Effects of soy protein containing isoflavones in patients with chronic kidney disease: A systematic review and meta-analysis

Background & aims: Recent studies have demonstrated mixed results on the effects of soy intake in patients with CKD, and this have not been systematically analyzed. We conducted this meta-analysis to identify and evaluate the effects of soy protein intake in patients with CKD.

Methods: A comprehensive search of Medline, Embase and the Cochrane Database of Systematic Reviews was performed in December 2013 and updated in April 2014 for any new trials. Randomized trials designed to evaluate the effects of dietary soy in patients with CKD were collected. Weighted mean effect sizes were calculated for net changes using random-effect or fixed-effect model. All statistical analysis were calculated by RevMan software 5.2 available free from the Cochrane Collaboration.

Results: 12 studies (280 participants) were included. And we found that dietary soy was associated with significant decrease of serum creatinine, serum phosphorus, CRP (C reactive protein)and proteinuria in the predialysis subgroup. The mean difference was -0.05 mg/dL (95% CI: -0.10, -0.00 mg/dL; P = 0.04) for serum creatinine, -0.13 mg/dL (95% CI: -0.26, -0.01 mg/dL; P = 0.04) for serum phosphorus, -0.98 mg/L (95% CI: -1.25, -0.71 mg/L; P < 0.00001) for CRP, and -0.13 mg/d (95% CI: -0.18, -0.08 mg/d; P < 0.00001) for proteinuria. We did not find any significant change in serum phosphorus, CRP in the dialysis subgroup. Blood urea nitrogen (BUN) was reduced with statistical significance in the soy-treated group compared with control when the predialysis and dialysis subgroup were analyzed as a whole. The pooled estimated effects of change for BUN was -0.37 mg/dL (95% CI: -6.03, -0.11 mg/dL; P = 0.04). No significant change was detected in creatinine clearance, glomerular filtration rate, serum albumin, body weight and body mass index(BMI).

Conclusions: Soy protein containing isoflavones intake significantly decreased serum creatinine, serum phosphorus, CRP and proteinura in predialysis patients, while no significant change was found in creatinine clearance and glomerular filtration rate. We also found that soy protein intake could maintain the nutritional status in dialysis patients, though no significant change in CRP, BUN, and serum phosphorus was detected. Future large, long-term RCTs are still needed to clarify the effects of soy protein intake in patients with CKD.