The effects of saffron supplementation on the measures of renal function indicators: a systematic review and meta-analysis

Context: Saffron (Crocussativus L.) has been proposed as a potential agent to improve renal function in animal studies. But, due to insufficient evidence in human research, further investigation is needed. Objective: To fill this knowledge gap, we conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) to evaluate the effect of saffron supplementation on the measures of renal function indicators in adults. Renal function was assessed based on serum urea, blood urea nitrogen, and creatinine levels. Method and materials: A systematic search in PubMed/Medline, Scopus, Web of Science, Embase, and Google Scholar databases was done until March 2021 using relevant keywords. A random-effects model was used to estimate the weighted mean difference (WMD) and 95% confidence (95% CI). Nine RCTs were included in the meta-analysis, and their quality was assessed using the Cochrane risk of bias tool. Results: The pooled analysis showed that saffron supplementation had no significant effect on serum urea concentrations (WMD: − 1.05 mg/dl; 95% CI − 5.1 to 3; P = 0.6, I = 93%, P < 0.001) and serum creatinine levels (WMD: − 0.006 mg/dl; 95% CI − 0.08 to 0.06; P = 0.8, I = 79%, P < 0.001) when compared to the placebo group. In the dose–response analysis, we observed a significant non-linear relationship between the duration of saffron supplementation and serum urea and creatinine levels. Conclusions: Based on our findings, Saffron supplementation had no significant effect on renal function markers, including urea and creatinine. However, further trials are required to determine the actual effect and safety of saffron intervention in human studies. PROSPERO submission ID: 248081.