Scientific Name(s): Olea europaea L.
Common Name(s): OLE, Olive leaf, Olive leaf extract
Medically reviewed by Drugs.com. Last updated on Jun 17, 2019.
Interest in olive leaf use centers on antioxidant and antiviral activity, as well as its possible role in diabetes and cardiovascular conditions. However, clinical trials do not support its use for any indication.
Traditional dosages of olive leaf include 7 to 8 g of dry leaf in 150 mL water. In 1 clinical trial, patients with stage 1 hypertension were administered 500 mg of olive leaf extract twice daily for 8 weeks. A clinical trial in overweight men used oleuropein 51.1 mg and hydroxytyrosol 9.7 mg daily for 12 weeks.
Contraindications have not been identified. Caution may be warranted in hepatic disease.
Information regarding safety and efficacy during pregnancy and lactation is lacking.
None well documented.
None well documented. Diabetic patients should be supervised carefully because of potential hypoglycemic effects.
Information is limited. Moodiness and aggressive behavioral changes likely related to olive leaf extract have been reported in an elderly woman at a dose of 85 mg/kg.
The olive tree (O. europaea) is an evergreen that grows to approximately 10 m in height. Native to Mediterranean regions, olive trees also are cultivated in similar climate zones in the Americas. The small, leathery leaves are gray-green on top, and the underside contains fine, white, scale-like hairs. The leaves are gathered throughout the year.1, 2, 3
The olive tree was cultivated in Crete, where the leaves were used to clean wounds as early as 3500 BC. The leaves were worn by athletes in ancient Olympic Games, and the olive branch has traditionally been a symbol of peace. In the 1800s, the plant was used to treat malaria.2, 3, 4, 5
Olive leaf contains the iridoid oleuropein (up to 240 mg per gram of dry leaves).6 Other secoiridoids include demethyloleuropein, esters of oleoside, ligustroside, oleuroside, and unconjugated secoiridoid aldehydes. Triterpenes and flavonoids, including luteolin and related glucopyranosides, tyrosol and hydroxytyrosol, apigenin, rutin, and diosmetin, are also present. Other compounds found in the leaves are oleasterol, leine, choline, cinconine, olivine, tannin, calcium, phosphorus, carbohydrates, fat, and fiber.7, 8, 9, 10, 11, 12
Uses and Pharmacology
A study in mice with castor oil–induced diarrhea suggested that olive leaf extract reduced the number of diarrheal episodes and could affect gastric transit time.68
Studies in rodents have shown antioxidant activity in brain tissue injury, gentamicin-induced nephrotoxicity, reperfusion injury, major organ injury, and induced gastric ulceration, as well as in other conditions.19, 20, 21, 22, 23, 24, 25, 26, 27, 28 In a model of Parkinson disease, olive leaf extract inhibited adrenal pheochromocytoma cell damage via antioxidant and antiapoptotic activity.29
The oral bioavailability of olive leaf extract and associated antioxidant biomarkers was evaluated in pre- and postmenopausal women. The findings suggest that postmenopausal status increases the production of olive leaf extract metabolites.30 In young healthy volunteers (N = 45), supplementation with olive leaf extract did not alter oxidative status, and wide interperson variability was seen.31
In rat, mice, and rabbit studies, olive leaf extract decreased the production of proinflammatory cytokines. Studies have included models of osteoarthritis, colitis, wound healing, and gout (xanthine oxidase inhibition).17, 32, 33, 34, 35, 36
A small (N = 25) clinical study evaluated the effect of olive leaf extract (equivalent to 10 mg/day hydroxytyrosol) administration for 4 weeks versus placebo in osteoarthritis of the knee. Improved scores on pain rating scales were achieved.37 A crossover clinical study evaluated olive leaf extract in the form of a mouth rinse for efficacy in oral mucositis caused by chemotherapy in 25 patients. At 2 weeks, a difference in the rate and severity of mucositis was found, as well as a down-regulation of tumor necrosis factor and interleukin-1 beta.38
Animal experiments and in vitro studies suggest that olive leaf extracts possess antiviral activity.5, 39 In an in vitro experiment, cell-to-cell transmission of HIV was inhibited in a dose-dependent manner, and HIV-1 replication was inhibited.5 In vitro activity against rotavirus has been demonstrated.40 Oleuropein has been patented in the United States for antiviral activity against viral diseases, including herpes, mononucleosis, and hepatitis.41 In vitro studies demonstrate activity against a range of human pathogens,16, 42, 43 as well as against Leishmania species.44
There are no clinical data regarding the antimicrobial use of olive leaf extract.
In vitro studies have demonstrated growth inhibition against human cancer cell lines, as well as cell membrane disruption and apoptosis.45, 46, 47, 48, 49, 50, 51 In 1 study in mice, activity against melanoma was demonstrated. When olive leaf extract was combined with different chemotherapeutics, antagonism and synergy were found.52
Clinical studies do not support the use of olive leaf extract as a chemotherapeutic agent.
