This study was aimed to quantify the anti-hyperglycemic effect of Nigella sativa (N. sativa).
An in-depth search to identify clinical trials investigating the impact of N. sativa on glycemic indices via MEDLINE, EMBASE, Scopus, Web of Science, Cochrane Library and Google scholar databases were performed up to November 2018. We used a random effects model to estimate pooled effect size of fasting plasma glucose (FPG), postprandial blood Glucose (PPBG), and hemoglobin A1C (HbA1C).
A total of 17 RCTs investigating the effects of N. sativa on FPG, PPBG and HbA1C were included. Meta-analysis suggested a significant association between N. sativa supplementation and reduction in FPG (weighted-mean-difference [WMD]: -9.93 mg/dl, 95%CI: -13.44, -6.41), PPBG (WMD: -14.79 mg/dl, 95% CI: -24.19, -5.39), and HbA1C (WMD: -0.57%, 95% CI: -0.77%, -0.37). Subgroup analysis revealed that N. sativa oil was more effective than N. Sativa powder in reduction of FPG.
To sum up, N. sativa consumption have a significant lowering effect on glycemic status. Further studies with prolonged durations and powerful design are needed to specify the exact mechanism, optimal dosage and duration of N. sativa supplementation to obtain a beneficial effect on glycemic status.