Folate-Depleted Diet Compared With Folate-Supplemented Diet in Preventing Colorectal Cancer in Patients at High Risk for Colorectal Cancer

DISEASE CHARACTERISTICS: Healthy persons at increased risk for colorectal neoplasia due to 1 of the following reasons: Personal history of colorectal adenomatous polyps Family history of colorectal adenoma or adenocarcinoma No history of multiple family members with colorectal neoplasia that is suggestive of dominant hereditary neoplasia PATIENT CHARACTERISTICS: Age 40 to 72 Performance status Ambulatory Life expectancy At least 6 months Hematopoietic No excessive bleeding or coagulation disorder Hepatic ALT or AST ≤ 2 times upper limit of normal No unexplained elevated alkaline phosphatase Renal Creatinine ≤ 2.0 mg/dL Cardiovascular Homocysteine concentration ≤ 17um/L No sustained blood pressure > 150/95 mm Hg for 3 consecutive readings Other Vitamin B_12 ≥ 250 pg/mL Folate level ≤ 20 mg/dL HIV negative Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception during and for 4 weeks after study participation No intestinal malabsorption or inflammatory bowel disease No prior malignancy except nonmelanoma skin cancer No calcium metabolism abnormalities or predisposing conditions, such as hyperparathyroidism No untreated hyperthyroidism No untreated insulin-requiring diabetes mellitus No daily alcohol intake > 2 ½ shot glasses of whiskey or three 8 ounce glasses of beer or wine No other serious illness that might limit life expectancy to < 6 months PRIOR CONCURRENT THERAPY: Biologic therapy None Chemotherapy None Endocrine therapy No concurrent hormone replacement therapy, including oral, transplanted, or injected contraceptives Concurrent thyroid hormone replacement is allowed as long as the patient is euthyroid for 3 months Radiotherapy None Surgery No prior gastrointestinal surgery, including gastrectomy or small or large bowel resections Prior appendectomy or surgery of the esophagus allowed Other More than 3 months since regular ingestion of ≥ 650 mg per day of aspirin (≥ 2 tablets of 325 mg regular strength OR > 1 tablet of 500 mg extra strength aspirin) More than 3 months since regular daily ingestion of nonsteroidal anti-inflammatory drugs At least 1 month since vitamin, mineral, or herbal supplementation No other concurrent vitamin, mineral, or herbal supplementation No concurrent anticoagulants No concurrent sterol-binding resins (i.e., cholestyramine) No other concurrent investigational drugs or medications that might alter rectal mucosal proliferation, folate metabolism, or renal/hepatic impairment No concurrent weight control medications No concurrent supplemental folate preparations containing > 400 mcg of folic acid per day No concurrent lipid-lowering medications The following concurrent statin drugs are allowed provided patient has been taking a stable dose for ≥ 1 month: Atorvastatin 10 or 20 mg/day Fluvastatin 20 or 40 mg/day Lovastatin 10 or 20 mg/day Pravastatin 10 or 20 mg/day Simvastatin 5 or 10 mg/day