. there is some confusion between oleic acid
and virgin olive oil rich in oleic acid .
. frying with refined oils is not healthy,
but simmering virgin olive oil in herbs may be ok .
Although mainstream media portrays olive oil aswiki`since when is olive oil dangerous?:
the "healthiest oil,"
this title does not extend to cooking.
Olive oil is primarily a [oleic] monounsaturated fat,
[ and ] the overabundance of oleic acid in olive oil
creates an imbalance that has been associated with
increased risk for breast cancer and heart disease.
Adverse effects also have been documented, however,foodforbreastcancer`avoid refined:
since both oleic and monounsaturated fatty acid levels
in the membranes of red blood cells
have been associated with increased risk of breast cancer,
although the consumption of oleate in olive oil
has been associated with a decreased risk of breast cancer 
23:(2001). "Erythrocyte Membrane Fatty Acids and Subsequent Breast Cancer:
A Prospective Italian Study".
JNCI Journal of the National Cancer Institute
24:(1994). "Dietary fat, olive oil intake and breast cancer risk".
International Journal of Cancer
. consuming extra-virgin olive oil is probably
preferable to using highly refined olive oil,
which may have more of the characteristics of
the "pure" oleic acid used in the study.
Olive oil has been shown to be protective against
HER2 overexpressing breast cancer.