The results of studies analyzing the association between the Mediterranean diet and breast cancer have been inconspicuous. Alcohol, especially wine and consumed at meals, is one of the components that define the Mediterranean dietary pattern, but higher alcohol consumption has repeatedly been associated with an increased risk of different types of cancer. Interestingly, when studies did not consider alcohol intake component for calculating adherence to Mediterranean dietary pattern, the results of the association between adherence to Mediterranean diet and breast cancer were much more surprising.

A study1 with the EPIC (European Prospective Investigation into Cancer) cohort, including women from Italy, Greece and Spain, found that the group with high adherence to the Mediterranean dietary pattern showed a significant 7% reduction in the risk of postmenopausal breast cancer compared to the group with low adherence.

PREDIMED2 is the first clinical trial assessing the intervention with Mediterranean diet for the primary prevention of cardiovascular disease, but investigators also collected information on breast cancer incidence as a secondary outcome. PREDIMED participants were randomized to one of the three study groups: Mediterranean diet enriched with extra-virgin olive oil, Mediterranean diet enriched with nuts or control diet. Among the 4152 women in the study, those assigned to the Mediterranean Diet enriched with extra-virgin olive oil presented a 68% lower risk of postmenopausal breast cancer than women in the control group. Moreover, a 5% increase of calories from extra-virgin olive oil was associated with a 28% reduction in the risk of breast cancer. The higher the intake of extra-virgin olive oil, the lower the risk of postmenopausal breast cancer. On the other hand, the risk of breast cancer of women allocated in the group of Mediterranean diet enriched with nuts was similar to the risk observed in the control group.

1 Buckland G, Travier N, Cottet V, González CA, Luján-Barroso L, Agudo A, Trichopoulou A, Lagiou P, Trichopoulos D, Peeters PH, May A, Bueno-de-Mesquita HB, Bvan Duijnhoven FJ, Key TJ, Allen N, Khaw KT, Wareham N, Romieu I, McCormack V, Boutron-Ruault M, Clavel-Chapelon F, Panico S, Agnoli C, Palli D, Tumino R, Vineis P, Amiano P, Barricarte A, Rodríguez L, Sanchez MJ, Chirlaque MD, Kaaks R, Teucher B, Boeing H, Bergmann MM, Overvad K, Dahm CC, Tjønneland A, Olsen A, Manjer J, Wirfält E, Hallmans G, Johansson I, Lund E, Hjartåker A, Skeie G, Vergnaud AC, Norat T, Romaguera D, Riboli E. Adherence to the editerranean diet and risk of breast cancer in the European prospective investigation into cáncer and nutrition cohort study. Int J Cancer 2013;132:2918-27

2 Toledo E, Salas-Salvadó J, Donat-Vargas C, Buil-Cosiales P, Estruch R, Ros E, Corella D, Fitó M, Hu FB, Arós F, Gómez-Gracia E, Romaguera D, Ortega-Calvo M, Serra-Majem L, Pintó X, Schröder H, Basora J, Sorlí JV, Bulló M, Serra-Mir M, Martínez-González MA. Mediterranean Diet and Invasive Breast Cancer Risk Among Women at High Cardiovascular Risk in the PREDIMED Trial: A Randomized Clinical Trial. JAMA Intern Med 2018;178:1731-1732.