title: Folate, vitamin B12 and postmenopausal breast cancer in a prospective study of French women.
abstract: OBJECTIVE
  Adequate folate intake may be important for breast cancer prevention. Its protective effect may be influenced by factors associated with folate metabolism. We sought to evaluate folate intake in relation to breast cancer risk and examine whether the relation is affected by alcohol and intake of vitamin B(2) and B(12).
  
  
  METHODS
  A prospective cohort analysis of folate intake was conducted among 62,739 postmenopausal women in the French E3N cohort who had completed a validated food frequency questionnaire in 1993. During nine years' follow-up, 1,812 cases of pathology-confirmed breast cancer were documented through follow-up questionnaires. Nutrients were categorized in quintiles and energy-adjusted using the regression-residual method. Cox model-derived relative risks (RRs) were adjusted for known breast cancer determinants.
  
  
  RESULTS
  The multivariate RR for extreme quintiles of folate intake was 0.78 (95% CI: 0.67-0.90; p-trend = 0.001) [Median intake for Q(1) = 296 microg/day and Q(5) = 522 microg/day]. There was no evidence to support effect modification by alcohol or B(2) intake. The decreasing trend was most marked in women with higher folate and vitamin B(12 )intake. However, test for interaction was not statistically significant (p = 0.29).
  
  
  CONCLUSIONS
  High folate intake was associated with decreased breast cancer risk. Vitamin B(12) intake may modify this association.
authors.affiliation: Inserm, (Institut National de la Santé et de la Recherche Médicale), ERI 20, Institut Gustave Roussy, 39 rue Camille Desmoulins, F-94805, Villejuif Cedex, France.
authors.forename: Martin
authors.initials: M
authors.lastname: Lajous
authors.forename: Isabelle
authors.initials: I
authors.lastname: Romieu
authors.forename: Severine
authors.initials: S
authors.lastname: Sabia
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Boutron-Ruault
authors.forename: Françoise
authors.initials: F
authors.lastname: Clavel-Chapelon
mesh_terms: D000328:Adult; D000428:Alcohol Drinking; D001943:Breast Neoplasms / Q000453:epidemiology*; D004435:Eating; D002149:Energy Intake; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage*; D005500:Follow-Up Studies; D005602:France / Q000453:epidemiology; D006801:Humans; D008875:Middle Aged; D015999:Multivariate Analysis; D017698:Postmenopause; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012107:Research Design; D012256:Riboflavin / Q000008:administration & dosage; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014805:Vitamin B 12 / Q000008:administration & dosage*; D014803:Vitamin B Complex / Q000008:administration & dosage*
chemical_list: D014803:Vitamin B Complex; D005492:Folic Acid; D014805:Vitamin B 12; D012256:Riboflavin