Olive oil is a key component of the Mediterranean diet and is considered by many to be a natural health-food product. Until recently, the known protective effects of olive oil against oxidative stress-associated diseases, such as cardiovascular, cancer, or neurodegenerative diseases, had been attributed to its high monounsaturated fat content.
The EU-funded project EUROLIVE ('The effect of olive oil consumption on oxidative damage in European populations') investigated whether there might be other chemical factors contributing to the documented beneficial health effects of olive oil.
In particular, project partners, led by researchers at the Mar Institute of Medical Research in Barcelona, wanted to know if olive oil rich in phenolic compounds, such as virgin olive oil, would have particular health benefits beyond those already established for olive oil in general.
The researchers did six clinical trials in which 200 healthy volunteers were given 25 millilitres per day of three similar olive oils for three weeks. The olive oils had different polyphenol content. The dose was similar to the amount typically ingested daily in Mediterranean countries.
The results showed that the higher the polyphenolic content of the olive oil consumed, the higher the increase in HDL cholesterol levels (so-called good cholesterol).
Positive effects were also recorded for the atherogenic index - the total cholesterol/HDL cholesterol, and the oxidative damage of lipids decreased in a linear manner with olive oil polyphenolic content. Lipid oxidation is considered a high risk factor for the development of coronary heart disease.
Finally, the results of the EUROLIVE project demonstrated that consuming 25 millilitres of olive oil per day, in place of other fats, did not lead to participants gaining weight.
For many, these results put an end to the debate over the antioxidant properties of olive oil polyphenols when consumed, and confirm the added value of virgin olive oil as opposed to other oils in protecting against cardiovascular disease and other risk factors.
EUROLIVE received EUR 1.9 million in EU funding. The researchers completed their work in December 2004.