The effects of olive leaf extract on cardiovascular risk factors in the general adult population: a systematic review and meta-analysis of randomized controlled trials
What this study found
Olive leaf extract produced modest but favorable effects on blood pressure and lipid measures, with the clearest benefits seen in participants with hypertension and in normal-weight subgroups. Compared with placebo, triglycerides decreased by -9.51 mg/dl (95% CI -17.83 to -1.18; P = 0.025) and systolic blood pressure decreased by -3.86 mmHg (95% CI -6.44 to -1.28; P = 0.003). In hypertensive subgroups, effects were larger for TG (-14.42 mg/dl), TC (-9.14 mg/dl), LDL-C (-4.6 mg/dl), and SBP (-4.81 mmHg); in normal-weight subgroups, TC (-6.69 mg/dl), TG (-9.21 mg/dl), and SBP (-7.05 mmHg)…
- Study & population
- Systematic review and meta-analysis of randomized controlled trials in adults from the general population, including participants with hypertension, dyslipidemia, obesity, or type 2 diabetes.
- Intervention
- Olive leaf extract was given orally, most often as tablets or capsules, with two studies using liquids or beverages.
- Key limitation
- The evidence base was limited by low-to-very low certainty for several outcomes, heterogeneity in some pooled analyses, and substantial variation in OLE formulation, dose, and duration across studies.
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Open PDFOriginal abstract
Background The aim of this systematic review and meta-analysis was to determine the effect of olive leaf extract (OLE) supplementation on cardiovascular-related variables, including lipid, glycemic, inflammatory, liver and renal-related factors, as well as blood pressure. Methods PubMed, ISI Web of Science, Scopus, and Cochrane library were searched, up to October 2021, for relevant controlled trials. Mean differences and standard deviations were pooled for all outcomes, using a random-effects model. The methodological quality, as well as quality of evidence were assessed using standard tools. Results Twelve studies (n = 819 participants) were included in our analyses. Overall analyses showed that OLE supplementation significantly decreased triglyceride (TG) levels (WMD = − 9.51 mg/dl, 95% CI − 17.83, − 1.18; P = 0.025; I 2 = 68.7%; P -heterogeneity = 0.004), and systolic blood pressure (SBP) (WMD = − 3.86 mmHg, 95% CI − 6.44, − 1.28 mmHg; P = 0.003; I 2 = 19.9%; P -heterogeneity = 0.28). Subgroup analyses also revealed a significant improvement in SBP (− 4.81 mmHg) and diastolic blood pressure (− 2.45 mmHg), TG (− 14.42 mg/dl), total cholesterol (TC) (− 9.14 mg/dl), and low-density lipoprotein-C (LDL-C) (− 4.6 mg/dl) measurements, in patients with hypertension. Significant reductions were also observed in TC (− 6.69 mg/dl), TG (− 9.21 mg/dl), and SBP (− 7.05 mmHg) in normal-weight individuals. However, no meaningful changes were seen in glucose hemostasis, liver and kidney, or inflammatory markers. Conclusion The present study revealed that supplementation with OLE yielded beneficial effects for blood pressure and lipid profile in adults, especially in patients with hypertension. As the quality of evidence for glucose hemostasis variables, liver, kidney, and inflammatory markers, were low-to-very low, higher quality RCTs may impact the overarching results. This study was registered at PROSPERO with the code CRD42022302395.