Supplement analysis backed by scientific evidence · PT

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Limited evidenceHeart & metabolic

Olive Leaf Extract

Olive leaf extract shows small, inconsistent improvements in blood pressure and lipids across a thin set of mostly short trials — nowhere near the antiviral and immune claims made for it in marketing. The cardiometabolic signal is the only one worth taking seriously, and even that is preliminary.

What the science says

  • Blood pressure Limited evidence

    A 2022 systematic review and meta-analysis of RCTs in general adult populations found only small and inconsistent changes in systolic and diastolic pressure, with high heterogeneity and few trials at low risk of bias. The individual studies most often cited used 500-1,000 mg/day for 6-8 weeks in people with mildly elevated pressure; a well-conducted 6-week crossover in 60 adults found no significant blood-pressure change despite measurable phenolic absorption.

  • Lipids and insulin sensitivity Limited evidence

    A 12-week randomized crossover trial in 46 overweight middle-aged men reported a 15% improvement in insulin sensitivity and 28% improvement in pancreatic beta-cell responsiveness with olive leaf polyphenols (51.1 mg oleuropein plus 9.7 mg hydroxytyrosol daily). This single small trial has not been convincingly replicated, and pooled lipid effects across trials are modest and unstable.

  • Antiviral and immune claims Limited evidence

    Oleuropein and hydroxytyrosol inhibit viruses and bacteria in vitro at concentrations far above what oral dosing achieves in blood. There are no controlled human trials showing olive leaf extract prevents or treats any infection.

Dosage & safety

Studied doseTrials have used 500-1,000 mg/day of olive leaf extract, typically standardized to 16-20% oleuropein (roughly 50-100 mg oleuropein per day), for 6-12 weeks. Phenolic content of commercial products varies widely, so oleuropein milligrams matter more than total extract weight.
SafetyGenerally well tolerated; mild GI discomfort, headache and, at higher doses, a reported drop in energy are the usual complaints. Because it can modestly lower blood pressure and blood glucose, it may add to antihypertensive and antidiabetic medication effects — monitor if combining. Theoretical interaction with anticoagulants. People allergic to olive pollen may react. Not enough data to recommend in pregnancy or lactation. Not an approved treatment for any condition in the EU or US; claims of antiviral or antibiotic action are unsubstantiated marketing.

Scientific references

Where to buy

NOW Foods, Olive Leaf Extract, 500 mg, 120 Veg Capsules

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