PREDIMED, a clinical trial carried out in Spain to test the effect of Mediterranean diet (MeDiet) on the primary prevention of cardiovascular diseases, suggested a strong protective effect of MeDiet against the occurrence of postmenopausal breast cancer (BC): adjusted hazard ratio (HR) of 0.43 (95% CI, 0.21-0.88), even stronger in the intervention subgroup supplemented with extra-virgin olive oil (HR, 0.32; 95% CI, 0.13-0.79), while in the subgroup supplemented with nuts the decrease of BC was less notable.1 Breast cancer was not a primary aim of the PREDIMED study, and the statistical power to detect the observed result, with only about 1400 women per randomized group, was less than 15%. The published point estimates of the HR, therefore, are hardly credible, and the authors themselves conclude that larger studies are necessary. There are several reasons to think, however, that adopting a traditional MeDiet protects against breast and other cancers.
Berrino F. Mediterranean Diet and Its Association With Reduced Invasive Breast Cancer Risk. JAMA Oncol. 2016;2(4):535–536. doi:10.1001/jamaoncol.2015.5679
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