Evidence from epidemiological studies suggests that a higher proportion of monounsaturated fats in the diet is linked with a reduction in the risk of coronary heart disease.] This is significant because olive oil is considerably rich in monounsaturated fats, most notably oleic acid.
Another health benefit of olive oil seems to be its property to displace omega-6 fats, while not having any impact on omega-3 fats. This way, olive oil helps to build a more healthy balance between omega-6 fats and omega-3 fats.
Olive oil contains the monounsaturated fat oleic acid, having antioxidants such as vitamin E and carotenoids, and oleuropein, a chemical that prevents the oxidation of LDL particles. It is these properties that are thought to contribute to the health benefits of olive oil.
As they are the least processed forms of olive oil, extra virgin or virgin olive oil have more monounsaturated fat than olive oil. These types of olive oil contain more polyphenols, leading to a healthier heart and lower “bad” cholesterol.
Preliminary research indicates that olive oil could possibly be a chemopreventive agent for peptic ulcer or gastric cancer, but confirmation requires further in vivo study. Olive oil was also found to reduce oxidative damage to DNA and RNA, which may be a factor in preventing cancer.
A high consumption of omega-6 polyunsaturated fatty acids, which are found in most types of vegetable oil including olive oil, may increase the likelihood that postmenopausal women may develop breast cancer. A similar effect was observed on prostate cancer. Other analysis suggested an inverse association between total polyunsaturated fatty acids and breast cancer risk.