Olive leaf extract effect on cardiometabolic profile among adults with prehypertension and hypertension: a systematic review and meta-analysis

Abstract

Background This systematic review and meta-analysis aimed to determine the effectiveness of olive leaf extract on cardiometabolic profiles among prehypertensive and hypertensive groups. Methodology The Cochrane central register of controlled trials, Medline (1966 to April week 1, 2020), Embase (1966 to April week 1, 2020) and trial registries for relevant randomized clinical trials were used. Published and unpublished randomized clinical trials were reviewed and evaluated. Random effects models were used to estimate the continuous outcomes and mean differences (MDs); both with 95% confidence intervals (CIs). The primary outcomes were changes in systolic and diastolic BP. The secondary outcomes were changes in lipid profile, glucose metabolism, inflammatory markers for CVD, kidney and liver functions safety parameters. We assessed the data for risk of bias, heterogeneity, sensitivity, reporting bias and quality of evidence. Results Five trials were included involving 325 patients aged 18–80 years. Two trials involved high-income countries and three trials involved moderate-income countries. The analysis performed was based on three comparisons. No significant changes were found between systolic or diastolic blood pressure (BP) for the first comparison, 1,000 mg per day for a combined formulation of olive leaf extract versus a placebo. The second comparison, 500 mg per day of olive leaf extract versus placebo or no treatment, showed a significant reduction in systolic BP over a period of at least 8 weeks of follow up (MD −5.78 mmHg, 95% CI [−10.27 to −1.30]) and no significant changes on diastolic BP. The third comparison, 1,000 mg per day of olive leaf extract versus placebo shows no significant difference but an almost similar reduction in systolic BP (−11.5 mmHg in olive leaf extract and −13.7 mmHg in placebo, MD 2.2 mmHg, 95% CI [−0.43–4.83]) and diastolic BP (−4.8 mmHg in olive leaf extract and −6.4 mmHg in placebo, MD 1.60 mmHg, 95% CI [−0.13–3.33]). For secondary outcomes, 1,000 mg per day of olive leaf extract versus captopril showed a reduction in LDL (MD −6.00 mg/dl, 95% CI [−11.5 to −0.50]). The 500 mg per day olive leaf extract versus placebo showed a reduction in inflammatory markers for CVD IL-6 (MD −6.83 ng/L, 95% CI [−13.15 to −0.51]), IL-8 (MD −8.24 ng/L, 95% CI [−16.00 to −0.48) and TNF-alpha (MD −7.40 ng/L, 95% CI [−13.23 to −1.57]). Conclusions The results from this review suggest the reduction of systolic BP, LDL and inflammatory biomarkers, but it may not provide a robust conclusion regarding the effects of olive leaf extract on cardiometabolic profile due to the limited number of participants in the included trials. Review registrations PROSPERO CDR 42020181212.

The Effect of Olive Leaf Extract on Systolic and Diastolic Blood Pressure in Adults: A Systemic Review and Meta-Analysis

“…There are various extracting methods of phenolic compounds from olive leaves (after drying and milling), including solid-liquid extraction by maceration and soxhlet extraction utilizing water-methanol blends or hexane to yield OLE [1,35,36]. For more explanation on one of the most common techniques, mixing the specific quantity of dried olive leaf powder with an aqueous alcohol solution, incubating there to produce an alcohol extract.…”

“…The most important differences between this study and other studies might be related to the study design, type of disease, nature of OLE, duration of extract in-take, patients' compliance and inclusion/exclusion criteria [4]. There is a systemic review and meta-analysis conducted by Muhammad Asyraf Ismail et al in 2021 to show the effect of OLE on cardiometabolic profile in prehypertensive and hypertensive adults [1]. However, with all due respect to the authors of this study, there were a number of cases that encouraged us to make some updates with more accurate results.…”

“…De Bock et al [15] were deleted because of not involving prehypertensive or hypertensive group in the study. Saberi et al [5], was also deleted due to being a non-English RCT in addition to Lockyer et al [7], who could not retrieve data after contacting the author [1]. Ultimately, the previous meta-analysis could not demonstrate the accurate effect of OLE on blood pressure.…”

“…Olive tree polyphenols are present in the plant to combat pathogens inducing bacterial infections and to react to pests and insect injuries [19,20]. There are a wide variety of phenolic compounds in Olea europaea and its by-products with much more concentration in olive leaves (comparison, 145 mg total phenolics/100 g fresh leaf compared to 110 mg/100 g olive fruit and 23 mg/100 ml extra virgin olive oil) [1,7,15]. Another comparison confirms the much more concentration of total polyphenols in olive leaves is relative to the olive oil and fruit; 1350 mg/kg fresh olive leaf versus 232 ± 15 mg/kg of extra virgin olive oil [21,22].…”

“…CVD is one of the most common causes of death in the world [1]. Some disorders such as HTN, type 2 diabetes mellitus (DM2), hypercholesterolemia, atherosclerosis and inflammatory disorders can increase the risk of CVD [2].…”