Olive leaves have been traditionally used in many Mediterranean, North African, and Middle Eastern cultures. They’re rich in flavonoids and other health-promoting compounds, including oleuropein, (R) which is highlighted in a number of the studies discussed below.
These compounds have various antioxidant, anti-inflammatory, anti-diabetic, heart-protecting, (R) anti-cancer, antiviral, and antibacterial effects. (R)
Olive leaf extract contains more antioxidants, and more types of antioxidants, than olive oil. The differences in the antioxidants’ structure may (also) make olive leaf extract more attractive in supporting health. (R)
If you’re interested in the Mediterranean diet for health, know that the compounds in olive oil and olive leaf are at least partly to thank for the lower risk of cancer and heart disease in the region. (R1, R2)
Table of Contents
The olive leaf extract I use
Healths Harmony Olive Leaf (Amazon)
OLE’s antioxidant power
One study involving human subjects taking phenols present in olive leaf extract found that these phenols reduced levels of a key marker of oxidative stress in urine. (R)
OLE inhibits reactive oxygen species (ROS), (R) which can induce immense oxidative stress. (R)
Oleuropein triggers a powerful antioxidant response to proinflammatory substances, including cytokines and LPS (explained below). (R)
Oleuropein also reduced oxidation of sensitive lipids (fats) in an animal model of heart disease, which indicates it lowered oxidative stress. (R)
OLE is anti-inflammatory
Researchers using models of inflammation have found that olive leaf’s polyphenols exhibit anti-inflammatory activity. (R)
The olive plant’s most powerful phenols, oleuropein and hydroxytyrsol, have been shown to act as powerful antioxidants in both in vitro and animal studies. Their antioxidant activity accounts for OLE’s anti-inflammatory, antimicrobial, heart-protecting, and cancer-fighting effects. (R)
The ability of olive leaf extracts to modulate the immune system in complex ways led researchers to conclude that they are promising therapies in the treatment of chronic inflammatory disease. (R)
Olive leaf extract appears to reduce insulin resistance in the diabetic through preventing expression of proinflammatory proteins called cytokines. (R)
One study found that cells treated with OLE had significantly reduced levels of TNF-alpha, (R) a cytokine involved in acute inflammation. (R)
OLE benefits the heart
Olive leaf extract lowered blood pressure in animals, (R) and in one study, six weeks of OLE treatment normalized blood pressure in hypertensive rats. (R)
OLE relaxes and dilates blood vessels. (R1, R2)
Six weeks of oleuropein treatment in animals reduced total cholesterol and triglycerides. (R)
In animals fed a high-cholesterol diet, OLE reduced total and LDL cholesterol. (R)
Animals fed oleuropein had LDL cholesterol that was more resistant to oxidation – a key to preventing heart disease (R) – and also saw reduced levels of total, free, and esterified cholesterol. (R)
A number of compounds in OLE made lipids (fats) more resistant to oxidation, most likely through their antioxidant activity. (R)
OLE fights diabetes
Olive leaf extracts lowers blood sugar by triggering insulin release and increasing glucose uptake. (R)
In diabetic animals, four months of treatment with OLE normalized blood sugar levels and levels of most antioxidants. (R)
In a similar study, two months of treatment in diabetic animals significantly lowered blood sugar, total cholesterol, and triglycerides. (R)
Animals with metabolic syndrome treated with OLE saw most abnormal cardiovascular, metabolic, and liver markers improve or normalize, including glucose tolerance and markers of oxidative stress. (R)
Researchers have theorized that OLE helps keep blood sugar stable by making digestion of starches less efficient. (R)
OLE benefits skin
OLE’s phenols – oleuropein in particular – exhibit antioxidant action directly on the skin. (R)
Researchers testing whether olive leaf extract might mitigate the damage induced by high UVB radiation near the equator (i.e., in the Mediterranean) found that OLE indeed averts the skin thickening and aging associated with high UVB. (R)
OLE also reduced UVB-triggered activity of reactive oxygen species (R).
These effects are explained by OLE’s ability to inhibit COX-2 (R), an enzyme responsible for inflammation and pain with diverse effects. (R)
OLE fights aging
Cells treated with oleuropein age more slowly, with their lifespan extended by 15%. This effect is explained by oleuropein’s antioxidant activity. (R)
OLE decreases or prevents aggregation of amyloid beta (Aβ) peptides, a key process in the development of Alzheimer’s. (R)
OLE is antibacterial
One study found that olive leaf extract is antibacterial against some strains of gram-positive bacteria, one of the two types, though gram-negative bacteria were resistant to it. (R) Another found OLE to inhibit strains of both types. (R)
Oleuropein and other polyphenols in OLE have been shown to inhibit or delay the growth of many bacteria and fungi. (R)
OLE completely stopped growth of E. coli, K. pneumoniae, and Bacillus Cereus. (R)
OLE was also effective against strains of mycoplasma, a type of microscopic bacteria, including Mycoplasma hominis, Mycoplasma fermentans, Mycoplasma pneumoniae, and Mycoplasma pirum. (R)
Researchers have noted that OLE is “a potential source of promising antimicrobial agents for treatment of intestinal or respiratory tract infections.” (R)
OLE confers protection against lipopolysaccharides (LPS), or endotoxins, (R) a toxic component of some bacteria. (R)
OLE is antiviral
Olive leaf extract has proven to be effective against many viruses, including Campylobacter jejuni, H. pylori, and Staph (including MRSA) (R); respiratory syncytial virus and para-influenza type 3 virus (R);
and viral haemorrhagic septicaemia virus (R).
OLE also fights HIV-1, inhibiting acute infection, preventing DNA damage, and ameliorating much of the cell-level harm the virus induces. (R)
OLE and cancer
Various constituents of olive oil have been found to inhibit the development of a number of cancers in varied stages. (R)
In one study, every polyphenol present in extra-virgin olive oil was proven to potently fight tumors by triggering programmed cell death. (R)
Another study highlighted oleuropein and another component of OLE, hydroxytyrosol, which both powerfully obstructed development of breast cancer, including by inducing programmed cell death. (R)
Olive leaf extract may inhibit the development of skin cancer through its reduction in COX-2 (R), a key enzyme in inflammation and pain with diverse effects. (R)
OLE extracts inhibited bladder and breast cancers, with oleuropein and other flavonoids and phenols in OLE responsible for this activity. Researchers noted their potency and the low doses required for efficacy. (R)
One study found that oleuropein rounded cancer cells, leaving them unable to move and grow. When oleuropein was injected into mice with tumors, those tumors “completely regressed” within 12 days. (R)
OLE increases the number of immune cells known as natural killer cells, which may explain part of its tumor-fighting power. (R)
Polyphenols from the olive plant may prevent development of hormonal cancers due to their similarity to estrogens. (R)
Oleuropein reduced the toxicity of doxorubicin, a chemotherapy drug toxic to the heart, and improved many markers of heart disease elevated by the drug. (R)
Oleuropein made the chemotherapy drug trastuzumab up to 50 times more effective. (R)
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