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Olive Oil Curbs Breast Cancer Gene: Extra Virgin Grade is Best


Findings follow discovery that the dominant fat in olive oil suppresses a breast-cancer-promoting gene; only extra virgin olive oil (EVOO) provides antioxidants that further suppress the same HER2 gen

by Craig Weatherby

Three years ago, we reported on research showing that oleic acid suppresses “expression” of the HER-2 gene responsible for many cases of breast cancer.

Olive oil is the only common cooking oil abundant in omega-9 oleic acida monounsaturated fatinstead of the relatively tumor-reinforcing omega-6 fats that predominate in most other oils (except macadamia nut oil).

For more on oleic acid's suppression of the HER-2 gene, see “Olive Oil May Reduce Breast Cancer Risk.

But it now appears that only extra virgin olive oilEVOO for shortpacks the full anti-cancer potential associated with this traditional Mediterranean food.

Only EVOO is rich in antioxidants

As with its cardiovascular benefits, the breast-cancer-curbing potential of olive oil flows largely from the antioxidant, anti-inflammatory factors found only in EVOO, which is pressed mechanically from olives.

Solvents and heat are used to extract plain olive oil from the olive dregs left behind after pressing out the EVOO.

This harsh treatment removes all of the beneficial phytochemicals that abound in olives and in EVOO.

In fact, like whole olives, EVOO contains two of the most powerful food-borne antioxidants ever measured: tyrosol and hydroxytyrosol.

This potent pair belongs to the family of antioxidants known as polyphenols, which includes the strong antioxidants abundant in berries, raw cocoa, and tea.

But EVOO is also rich in a wide range of polyphenols, including lignans, secoiridoids, and lignanstyrosols.

New anti-cancer components of extra-virgin olive oil revealed

Spanish researchers have published the results of a test tube experiment in which all of the polyphenol compounds abundant in EVOO displayed strong “tumoricidal” effects on breast cancer cells.

Like the monounsaturated fat (oleic acid) abundant in all grades of olive oil, the beneficial compounds abundant only in EVOO suppress the breast-cancer-promoting HER2 gene.

As lead author Javier Menendez said, “Our findings reveal for the first time that all the major complex phenols present in extra-virgin olive oil drastically suppress over-expression of the cancer gene HER2 in human breast cancer cells.”

Dr. Menendez' team separated the oil into fractions and tested each one against breast cancer cells.

All of the fractions containing EVOO's characteristic polyphenols inhibited the HER2 gene very effectively.

Of course, we cannot apply these lab results directly to the effects of EVOO in women.

As the authors point out, “The active phytochemicals (i.e. lignans and secoiridoids) exhibited tumoricidal effects against cultured breast cancer cells at concentrations that are unlikely to be achieved in real life by consuming olive oil.”

Nevertheless, according to the authors, “These findings, together with the fact that that humans have safely been ingesting significant amounts of... olives and extra-virgin oil [for millennia], strongly suggest that these polyphenols might provide an excellent and safe platform for the design of new anti-breast-cancer drugs.”

We'd go further, and suggest that it seems very smart to make EVOO your primary kitchen oil.

In addition to its beneficial polyphenols, EVOO and all olive oils boast the lowest proportion of omega-6 fatty acids of all major cooking oils.

Omega-6s are essential fats, but the average American consumes them in the extreme excess that appears to promote tumor growth.

This excess is traceable to the fact that omega-6 fatty acids predominate in grains, seeds, and our cheapest, most common vegetable oils… and therefore in standard meats, poultry, farmed fish, and packaged or prepared foods.


  • Menendez JA et al. Anti-HER2 (erbB-2) oncogene effects of phenolic compounds directly isolated from commercial Extra-Virgin Olive Oil (EVOO). BMC Cancer 2008, 8:377doi:10.1186/1471-2407-8-377