Olive leaf extract is made from the leaves of the olive tree, Olea europaea, the same tree that gives us olives and olive oil. Olive trees have been cultivated around the Mediterranean for thousands of years, and their silvery-green leaves have their own long history in folk tradition, often brewed as a bitter tea.
Olive leaves are traditionally used to support immune and heart health. Their main compound of interest is oleuropein, a bitter polyphenol that is also responsible for the bitterness of fresh, uncured olives. Researchers have studied olive leaf extract in small trials, including on blood pressure, and a systematic review found the evidence promising but limited. It has no authorised health claim.
On labels you will see olive leaf extract, Olea europaea leaf extract, or extracts standardised to a percentage of oleuropein, such as 20%. That percentage is the most useful figure for comparing products. Olive leaf extract is different from olive fruit extract and olive oil, which are richer in hydroxytyrosol.