the 245 potassium binder nonusers in the study, total potassium intake was only weakly associated with serum potassium (β=0.147; 95% CI, 0.018-0.277; P=.026). No association with hyperkalemia was observed (first vs third tertile: adjusted odds ratio [aOR], 0.98; 95% CI, 0.29-3.26). Looking at different food groups, potassium from pulses, potatoes, and green/yellow vegetables had a positive association with serum potassium (β=0.847; 95% CI, 0.159-1.535; P=.016; β=0.574; 95% CI, 0.102-1.046; P=.017; and β=0.358; 95% CI, 0.012-0.704; P=.042, respectively).

Total potassium intake was not associated with hyperkalemia (first vs third tertile: aOR, 0.98; 95% CI, 0.29-3.26; P=.975). Only potassium from potatoes was associated with hyperkalemia; patients in the highest tertile of potassium intake from potatoes had higher odds of hyperkalemia versus those in the lowest tertile (aOR, 4.12; 95% CI, 1.19-14.34; P=.026). Furthermore, only potassium intake from potatoes remained associated with serum potassium levels among patients with more advanced CKD (eGFR <30 mL/min/1.73 m²).

The authors acknowledged some limitations of their study. Its observational nature did not allow for examination of a causal relationship between dietary potassium intake and serum potassium level or the effects of unmeasured or residual confounders. There was a risk of misreporting, recall bias, and selection bias. Results may not be directly extrapolated to the overall CKD population in Japan and may not be generalizable to patients with CKD in non-Japanese populations.

In conclusion, the researchers observed associations between higher potassium intake from potatoes, pulses, and green/yellow vegetables and greater serum potassium levels. However, only the potassium intake from potatoes remained associated with serum potassium levels among patients with more advanced CKD, and only potassium intake from potatoes had an association with hyperkalemia.

“These findings suggest the possibility that replacing potatoes, which have high potassium bioavailability, with other types of vegetables with lower potassium bioavailability may decrease serum potassium levels while maintaining dietary fiber intake that may confer cardiovascular benefits,” they wrote.

Source: Journal of Renal Nutrition