title: Plasma folate, vitamin B-6, vitamin B-12, and risk of breast cancer in women.
abstract: BACKGROUND
  B vitamins such as folate, vitamin B-6, and vitamin B-12 are coenzymes that are important for DNA integrity and stability. Deficiency in these B vitamins may promote tumor carcinogenesis.
  
  
  OBJECTIVE
  We prospectively evaluated plasma concentrations of folate, pyridoxal 5-phosphate (PLP; the principal active form of vitamin B-6), and vitamin B-12 in relation to breast cancer risk.
  
  
  METHODS
  We included 848 incident cases of invasive breast cancer identified as of 31 March 2004, and 848 individually matched control subjects from 28 345 women in the Women's Health Study aged > or =45 y who provided blood samples and had no history of cancer and cardiovascular disease at baseline in 1993. Logistic regression controlling for matching factors and other risk factors for breast cancer was used to estimate relative risks (RRs) and 95% CIs. All statistical tests were 2 sided.
  
  
  RESULTS
  Plasma concentrations of folate, PLP, and vitamin B-12 were not associated with overall risk of breast cancer. Women in the highest quintile group relative to those in the lowest quintile had multivariate RRs of 1.42 (95% CI: 1.00, 2.02) for plasma folate (P for trend = 0.21), 0.91 (95% CI: 0.63, 1.30) for plasma PLP (P for trend = 0.48), and 1.29 (95% CI: 0.92, 1.82) for plasma vitamin B-12 (P for trend = 0.18). However, higher plasma folate concentrations were moderately associated with an increased risk of developing premenopausal breast cancer (P for trend = 0.04) and for developing estrogen receptor (ER)-positive or progesterone receptor (PR)-positive breast tumors (P for trend < or = 0.06). Conversely, an inverse association was seen between plasma PLP and postmenopausal breast cancer (P for trend = 0.04).
  
  
  CONCLUSIONS
  Data from this study suggest that B vitamins, including folate, vitamin B-6, and vitamin B-12, may confer little or no reduction in overall risk of developing breast cancer. The observed positive associations of folate status with risk of developing premenopausal breast cancer and ER-positive or PR-positive tumors are unexpected. Additional research is needed to elucidate the role of folate in breast cancer development.
authors.affiliation: Division of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02215, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Lin
authors.forename: I-Min
authors.initials: IM
authors.lastname: Lee
authors.forename: Nancy R
authors.initials: NR
authors.lastname: Cook
authors.forename: Jacob
authors.initials: J
authors.lastname: Selhub
authors.forename: JoAnn E
authors.initials: JE
authors.lastname: Manson
authors.forename: Julie E
authors.initials: JE
authors.lastname: Buring
authors.forename: Shumin M
authors.initials: SM
authors.lastname: Zhang
mesh_terms: D001943:Breast Neoplasms / Q000097:blood* / Q000453:epidemiology*; D016022:Case-Control Studies; D015331:Cohort Studies; D016001:Confidence Intervals; D005260:Female; D005492:Folic Acid / Q000097:blood*; D006801:Humans; D016015:Logistic Models; D008875:Middle Aged; D017698:Postmenopause; D011446:Prospective Studies; D011960:Receptors, Estrogen / Q000378:metabolism; D011980:Receptors, Progesterone / Q000378:metabolism; D018570:Risk Assessment; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology; D014805:Vitamin B 12 / Q000097:blood*; D025101:Vitamin B 6 / Q000097:blood*
chemical_list: D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D025101:Vitamin B 6; D005492:Folic Acid; D014805:Vitamin B 12