Effects of dietary interventions for metabolic acidosis in chronic kidney disease: a systematic review and meta-analysis

Background and hypothesis Metabolic acidosis is a common complication of kidney disease and can result in further disease progression. Alkali therapy has been used to treat metabolic acidosis for decades. However, some concerns have been raised regarding its safety and long-term tolerability. Existing data suggest that dietary interventions can be beneficial in the management of chronic kidney disease (CKD). This systematic review and meta-analysis aims to summarize findings from studies comparing dietary interventions with placebo/usual care/no treatment in the management of metabolic acidosis in outpatient adults with CKD. Methods Medline, Embase, Cochrane Central, CINAHL, and Web of Science Core Collection were searched from inception to June 2022. Our primary outcome measure was change in serum bicarbonate. Any dietary intervention looking to manipulate dietary acid load was considered as an intervention. Data screening and extraction were performed by two independent reviewers. Random effects meta-analysis was performed to pool data. Results Dietary interventions resulted in clinically significant improvement in serum bicarbonate (mean difference (MD):2.98, 95% CI: [0.77, 5.19]; I2: 91%) and higher eGFR levels (MD: 3.16, 95%CI: [0.24, 6.08], I2: 67%) compared to controls. Serum potassium, albumin and body mass index remained unchanged. Dietary interventions were reported to be safe. Subgroup analyses indicated a superiority of plant-based over non-plant-based interventions in the improvement of acid-base balance and eGFR, however, these findings are from low quality and heterogenous studies. Conclusion Our findings support the beneficial effects of dietary interventions aimed at reducing acid or adding base in the management of metabolic acidosis and kidney function in adults with CKD, with no adverse effects on serum potassium and nutritional status. Well-designed clinical trials looking at the treatment of metabolic acidosis with dietary interventions with a focus on adding base through fruit and vegetables are required.