Historically the Mediterranean countries have had low incidences of chronic diseases in sharp contrast to other countries. Researchers have focused on diet as a specific cause, specifically the traditional Mediterranean Diet with its reliance on olive oil as the main fat.
Extra virgin olive oil is primarily a monounsaturated fat which was believed to be the reason it was so healthy. However, research in the last twenty years has zeroed in on the small plant chemicals, known as the phenolic content of extra virgin olive oil. These phenolic compounds are small, numerous, and potent for health. These phenolic compounds vary widely and include flavonoids, lignans, sterols, phytosterols, and particular phenols unique to extra virgin olive oil such as oleocanthal, hydroxytrosol, and oleuropein.
These phenolic compounds also help keep the olive oil stable and are an indicator of EVOO quality. These complex phenolic compounds have been reported to have antioxidant and anti-inflammatory properties based on numerous peer-reviewed studies.
The phenolic content of olive oils varies according to the climatic conditions in the producing area, when the olives are harvested and how ripe they are when picked. Oil production and storage methods also have an influence.
Below are a few of the peer-reviewed research studies examining olive oil consumption and outcomes.
Spanish researchers in the SOLOS Study tested olive oil vs extra virgin olive. The study, “Anti-inflammatory effect of virgin olive oil in stable coronary disease patients: a randomized, crossover, controlled trial” was designed to compare olive oil and extra virgin olive oil on inflammatory markers in heart disease patients; specifically, the impact phenolic compounds would have on people after many experimental studies showed a positive effect on inflammatory markers. In fact, inflammatory markers, Interleukin-6 and C-reactive protein, decreased after virgin olive oil use, but not with olive oil. (European Journal of Clinical Nutrition (2008) 62, 570-574)
The Predimed Study is one of the best studies on the Mediterranean Diet and EVOO. This study is one of the most important dietary studies in many years because it was large, 7500 people; it took place over a long period, 5-7 years; and most important, it was a randomize control trial, the gold standard. This type of study is the most rigorous because it establishes cause and effect
There were three dietary groups: Med Diet with EVOO, Med Diet with nuts, and a low fat control group. This study found that the Med Diet with EVOO and Med Diet with nuts reduced by 30% the risk of cardiovascular events (heart attack, stroke, cardiovascular mortality) compared to the low fat control group. This was such an important finding that this study was published in the New England Journal of Medicine, one of the top three medical journals in the world.
A further study examined the role of extra virgin olive oil in the Predimed Study, using 7200 individuals at high cardiovascular risk. Participants using high amounts of olive oil and extra virgin olive oil had 35-39% reduction in cardiovascular disease risk and 48% reduced risk of cardiovascular mortality compared to the control group. (BMC Medicine 2014; 12: 77)
THISEAS, a randomized control trial in Greece also showed the importance of olive oil for reducing heart disease. The THISEAS study conducted in Greece involved 2500 individuals. It looked at consumption of olive oil irrespective of diet to judge the impact on coronary artery disease. This study showed that olive oil reduced coronary artery disease by 37%. (Atherosclerosis 241(1):e192-e193 · July 2015)
The Predimed Study Results: The Mediterranean Diet with EVOO may reduce diabetes risk among people with high cardiovascular risk. A subset of the Predimed Study looked at Type 2 Diabetes within the randomized control trial. There were 3500 individuals without diabetes but at high cardiovascular risk. This was a long-term study from 2003 to 2010. The Mediterranean Diet with EVOO reduced Type2 diabetes risk by 40%. (Annals of Internal Medicine. 2014; 160(1):1-10)
The Predimed Study Results: Mediterranean Diet with EVOO may help reduce cognitive decline. Another subset within the Predimed study focused on cognitive decline. The study started with 447 cognitively healthy people who had Type 2 diabetes or at risk for cardiovascular disease with an average age of 67. At the end of the study, those participants in the Med Diet with EVOO or nuts had improved cognition function while those on the control diet showed a decline in cognitive function. (JAMA Internal Medicine 2015;175(7):1094-1103)
Predimed Study Results: Mediterranean Diet with EVOO may help reduce the risk of breast cancer of postmenopausal women. The Predimed study had a subset study on breast cancer. It comprised 4200 women with no history of breast cancer. This risk of breast cancer was reduced by 68% for the group on the Med Diet with extra virgin olive oil. Of note, the reduction was not seen in the Med Diet with nuts or the low fat control group. (JAMA Internal Medicine 2015;175(11):1752-1760)
Predimed Study Results: Mediterranean Diet with EVOO may reduce the risk of bone fractures for middle aged and elderly. As part of the Predimed Study, 870 individuals, aged 55-80 years at high cardiovascular risk, participated in the randomized control study. Over an 8 year follow up, the individuals who used higher amounts of extra virgin olive oil had a 51% lower incidence of fractures compared to the individuals who used small amounts of extra virgin olive oil. (Clinical Nutrition 2017 Jan 13.)
Alienor Study Results: Olive oil may help protect against Age Related Macular Degeneration. This was a population based study focused on eyes disease, using 950 elderly individuals in France. There have been many suggestions via observation studies that the Med Diet with olive oil seems to be related to lower rates of macular degeneration. This study was able to conclude that olive oil is associated with a reduced risk for late age related macular degeneration. (PLoS One. 2016; 11(7))