Dec. 18, 2008 - Can EVOO -- extra-virgin olive oil --- cut the risk of breast cancer?
The Spanish researchers wondered why some studies show that the olive-oil-rich Mediterranean diet cuts breast cancer risk while other studies do not. They theorized that the active compounds in olive oil only affect certain cancers.
Menendez's team first isolated various compounds from EVOO -- which, because it is made without heat, keeps most of the olive compounds that are lost in more processed, lower quality olive oils.
They found that two types of these compounds, secoiridoids and lignans, killed off HER2-positive human breast cancer cells but had little effect on HER2-negative cells.
They also found that when they fed large amounts of EVOO to rats with carcinogen-induced breast cancers, the animals' tumors became less malignant.
But this does not mean that eating a lot of EVOO will prevent or treat breast cancer.
"Extreme caution must be applied" in interpreting their findings, Menendez and colleagues warn.
One class of EVOO anticancer compounds, the secoiridoids, "rapidly split into inactive compounds" when eaten. These compounds likely won't help if eaten, but could be a starting point for development of new breast cancer drugs.
On the other hand, the lignan compounds "may represent a different molecular scenario," Menendez and colleagues suggest. In mouse-feeding studies, tumor tissues accumulate lignans, "thus suggesting that the anti-cancer activity of lignans may be due to their direct local effects on the breast cancer tissues."
A recent study suggested that eating flaxseed is beneficial to women with newly diagnosed breast cancer. Flaxseed has high lignan concentrations.
Even so, Menendez and colleagues note that much more study will be needed before doctors can recommend EVOO for breast cancer prevention or treatment.
The Menendez study appears in the open-access journal BMC Cancer.