Effect of Aromatic Herbs and Spices Present in the Mediterranean Diet on the Glycemic Profile in Type 2 Diabetes Subjects: A Systematic Review and Meta-Analysis

Background: The Mediterranean Diet (MedDiet) is the dietary pattern par excellence for managing and preventing metabolic diseases, such as Type 2 Diabetes (T2DM). The MedDiet incorporates spices and aromatic herbs, which are abundant sources of bioactive compounds. The aim of this study was to analyze the effect of all aromatic herbs and spices included in the MedDiet, such as black cumin, clove, parsley, saffron, thyme, ginger, black pepper, rosemary, turmeric, basil, oregano, and cinnamon, on the glycemic profile in T2DM subjects. Methods: PubMed, Web of Science, and Scopus databases were searched for interventional studies investigating the effect of these aromatic herbs and spices on the glycemic profile in T2DM subjects. Results: This systematic review retrieved 6958 studies, of which 77 were included in the qualitative synthesis and 45 were included in the meta-analysis. Our results showed that cinnamon, turmeric, ginger, black cumin, and saffron significantly improved the fasting glucose levels in T2DM subjects. The most significant decreases in fasting glucose were achieved after supplementation with black cumin, followed by cinnamon and ginger, which achieved a decrease of between 27 and 17 mg/dL. Conclusions: Only ginger and black cumin reported a significant improvement in glycated hemoglobin, and only cinnamon and ginger showed a significant decrease in insulin.