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.[29] This is significant because olive oil is considerably rich in monounsaturated fats, most notably oleic acid.

In the United States, producers of olive oil may place the following health claim on product labels:

Limited and not conclusive scientific evidence suggests that eating about 2 tbsp. (23 g) of olive oil daily may reduce the risk of coronary heart disease due to the monounsaturated fat in olive oil. To achieve this possible benefit, olive oil is to replace a similar amount of saturated fat and not increase the total number of calories you eat in a day.[30]

This decision was announced November 1, 2004, by the Food and Drug Administration after application was made to the FDA by producers. Similar labels are permitted for foods rich in omega-3 fatty acids such as Almonds and hemp seed.[31]

There is a large body of clinical data to show that consumption of olive oil can provide heart health benefits such as favourable effects on cholesterol regulation and LDL cholesterol oxidation, and that it exerts antiinflamatory, antithrombotic, antihypertensive as well as vasodilatory effects both in animals and in humans.[32]

As they are the least processed forms of olive oil, extra virgin or virgin olive oil have more monounsaturated fatty acids than other olive oil. These types also contain more polyphenols, which may have benefits for the heart.[33]

A high consumption of omega-6 polyunsaturated fatty acids (PUFAs), which are found in most types of vegetable oil (e.g. soybean oil, corn oil - the most consumed in USA, sunflower oil, etc.), may increase the likelihood that postmenopausal women will develop breast cancer.[17] A similar effect was observed on prostate cancer in mice.[18] Plant based oils high in Monounsaturated Fatty Acids, such Olive oil, peanut oil, and canola oil are relatively low in omega-6 PUFAs and can be used in place of high-polyunsaturated oils.[citation needed] However, palm oil and coconut oil, even as unhydrogenated "natural" oils, are high in saturated fatty acids (lauric and myristic acid) that have demonstrated negative effects upon plasma cholesterol and cardiovascular risk factors.[19][20][21][22][23] In fact, they are commonly used in animal studies to induce atherosclerosis to investigate the possible causes of the disease