Mediterranean diet and cancer.

OBJECTIVE: To analyse the role of various aspects of the Mediterranean diet in several common epithelial cancers, including digestive and selected non-digestive tract neoplasms.
DESIGN: Systematic analysis of data from a series of case-control studies.
SETTING: Northern Italy, between 1983 and 1998.
SUBJECTS: Over 12,000 cases of 20 cancer sites and 10,000 controls.
RESULTS: For most epithelial cancers, the risk decreased with increasing vegetable and fruit consumption, with relative risk (RR) between 0.3 and 0.7 for the highest versus the lowest tertile. For digestive tract cancers, population-attributable risks for low intake of vegetables and fruit ranged between 15 and 40%. A protective effect was observed also for breast, female genital tract, urinary tract and a few other epithelial neoplasms. A number of antioxidants and other micronutrients showed an inverse relationship with cancer risk, but the main components responsible for the favourable effect of a diet rich in vegetables and fruit remain undefined. Fish tended to be another favourable diet indicator. In contrast, subjects reporting frequent red meat intake showed RRs above unity for several common neoplasms. Intake of whole-grain foods was related to a reduced risk of several types of cancer, particularly of the upper digestive tract. This may be due to a favourable role of fibre, but the issue is still open to discussion. In contrast, refined grain intake and, consequently, glycaemic load and glycaemic index were associated with increased risk of different types of cancer including, among others, breast and colorectal.
CONCLUSIONS: A low-risk diet for cancer in the Mediterranean would imply increasing the consumption of fruit and vegetables, as well as avoiding increasing the intakes of meat and refined carbohydrates. Further, olive oil and other unsaturated fats, which are also typical aspects of the Mediterranean diet, should be preferred to saturated ones.