Fruit and vegetable intake and prevalence of colorectal adenoma in a cancer screening trial

BACKGROUND: Research on the association between fruit and vegetable intake and risk of colorectal adenoma is inconclusive. OBJECTIVE: We studied whether intake of fruit, vegetables, or their subgroups is associated with a lower risk of prevalent colorectal adenoma. DESIGN: In men and women (aged 55-74 y) who were screened for colorectal cancer in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO) (1993-2001), we compared 3,057 cases with at least one prevalent histologically verified adenoma of the distal large bowel with 29,413 control subjects. Using a food-frequency questionnaire, we quantified intake of fruit and vegetables in the 12 mo before screening as energy-adjusted pyramid servings/d (ps/d). Adjusted odds ratios (ORs) and 95% CIs were estimated by logistic regression. RESULTS: Risk of distal adenoma was significantly lower among subjects in high (approximately 5.7 ps/d) versus low (approximately 1.2 ps/d) quintiles of total fruit intake (OR: 0.75; 95% CI: 0.66, 0.86, P for trend <0.001), which was not completely explained by dietary folate or fiber intake. Inverse associations between adenoma and total fruit intake were observed regardless of adenoma histopathology and multiplicity. However, the protective effect was seen only for colon and not rectal adenoma. Total vegetable intake was not significantly associated with reduced risk of adenoma. ORs for colorectal adenoma among persons with high versus low intakes of deep-yellow vegetables, dark-green vegetables, and onions and garlic were significantly related to lower risk of adenoma, although the P for trend for dark-green vegetables was not significant. CONCLUSION: Diets rich in fruit and deep-yellow vegetables, dark-green vegetables, and onions and garlic are modestly associated with reduced risk of colorectal adenoma, a precursor of colorectal cancer.