Fruit, vegetables, fibre and micronutrients and risk of US renal cell carcinoma

The association between renal cell cancer (RCC) and intake of fruit, vegetables and nutrients was examined in a population-based case-control study of 323 cases and 1827 controls; dietary intake was obtained using a mailed questionnaire. Cancer risks were estimated by OR and 95% CI, adjusting for age, sex, smoking, obesity, hypertension, proxy status, alcohol consumption and dietary fat intake and energy. Intake of vegetables was associated with a decreased risk of RCC (OR 0.5; 95% CI 0.3, 0.7; P-trend = 0.002), (top compared to the bottom quartile of intake). When intake of individual nutrients was investigated, vegetable fibre intake was associated with decreased risks (OR 0.4; 95% CI 0.2, 0.6; P<0.001), but this was not the case with fruit fibre (OR 0.7; 95% CI 0.4, 1.1) or grain fibre (OR 1.0; 95% CI 0.6, 1.5). beta-Cryptoxanthin and lycopene were also associated with decreased risks, but when both were included in a mutually adjusted backwards stepwise regression model, only beta-cryptoxanthin remained significant (OR 0.5; 95% CI 0.3, 0.8). When other micronutrients and types of fibre were investigated together, only vegetable fibre and beta-cryptoxanthin had significant trends (P<0. 01) (OR 0.6; 95% CI 0.3, 0.9) (OR 0.5; 95% CI 0.3, 0.9), respectively. These findings were stronger in those aged over 65 years (P-interaction = 0.001). Among non-smokers, low intake of cruciferous vegetables and fruit fibre was also associated with increased risk of RCC (P-interaction = 0.03); similar inverse associations were found for beta-cryptoxanthin, lycopene and vitamin C. When nutrients were mutually adjusted by backwards regression in these subgroups, only beta-cryptoxanthin remained associated with lower RCC risk. These findings deserve further investigation in ongoing prospective studies when sample size becomes sufficient.