Updated June 2026 · Ireland Health Shop · The Honey Pot, Clonmel
The ancient Egyptians considered the olive tree divine and used olive leaf preparations medicinally. Greek and Roman physicians prescribed olive leaves for fever and infections. Throughout the Mediterranean, olive leaf tea was a traditional remedy for colds, fevers, hypertension, and wound infections. In the 19th century, a bitter compound from olive leaves — oleuropein — was extracted and used clinically for malaria in some European countries before quinine became standard.
The modern scientific investigation of olive leaf extract began in earnest in the 1960s and has accelerated significantly in recent decades, revealing mechanisms that validate the traditional uses and uncovering new applications.
Olive leaves contain a complex mixture of polyphenols, with oleuropein being the most abundant and most studied. Related compounds include hydroxytyrosol (one of the most potent natural antioxidants known), elenolic acid, ligstroside, and various flavonoids (luteolin, apigenin, quercetin).
Oleuropein's chemical structure is unusual — it's a secoiridoid glucoside, a class of bitter-tasting compounds. This bitterness was traditionally a quality marker for potent olive leaf preparations. Standard supplements are typically standardised to 15–25% oleuropein content; higher-potency products may go to 40% or above.
The antimicrobial properties of olive leaf extract have been extensively studied. Oleuropein and hydroxytyrosol have demonstrated activity against a broad spectrum of pathogens in laboratory studies:
The antimicrobial mechanism involves interference with amino acid production in microorganisms, disruption of viral envelope fusion with host cells, and direct free-radical scavenging. In clinical settings, olive leaf extract has been investigated for acute upper respiratory infections — a 2009 study found it significantly outperformed placebo for common cold duration and severity.
This is where olive leaf extract has the strongest clinical evidence. Multiple randomised controlled trials have evaluated its effects on blood pressure and lipid profiles:
A landmark 2011 study published in Phytomedicine compared olive leaf extract (EFLA®943, 500mg twice daily) directly to captopril (an ACE inhibitor pharmaceutical) for mild-to-moderate hypertension. The olive leaf extract was non-inferior to captopril for blood pressure reduction — both groups showed a reduction of approximately 11 mmHg systolic and 5 mmHg diastolic. The olive leaf group also showed significant improvements in triglycerides.
The mechanisms for blood pressure reduction include: vasodilation (through NO production and calcium channel modulation), ACE inhibitor-like activity, and reduction of arterial inflammation.
Several trials have found olive leaf extract reduces LDL cholesterol (by 10–15%) and triglycerides while maintaining or improving HDL. The antioxidant activity of oleuropein also prevents LDL oxidation — oxidised LDL is the most atherogenic (artery-damaging) form of cholesterol.
Oleuropein has shown insulin-sensitising effects in multiple studies, improving glucose uptake and reducing fasting blood glucose in people with insulin resistance and type 2 diabetes. A clinical trial in people with type 2 diabetes found significant improvements in HbA1c with olive leaf extract supplementation.
Hydroxytyrosol — the metabolite of oleuropein — is one of the most potent natural antioxidants identified, with an ORAC (Oxygen Radical Absorbance Capacity) value roughly 10 times that of green tea. Olive leaf extract significantly raises blood antioxidant capacity (measured by FRAP and ORAC assays) and reduces inflammatory markers including CRP (C-reactive protein) and IL-6.
This combination of antioxidant and anti-inflammatory activity makes olive leaf extract relevant for a wide range of chronic conditions with an inflammatory component — from cardiovascular disease and arthritis to metabolic syndrome and age-related cognitive decline.
Emerging research suggests olive leaf extract may support the gut microbiome — it appears selectively beneficial for Lactobacillus and Bifidobacterium species while inhibiting pathogenic bacteria. It may also support the intestinal barrier (reducing "leaky gut") through its anti-inflammatory effects on the gut epithelium. Topically, oleuropein has anti-aging skin benefits through antioxidant and collagen-protective mechanisms.
Olive leaf extract has an excellent safety profile with centuries of traditional use and decades of clinical study. Most people tolerate it very well. Occasionally, a "die-off" reaction (Herxheimer reaction) may occur when first starting olive leaf extract — transient flu-like symptoms caused by the rapid killing of pathogens. Starting at a lower dose and building up gradually minimises this. Olive leaf may have mild blood pressure-lowering effects — if you're on antihypertensive medications, monitor your blood pressure and consult your GP. Mild blood sugar-lowering effects mean people on diabetes medication should also monitor closely.
Find olive leaf extract at The Honey Pot, 14 Abbey Street, Clonmel
Shop The Honey Pot → 📞 052-612 1457