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 evidence.
It is true that oleuropein, enolinate, and other olive leaf constituents or their breakdown products can kill microbes in
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.
In addition to the claim that olive leaf can kill harmful substances in the body, proponetns also advocate its use to reduce
blood pressure. Test-tube and
animal studies have produced some positive preliminary findings.13-16 And a small study did find evidence to support this, but there were flaws in its design.12
A more recent, larger study offers more promising news, though. Two hundred and thirty-two people (aged 25-60) with high blood pressure were randomized to receive olive leave extract (500 mg, twice daily) or a commonly used anti-hypertensive medication called captopril (12.5 mg, twice daily) for a total of 8 weeks. Both treatment groups experienced similar reductions in blood pressure levels.
Olive leaf has also been studied as a potential treatment for other conditions.
For example, animal studies weakly suggest that olive leaf might help control blood sugar levels in
and reduce symptoms of
Because olive leaf extracts vary widely, we recommend following label instructions.
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.
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Last reviewed August 2013 by EBSCO CAM Review Board
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