Epidemiological aspects of diet and cancer: a summary review of case-control studies from northern Italy.

The major findings on dietary aspects of cancer risk are reviewed from a series of hospital-based case-control studies conducted in Northern Italy. Information collected using simple frequency questionnaires indicated that green vegetable consumption was inversely related with the risk of cancers of the breast and of the female genital tract, as well as with oesophageal and gastric neoplasms, whereas there were positive associations between fats in seasonings and other foods (e.g., meat) and cancers of the breast, ovary, endometrium and prostate. Fruits, and specifically citrus fruits, were inversely related with cancers of the oesophagus and of the stomach, and there were positive associations between various sources of starches (but not fibres) and gastric cancer risk. Thus, extremely simplified questionnaires apparently permitted identification of a number of significant and consistent differences between cancer cases and hospital-based comparison groups, which were not obviously explainable in terms of selection, confounding, information or other biases. Nonetheless, epidemiological evidence on diet and cancer from this and several other investigations is rather crude and imprecise and, hence, its implications in terms of public health policy are still open to question.