ascorbic-acid and Polyps

Over a 4-year period in a chemoprevention trial on large bowel neoplasia, 58 patients with familial adenomatous polyposis were treated with 4 g of ascorbic acid (vitamin C)/day plus 400 mg of alpha-tocopherol (vitamin E)/day alone or with a grain fiber supplement (22.5 g/day). In this randomized, double-blind, placebo-controlled study, we determined the effects of these supplements on rectal polyps in these patients. Analysis by intent to treat suggested that the high-fiber supplement had a limited effect. Analysis adjusted for patient compliance showed a stronger benefit from the high-fiber supplement during the middle 2 years of the trial. The results provide evidence for inhibition of benign large bowel neoplasia by grain fiber supplements in excess of 11 g/day in this study population. The findings are consistent with the hypothesis that dietary grain fiber and total dietary fat act as competing variables in the genesis of large bowel neoplasia.

Topics: Adenomatous Polyposis Coli; Adult; Ascorbic Acid; Clinical Trials as Topic; Diet; Dietary Fiber; Double-Blind Method; Humans; Patient Compliance; Placebos; Polyps; Random Allocation; Rectal Diseases; Triticum; Vitamin E

The possibility of pharmacological control of large bowel adenomas has been suggested by effectiveness of antioxidants in experimental tumor models and by the results of a limited clinical study using ascorbic acid. Over a two year period we tested this hypothesis in a randomized, double-blind study of 49 patients with polyposis coli. Of 36 patients who were evaluable at completion, 19 had received ascorbic acid, 3 g/day, and 17 had received a placebo. We found a reduction in polyp area in the ascorbic acid-treated group at nine months of follow-up (P less than 0.03) and trends toward reduction in both number and area of rectal polyps during the middle of the trial. A labeling study of rectal epithelium with tritiated thymidine also hinted at a treatment effect. Our data suggest that ascorbic acid temporarily influenced polyp growth or turnover. Although these results have no current therapeutic value, our findings support continued studies of chemoprevention in this and other high risk settings.

Topics: Adult; Ascorbic Acid; Clinical Trials as Topic; Colonic Neoplasms; Diet; Double-Blind Method; Epithelium; Female; Humans; Male; Middle Aged; Polyps; Probability; Random Allocation; Rectal Neoplasms; Time Factors

Topics: Ascorbic Acid; Citrus; Colonic Neoplasms; Cyclic AMP; Diet; DNA; Humans; Models, Biological; Polyps; United States

Traditional methods for prevention of large bowel cancer rely on surveillance of patients with known precursors of bowel cancer, namely ulcerative colitis and those genetically linked polyposis syndromes that have malignant potential. Identification of heritable bowel cancer families and solitary polyp--cancer families provide additional populations that merit intensive scrutiny. Persuasive, if circumstantial, evidence suggests that maintaining patients free of large bowel polyps reduces the risk of developing large bowel cancer. Prospects for prevention of large bowel cancer are extended by recognition that a diet low in fat may reduce the risk of large bowel cancer. Furthermore, there is considerable evidence in animals that a variety of antioxidants limit large bowel carcinogenesis and preliminary evidence in man that these agents may control large bowel neoplasia.

Topics: Adenoma; Ascorbic Acid; Colitis, Ulcerative; Colonic Neoplasms; Diet; Humans; Polyps; Precancerous Conditions

Topics: Ascorbic Acid; Humans; Intestinal Polyps; Polyps; Rectal Neoplasms