Olive leaf extract (Olea europaea) has many beneficial substances and contains oleuropein and the flavonoids apigenin,  luteolin, chrysoeriol, hesperidin, rutin, quercetin, and kaempferol. Major isolated constituents strongly inhibit the classical pathway of the complement system.

Benefit of olive leaf extract supplement pills
There have not been any good human studies with olive leaf extract to know which medical conditions it would benefit. Olive leaf extract is just beginning to be tested in humans so it may take some time until we find out the right dosage for the right condition. A study in rodents shows this herb may have blood pressure lowering effect.

Anti-inflammatory benefit
Most flavonoids in olive leaf extract have antiinflammatory properties.

Int J Mol Sci. 2016. Human Intervention Study to Assess the Effects of Supplementation with Olive Leaf Extract on Peripheral Blood Mononuclear Cell Gene Expression. Olive leaf extract (OLE) has been used for many years for its putative health benefits. Although recent literature has described a link between ailments such as cardiovascular disease, diabetes and cancer and a protective effect of polyphenols in the OLE, the mode of action is still unclear. Here, we describe a study in which gene expression profiles of peripheral blood mononuclear cells from healthy male volunteers were analyzed to identify genes that responded to OLE, following an eight-week intervention with 20 mL daily consumption of either OLE or placebo. There was downregulation of genes important in inflammatory pathways, lipid metabolism and cancer as a result of OLE consumption. Gene expression was verified by real-time PCR for three genes (EGR1, COX-2 and ID3). The results presented here suggest that OLE consumption may result in health benefits through influencing the expression of genes in inflammatory and metabolic pathways.

Anti-viral
The olive leaf extract exhibits antiviral activity against viral haemorrhagic septicaemia rhabdovirus (VHSV).
Antiviral Res. 2005.
A commercial plant extract derived from olive tree leaf (Olea europaea) and its major compound, oleuropein, inhibited the in vitro infectivity of the viral haemorrhagic septicaemia virus (VHSV), a salmonid rhabdovirus. Incubation of virus with olive tree leaf extract or oleuropein before infection reduced the viral infectivity to 10 and 30%, respectively. Furthermore, olive tree leaf extractdrastically decreased VHSV titers and viral protein accumulation (virucidal effect) in a dose dependent manner when added to cell monolayers 36 h post-infection. On the other hand, both the olive tree leaf extract and oleuropein were able to inhibit cell-to-cell membrane fusion induced by VHSV in uninfected cells, suggesting interactions with viral envelope. Therefore, we propose that olive tree leaf extract could be used as a potential source of promising natural antivirals, which have demonstrated to lack impact on health and environment. In addition, oleuropein could be used to design other related antiviral agents.

Olive leaf extract has been tested in oral herpes.

Cancer
Int J Oncology. 2012. Antiproliferative effect of oleuropein in prostate cell lines.

Saudi Dent J. 2013. The effect of olive leaf extract in decreasing the expression of two pro-inflammatory cytokines in patients receiving chemotherapy for cancer. A randomized clinical trial. Preliminary findings indicate that OLE is effective in reducing IL-1β and TNF-α levels after chemotherapy and exert a therapeutic effect and prevent development of severe oral mucositis.

Biomed Pharmacother. 2017. Olea europaea leaf extract and bevacizumab synergistically exhibit beneficial efficacy upon human glioblastoma cancer stem cells through reducing angiogenesis and invasion in vitro.

Diabetes and blood sugar
PLoS One. 2013. Olive leaf polyphenols improve insulin sensitivity in middle-aged overweight men: a randomized, placebo-controlled, crossover trial.

The blood sugar lowering activity of olive leaf extract was studied as a treatment for diabetes. One of the compounds responsible for this activity was oleuropeoside, which showed activity at a dose of 16 mg/kg. This compound also demonstrated antidiabetic activity in animals with alloxan-induced diabetes.

Immune system effect
Most flavonoids in olive leaf extract have anti-microbial activity. There are many supplements, herbs or herbal extracts that play a role in immune system support. A few of these include oregano oil supplement, colostrum supplement and Andrographis.

Q. I am a nurse and started to research olive leaf for treatment of infections, etc and have found many therapeutic benefits one of which is superior antioxidant capability. However, there is one thing that disturbs me that I discovered in one of your posts regarding olive leaf as well as some other sites, but this is not clarified. It has been stated that olive leaf strongly inhibits the complement system. As a nurse, I am trying to learn exactly what this means. The human immune system is extremely complex, and studies can differ in vitro versus in vivo. There is a grave difference between an agent ie supplement, herbal extract or drug that acts as an anti-inflammatory, reducing cytokines and inflammatory enzymes, and suppressing all or one part of the immune system. The complement system is probably the most important aspecit of innate immunity. I have read that it seems to be safe and is a powerful antibacterial, antiviral compound and is being touted as beneficail for one's health. However, immunomodulatory actions can have serious consequences... Are you in any way able to clarify in detail this so called inhibition of the complement system. I would very much like to take olive leaf for some chronic infections that I have been harboring, but not at the expense of risking harm to my immunity.
   A. You are right that the immune system is very complicated, and the complement system is very difficult to understand. Not enough research is available to determine how olive leaf extract influences the various aspects of the immune system. So much depends on the initial herbal quality, where it grows, how it is processed, how long it has been stores before use, how it is extracted and the dosage used along with frequency of use. There are too many variables that influence its overall effect, including each person's unique response. Hence I feel comfortable in using it a few days a week and a full week off each month. We do wish to have clearer answers on these topics but clinical trials in humans are not sufficient enough to provide such answers at this time.

