Diet and vitamin or mineral supplements and risk of renal cell carcinoma in Canada

Objective: To assess the role of diet and vitamin or mineral supplements in renal cell carcinoma (RCC) risk. Methods: Mailed questionnaires were completed by 1279 ( 691 male and 588 female) newly diagnosed histologically confirmed RCC cases and 5370 (2696 male and 2674 female) population controls between 1994 and 1997 in eight Canadian provinces. Measurement included information on socioeconomic status, smoking habits, alcohol use, diet, and vitamin or mineral supplements. Odds ratios (ORs) and 95% confidence intervals (CIs) were derived through unconditional logistic regression. Results: A significant inverse association with RCC was observed with increasing total consumption of vegetables and vegetable juices for males and females combined. Increased consumption for two specific vegetable groups was inversely associated among females but not males: for females, the adjusted ORs for the highest quartile of consumption compared with the lowest were 0.5 (95% CI = 0.4 - 0.7) and 0.6 (95% CI = 0.4 - 0.8), p < 0.0001 and p = 0.0002 for dark-green vegetables and cruciferous vegetables, respectively. An increased risk was observed (for males and females combined) with increased consumption of hamburger and sausage: adjusted ORs for highest level versus lowest level were 1.4 (95% CI = 1.1 - 1.8) and 1.5 (95% CI = 1.2 - 2.0), respectively, p = 0.003 and 0.01. Beef, pork or lamb as a main dish and processed meats were also associated with increased RCC. Red meats and processed meats had a positive association with RCC among males who had smoked or were overweight; among females this was the case for hamburger only. Significant inverse associations were observed for females taking vitamin E or calcium supplements. Among males, those taking vitamin E or iron for more than 5 years had reduced risks. Conclusions: Our findings add to the evidence that diet may play an important role in the etiology of RCC; the risk of RCC may be reduced by changes in nutritional habits.