Effects of Nigella sativa supplementation on blood parameters and anthropometric indices in adults: A systematic review on clinical trials

Background: Nigella sativa (N. sativa) has been used in traditional medicine and several studies have been performed in the last decades to reveal the effects of it on different medical disorders such as diabetes, dyslipidemia, hypertension, and obesity. We evaluated the effects of N. sativa supplementation on lipid profiles, glycemic control, blood pressure (BP), and some anthropometric indices in humans. Materials and Methods: A search on published studies was done by using databases including PubMed, Google Scholar, Thomas Reuters Web of Science, and Cochrane. Medical subject headings (MeSH) terms searched included “N. sativa,” “Black seed,” “Black cumin,” “kalonji,” and “Triglycerides,” “Cholesterol,” “Lipoproteins,” “LDL,” “Lipoproteins,” “HDL,” “Blood glucose,” “Hemoglobin A,” “Glycosylated,” “Blood pressure”, “Body mass index,” “Waist circumference”. Initially 515 articles were extracted. Four hundred ninety-two papers that were unrelated, reviews, animal studies, and combined and duplicated studies were excluded, 23 articles were eligible for this review. Results: After analyzing 23 articles including 1531 participants, these results were achieved: In 4 trials, N. sativa reduced BP, but in 5 trials it could not. Fasting blood sugar (FBS) was reduced significantly in 13 studies. In addition, N. sativa reduced levels of glycosylated hemoglobin (HbA1c). Although weight and waist circumference (WC) in 2 articles were reduced significantly, in 6 articles they were not. Fluctuation in lipid profile in the articles was very controversial, being significant in many of them but not in others. Conclusion: Our systematic review revealed that N. sativa supplementation might be effective in glycemic control in humans.