title: Vitamin C supplement intake and postmenopausal breast cancer risk: interaction with dietary vitamin C.
abstract: Experimental and epidemiologic studies have yielded conflicting results on the relation between vitamin C intake and breast cancer risk.
  
  
  
  We investigated the relation between vitamin C supplement intake and breast cancer risk while considering dietary vitamin C intake.
  
  
  
  Between 1995 and 2008, 2482 invasive breast cancer cases occurred in 57,403 postmenopausal women from the Etude Epidémiologique auprès de femmes de la Mutuelle Générale de l'Education Nationale (E3N) prospective cohort during 581,085 person-years. We estimated vitamin C intake from foods with the use of a validated food-frequency questionnaire that was sent to subjects in 1993-1995 and vitamin C supplement use via questionnaires sent in 1995, 2000, 2002, and 2005. Multivariable HRs (95% CIs) for primary invasive breast cancer were estimated with the use of Cox regression models. All statistical tests were 2-sided.
  
  
  
  Vitamin C supplement use (ever compared with never) was not associated with breast cancer risk overall; it was associated with higher breast cancer risk in women in the fourth quartile of vitamin C intake from foods (HR: 1.32; 95% CI: 1.04, 1.67) but not in other quartiles of dietary vitamin C intake (P-interaction = 0.03).
  
  
  
  We observed that vitamin C supplement use was associated with increased postmenopausal breast cancer risk in women with high vitamin C intake from foods. Our data suggest a potential U- or J-shaped relation between total vitamin C intake and postmenopausal breast cancer risk that deserves further investigation.
authors.affiliation: Center for Research in Epidemiology and Population Health (CESP), French Institute of Health and Medical Research (INSERM), University of Paris-Sud, University of Versailles Saint-Quentin-en-Yvelines, University of Paris-Saclay, Villejuif, France; and Gustave Roussy, Villejuif, France.
authors.forename: Claire
authors.initials: C
authors.lastname: Cadeau
authors.affiliation: Center for Research in Epidemiology and Population Health (CESP), French Institute of Health and Medical Research (INSERM), University of Paris-Sud, University of Versailles Saint-Quentin-en-Yvelines, University of Paris-Saclay, Villejuif, France; and Gustave Roussy, Villejuif, France.
authors.forename: Agnès
authors.initials: A
authors.lastname: Fournier
authors.affiliation: Center for Research in Epidemiology and Population Health (CESP), French Institute of Health and Medical Research (INSERM), University of Paris-Sud, University of Versailles Saint-Quentin-en-Yvelines, University of Paris-Saclay, Villejuif, France; and Gustave Roussy, Villejuif, France.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Mesrine
authors.affiliation: Center for Research in Epidemiology and Population Health (CESP), French Institute of Health and Medical Research (INSERM), University of Paris-Sud, University of Versailles Saint-Quentin-en-Yvelines, University of Paris-Saclay, Villejuif, France; and Gustave Roussy, Villejuif, France.
authors.forename: Françoise
authors.initials: F
authors.lastname: Clavel-Chapelon
authors.affiliation: Center for Research in Epidemiology and Population Health (CESP), French Institute of Health and Medical Research (INSERM), University of Paris-Sud, University of Versailles Saint-Quentin-en-Yvelines, University of Paris-Saclay, Villejuif, France; and Gustave Roussy, Villejuif, France.
authors.forename: Guy
authors.initials: G
authors.lastname: Fagherazzi
authors.affiliation: Center for Research in Epidemiology and Population Health (CESP), French Institute of Health and Medical Research (INSERM), University of Paris-Sud, University of Versailles Saint-Quentin-en-Yvelines, University of Paris-Saclay, Villejuif, France; and Gustave Roussy, Villejuif, France marie-christine.boutron@gustaveroussy.fr.
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Boutron-Ruault
mesh_terms: D000368:Aged; D001205:Ascorbic Acid / Q000008:administration & dosage* / Q000009:adverse effects; D001943:Breast Neoplasms / Q000209:etiology*; D004032:Diet; D019587:Dietary Supplements / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008875:Middle Aged; D017698:Postmenopause; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014815:Vitamins / Q000008:administration & dosage* / Q000009:adverse effects
chemical_list: D014815:Vitamins; D001205:Ascorbic Acid
keywords: breast cancer; diet; dietary supplements; interaction; prospective study; vitamin C