A Comparison of Treating Metabolic Acidosis in CKD Stage 4 Hypertensive Kidney Disease with Fruits and Vegetables or Sodium Bicarbonate

Abstract

Background and objectives 

Current guidelines recommend Na⁺-based alkali for CKD with metabolic acidosis and plasma total CO₂ (PTCO₂) < 22 mM. Because diets in industrialized societies are typically acid-producing, we compared base-producing fruits and vegetables with oral NaHCO₃ (HCO₃) regarding the primary outcome of follow-up estimated GFR (eGFR) and secondary outcomes of improved metabolic acidosis and reduced urine indices of kidney injury.

Design, setting, participants, & measurements 

Individuals with stage 4 (eGFR, 15–29 ml/min per 1.73 m²) CKD due to hypertensive nephropathy, had a PTCO₂ level < 22 mM, and were receiving angiotensin-converting enzyme inhibition were randomly assigned to 1 year of daily oral NaHCO₃ at 1.0 mEq/kg per day (n=35) or fruits and vegetables dosed to reduce dietary acid by half (n=36).

Results 

Plasma cystatin C–calculated eGFR did not differ at baseline and 1 year between groups. One-year PTCO₂ was higher than baseline in the HCO₃ group (21.2±1.3 versus 19.5±1.5 mM; P<0.01) and the fruits and vegetables group (19.9±1.7 versus 19.3±1.9 mM; P<0.01), consistent with improved metabolic acidosis, and was higher in the HCO₃ than the fruits and vegetable group (P<0.001). One-year urine indices of kidney injury were lower than baseline in both groups. Plasma [K⁺] did not increase in either group.

Conclusions 

One year of fruits and vegetables or NaHCO₃ in individuals with stage 4 CKD yielded eGFR that was not different, was associated with higher-than-baseline PTCO₂, and was associated with lower-than-baseline urine indices of kidney injury. The data indicate that fruits and vegetables improve metabolic acidosis and reduce kidney injury in stage 4 CKD without producing hyperkalemia.