Epidemiologic studies on fried foods and cancer in Sweden

Three population-based case-control studies in Sweden have found an association between fried foods and pancreatic cancer, urothelial cancer and colorectal cancer, respectively. Only one of these studies included questions about the preferred method of frying the meat surface. This study was performed in Stockholm in 1986-88 and included 347 cases of colon cancer, 212 cases of rectal cancer and 505 controls. Total meat intake, frequent consumption of brown gravy, and a preference for a heavily browned meat surface each independently increased the risk for colorectal cancer. The relative risks (RRs) were higher for frequent intake of boiled meat (RR colon = 1.7, RR rectum = 2.7) than for frequent intake of meat fried with a medium or lightly browned surface (RR colon = 0.8, RR rectum = 1.1), but the highest risks were for frequent intake of meat fried with a heavily browned surface (RR colon = 2.8, RR rectum = 6.0). The analyses were adjusted for year of birth, gender and fat intake. Further adjustments for total energy, dietary fiber intake, body mass and physical activity had little or no influence on the relative risks. These results indicate that the cooking method is a neglected risk factor for cancer, but also that the measurements of exposure, used so far, are inadequate. First, the agents (exposure) of interest have to be identified in laboratory studies; secondly, accurate methods to measure the exposure in epidemiologic studies have to be established; and thirdly, these methods have to be used in well-designed epidemiologic studies.