Olive leaf extract is a concentrated extract of the leaves of the olive tree (Olea europaea), and its main phenolic compound is oleuropein, with smaller amounts of hydroxytyrosol. In small human trials, extracts taken at 500 to 1,000 mg a day for six to 12 weeks were linked to modest drops in blood pressure and, in one trial, better insulin sensitivity. Reviews of these trials call the results promising but limited by small numbers and uneven quality. Much of the rest of the research is in animals or cells.
What olive leaf extract is
Olive leaves are a by-product of every olive grove. Dried and cut, they are sold as herbal tea, and the European Medicines Agency lists olive leaf as a traditional herbal medicine. An extract goes a step further: the leaves are soaked in a solvent such as water or alcohol, and the liquid is dried into a powder. Makers often standardize the powder to a stated percentage of oleuropein. The trials below used named commercial extracts, and results from one extract cannot be assumed for another.
What's in it
Oleuropein is the bitter compound that gives raw olives their bite. It is far more concentrated in the leaf than in the oil, which is why leaf extracts are the usual way to take it in capsule form. Our page on oleuropein covers the compound itself.
When oleuropein breaks down, in the plant or in the body, one of its products is hydroxytyrosol. This is the compound behind the EU's olive polyphenol health claim, explained on our hydroxytyrosol page. In a British trial, volunteers' urine contained hydroxytyrosol and oleuropein breakdown products in the hours after they took olive leaf extract (Lockyer et al., 2015).
Leaf extracts also contain other plant compounds. The extract used in one blood pressure trial was described as containing verbascoside and luteolin-7-glucoside as well as oleuropein (Ismail et al., 2021). Japanese researchers also point to oleanolic acid, a non-phenolic compound found in the leaf (Mikami et al., 2021).
| Olive leaf extract | Olive oil polyphenols | |
|---|---|---|
| Main compounds | Oleuropein, with some hydroxytyrosol | Breakdown products of oleuropein, such as oleacein and oleocanthal, plus hydroxytyrosol and tyrosol |
| Typical source | Dried leaves of the olive tree | Fresh oil pressed from the olive fruit |
| Usual form | Dry powder in capsules or tablets, or leaf tea | Liquid oil, or oil-based ingredients in capsules |
| How it is labeled | Often by % oleuropein | Often by total polyphenols in mg/kg |
What the human research shows
Blood pressure. This is the best-studied area, and most trials are small.
- In an open (unblinded) study of 40 identical twins with borderline high blood pressure, the twins in each pair were assigned to different groups: 500 mg or 1,000 mg of extract a day, or lifestyle advice. After eight weeks, blood pressure in the 1,000 mg a day group fell from an average of 137/80 to 126/76 mmHg. The 500 mg a day group and the controls did not change significantly from baseline (Perrinjaquet-Moccetti et al., 2008).
- In an eight-week double-blind trial in Indonesia, adults with stage-1 hypertension took 500 mg of olive leaf extract twice a day or the blood pressure drug captopril. Systolic pressure fell by an average of 11.5 mmHg with the extract and 13.7 mmHg with captopril, and the difference between groups was not significant. Triglycerides fell in the extract group only (Susalit et al., 2011). The trial had no placebo group. Both this trial and the twin study used the same commercial extract.
- In a controlled, double-blind crossover trial, 60 men with prehypertension took an extract providing 136 mg oleuropein and 6 mg hydroxytyrosol a day for six weeks. Compared with the control, 24-hour systolic pressure was 3.3 mmHg lower and 24-hour diastolic pressure 2.4 mmHg lower. Total cholesterol, LDL cholesterol and triglycerides also fell (Lockyer et al., 2017).
Blood sugar. In a placebo-controlled crossover trial in New Zealand, 46 overweight men in their forties took olive leaf capsules (51.1 mg oleuropein and 9.7 mg hydroxytyrosol a day) for 12 weeks. Insulin sensitivity improved by 15% compared with placebo. This trial found no effect on blood pressure, blood lipids or body composition (de Bock et al., 2013).
