title: Red blood cell folate and plasma folate are not associated with risk of incident colorectal cancer in the Women's Health Initiative observational study.
abstract: The relationship between folate and colorectal cancer (CRC) risk is unclear. We investigated the association of two biomarkers of folate status, plasma folate and red blood cell (RBC) folate, with CRC risk using a nested case-control design in the Women's Health Initiative Observational Study. Postmenopausal women (n = 93,676) aged 50-79 years were enrolled in the Women's Health Initiative Observational Study (1993-1998). A fasting blood draw and extensive health, dietary and lifestyle data were collected upon enrollment. Through 2008, 988 incident CRC cases were reported and confirmed with medical records adjudication. Cases and controls were matched on age (± 3 years), enrollment date (± 1 year), race/ethnicity, blood draw date (± 6 months) and hysterectomy status. Plasma and RBC folate were determined by radio assay. Folate biomarker values were divided into quartiles, and conditional logistic regression estimated odds ratios (ORs) and 95% confidence intervals (CI) for the associations of folate with total CRC, by tumor site and by stage at diagnosis. Additional analyses examined whether risks varied across time periods corresponding to the United States folic acid fortification policy: prefortification (1994-1995), perifortification (1996-1997) and postfortification (1998). ORs for overall CRC risk comparing Q4 vs. Q1 were 0.91 (95% CI 0.67-1.24) and 0.91 (95% CI 0.67-1.23) for RBC and plasma folate, respectively. There were no changes in risk attributable to food supply fortification. These results do not support an overall association of folate with CRC risk and suggest that folic acid fortification of the US food supply did not alter the associations in these postmenopausal women.
authors: Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA.|Department of Epidemiology, School of Public Health, University of Washington, Seattle, WA.
authors: Marian L
authors: ML
authors: Neuhouser
authors: Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA.|Department of Epidemiology, School of Public Health, University of Washington, Seattle, WA.|Department of Cancer Prevention and Control, Roswell Park Cancer Institute, Buffalo, NY.
authors: Ting-Yuan David
authors: TY
authors: Cheng
authors: Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA.|Department of Epidemiology, School of Public Health, University of Washington, Seattle, WA.
authors: Shirley A A
authors: SA
authors: Beresford
authors: Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA.
authors: Elissa
authors: E
authors: Brown
authors: Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA.
authors: Xiaoling
authors: X
authors: Song
authors: Department of Nutritional Sciences, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, NJ.|Department of Medical Pathology and Laboratory Medicine, School of Medicine, University of California, Davis, Sacramento, CA.
authors: Joshua W
authors: JW
authors: Miller
authors: Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA.
authors: Yingye
authors: Y
authors: Zheng
authors: Canyon Ranch Center for Prevention and Health Promotion, University of Arizona, Tucson, AZ.
authors: Cynthia A
authors: CA
authors: Thomson
authors: Division of Preventive Medicine, University of Alabama at Birmingham, Birmingham, AL.
authors: James M
authors: JM
authors: Shikany
authors: Department of Epidemiology and Prevention, Wake Forest School of Medicine, Winston-Salem, NC.
authors: Mara Z
authors: MZ
authors: Vitolins
authors: Department of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, NY.
authors: Thomas
authors: T
authors: Rohan
authors: Department of Medical Pathology and Laboratory Medicine, School of Medicine, University of California, Davis, Sacramento, CA.
authors: Ralph
authors: R
authors: Green
authors: Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA.|Population Sciences, Huntsman Cancer Institute, Salt Lake City, UT.
authors: Cornelia M
authors: CM
authors: Ulrich
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D015179:Colorectal Neoplasms / Q000097:blood* / Q000453:epidemiology* / Q000473:pathology; D004912:Erythrocytes / Q000378:metabolism; D005260:Female; D005492:Folic Acid / Q000097:blood*; D006801:Humans; D008875:Middle Aged; D010949:Plasma / Q000378:metabolism; D017698:Postmenopause; D012307:Risk Factors
chemical_list: D005492:Folic Acid
keywords: colorectal cancer; folate; observational studies; postmenopausal women
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