What is Olive Leaf Extract Used for Today?

Olive leaf contains a substance called oleuropein, which breaks down in the body to another substance called enolinate. On websites that promote olive leaf extracts, it is stated that enolinate kills harmful bacteria, viruses, and fungi in the body, but at the same time nurtures microbes that are good for health. This remarkable claim, however, has no meaningful scientific justification.

It is true that oleuropein, enolinate, and other olive leaf constituents or their breakdown products can kill microbes in test-tube studies . 1-11

However, it is a long way from test-tube studies to evidence of efficacy in humans. Only double-blind , placebo-controlled studies can prove a treatment effective, and the only study of this type reported for olive leaf was too flawed to prove anything. This small, poorly designed trial supposedly found that olive leaf extract reduces blood pressure . 12 However, the study was too small and too poorly designed to produce meaningful results. The only other support for the widespread claim that olive leaf reduces blood pressure comes from test-tube and animal studies that are too preliminary to rely upon at all. 13-16

Other animal studies weakly suggest that olive leaf might help control blood sugar levels in diabetes17-19 and reduce symptoms of gout . 17


Because olive leaf extracts vary widely, we recommend following label instructions.

Safety Issues

Olive leaf has not undergone comprehensive safety testing. However, based on the limited evidence available, it does not appear to commonly cause much more in the way of immediate side effects than occasional digestive distress. Safety in young children, pregnant or nursing women, or people with severe liver or kidney disease has not been established.