The phenolic compounds present in olive leaves, especially oleuropein, have been suggested to have therapeutic effects for many conditions. Olive leaf extract may help with high blood pressure, diabetes, obesity, Alzheimer’s, or heart disease. It’s even claimed to prevent genetic damage and cancer growth. If you suffer from any of these conditions, find out how olive leaf extracts may help you
What Is Olive Leaf Extract?
Olive leaf extract is characterized by a high content of polyphenols, which are micronutrients we get through our diet (such as by eating olive oil) .
Olive phenols and their derivatives are associated with many therapeutic properties. The health benefits gained from these polyphenols depend on both how much is consumed and how much the body can absorb .
The ability of olive leaf extracts to scavenge reactive oxygen species is associated with its potential role in preventing heart disease and metabolic disorders .
Olive Leaf Extract Snapshot
- Antioxidant and anti-inflammatory
- May reduce the risk of heart disease
- May lower blood sugar
- May promote bone health
- May interact with blood pressure and antidiabetic medication
- Insufficient evidence for several benefits
- Reduced expression of fat-promoting genes: PPARy, lipoprotein lipase, fatty acid-binding protein 4 
- Enhanced differentiation of osteoblast (increased production of osteoblastogenesis markers RUNXII, osterix, collagen type 1, osteocalcin, and alkaline phosphatase) 
- Increased blood vessel development (VEGF production) 
- Reduced and normalized MDA and blood glucose levels 
- Reduced left ventricular developed and systolic pressures, stroke volume, ejection fraction and cardiac output, and blood superoxide dismutase and glutathione reductase 
- Prevented increase of serum malondialdehyde, interleukin-1β, TNF-α, creatine kinase-MB, troponin I, lactate dehydrogenase, and infarct area 
- Increased production of proteins that prevent cell death (Bcl-2, Bcl-XL, Bim, and p53) 
Benefits of Olive Leaf Extract
Likely Effective for:
In 2 clinical trials on 62 elderly people and 8 healthy volunteers, both extra virgin olive oil and dietary olives increased their general antioxidant status [9, 10].
Similarly, extra virgin olive oil reduced oxidative damage to the DNA in a small trial on 10 postmenopausal women .
Olive oil also prevented oxidative processes (measured as reduced LDL oxidation) in 2 clinical trials on 230 healthy volunteers [12, 13].
Hydroxytyrosol is the olive leaf phenol that is most effective at neutralizing free radicals, followed by oleuropein and tyrosol .
Hydroxytyrosol improved antioxidant status in several clinical trials on 144 people [15, 16, 17, 18].
As previously mentioned, the blood sugar-lowering effects of oleuropein were due to its ability to block free radical production by Nox2 in a small trial on 20 healthy people .
Topical oleuropein reduced the oxidative damage to the skin caused by UV radiation in 10 healthy volunteers .
In an experiment with mice poisoned by arsenic, oleuropein reduced oxidative damage in blood, liver, kidney, and brain tissues .
The existing evidence suggests that olive leaf extract has antioxidant activity. You may discuss with your doctor how it may help your antioxidant status.
2) Cardiovascular Health
In a clinical trial on 60 men at risk of developing high blood pressure, oleuropein significantly lowered systolic and diastolic blood pressure, as well as blood fat and cholesterol levels .
In another trial on 232 patients with high blood pressure, taking 500 mg of oleuropein 2x/day for 8 weeks was as effective as a diuretic (captopril, 12.5-25 mg 2x/day) at lowering both systolic and diastolic blood pressure .
The blood pressure-lowering effects of olive leaf extract are possibly due to its ability to preserve blood vessel function, as seen in a small trial on 13 people with mildly high blood pressure .
Olive leaf extract reduced blood pressure, heart rate, and enlargement of the heart and kidney tissues while improving blood vessel function in rats with high blood pressure .
Blood Fat levels
In a clinical trial on 200 healthy volunteers, olive oil polyphenols reduced heart risk markers such as cholesterol (both free and bound to LDL), triglycerides, and oxidative stress .
In 4 clinical trials on almost 150 people with high blood cholesterol levels, olive polyphenols (taken as virgin olive oil, olive pomace-enriched biscuits, and a dietary supplement) lowered blood fat (total cholesterol, LDL cholesterol, and triglyceride) levels [26, 27, 28].
The combination of olive extract and red yeast rice lowered blood fat levels (especially LDL cholesterol) in 2 clinical trials on almost 700 people at high risk of heart disease [29, 30].
Olive oil decreased LDL oxidation in 2 small trials on 42 people, thus helping prevent clogged arteries. Hydroxytyrosol had the same effects in another trial on 84 people [13, 31, 16].
To sum up, the evidence suggests that olive leaf extract may help prevent heart disease by lowering blood pressure and preventing artery clogging. Note, however, that it’s not approved by the FDA to treat or prevent these conditions. You may use it to improve your cardiovascular health if your doctor determines that it may help in your case.
