Onion supplementation and health metabolic parameters: A systematic review and meta-analysis of randomized controlled trials

Introduction: Functional foods, such as onions, have been the center of many recent investigations. In this systematic-review and meta-analysis, we aimed to gather up the existing information with regard to the impact of onion supplementation on anthropometric measurements/indices, lipid profile, indices of glycemic control and hepatic health, systolic and diastolic blood pressures (SBP and DBP), and adiponectin and leptin. Methods: All major online datasets (PubMed, Web of Science, Cochrane, and Scopus) were thoroughly searched from inception up to October 2022. Relevant randomized controlled trials (RCTs) were obtained using the eligibility criteria. Weighted mean differences (WMDs) were calculated and reported. Statistical significance was set as p-values <0.05. Results: Among all the retrieved data, 14 RCTs were eligible to be included. The results of the crude analysis showed that onion supplementation significantly improved body fat percentage (BFP), low density lipoprotein-cholesterol (LDL-c), total cholesterol (TC), high-density lipoprotein-cholesterol (HDL-c), systolic blood pressure, adiponectin, and aspartate aminotransferase (AST). Subgroup analysis revealed that interventions lasting more than 12 weeks can significantly alter weight, waist circumference (WC), body mass index (BMI), BFP, LDL-c, TC, SBP, and DBP. Moreover, the intake of dosages of >300 mg/day of onion supplementation could significantly improve weight, WC, BMI, BFP, LDL-c, HDL-C, TC, AST, ALT, SBP and DBP. Conclusion: It seems that the intake of onion supplementation can improve health metabolic parameters. We observed that with either longer follow-up periods or higher dosages of onion supplementation, improvements in cardio-metabolic parameters could be expected.(c) 2023 European Society for Clinical Nutrition and Metabolism. Published by Elsevier Ltd. All rights reserved.