The antioxidants in olive leaf extract are mainly polyphenols. Scientists believe these plant-based nutrients play a role in preventing conditions like cognitive decline, cancer, and osteoporosis.
Olive leaf also contains a uniquely powerful polyphenol called oleuropein. Studies show that in addition to its antioxidant activity, oleuropein has anti-inflammatory, antiviral, and antimicrobial effects. These properties point to research-backed health benefits like: 
Improved Cardiovascular Health
Research shows that olive leaf extract helps prevent LDL (bad) cholesterol from building up in your arteries. This effect helps increase blood flow and lower blood pressure, reducing your risk of heart disease. 
A study using rats also points to olive leaf extract’s effectiveness in helping restore a normal heartbeat in those with arrhythmia, although further research with human subjects would be more conclusive.
Lower Risk of Diabetes
The antioxidants in olive leaves can lower your blood sugar and help stabilize it to maintain healthy levels. Researchers find that this effect helps treat people with diabetes and may prevent you from developing the disease.