Diet and risk of renal cell cancer: a population-based case-control study.

In a few previous studies on diet and renal cell cancer, an inconsistent positive association with meat, milk, and protein and a negative association with vegetable and fruit consumption have been found. Whereas earlier studies have dealt with recent diet only, our study explored the effect of foods consumed both during the usual adult lifetime and 20 years prior to interview. The study included 379 individuals with incident histologically verified renal cell cancer and 350 control subjects residing in eight counties in Sweden between June 1989 and December 1991. Usual adult dietary intake and dietary habits 20 years prior to interview were assessed by a structured face-to-face interview and a self-administered questionnaire, respectively. Odds ratios were estimated through unconditional logistic regression. We have not observed an association of renal cell cancer with milk or total meat consumption per se; however, frequent intake of fried/sautéed meat increased the risk of renal cell cancer by about 60%; frequent consumption of poultry was also associated with an increased risk (P for trend, 0.05). A significantly protective effect on risk of renal cell cancer was observed with increasing consumption of fruit (P for trend, 0.05). When analyzed by smoking status, total fruit and especially citrus fruit consumption among nonsmokers showed an even stronger protective effect; the highest quartiles of total fruit, apple, and citrus fruit consumption entailed a 50-60% reduction in risk of renal cell cancer compared with the lowest quartiles. There was a suggestion of a protective effect of high total vegetable consumption. A protective effect of vitamin C and alpha-tocopherol was also more pronounced in nonsmokers (P for trend, 0.004 and 0.007, respectively). Our study adds to the evidence that diet may have an important role in the etiology of renal cell cancer.