HIV treatment
Olive leaf may have anti-HIV activity.

Anti-HIV activity of olive leaf extract and modulation of host cell gene expression by HIV-1 infection and olive leaf extract treatment.
York University School of Medicine, New York
Biochem Biophys Res Commun. 2003.
We investigated the antiviral activity of olive leaf extract preparations against HIV-1 infection and replication. We find that it inhibits acute infection and cell-to-cell transmission of HIV-1.

Hypertension - does olive leaf extract lower blood pressure?
Q. I am currently working on a series on a TV series on hypertension, new information has been published about the benefits of olive leaf extract, EFLA®943. I was wondering if you have any information about olive leaf extract.
   A. A pilot trial completed in 2008 with 20 identical (monozygotic) twin pairs who had an increased blood pressure was conducted for a period of 20 weeks. Patients were either given placebo capsules or capsules containing doses of 500mg or 1000mg of olive leaf extract EFLA®943. Olive leaf extract EFLA®943 was able to lower blood pressure when used in the higher dosage. Blood pressure changed significantly within pairs, depending on the dose, with mean systolic differences of ≤ 6 mm Hg (500 mg vs. control) and ≤ 13 mm Hg (1000 vs. 500 mg), and diastolic differences of ≤ 5 mm Hg. After eight weeks, mean blood pressure remained unchanged from baseline in controls and the low-dose group, but had significantly decreased for the high-dose group. Cholesterol levels decreased for all treatments with significant dose-dependent, within-pair differences for low-density lipoprotein (LDL) cholesterol. Phytotherapy Research 2008.

Q. Can you direct me in purchasing EFLA®943 product? Having trouble locating this.
   A. This particular extract was used in a study, but it does not seem to be commercially available. It is likely that other extracts would have similar benefits.

Parkinson's disease prevention
Rejuvenation Res. 2013. Inhibition of 6-hydroxydopamine-induced PC12 cell apoptosis by olive leaf extract is performed by its main component oleuropein. The protective effects of OLE and oleuropein are correlative with their anti-oxidative and anti-apoptotic properties and suggest their therapeutic potential in the treatment of PD.

Vascular dilation, blood pressure
Researchers studied the importance of the smooth vascular muscle endothelium in the vasodilator action of the decoction of olive leaf. The decoction caused relaxation of isolated rat aorta preparations both in the presence and in the absence of endothelium. The results indicate that the relaxant activity of the lyophilized decoction is independent of the integrity of the vascular endothelium. We also showed that oleuropeoside is a component responsible for vasodilator activity but, from the results, it seems likely that at least one other principle is to be found in the olive leaf which is either a vasodilator itself or else potentiates the relaxant effect of oleuropeoside.

Blood pressure lowering effect of an olive leaf extract in L-NAME induced hypertension in rats.
Arzneimittelforschung. 2002.
Department of Pharmacology, Faculty of Pharmacy, Cairo University, Cairo, Egypt.
A specially prepared olive leaf extract has been tested for its blood pressure lowering activity in rats rendered hypertensive by daily oral doses of L-NAME (NG-nitro-L-arginine methyl ester, 50 mg/kg) for at least 4 weeks. Oral administration of the extract at different dose levels at the same time as L-NAME for a period of 8 weeks showed a dose dependent prophylactic effect against the rise in blood pressure induced by L-NAME, best effects being induced by a dose of 100 mg/kg of the extract. In rats previously rendered hypertensive by L-NAME for 6 weeks and then treated with that dose of the extract for a further 6 weeks without discontinuation of L-NAME, normalisation of the blood pressure was observed. The findings confirm previous reports on the hypotensive effects of olive leaf extract. The special extract, EFLA 943, was shown to give consistent results with little individual variability. The antihypertensive effect of the olive leaf extract may be related to a variety of factors involving reversal of vascular changes involved in the L-NAME induced hypertension.

Absorption in the body
Mol Nutr Food Res. 2013. Human absorption and metabolism of oleuropein and hydroxytyrosol ingested as olive (Olea europaea) leaf extract. Liggins Institute, University of Auckland, Auckland, New Zealand. Phenolic compounds derived from the olive plant (Olea europaea), particularly hydroxytyrosol and oleuropein, have many beneficial effects in vitro. Olive leaves are the richest source of olive phenolic compounds, and OLE is now a popular nutraceutical taken either as liquid or capsules. Test results show OLE effectively delivers oleuropein and hydroxytrosol metabolites to plasma in humans.

