Effect of Folate on DNA in Colon Tissue and Blood Samples From Patients at Increased Risk of Developing Colorectal Neoplasia

DISEASE CHARACTERISTICS: * At increased risk for developing colorectal neoplasia due to 1 of the following: * Personal history of colorectal adenomatous polyps * Family history of colorectal adenoma or adenocarcinoma * No hereditary nonpolyposis colorectal cancer (HNPCC) * No more than one first-degree family member with colorectal or endometrial malignancies PATIENT CHARACTERISTICS: * Ambulatory * Female patients must be ≥ 2 years post-menopausal (i.e., 2 years after the last menstrual period) * Negative pregnancy test * Male patients must use effective contraception during and for 2 months after completion of study treatment (for male patients enrolled in the folate depletion group) * Serum folate level ≤ 20 ng/mL * Plasma vitamin B12 level ≥ 250 pg/mL * Serum homocysteine level ≤ 17 μmol/L * ALT or AST ≤ 2 times upper limit of normal * No unexplained elevated alkaline phosphatase * Creatinine ≤ 2.0 mg/dL * HIV negative * No folate metabolism abnormalities or predisposing conditions * No prior malignancy except nonmelanoma skin cancer * No intestinal malabsorption or inflammatory bowel disease * No excessive bleeding or coagulation disorder * No untreated hyperthyroidism * No diabetes mellitus requiring insulin * No daily alcohol intake \> 2 ½ shot glasses of whisky or three 8-ounce glasses of beer or wine * No sustained blood pressure \> 150/95 mm Hg for three consecutive readings * No other serious illness that would limit life expectancy to \< 6 months PRIOR CONCURRENT THERAPY: * No prior gastrointestinal surgery, including gastrectomy or small or large bowel resections * Prior appendectomy or surgery of the esophagus allowed * More than 3 months since regular ingestion of ≥ 650 mg of aspirin (≥ 2 tablets of 325 mg regular strength OR \> 1 tablet of 500 mg extra strength aspirin) per day * The following drugs are allowed for cardiovascular prophylaxis provided the patient has been taking the drug regularly for ≥ 1 month and continues to take the same dose during study participation: * One or two regular strength aspirin tablets (i.e., 325 mg per tablet) per day * One baby aspirin tablet (81 mg tablet) per day * More than 3 months since regular daily ingestion of other non-steroidal anti-inflammatory drugs (NSAIDs) * No concurrent anticoagulation therapy * No concurrent sterol-binding resins, such as cholestyramine (for the treatment of high blood cholesterol) * No other concurrent investigational drugs * No other concurrent medications that might, in the view of the study physicians, alter rectal mucosal proliferation, folate metabolism, or renal/hepatic metabolism * No concurrent weight control medications * No concurrent supplemental folate preparation containing \> 400 mcg of folic acid per day * No concurrent hormone replacement therapy, including oral, transplanted, or injected contraceptives * Concurrent thyroid hormone replacement allowed provided the patient is euthyroid * No concurrent medication interfering with folic acid metabolic effects, including any of the following: * Methotrexate * Phenytoin * Phenobarbital * Primidone * Sulfonamides * Folinic acid derivatives * No concurrent lipid-lowering medications other than usual doses of the class of drugs known as statins * The following statin drugs are allowed provided the patient has been taking the drug regularly for ≥ 1 month and continues to take the same dose during study participation: * Atorvastatin (10 or 20 mg/day) * Fluvastatin (20 mg or 40 mg/day) * Lovastatin (10 or 20 mg/day) * Pravastatin (10 or 20 mg/day) * Simvastatin (5 or 10 mg/day)