Not just for your heart: Olive oil associated with dramatic reduction in breast cancer risk

The fight against breast cancer may begin in the kitchen. A new study suggests that women can dramatically reduce their risk of the disease by following a version of the Mediterranean diet that goes heavy on extra virgin olive oil.

Data from a large, randomised clinical trial show that women who did so were 62 per cent less likely to be diagnosed with breast cancer compared with women who were simply asked to reduce the overall amount of fat in their diets. The results were published Monday in the journal JAMA Internal Medicine.

The clinical trial, known as PREDIMED, was designed to assess the cardiovascular benefits of the Mediterranean diet, which emphasises fruits, vegetables, whole grains, fish and olive oil. Participants were randomly assigned to one of three groups - Mediterranean diet supplemented with extra virgin olive oil, Mediterranean diet supplemented with mixed nuts, or a regular low-fat diet.

After tracking nearly 7,500 people for about five years, the researchers had compelling evidence that those who were on either type of Mediterranean diet had better heart health than their counterparts who weren’t. The trial was ended in 2010.

Although the study’s main focus was cardiovascular disease, researchers also tracked the incidence of five types of cancer, including breast cancer. Among the 4,282 women who participated in the trial, there were 35 confirmed cases of invasive breast cancer.  

The risk of being diagnosed with invasive breast cancer was highest for women who were advised to eat less fat - 2.9 cases for every 1,000 person-years. That compared to a diagnosis rate of 1.8 cases per 1,000 person-years for women who were on the Mediterranean diet with extra nuts and a rate of 1.1 cases per 1,000 person-years for women who were on the Mediterranean diet with additional extra virgin olive oil.