Experiments in rabbit and rat tissue preparations found that oleuropein had a hypotensive effect, possibly via direct action on smooth muscle. Oleuropein also may exert vasodilator activity. In another study in rats with metabolic syndrome, olive leaf extract had no effect on blood pressure, despite improving the lipid profile and glucose tolerance.53 Olive leaf extracts may also possess antispasmodic, vasodilator, and antiarrhythmic properties.54, 55 In a model of stroke in rats, pretreatment with olive leaf for 30 days attenuated the biochemical effects induced by brain ischemia.56 In rabbits pretreated with olive leaf extract for 8 weeks, the prothrombin time was prolonged and the morphology of induced thrombi differed from that of untreated animals. Activated partial prothrombin time was unaffected.57
A randomized clinical trial among patients with stage 1 hypertension compared the effectiveness of olive leaf extract with that of captopril in reducing systolic blood pressure. A dosage of 500 mg of olive leaf extract taken twice daily over 8 weeks achieved a reduction of 11.5 +/− 8.5 mm Hg, compared with a reduction of 13.7 +/− 7.6 mm Hg by captopril (P = 0.098). Triglycerides were also reduced, but no other biochemical indices were altered by the treatment.58
A dose-dependent analgesic effect has been demonstrated in rats,69 and the same group of researchers demonstrated that olive leaf extract prevented morphine tolerance in rats.70 Another study in rats demonstrated decreased neuropathic pain.71
Studies in rodents consistently report decreased blood glucose levels.53, 59, 60 In addition, reduced triglycerides and cholesterol have been found.61, 62 In rats fed a high-fat diet, olive leaf extract positively modulated adipogenesis and thermogenesis.63 Suggested mechanisms include potentiation of glucose-induced insulin release and increased peripheral uptake of glucose.20, 64, 65
In patients with type 2 diabetes (N = 79), 500 mg of olive leaf extract daily significantly decreased glycated hemoglobin (HbA1c) and fasting plasma insulin levels over placebo; however, it had no effect on postprandial plasma insulin.66 A crossover study conducted among overweight men (N = 46) found a 15% increase (P = 0.024) in insulin sensitivity with olive leaf extract (oleuropein 51.1 mg and hydroxytyrosol 9.7 mg daily for 12 weeks) versus placebo. In addition, increased pancreatic beta-cell responsiveness was found. No effect on the lipid profile, blood pressure, body composition, or liver function was reported.67
An aqueous extract of olive leaf administered to rats for 14 days increased triiodothyronine levels and reduced circulating thyroid-stimulating hormone levels, possibly via a feedback mechanism.72
Traditional dosages of olive leaf include 7 to 8 g of dry leaf in 150 mL water.73 Many commercial preparations of olive leaf and its extracts are available and vary in strength. The 500 and 750 mg capsules contain approximately oleuropein 20 mg per capsule. In 1 clinical trial, patients with stage 1 hypertension were administered 500 mg of olive leaf extract twice daily for 8 weeks.58 A crossover study of overweight men used oleuropein 51.1 mg and hydroxytyrosol 9.7 mg daily for 12 weeks.67
Based on studies with healthy volunteers, olive leaf extracts appear to be more bioavailable in liquid than in capsule or tablet form, with wide individual variation.6
Pregnancy / Lactation
Information regarding safety and efficacy during pregnancy and lactation is lacking.
Based on a study in mice, olive leaf extract should be used with caution with concomitant chemotherapy because both antagonism and synergy were found.52 In a study in rabbits, increased prothrombin times were demonstrated,57 whereas another clinical study demonstrated no effect on platelets.58
None well documented. Diabetic patients should be supervised carefully because of potential hypoglycemic effects. Hepatotoxicity has been demonstrated in 1 animal study. (See Toxicology.)74
The potential toxicity of olive leaf is not well documented. In mice fed 0.5% to 0.75% olive leaf extract ad libitum for 14 weeks, increased liver enzymes, hyperplasmia of the bile ducts, cholestatis, and hepatic fibrosis and necrosis were found.74
Oleuropein in dosages up to 1 g/kg body weight was not lethal in albino mice.7 At 1 mg/mL, an extract of olive leaf was not toxic to human cells.5 Olive leaf extract has an estimated oral median lethal dose of more than 3,000 mg/kg in mice.73, 74 However, unusual symptoms in mood and aggression reported in a 67-year-old female was suspected to be a result of excessive olive leaf extract from a dose of 85 mg/kg body weight. The authors hypothesized that hydroxytyrosol, a constituent of olive leaf extract that is structurally similar to dopamine, could have caused changes in synaptosomal dopamine levels.75
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