Olive Leaf Extract

Olive leaf extract is a botanical product prepared from the leaves of Olea europaea, the same tree that yields olives and olive oil ^[3]. The leaves, dusty green above and silvery beneath, carry a sharply bitter, astringent taste and are notably concentrated in polyphenols, containing more total phenolic compounds by weight than the fruit or the oil ^[1]. The dominant active constituent is the secoiridoid oleuropein, accompanied by hydroxytyrosol and a range of other polyphenols such as luteolin, rutin, caffeic acid, and apigenin ^[1][3].

The leaf has a long folk-medicine pedigree around the Mediterranean, where it was traditionally steeped as a herbal tea and used as a remedy for fever and other ailments ^[3]. This heritage, together with the broad interest in olive polyphenols, underlies its modern popularity as a supplement.

Commercially the leaf is consumed as a tea infusion, as a powder, and, most commonly, as capsules of concentrated extract, which are often standardized to their oleuropein content so that the active polyphenol level is consistent ^[1]. It is marketed as a dietary supplement and herbal product rather than as an approved medicine.

The research literature has focused chiefly on cardiovascular and metabolic effects ^[2]. A randomized controlled trial in men with mildly elevated blood pressure found that a phenolic-rich olive leaf extract modestly lowered blood pressure and improved plasma lipids compared with a control ^[1]. A separate randomized crossover trial reported that olive leaf polyphenols improved insulin sensitivity in overweight middle-aged men ^[3]. Systematic reviews and meta-analyses of the available trials have found signals of benefit for blood pressure, blood lipids, glucose metabolism, and inflammatory markers, but they consistently note that the studies are few, small, and varied, so the conclusions remain tentative ^[2][4].

Reflecting this uncertainty, regulatory and scientific bodies have generally judged the evidence insufficient to support specific health claims, such as for blood glucose control, and reviewers repeatedly call for larger, better-designed human studies before firm recommendations can be made ^[2][4]. Olive leaf extract is therefore best understood as a polyphenol-rich supplement with promising but not yet definitive clinical support.

Olive leaf extract is generally well tolerated; side effects are uncommon and mild, like GI upset or headache. Because it can lower blood pressure and blood sugar, people on medications for those conditions should monitor for additive effects. It's regarded as safe for most people at typical supplement doses.