The magazine Circulation has published a study conducted by a team of researchers from the Hospital del Mar Medical Research Institute (IMIN) in Spain. In the study it was shown that having a diet rich in olive oil helps the body's high density lipoproteins (HDLs) to function better. HDLs are also known as 'good cholesterol'. For the first time, the full effect of one's diet on the cardioprotective function of 'good cholesterol' has been made clear. Until now, only the effects of certain medicines had been proven.

The principal function of HDLs is to remove any excess cholesterol from the arteries and to transport it towards the liver for its excretion. The Cardiovascular and Nutrition Research Group Co-ordinator at IMIN, Montsé Fitó, explained the study as follows: ''We compared two types of Mediterranean diet, one rich in olive oil and the other rich in nuts with a typical low-fat diet. The result was that we saw that adherence to a traditional Mediterranean diet, especially one rich in olive oil is strongly linked to an improvement in the function of HDLs.'' Fitó, who is also a researcher at the Biomedical Centre of Research into the Physiopathology of Obesity and Nutrition (CIBEROBN), also pointed out that numerous researchers have recently noted that the biological functions of HDLs, and not so much the levels of 'good cholesterol' which they have, are what helps explain their cardioprotective role. In this way, we can hypothetically explain why people with cardiovascular diseases have HDLs which do not work as well.

In order to carry out this study, the researchers randomly selected a sub-sample of 296 volunteers from the PREDIMED study (Prevention with a Mediterranean Diet) and isolated the lipoproteins from the blood samples obtained before and after the research period (one year). This study has received attention from one of the most important cardiovascular health organisations in the world, The American Heart Association. This is because previously no-one had completed a study in this field as meticulously as this one, with so many participants, and for such a long period.