Effects of black seed (Nigel la sativa) on metabolic parameters in diabetes mellitus: A systematic review

Background: Current evidence indicated beneficial effects of some medicinal herbs on metabolic parameters. Nigella sativa is an example of herbs which can ameliorate metabolic factors in diabetes mellitus. Despite several narrative review studies on medicinal properties of NS, it seems that there is no systematic review to summarize effects of NS on glucose homoeostasis and lipid profile in diabetes mellitus. Therefore, the aim of present study was to review effects of N. sativa on metabolic parameters in diabetes mellitus. Methods: Pubmed, Science Direct, Google scholar and Springer databases were searched from 1995 till January 2014. Key words were included: N. sativa, black seed, diabetes, glucose level, lipid and insulin. Searching was limited to articles with English language. Review articles, case reports, abstract in symposium and congress, studies on N. sativa mixed with other plants were excluded. Based on critically appraise, eligibility of included articles were evaluated. Results: Finally 19 eligible articles (2 human trials, 14 animal models and 3 in vivo/in vitro studies) were selected. They indicated that N. sativa can modulate hyperglycemia and lipid profile dysfunction with various potential mechanisms including its antioxidant characteristics and effects on insulin secretion, glucose absorption, gluconeogenesis and gene expression. Some studies compared effects of various types (extract, oil, powdered) of N. sativa with each other and they reported different characteristics with various types of black seed. Conclusion: N. sativa can improve glycemic status and lipid profile in diabetes models. However, more clinical trials are necessary to clarify beneficial effects of N. sativa, its effective type and dosage for diabetes management and its complications. (C) 2015 Elsevier Ltd. All rights reserved.