title: Plasma vitamin B6 and the risk of colorectal cancer and adenoma in women.
abstract: BACKGROUND
  Vitamin B6, whose main circulating form is pyridoxal 5'-phosphate (PLP), is important in one-carbon metabolism, which is critical for DNA synthesis and DNA methylation, both of which are potentially involved in colorectal carcinogenesis. However, no previous epidemiologic studies have directly evaluated the association of plasma PLP with risk for colorectal neoplasia.
  
  
  METHODS
  We conducted a prospective nested case-control study of 32,826 female participants of the Nurses' Health Study who provided blood specimens in 1989-1990. From 1989-1990 to 2000 (1998 for adenoma), a total of 194 incident colorectal cancer cases and 410 incident colorectal adenoma cases were identified from medical records. Multivariable-adjusted relative risks (RRs) and 95% confidence intervals (CIs) were calculated using logistic regression. All statistical tests were two-sided.
  
  
  RESULTS
  A suggestive inverse association was observed between plasma PLP concentration and risk for colorectal cancer when comparing the highest quartile versus the lowest (RR = 0.56, 95% CI = 0.31 to 1.01; P(trend) = .07); the association of PLP concentration with colon cancer was statistically significant (RR = 0.42, 95% CI = 0.21 to 0.85; P(trend) = .02). Both associations were statistically significant and stronger after controlling for intakes of folate, of multivitamins, and of methionine (for colorectal cancer, RR = 0.48, 95% CI = 0.25 to 0.92; P(trend) = .03; for colon cancer, RR = 0.38, 95% CI = 0.18 to 0.80; P(trend) = .01). Total vitamin B(6) intake was also statistically significantly inversely associated with colon cancer risk (RR = 0.51, 95% CI = 0.27 to 0.97; P(trend) = .007). There was a suggestive inverse association between plasma PLP concentration and advanced distal colorectal adenoma (RR = 0.65, 95% CI = 0.37 to 1.11; P(trend) = .08), but the association with early-stage adenoma was weaker (RR = 0.85, 95% CI = 0.52 to 1.38; P(trend) = .52).
  
  
  CONCLUSIONS
  Our results suggest that vitamin B6 may be inversely associated with risk of colorectal neoplasia.
authors.affiliation: Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA. esther.wei@channing.harvard.edu
authors.forename: Esther K
authors.initials: EK
authors.lastname: Wei
authors.forename: Edward
authors.initials: E
authors.lastname: Giovannucci
authors.forename: Jacob
authors.initials: J
authors.lastname: Selhub
authors.forename: Charles S
authors.initials: CS
authors.lastname: Fuchs
authors.forename: Susan E
authors.initials: SE
authors.lastname: Hankinson
authors.forename: Jing
authors.initials: J
authors.lastname: Ma
mesh_terms: D000236:Adenoma / Q000097:blood* / Q000453:epidemiology* / Q000517:prevention & control; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D015179:Colorectal Neoplasms / Q000097:blood* / Q000453:epidemiology* / Q000517:prevention & control; D016001:Confidence Intervals; D005260:Female; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D008875:Middle Aged; D015999:Multivariate Analysis; D009726:Nurses; D016017:Odds Ratio; D011446:Prospective Studies; D011732:Pyridoxal Phosphate / Q000097:blood*; D012107:Research Design; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology; D025101:Vitamin B 6 / Q000097:blood
chemical_list: D011732:Pyridoxal Phosphate; D025101:Vitamin B 6