It is now years that epidemiologists have gathered proofs that show that a Mediterranean diet that is rich in olive oil helps to protect against breast cancer. However, they never really understood the reason behind it. Javier Menendez form the Northwestern University School of Medicine has recently tried to figure out how it functions.
Olive oil is a mixture that is rich in fatty acids, mainly oleic acid. Menendez took a sample of breast cancer cells and bathed them with purified oleic acid. Consequently, the cells reduced the production of HER2, a gene that causes cancer, by around 50 percent. Moreover, the fatty acid enhanced the efficacy of Herceptin. Herceptin is a drug that is made from antibodies which latch onto the HER2 proteins which then cause the cancer cells to die.
The HER2 gene is an overactive one among more than one-fifth of all breast cancers. It operates with other tumors that may prove to be vulnerable to the oleic acid. Till date, Menendez and his colleagues have found out that the fatty acids reduce the expression of the gene in stomach, ovarian as well as colon cancer cell lines. He explains that the effect might be a universal one.
The researchers also discovered that dietary fatty acids other than those mentioned above, such as omega-3 fatty acids found in fish has the ability to block HER2. This may imply that there exists an “ultimate molecular mechanism” through which fatty acids found in foods can prevent cancer. Menendez believes that the compounds allow the malevolent cells to survive and grow. However, when a person consume fatty acids that are available from his diet, it blocks the cancer cells fatty acid production.
The preventive method comes in moderately small doses; researchers studying olive-oil and health experts suggested around 40 to 50 grams of olive oil on a daily basis (around 4 to 6 tablespoons) to lend a helping hand in staving off cancers and to decrease the probability of heart diseases. This amount of olive oil can easily be consumed in a salad each day. According to Menendez, it might be important to consume more of olive oil in order to fight against existing breast tumors and other cancers, although the quantity to be consumed remains unknown

By Dean Moyer M.D., Infinite Well-Being
04/15/2010
The health benefits of olive oil are well known. Olive oil is the main source of fat shown to be associated with longevity in those persons living in the Mediterranean region.

Scientists have assumed previously that monounsaturated fat (MUFA) contained in olive oil was responsible for wellness and longevity. Recently, researchers have shown that the effects of polyphenols in olive oil are just as important as MUFA, if not more so. Maria Covas and co-workers studied 200 healthy men in six research centers located in five European countries. The participants were assigned to receive a daily administration of 25ml (about 2 tablespoons) of one of three different types of olive oil. The olive oil types had a concentration of polyphenols ranging from 2.7 mg/kg of olive oil (low-type) to 366 mg/kg (high) in the olive oils.
The results showed that there was a linear increase in the high density lipoprotein fraction (HDL-the good type) from the low to the high polyphenol containing olive oils. The low density lipoprotein (LDL-the bad type) was decreased following the intake of the oil containing the highest concentration of polyphenols when compared to the low polyphenol content olive oil. These changes are beneficial and accentuate the importance of extra virgin olive oil.

The scientists concluded that the polyphenols are equally (or more) important for a healthy heart than are the monounsaturated fats. The higher the polyphenol content the more strongly it correlated with a higher level of HDL lipoproteins (this is beneficial). Extra virgin olive oil contains the highest amount of polyphenols.

COVAS, M. et al, Ann Intern Med 2006: 145: 333-341 – The Effect of Polyphenols in Olive Oil on Heart Disease Risk Factors.