This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Figueiredo, J. C. Articles by Baron, J. A. Search for Related Content PubMed PubMed Citation Articles by Figueiredo, J. C. Articles by Baron, J. A. Related Collections Epidemiology Epidemiology: Nutritional Epidemiology

Colorectal Adenomas in a Randomized Folate Trial: The Role of Baseline Dietary and Circulating Folate Levels

¹ Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California; ² Departments of Medicine and Community and Family Medicine, Dartmouth Medical School, Hanover, New Hampshire; ³ Section for Pharmacology, Institute of Medicine, University of Bergen and Haukeland University Hospital, Bergen, Norway; Departments of ⁴ Medicine and ⁵ Preventive Medicine and Biometrics, University of Colorado, Denver, Colorado; ⁶ Department of Gastrointestinal Medicine and Nutrition, The University of Texas M. D. Anderson Cancer Center, Texas; ⁷ Division of Gastroenterology/Hepatology, University of Iowa Carver College of Medicine, Iowa City, Iowa; ⁸ Department of Medicine, Minneapolis Veterans Affairs Medical Center, Minneapolis, MN ⁹ Dala Lana School of Public Health, University of Toronto and Department of Nutritional Sciences, University of Toronto, Toronto, Canada; and ¹⁰ Center for Gastrointestinal Biology and Disease, University of North Carolina, Chapel Hill, North Carolina

Requests for reprints: Jane C. Figueiredo, University of Southern California, 1450 Biggy Street #1509B, Los Angeles, CA 90033. Phone: 3234427752; Fax: 3234427787. E-mail: janefigu{at}usc.edu

The Aspirin/Folate Polyp Prevention Study is a randomized, placebo-controlled trial of aspirin use and folic acid supplementation and incidence of colorectal adenomas in individuals with a history of these lesions. The trial showed that folic acid supplementation does not prevent the occurrence of new adenomas and may increase risk. We extend these results by investigating whether the effect of folic acid treatment differed by baseline dietary and circulating folate levels. Diet and supplement use were ascertained at baseline through a food-frequency questionnaire; a blood sample was used to determine plasma and RBC folate levels. Individuals were followed for 3 years (first follow-up) and subsequently for an additional 3 to 5 years (second follow up). We used generalized linear regression to estimate risk ratios and 95% confidence limits as measures of association. There was little evidence that baseline dietary and total folate intake, and plasma and RBC folate modified the association between folic acid treatment and risk of any adenomas or advanced lesions. However, there was a protective association of the highest tertile of dietary and total intake as well as circulating folate with risk of any adenomas among those in the placebo group but no association among individuals in the folic acid group. Our findings support the idea that although moderate doses of folate may be protective compared with deficiency, at some point of sufficiency, supplementation provides no additional benefit. (Cancer Epidemiol Biomarkers Prev 2008;17(10):2625–31)