Olive leaf extract side effects, safety, danger
There have not been any side effects reported yet with olive leaf extract supplement, but few human studies are available.

Q. Is it okay to take olive leaf extract supplement every day?
   A. It would be cautious, until we learn more about the long term benefit and side effects, to take a couple of days off a week and a week off each month.

Benefit of extra virgin olive oil
It has a benefit over other vegetable fats. Virgin olive oil may be particularly effective at lowering heart disease risk because of its high level of antioxidant plant compounds. Virgin olive oil -- rich in antioxidants called polyphenols -- has stronger heart-health effects than the more extensively processed "non-virgin" variety. Polyphenols are likely to account for some of the health benefits. Virgin olive oil may be the only vegetable oil that's rich in polyphenols. All vegetable oils other than virgin olive oil are submitted to a (refining) process in which polyphenols are practically lost. Even "ordinary" olive oil has a lower polyphenol content because it's a mixture of virgin olive oil and a more-processed form of the oil. Annals of Internal Medicine, 2006.
   Eating foods prepared with olive oils that are rich in phenols, help ward off harmful blood clots in people with high cholesterol.
   Oleocanthal has a potency strikingly similar to that of the drug ibuprofen in inhibiting the cyclooxygenase (Cox) enzyme that causes pain and inflammation.

Composition
Olive oil has mixed triglyceride esters of oleic acid and palmitic acid and of other fatty acids, along with traces of squalene and sterols. The composition varies by cultivar, region, altitude, time of harvest, and extraction process. Olive oil contains a group of related natural products with potent antioxidant properties that give extra-virgin unprocessed olive oil its bitter and pungent taste and are esters of tyrosol and hydroxytyrosol, including oleocanthal and oleuropein.

Research
A mixture of compounds called phenols inhibits the process by which colon cells become cancerous. Incubation of one cancer cell line with increasing concentrations of olive oil phenols for 24 hours protected the cells from DNA damage. Phenols extracted from virgin olive oil are capable of inhibiting several stages in colon carcinogenesis in vitro.

J Nutr Health Aging. 2015. Twelve-month consumption of a polyphenol extract from olive (Olea europaea) in a double blind, randomized trial increases serum total osteocalcin levels and improves serum lipid profiles in postmenopausal women with osteopenia. This exploratory study supports preclinical observations and warrants further research by showing that a specific olive polyphenol extract (Bonolive®) affects serum osteocalcin levels and may stabilize lumbar spine BMD. Moreover, the improved blood lipid profiles suggest additional health benefits associated to the intake of the olive polyphenol extract.

Emails
Q. Hello from Greece. I am coming in touch with you on behalf of Alter Channel, a TV nationwide station. As far as I am aware you have a lot of knowledge on therapeutic use of olive extracts. There is a big discussion here in Greek media regarding the use of olive extracts for the prevention of cancer and there is a lot of speculation about this method and its validity. For this reason I kindly request you to give me your phone details so as to arrange a telephone discussion with you.

Q. Can I take olive leaf extract with L-lysine & neem extract (Azadirachta Indica) Leaf or seeds)? Or can I take it with Lemon balm extract. Also can I take with acyclovir herpes medicine?
   A. Many herbs can be taken together if the dosage is low of each, but each person is different and it is best to learn how each herb works by itself for a week or two before combining. The interactions with medications is quite complicated and has not been studied.

Olive leaf extract has gotten great reviews on at least one other site, but one person says that it kills good bacteria as well as bad bacteria, so it must be taken with a probiotic. The same thing has been said in regards to oregano oil. So my question is this: if olive leaf extract and oregano oil really do kill the good bacteria, is it advisable to take them internally when you don’t seem to have any serious infections, even if you take probiotics to restore the good bacteria?
    There is no reason to take OLE or oregano oil products if there is no medical condition that is being treated. I have not seen studies that indicate these dietary supplements kill good bacteria in the gut in enough of a volume to cause harm. However, since probiotics are safe supplements and have many benefits, one could take them anyway on a regular basis.

Since olive leaf contains oleuropein also called calcium elenolate, can someone who has calcifications of bones or soft tissues still take it to boost the immune system or as an antibacterial supplement? Is calcium elenolate the same as dairy calcium?
   Since the amount of calcium is so small it would not play a significant role.

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Planetary Formulas Full Spectrum Olive Leaf Extract combines a concentrated olive leaf extract standardized to 15% of its key constituent, oleuropein, with a pure olive leaf concentrate.  Combining standardized extract with whole herb concentrate guarantees the presence of all primary and secondary compounds that give olive leaf its immune-supportive effects.

Purchase Olive Leaf Extract supplement