SUMMARY
The relationship between fish consumption and risk of major cancers such as cancer of the breast, colon, rectum and prostate has been insufficiently clarified. The present literature review of epidemiological studies shows somewhat inconsistent results, but overall there seems to be either no association or an inverse association between fish consumption and risk of breast, colorectal and prostate cancer. However, very few of the published studies have been designed to investigate properly hypotheses regarding fish consumption and cancer risk. Rather, the studies have focused on cancer risk related to meat or fat consumption. Common methodological weaknesses in the studies are combined consumption of lean and fatty fish, or even mixed fish consumption with consumption of chicken, ignoring seasonal variation and different ways of storing, preparing and serving fish, and narrow ranges of exposure. The methodological weaknesses should be borne in mind when evaluating current knowledge on the impact of fish consumption on cancer risk, and when designing new studies. Keywords: case-control studies; cohort studies; diet; ecological studies; epidemiology; marine foods