Dietary potassium restriction appears prudent in normokalemic patients with chronic kidney disease (CKD) to keep serum potassium levels in check and reduce mortality risk, but this advice is based on very low-quality evidence, according to the authors of a new review published in the Journal of Renal Nutrition.
Andrew Morris, MRes, of Coventry University in Coventry, United Kingdom, and colleagues performed a systematic review and meta-analysis of 2 randomized trials and 5 observational studies involving 3489 normokalemic patients with CKD stages 3 to 5D. A restricted (1295 mg/d) versus unrestricted (1570 mg/d) potassium diet lowered serum potassium by just 0.22 mEq/L, although the absolute differences in potassium intake between cohorts seemed small.
In further analyses, a relatively low dietary potassium intake of 1670 mg/d was associated with a 40% reduction in mortality compared with a high potassium intake of 4414 mg/d. Low dietary potassium intake did not significantly correlate with slower CKD progression, however.
“Our meta-analyses also offer support to the current opinion that dietary potassium intakes should be limited to 2,000-2,500 mg/d (50-65 mmol/d) in those with CKD stage 5 on maintenance hemodialysis to help maintain normokalemia,” Morris’ team wrote.
The reviewers found no studies supporting potassium supplementation to reduce blood pressure in patients with nondialysis CKD.
Morris and colleagues deemed the quality of the evidence “very low” according to GRADE criteria. They encouraged future high-quality trials in this area that include patients with hyperkalemia.
In a recent paper in Kidney International, the authors reported specific areas for future research based on a Kidney Disease: Improving Global Outcomes (KDIGO) controversies conference on the management of dyskalemia. Investigators should:
- Investigate the effect of dietary potassium restriction in CKD on circulating levels
- Investigate the effect of fruit- and vegetable-rich diets in CKD
- Develop new methods and validate existing methods to estimate dietary potassium intake in patients with CKD
- Evaluate the impact of dietary potassium on serum concentration in people with CKD
- Evaluate the effects of dietary potassium restriction in patients with CKD on clinically important outcomes, including harms
- Evaluate the effects of unrestricted fruit/vegetable intake on the risk of hyperkalemia in patients with advanced CKD or who are undergoing dialysis
The authors of the paper observed: “Generalized dietary [potassium] restriction in people with CKD may deprive them from other beneficial effects and nutrients of [potassium]-rich diets.”
Morris A, Krishnan N, Kimani PK, Lycett D. Effect of dietary potassium restriction on serum potassium, disease progression, and mortality in chronic kidney disease: a systematic review and meta-analysis. J Renal Nutr. 2020; 30(4):276-285. doi:10.1053/j.jrn.2019.09.009
Clase CM, Carrero JJ, Ellison DH, et al. Potassium homeostasis and management of dyskalemia in kidney diseases: conclusions from a Kidney Disease: Improving Global Outcomes (KDIGO) controversies conference. Kidney Int. 2020;97(1):42-61. doi:10.1016/j.kint.2019.09.018