The effects of soy protein on chronic kidney disease: a meta-analysis of randomized controlled trials

There is a growing body of evidence to indicate that soy protein consumption may have a beneficial effect on kidney function. We performed a meta-analysis to evaluate the effects of soy protein consumption compared with animal protein consumption in patients with pre-dialysis chronic kidney disease (CKD). We conducted a structured electronic search of the databases PubMed, EMBASE, Cochrane Library and Chinese Biological Medicine for randomized controlled trials published up to March 2014. The outcome measures were serum creatinine (SCR), triglyceride (TG), total cholesterol (TC), calcium (Ca) and phosphorus concentrations. Weighted or standard mean differences were calculated for net changes using random-effects models. The meta-analysis consisted of nine trials, comprising 197 subjects. Soy protein intake significantly reduced SCR and serum phosphorus concentrations. The mean difference was −6.231 μmol/l (95% confidence interval (CI): −11.109, −1.352 μmol/l) for SCR (P=0.012) and −0.804 (95% CI: −1.143, −0.464 μmol/l) for serum phosphorus (P=0.00). It also significantly reduced serum TG, with a pooled estimated change of −0.223 mmol/l (95% CI: −0.396, −0.051 mmol/l; P=0.011) after the exclusion of one trial indicated by sensitivity analyses. No statistically significant effects were observed for TC (−0.135 mmol/l (95% CI: −0.289, 0.019 mmol/l)) or Ca (0.023 mmol/l (95% CI: −0.016, 0.062 mmol/l)). The meta-analysis suggested a protective effect of soy protein consumption on SCR and serum phosphorus concentrations in pre-dialysis CKD patients. It may also have a significant effect on lowering serum TG concentrations. However, nonsignificant effects on TC and Ca were observed. Evidence was limited because of the relatively small number of available trials and subjects.