The effect of garlic intake on glycemic control in humans: a systematic review and meta-analysis

Abstract

Objective: To conduct a systematic review and meta-analysis of the effects of garlic intake on glycemic control in humans. Methods: We searched MEDLINE, EMBASE, EBSCO, and Science Direct as international data bases, and IranMedex, Magiran, and SID as local databases for studies on effect of garlic intake on glycemic control in humans published until March 2015.  Our search included MeSH and non-MeSH terms.The quality of included studies was assessed using the Jadad scale.  Results: Ten articles were eligible for current meta-analysis. The results showed that garlic intake could decrease fasting blood sugar (FBS) (P<0.001). To overcome the heterogeneity, studies were categorized into five subgroups. Accordingly, consumption of garlic as a food decreased FBS in comparison with garlic supplements (P=0.01). In addition, in comparison with healthy, diabetic, and hypercholesterolemic participants, garlic intake significantly reduced FBS in diabetic patients with hypercholesterolemia  (P=0.001), and studies which had dependent design (cross-over or before-after) showed that garlic intake could decrease FBS (P<0.001). We could not observe any significant result through different subgroups of duration of intervention. Moreover, the results showed that garlic intake could decrease post prandial blood glucose (PPBG) (P=0.031), but could not significantly decrease Hemoglobin A1C (HbA1C) (P=0.1). Conclusion: The current analysis revealed that consumption of garlic as a food could significantly decrease FBS especially in patients suffering from both diabetes and hypercholesterolemia. However, it is suggested that garlic intake regardless of its source (food or supplement) might improve PPBG levels in humans.