Possibly Effective for:
In a small trial on 18 healthy volunteers, olive leaf extract (standardized to 51 mg oleuropein and 9 mg hydroxytyrosol) reduced the production of a pro-inflammatory cytokine (IL-8) and improved blood vessel function .
Hydroxytyrosol, combined with omega-3 fatty acids and curcumin, reduced inflammation (CRP levels and pain) when taken for 1 month in a clinical trial on 45 women with breast cancer .
Hydroxytyrosol also reduced inflammatory pain in a small trial on 25 people with joint disease (gonarthrosis) .
In colon samples isolated from 14 people with ulcerative colitis, treatment with olive leaf extract reduced the production of pro-inflammatory molecules (the enzyme COX-2 and the cytokine IL-17) and infiltration of immune cells (CD3, CD4, and CD20), resulting in decreased inflammatory damage 
In a study of mice injected with cisplatin to induce kidney damage, oleuropein reduced inflammation and prevented kidney cell death .
In mice with skin injuries, oleuropein reduced inflammation and sped up wound healing .
In human brain cells, olive leaf extracts prevented inflammation by reducing COX-2 production .
All in all, limited evidence suggests that olive leaf extract and its components have some anti-inflammatory activity. Further clinical research should confirm these findings and establish how to use them therapeutically.
Insufficient Evidence for:
1) Lowering Blood Sugar
In a small trial on 20 healthy people, oleuropein reduced blood sugar levels after meals by blocking free radical production (by Nox2) .
In another trial on 46 middle-aged overweight men (and thus, at risk of developing type 2 diabetes), supplementation with olive leaf extract for 12 weeks improved insulin sensitivity and the activity of the pancreatic cells that produce this hormone (beta-cells) .
In diabetic rabbits, oleuropein lowered and restored normal blood glucose levels and reduced a marker of oxidative damage (MDA) .
Additionally, oleuropein improved insulin sensitivity and increased the uptake of blood sugar in diabetic mice .
2) Bone Health
In a clinical trial on 64 women with bone loss (osteopenia), consuming olive leaf extract for 12 months maintained bone mineral density and increased the blood levels of a bone-forming cell production marker (osteocalcin) .
In female mice whose ovaries were removed to mimic menopause, both olive oil and its main polyphenol oleuropein prevented bone loss [42, 43]
A study in human bone marrow stem cells found that oleuropein increased bone cell production .
In a clinical trial on 32 high-school athletes, taking olive leaf extract (equivalent to 20 g olive leaves and 100 mg oleuropein) for 9 weeks slightly reduced the number of sick days due to upper respiratory illness. However, it had no effect on the incidence of the illness .
Toxoplasmosis was inhibited by oleuropein treatment in kidney cells and in mice. Oleuropein effectively prevented cell death and tumor formation in the spleens and livers of infected mice .
Oleuropein had no antimicrobial activity against lactic acid bacteria but two of its hydrolysis products, aglycone and oleanolic acid, inhibited the growth of the four species tested .
In cells infected with a common opportunistic fungus, hydroxytyrosol reduced fungal growth [1, 47].
Animal and Cell Research (Lack of Evidence)
No clinical evidence supports the use of olive leaf extract for any of the conditions listed in this section. Below is a summary of the existing animal and cell-based research, which should guide further investigational efforts. However, the studies should not be interpreted as supportive of any health benefit.
Preliminary research suggests that olive leaf extract may help fight obesity by preventing the body from generating more fat cells .
In rats fed high-fat diets, oleuropein reduced body weight, fat tissue mass, liver fat, and blood cholesterol [49, 3, 50].
This polyphenol reduced fat-cell production in bone marrow stem cells. Oleuropein and hydroxytyrosol also blocked the development of immature fat cells [4, 51].
Amyloid diseases, such as Alzheimer’s, are partly caused by the buildup of misfolded proteins in tissues, which triggers inflammation and tissue damage .
Olive leaf extracts can prevent these misfolded proteins from entering the brain. This effectively reduced toxicity and tissue damage in mouse studies .
Even in the late stages of Alzheimer’s, mice experienced improved brain cell function after being treated with oleuropein aglycone .
In rats with Parkinson’s disease, olive leaf extract reduced brain cell damage and death .
Oleuropein reduced spatial memory impairment and improved cognition in rats with anesthesia-induced oxidative stress .
Potential Risks and Side Effects
This list does not cover all possible side effects. Contact your doctor or pharmacist if you notice any other side effects.
Call your doctor for medical advice about side effects. In the US, you may report side effects to the FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada, you may report side effects to Health Canada at 1-866-234-2345.
Olive oil’s pinoresinol may prevent the absorption of vitamin D in the intestines. This may cause gastrointestinal disorders or increase their severity .
Olive oil and its extracts may lower blood pressure and blood sugar levels. Taking olive oil extracts in addition to medication for diabetes or high blood pressure may cause blood sugar levels or blood pressure to drop too low [57, 58, 59].