What reviews conclude. A 2022 meta-analysis pooled 12 trials with 819 adults. Olive leaf extract lowered systolic blood pressure by an average of 3.9 mmHg and triglycerides by 9.5 mg/dL, with no meaningful change in blood sugar markers. The authors rated the evidence for several outcomes as low to very low quality (Razmpoosh et al., 2022). A 2024 review of 12 trials found results too inconsistent for firm conclusions and called for more trials with similar methods (Álvares et al., 2024).
Animal and laboratory studies
The 2021 Japanese study was done in mice. Inactive mice fed a high-fat diet and given olive leaf extract gained less fat and did better on memory and endurance tests than mice that did not get the extract (Mikami et al., 2021). See our summary of the 2021 mouse study. Mouse results often do not carry over to people.
The 2005 Spanish study was done in vitro, in cell cultures. Olive leaf extract and oleuropein reduced the ability of a fish virus (viral hemorrhagic septicemia virus, which infects salmon and trout) to infect cells (Micol et al., 2005). It did not test people or human viruses. See our summary of the 2005 lab study.
How Phenolia uses it
Phenolia Daily is a dietary supplement. Its ingredients are high-phenolic olive oil (powdered), olive leaf extract and Greek Mountain Tea (Sideritis scardica), all extracted in Greece. The capsule shell is hydroxypropyl methylcellulose (plant-based). Read about the third ingredient in our guide to Greek Mountain Tea.
The serving is 2 capsules a day with a meal, and a box holds 60 capsules (30 servings). Each capsule provides 6 mg of polyphenols, or 12 mg per 2-capsule serving, calculated from the extract's certificate of analysis. That is about what 1.5 tablespoons (20 g) of a 600 mg/kg oil contains. Phenolia Recovery is the same base plus Greek beetroot extract, with 12 mg olive polyphenols per serving.
The label lists the blend. The polyphenol total is the verified figure; we do not publish a separate amount for the olive leaf extract or its oleuropein content. The human trials above gave roughly 50 to 200 mg of oleuropein a day from leaf extract alone; the Indonesian trial used 1,000 mg of extract from a batch containing 19.9% oleuropein (Ismail et al., 2021). Phenolia's whole serving provides 12 mg of polyphenols from all three ingredients, so those trial results cannot be transferred to Phenolia.
Phenolia is made by Doctors Labs in Greece, a GMP facility licensed by Greece's National Organization for Medicines (EOF), ISO 22000:2018. PharmaGnose S.A. (Greece) makes the extracts and certifies the extract lots, and final packaging is in Bettendorf, Iowa. Heavy metals and pesticides were tested on the capsule powder in August 2026. Finished-capsule HPLC testing and banned-substance screening are under way. See the full list of what's in Phenolia.
Safety and who should check with a doctor
The European Medicines Agency (EMA) has reviewed olive leaf as a traditional herbal medicine. Its monograph reports no known side effects and no reported interactions. It advises against use during pregnancy and breastfeeding because safety has not been established. It also says use under age 18 has not been established. People with severe heart or kidney disease should not take it, and anyone with heart disease or kidney problems should seek medical advice first (EMA HMPC, 2017). A 2025 periodic review found no reason to change the monograph.
The trials above were small and lasted between a few weeks and three months. They were not designed to detect rare side effects.
Because trials report lower blood pressure and, in one case, better insulin sensitivity, check with your doctor before taking olive leaf extract if you take blood pressure medicine or medicine that lowers blood sugar. The concern is that the effects could add together. This is a precaution based on the trial results, not on reported cases. The same applies if you have low blood pressure or are pregnant or breastfeeding.
Frequently asked questions
What is the main active compound in olive leaf extract?
