While it is well-known that the monounsaturated fats in olive oil are a key component of the Mediterranean diet, the rich mixture of antioxidant polyphenols is equally important.

Olive oil is the only vegetable oil that contains perceptible amounts of polyphenols, and the virgin olive oils are the only quality grades that contain considerable quantities – with Extra Virgin olive oils topping the charts. Generally, the lower, ordinary grades of olive oil contain 50 ppm or less of polyphenols, depending on their percentage of refined olive oil. Since imports to the U.S. are commonly labeled ‘Extra Virgin’ without meeting the international quality standards, the polyphenol content maybe anywhere up to, or within the typical range for Extra Virgins, which is about 100 to 250 ppm. The polyphenol content of some conventionally milled Extra Virgin olive oils maybe as high as 500 ppm, depending on factors such as the olive cultivar and degree of ripeness, as well as the production and extraction technologies employed, and the age of the oil.

Scientists in Spain and Italy are actively engaged in studying all aspects of these polyphenol compounds, including their health benefits and methods to increase the concentration in Extra Virgin olive oils. Several recent studies are cited here, each with a link to the scientific abstract:

Gallina-Toschi T, Cerretani L, Bendini A, Bonoli-Carbognin M, Lercker G.
Oxidative stability and phenolic content of virgin olive oil: an analytical approach by traditional and high resolution techniques.
J Sep Sci. 2005 Jun;28(9-10):859-70.

“The amount of phenolic compounds extracted during production is fundamental for the oxidative and nutritional quality of the oil. … the amount of phenolic compounds in virgin olive oil can be influenced by different factors including the olive cultivar and degree of ripeness, as well as by production and extraction technologies.”

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Medina E, de Castro A, Romero C, Brenes M.
Comparison of the concentrations of phenolic compounds in olive oils and other plant oils: correlation with antimicrobial activity.
J Agric Food Chem. 2006 Jul 12;54(14):4954-61.

“The oils from olive fruits had a strong bactericidal action against a broad spectrum of microorganisms. … Most of the foodborne pathogens tested did not survive after 1 h of contact with olive oils. Results indicated that not all oils classified as “olive oil” had similar bactericidal effects and that this bioactivity depended on their content of certain phenolic compounds.”

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Romero C, Medina E, Vargas J, Brenes M, Castro AD
In Vitro Activity of Olive Oil Polyphenols against Helicobacter pylori.
J Agric Food Chem. 2007 Feb 7;55(3):680-6

“H. pylori is linked to a majority of peptic ulcers and to some types of gastric cancer, and resistance of the microorganism to antibiotic treatment is now found worldwide. … These results open the possibility of considering virgin olive oil a chemopreventive agent for peptic ulcer or gastric cancer…”

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Olive oil polyphenols have been the recent subject of several encouraging scientific studies – several of which are cited here:

Weinbrenner T, Fito M, de la Torre R, et al.
Olive oils high in phenolic compounds modulate oxidative/antioxidative status in men.
J Nutr. 2004 Sep;134(9):2314-21.

This study on olive oils and oxidative stress was cited in articles of the Journal of Biochemistry, the Journal of Nutrition, and the Journal of American College of Cardiology.

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Wiseman SA, Tijburg LB, van de Put FH.
Olive oil phenolics protect LDL and spare vitamin E in the hamster.
Lipids. 2002 Nov;37(11):1053-7.

“The results of this study support the idea that extra virgin olive oil phenols improve the antioxidant defense system in plasma by sparing the consumption of vitamin E under normal physiological circumstances.”

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Marrugat J, Covas MI, Fito M, et al.
Effects of differing phenolic content in dietary olive oils on lipids and LDL oxidation—a randomized controlled trial.
Eur J Nutr. 2004 Jun;43(3):140-7.

Healthy volunteers participated in a randomized, double-blind, controlled crossover study. Subjects consumed three different extra-virgin olive oils with incrementally greater levels of polyphenols.

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Bratisl Lek Listy.
Effects of dietary extra virgin olive oil on serum lipid resistance to oxidation and fatty acid composition in elderly lipidemic patients.

“In conclusion, the daily consumption of extra virgin olive oil in elderly lipidemic patients favourably affected serum lipoprotein spectrum and fatty acid composition…”

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Owen RW, Giacosa A, Hull WE, Haubner R, Spiegelhalder B, Bartsch H.
The antioxidant/anticancer potential of phenolic compounds isolated from olive oil.
Eur J Cancer. 2000 Jun;36(10):1235-47.

“…the antioxidant phenolic compounds present in olive oil are potent inhibitors of free radical generation…”

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Several scientific studies on tocopherols are also cited:

Psomiadou E, Tsimidou M, Boskou D.
Alpha-tocopherol content of Greek virgin olive oils.
J Agric Food Chem. 2000 May;48(5):1770-5.

Alpha-Tocopherol, the main tocopherol homologue found in olive oil, was determined in 90 Greek virgin olive oils. … Storage of samples under domestic conditions showed that good handling is quite important for retaining high alpha-tocopherol levels and for increasing, thus, the storage life and nutritional value.

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Cunha SC, Amaral JS, Fernandes JO, Oliveira MB.
Quantification of tocopherols and tocotrienols in Portuguese olive oils using HPLC with three different detection systems
J Agric Food Chem. 2006 May 3;54(9):3351-6.

“Six different compounds of tocopherols and tocotrienols were quantified in 18 samples of Portuguese olive oils. Alpha-tocopherol (alpha-T) was the main vitamin E isomer in all samples ranging from 93 to 260 mg/kg. The total tocopherols and tocotrienols ranged from 100 to 270 mg/kg.”

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