Impact of different types of olive oil on cardiovascular risk factors: A systematic review and network meta-analysis

Background and aim: This network meta-analysis (NMA) compares the effects of different types of olive oil (OO) on cardiovascular risk factors. Methods and results: Literature search was conducted on three electronic databases (Medline, Web of Science, and Cochrane Central). Inclusion criteria: Randomized controlled trials (RCTs) (>= 3 weeks duration of intervention) comparing at least two of the following types of OO: refined OO (ROO), mixed OO (MOO), low phenolic (extra) virgin OO (LP(E)VOO), and high phenolic (extra) virgin OO (HP(E) VOO). Random-effects NMA was performed for seven outcomes; and surface under the cumulative ranking curve (SUCRA) was estimated, using an analytical approach (P-score). Thirteen RCTs (16 reports) with 611 mainly healthy participants (mean age: 26-70 years) were identified. No differences for total cholesterol, HDL-cholesterol, triacylglycerols, and diastolic blood pressure were observed comparing ROO, MOO, LP(E) VOO and HP(E) VOO. HP(E) VOO slightly reduce LDL-cholesterol (LDL-C) compared to LP(E) VOO (mean difference [MD]: -0.14 mmol/L, 95%-CI: -0.28, -0.01). Both, HP(E) VOO and LP(E) VOO reduces SBP compared to ROO (range of MD: -2.99 to -2.87 mmHg), and HP(E) VOO may improve oxidized LDL-cholesterol (oxLDL-C) compared to ROO (standardized MD: -0.68, 95%-CI: -1.31, -0.04). In secondary analyses, EVOO may reduce oxLDL-C compared to ROO, and a dose-response relationship between higher intakes of phenolic compounds from OO and lower SBP and oxLDL-C values was detected. HP(E) VOO was ranked as best treatment for LDL-C (P-score: 0.83), oxLDL-C (0.88), and SBP (0.75). Conclusions: HP(E) VOO may improve some cardiovascular risk factors, however, public health implications are limited by overall low or moderate certainty of evidence. (C) 2019 The Italian Society of Diabetology, the Italian Society for the Study of Atherosclerosis, the Italian Society of Human Nutrition, and the Department of Clinical Medicine and Surgery, Federico II University. Published by Elsevier B.V. All rights reserved.