The diet and cancer hypothesis: current trends.

The current decade has witnessed an increasing interest in the diet-cancer issue as a central one for public health. Notwithstanding a substantial amount of epidemiological investigations, firm evidence of carcinogenicity exists only for alcoholic beverages with respect to cancers at several sites, and for aflatoxin with respect to liver cancer; also, the relation is established between diet related excess of energy intake, as translated into obesity, and cancer of endometrium and gallbladder. For a number of other dietary factors the evidence for a causal or protective role still remains at a presumptive level (e.g. intake of fresh vegetables and fruits with respect to cancers at several sites), or is still frankly open to debate (e.g. fat with respect to breast and colon cancer). Methodological inadequacies in past studies have been identified and clearer results should derive in the coming decade from epidemiological investigations substantially improved in methodology, particularly from the long-term prospective studies as now planned by the International Agency for Research on Cancer. Fortunately for cancer prevention, such dietary advice as can be derived from the highly incomplete and unsatisfactory knowledge on the role of dietary factors on cancer, turns out to be in broad agreement with the advice aimed at preventing other major diseases such as ischaemic heart disease and hypertension. This allows the issuing of a set of simple but important 'prudent diet' recommendations.