Oleuropein. It is the leaf's characteristic phenolic compound, and extracts are often standardized to a stated percentage of it. Hydroxytyrosol is present in smaller amounts and is also formed when oleuropein breaks down.
Does olive leaf extract lower blood pressure?
Several small trials reported modest drops at 500 to 1,000 mg of extract a day. A 2022 meta-analysis found an average fall in systolic pressure of about 4 mmHg, but rated much of the evidence as low quality.
Is olive leaf extract the same as olive oil?
No. Leaf extract is rich in intact oleuropein. Olive oil contains mainly its breakdown products, such as oleacein and oleocanthal, along with hydroxytyrosol and tyrosol.
Do the olive leaf studies apply to Phenolia?
No. The trials used specific extracts at doses that provided roughly 50 to 200 mg of oleuropein a day. Phenolia provides 12 mg of total polyphenols per serving, so the study results cannot be transferred to it.
Sources
- Perrinjaquet-Moccetti T, Busjahn A, Schmidlin C, et al. Food supplementation with an olive (Olea europaea L.) leaf extract reduces blood pressure in borderline hypertensive monozygotic twins. Phytotherapy Research. 2008;22:1239-1242. doi.org/10.1002/ptr.2455
- Susalit E, Agus N, Effendi I, et al. Olive (Olea europaea) leaf extract effective in patients with stage-1 hypertension: comparison with Captopril. Phytomedicine. 2011;18:251-258. doi.org/10.1016/j.phymed.2010.08.016
- de Bock M, Derraik JGB, Brennan CM, et al. Olive (Olea europaea L.) leaf polyphenols improve insulin sensitivity in middle-aged overweight men: a randomized, placebo-controlled, crossover trial. PLoS One. 2013;8:e57622. doi.org/10.1371/journal.pone.0057622
- Lockyer S, Corona G, Yaqoob P, et al. Secoiridoids delivered as olive leaf extract induce acute improvements in human vascular function and reduction of an inflammatory cytokine. British Journal of Nutrition. 2015;114:75-83. doi.org/10.1017/S0007114515001269
- Lockyer S, Rowland I, Spencer JPE, et al. Impact of phenolic-rich olive leaf extract on blood pressure, plasma lipids and inflammatory markers: a randomised controlled trial. European Journal of Nutrition. 2017;56:1421-1432. doi.org/10.1007/s00394-016-1188-y
- Ismail MA, Norhayati MN, Mohamad N. Olive leaf extract effect on cardiometabolic profile among adults with prehypertension and hypertension: a systematic review and meta-analysis. PeerJ. 2021;9:e11173. doi.org/10.7717/peerj.11173
- Razmpoosh E, Abdollahi S, Mousavirad M, et al. The effects of olive leaf extract on cardiovascular risk factors in the general adult population: a systematic review and meta-analysis of randomized controlled trials. Diabetology & Metabolic Syndrome. 2022;14:151. doi.org/10.1186/s13098-022-00920-y
- Álvares AA, Garcêz A, Silva LT, et al. Olive leaf extract effect on cardiometabolic risk factors: a systematic review and meta-analysis of randomized clinical trials. Nutrition Reviews. 2024;82:1710-1725. doi.org/10.1093/nutrit/nuad164
- Mikami T, Kim J, Park J, et al. Olive leaf extract prevents obesity, cognitive decline, and depression and improves exercise capacity in mice. Scientific Reports. 2021;11:12495. doi.org/10.1038/s41598-021-90589-6
- Micol V, Caturla N, Pérez-Fons L, et al. The olive leaf extract exhibits antiviral activity against viral haemorrhagic septicaemia rhabdovirus (VHSV). Antiviral Research. 2005;66:129-136. doi.org/10.1016/j.antiviral.2005.02.005
- European Medicines Agency, Committee on Herbal Medicinal Products. European Union herbal monograph on Olea europaea L., folium (EMA/HMPC/359238/2016). 2017. ema.europa.eu
