Evidence Level
Emerging
Olive leaf extract research is primarily in vitro and animal studies, with growing human clinical trial data. Micol et al. (2005) demonstrated broad-spectrum antiviral activity of olive leaf polyphenols. A review by Barbaro et al. (2014) summarized the antimicrobial, antiviral, and anti-inflammatory mechanisms of oleuropein, confirming activity against bacteria, viruses, fungi, and parasites. Human trials have focused more on cardiovascular endpoints (blood pressure and lipid reduction) than immune outcomes specifically, but the antimicrobial mechanisms are well-established in laboratory settings and traditional use spanning Mediterranean cultures supports its immune applications.