Conformity to traditional Mediterranean diet and breast cancer risk in the Greek EPIC (European Prospective Investigation into Cancer and Nutrition) cohort.

BACKGROUND: Studies in the United States report inverse associations of the Mediterranean dietary pattern with breast cancer risk, and several studies in Mediterranean countries indicate inverse associations of breast cancer risk with intake of olive oil, a constitutional component of this diet. No study, however, has evaluated the association of the traditional Mediterranean diet with breast cancer in a Mediterranean country.
OBJECTIVE: We studied the relation of conformity to the Mediterranean diet with breast cancer risk in the context of the European Prospective Investigation into Cancer and Nutrition cohort in Greece.
DESIGN: We followed up 14,807 women for an average of 9.8 y and identified 240 incident breast cancer cases. Diet was assessed through a validated food-frequency questionnaire, and conformity to the Mediterranean diet was evaluated through a score (range = 0-9 points) incorporating the characteristics of this diet.
RESULTS: Increasing conformity to the Mediterranean diet was not associated with lower breast cancer risk in the entire cohort [hazard ratio (HR) = 0.88 for every 2 points; 95% CI: 0.75, 1.03] or in premenopausal women (HR = 1.01 for every 2 points; 95% CI: 0.80, 1.28), but there was a marginally significant inverse association among postmenopausal women (HR = 0.78 for every 2 points; 95% CI: 0.62, 0.98; P for interaction by menopausal status = 0.05).
CONCLUSIONS: Conformity to the traditional Mediterranean diet may be associated with lower breast cancer risk among postmenopausal women and could explain, in part, the lower incidence of this disease in Mediterranean countries.