Eating a Mediterranean diet supplemented with extra virgin olive oil (EVOO) was associated with a lower risk of breast cancer in a trial involving women in Spain. It’s the first randomized trial of a long-term dietary intervention to prevent breast cancer, although the study couldn’t determine whether the beneficial effect was due to the olive oil or to the Mediterranean diet (Toledo E et al. JAMA Intern Med. doi:10.1001/jamainternmed.2015.4838 [published online September 14, 2015]). The study analyzed the effects of 2 interventions: a Mediterranean diet supplemented with 1 L per week of EVOO (1476 women) or a Mediterranean diet supplemented with 30 g of mixed nuts daily (1285 women). The control group (1391 women) received advice to reduce their dietary intake of fat. This study is a secondary analysis of the large PREDIMED (Prevención con Dieta Mediterránea) trial, which was designed to test the effects of the Mediterranean diet on the primary prevention of cardiovascular disease.
Slomski A. Mediterranean Diet With Olive Oil May Reduce Breast Cancer Risk. JAMA. 2015;314(20):2122. doi:10.1001/jama.2015.15119