DIET, NUTRITION AND PROSTATE-CANCER

Although much has been written, little is known about the causes of pr ostate cancer, Variations between populations in the incidence of inva sive cancers, together with changes in the incidence of invasive cance rs in migrants, have pointed to environmental (lifestyle) factors that might be amenable to intervention. Conversely, there is a lack of int ernational variation in the prevalence of microscopic tumours, so the essential question is: what causes only some of the common microscopic tumours to become aggressive? Dietary factors hold the most promise i n this regard and have been the subject of recent reviews, The stronge st and most consistent effects are positive associations with animal p roducts such as red meats, eggs and dairy foods, and possibly by impli cation, fat. Evidence of a protective effect of fruit and vegetables i s weak and inconsistent, as is the relationship with vitamin A and car otenoids, such as beta-carotene. There are some interesting leads, Lyc opene, the carotenoid found in tomatoes, has been reported to be prote ctive; alpha-tocopherol supplementation has shown a protective effect in one intervention study; and vitamin D has been shown to be protecti ve in a prospective study, Interest is also growing in phytoestrogens and the extent to which dietary manipulation with these and other phyt ochemicals might influence prostate cancer by modifying male sex hormo ne levels or actions, There is limited evidence of associations with o besity, It is not known whether these are related to a particular diet ary pattern or to possible physiological effects on the male's hormona l milieu. Associations with lean body mass are likely to be related to the action of androgens during growth and development, Dietary and nu tritional effects on prostate cancer do not appear to be strong, but t hey may be subtle and attenuated by measurement error, To explore thes e aspects further will require large prospective studies that include improved (repeated) dietary measurements and also blood sampling, so t hat genetic polymorphisms can be adequately investigated, Such studies are underway. (C) 1997 Wiley-Liss, Inc.