Diet, obesity and risk for renal cell carcinoma: results from a case control-study in Germany.

Increasing incidence of renal cell carcinoma in Western countries raises particular attention to its etiology. Diet may be related to risk for renal cell carcinoma since obesity has been linked with this malignant condition. A case-control study with 277 incident renal cell cancer patients (ICD 189.0) and 286 population controls was conducted in the Rhein-Neckar-Odenwald area, Germany, in the period of 1989 to 1991. The core study protocol included a face-to-face interview about demographical parameters, previous diseases, medication, tobacco smoking, occupational history, occupational exposures, beverage consumption, and obesity. In addition, study participants were asked to fill in a self-administered food frequency questionnaire with 122 food items to estimate overall food intake. Fifty-six % of the cases and 74% of the controls participated in this part of the study (n = 155 cases and 212 controls). This was 47% of the original cases (n = 328) and 56% of the controls (n = 381). No selection bias could be identified with regard to age group, gender, educational status or recent BMI in the analyzed group compared with the eligible cases and controls. Relative risk (RR) estimates for tertiles of consumption revealed a significantly increased risk with increasing intake of fat spread (RR of high intake compared to low intake: 1.90 (95% CI 1.08-3.32)). Increased risk was also found for intake of meat and meat products (RR of high intake compared to low intake: 1.71 (95% CI 0.96-3.04)) and energy adjusted fat (RR of high intake compared to low intake: 1.64 (95% CI 0.95-2.83)). A decreased risk was seen with increasing intake of fruit (RR of high intake compared to low intake: 0.40 (95% CI 0.23-0.69)) and of vitamin C (RR of high intake compared to low intake: 0.62 (95% CI 0.37-1.05)). Beverage consumption, preparation of food and eating pattern were not linked with risk of renal cell cancer. The relative risk estimates of spreading fat (sauce and vitamin C intake were tested in two models, with and without including BMI as covariate. In both models significant associations of these nutritional variables with risk for renal cell cancer remained. The current results indicate that specific food pattern associated with obesity explain differences in incidence of renal cell carcinoma in industrialized countries.