Olive leaf extract

Olive leaf extract is a supplement derived from the leaves of the plant that bears olive (a fruit from which the cooking oil is derived from) and contains the main bioactives of hydroxytyrosol/tyrosol and oleuropein/ligstroside.

Olive phenolics in general, which are present in high levels in olive leaf supplements, appear to potently protect LDL cholesterol from oxidation. This is attributed to the anti-inflammatory effects of hydroxytyrosol, and appears to be active at a low enough dose to apply to consumption of olive product consumption. Olive leaf may also influence levels of lipoproteins in a beneficial manner (LDL, HDL, total cholesterol, although the actual changes in lipoprotein content is rather small. Overall, olive phenolics are more anti-artherosclerotic than they are cholesterol reducing.

There also appears to be beneficial effects on glucose metabolism, which may be related to the pancreas. The mechanisms of olive leaf and glucose metabolism are not fully elucidated at this point in time, but appear to be more of a preventative supplement than a rehabilitative one.

Although olive leaf has been implicated in fat burning through various mechanisms (increased thyroid hormones and adrenaline), trials have failed to show a fat burning effect with olive leaf supplement use. The reason for this is not known, but may be related to a decrease in levels of the receptor that adrenaline works through which may attenuate the effects.

Supplemental olive leaf is taken in the 500-1000 mg range daily, although supplements with even as low as 10 mg (as seen in olive oil products) may confer good protection against LDL oxidation. At least for LDL oxidation, olive food products may suffice rather than supplementation.

The Human Effect Matrix looks at human studies (it excludes animal and in vitro studies) to tell you what effects olive leaf extract has on your body, and how strong these effects are.

Grade	Level of Evidence [show legend]
	Robust research conducted with repeated double-blind clinical trials
	Multiple studies where at least two are double-blind and placebo controlled
	Single double-blind study or multiple cohort studies
	Uncontrolled or observational studies only

Level of Evidence ? The amount of high quality evidence. The more evidence, the more we can trust the results.	Outcome	Magnitude of effect ? The direction and size of the supplement's impact on each outcome. Some supplements can have an increasing effect, others have a decreasing effect, and others have no effect.	Consistency of research results ? Scientific research does not always agree. HIGH or VERY HIGH means that most of the scientific research agrees.	Notes
	Blood Pressure	Notable	High See all 4 studies	One study assessing the potency in hypertensive persons noted it was comparable to Captopril, and olive leaf appears to be potent when it can reduce blood pressure. It does not appear to reduce blood pressure in normotensive persons, however
	Oxidation of LDL	Notable	Very High See all 8 studies	The decrease in LDL oxidation seen with olive oil phenolics appears to be of notable potency due to its reliability (occurring in both healthy persons and diseased persons, chronically and acutely) and a reduction in LDL oxidation rates can exceed 25% in some studies with low intakes of olive phenolics (enough from virgin olive oil consumption)
	HDL-C	Minor	Moderate See all 7 studies	The increase in HDL seen with olive phenolics is somewhat inconsistent and not to a large magnitude when it occurs
	LDL-C	Minor	Moderate See all 5 studies	A decrease in LDL-C seems to be somewhat consistent, but the magnitude of decrease is not overly impressive relative to other agents
	Total Cholesterol	Minor	Moderate See all 4 studies	There appears to be somewhat of a decrease in total cholesterol (mostly due to LDL) with olive leaf consumption; it is not overly reliable
	Triglycerides	-	Very High See all 5 studies	The majority of the evidence suggests that there is no impressive effect on triglycerides with olive phenolic consumption
	Cell Adhesion Factors	Notable	- See study	A decrease was noted in CD40 and MCP1 adhesion factors, and this is notable as this downregulation was dose-dependently related to ingested tyrosol/hydroxytyrosol and may explain the reduced LDL oxidation
	DNA Damage	Notable	- See study	The one study to measure DNA damage (via 8-oxo-dGF as a biomarker) noted up to 50% reductions in mitochondrial and urine measurements; a fairly significant reduction.
	Anti-Oxidant Enzyme Profile	Minor	Very High See 2 studies	Appears to induce the activity of the enzyme known as glutathione peroxidase
	Blood Glucose	Minor	Moderate See 2 studies	There appears to be significant interactions with olive leaf and diabetes, and research is too preliminary to come to conclusions. Olive leaf may reduce blood glucose in diabetics only
	General Oxidation	Minor	- See study	Is able to reduce oxidative parameters in the blood when they are measured.
	HbA1c	Minor	- See study	A minor decrease in HbA1c has been noted with olive leaf consumption
	IGF Binding Protein	Minor	- See study	An increase in IGF binding proteins has been noted in one study (which would sequester and reduce the activity of IGF hormones); potency of this interaction unable to be determined (no reference drug)
	Insulin	Minor	Very High See 2 studies	A decrease of fasted and postprandial insulin with olive leaf consumption has been noted, not to a remarkable degree
	Insulin Sensitivity	Minor	- See study	An increase in insulin sensitivity has been noted in otherwise healthy persons (Matsuda Index and oral glucose tolerance test) and thought secondary to the pancreas; may be relevant to otherwise healthy persons
	Lipid Peroxidation	Minor	Very High See 2 studies	Appears to reduce biomarkers of lipid peroxidation.
	IGF-1	-	- See study	No significant influence on circulating IGF-1 nor IGF-2 levels
	Inflammation	-	- See study	No significant effects on biomarkers of inflammation when measured
	Liver Enzymes	-	Very High See 2 studies	No significant influences on liver enzymes have been noted in trials that assess them (safety reasons)
	Weight	-	Moderate See 2 studies	Overall, there does not appear to be a significant effect of olive phenolic consumption on weight
	Carbohydrate Absorption	Minor	- See study	There appears to be a decrease in either the rate or overall amounts of carbohydrate absorption seen with olive leaf consumption

Studies Excluded from Consideration

NOTE: The rubric contains studies comparing high phenolic olive oil against control (low or no phenolic olive oil) due to the practical difference being merely phenolics found in both leaf and oil extracts