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