Low Density Lipoprotein (LDL), also known as the "bad cholesterol" can eventually cause plaque and block the artery. Monounsaturated fats can lower LDL thus protecting against atherosclerosis. Plus, this type of fat does not affect the levels of High Density Lipoproteins (HDL) known as the "good cholesterol," which carry all cholesterol away from the arteries, and high levels of which are associated with a decreased risk of heart disease. Olive oil is one of the best sources of monounsaturated fats and has the advantage of being less susceptible to oxidation.
Several studies for different age groups, and with a large number of participants, have found that the consumption of olive oil is associated with a decrease in blood pressure.
The SUN (Seguimiento University of Navarra) study with over 6,000 participants found that olive oil intake reduced the incidence of hypertension in men, while another Spanish study published this month in the American Journal of Hypertension found that a diet containing polyphenol rich olive oil reduced blood pressure in young women with mild hypertension.
Results from the the Greek component of the EPIC study (European Prospective Investigation into Cancer and Nutrition) which included over 28,500 volunteers concluded that olive oil intake is inversely associated with both systolic and diastolic blood pressure. While it appears that the polyphenols in the olive oil may be responsible for this action, researchers have demonstrated that oleic acid; a fatty acid in olive oil may also induce this lowering effect.
A review conducted by Greek researchers from the University of Athens published last year of 19 observational studies, with over 36,000 participants, found that higher rates of olive oil consumption were associated with lower odds of having any type of cancer. Another review of 25 epidemiological studies concluded that "preferring olive oil to other added lipids, particularly those rich in saturated fats, can decrease the risk of upper digestive and respiratory tract neoplasms, breast and, possibly, colorectal and other cancer sites."
Apart from the monounsaturated fats in olive oil and specifically oleic acid, olive oil has another component that other sources do not have: polyphenols. Polyphenols are phytochemicals, components that have antioxidant activity.
Researchers found that consumption of olive oil at real-life doses of about 2 tablespoons per day improved the fatty acid profile in LDL, associated with a reduction of the oxidative damage to lipids. It appears that oxidized LDL is an important contributor to atherogenesis; the process of plaque buildup in the arteries that eventually can lead to atherosclerosis (hardening of the arteries).
Although olive oil is better known for its protection against heart disease and cancer, there is an emerging amount of research regarding the effect of olive oil on cognitive function and, specifically, on cognitive decline associated with aging.
Brigham and Women's Hospital, a teaching affiliate of Harvard Medical School, analyzed data from 6,000 women over the age of 65, a subset of the Women's Health Study. They found that women who consumed the highest amount of monounsaturated fats, which can be found in olive oil, had better patterns of cognitive scores over time.
But it appears that olive oil specifically has a protective effect. Results from the Three-City Study, an ongoing multicenter study of vascular risk factors for dementia using information from almost 7,000 participants, showed that individuals who had moderate to intensive use of olive oil had lower odds of cognitive deficit for verbal fluency and visual memory compared to individuals who had never used olive oil.
How much of a good thing?
When looking at the different studies in regards to the protective effect of olive oil for various conditions the amount generally ranges between 25 and 40 grams per day, or about 2-3 tablespoons.