title: An incident case-referent study on plasma enterolactone and breast cancer risk.
abstract: OBJECTIVE
  Using a nested case-referent design, we evaluated the relationship between plasma levels of the lignan enterolactone and the risk of developing breast cancer.
  
  
  METHODS
  248 cases and 492 referents were selected from three population-based cohorts in northern Sweden. Blood samples were donated at enrollment. All blood samples were stored at -80 degrees C. Cases and referents were matched for age, date of blood sample and sampling centre. Breast cancer cases were identified through the regional and national cancer registries.
  
  
  RESULTS
  Plasma enterolactone was lower among smokers in all cohorts and in subjects with BMI < 23 and BMI > 28 in one of the cohorts. Low plasma concentrations of enterolactone, below the 12.5(th) percentile (mean plasma enterolactone 2.9 nmol/l), were associated with an increased risk of breast cancer. Also, high values of plasma enterolactone, above the 87.5(th) percentile (mean plasma enterolactone 58.2 nmol/l) were significantly associated with an increased breast cancer risk among women from two cohorts with only incident cases and a higher number of pre-menopausal women. High plasma enterolactone concentrations among older women from a mammary screening project with mostly prevalent cases were associated with a non-significant slightly reduced breast cancer risk.
  
  
  CONCLUSIONS
  Very low plasma concentrations of enterolactone were associated with an increased breast cancer risk in all three cohorts. In two of the cohorts, with only incident cases, very high plasma concentrations were also associated with an increased breast cancer risk. In the third cohort with mainly screen-detected cases from a mammary screening program, high plasma enterolactone concentrations were associated with a weak decreased breast cancer risk.
authors.affiliation: Epidemiology Department of Public Health and Clinical Medicine, Umeå University, Sweden. kerstin.hulten@epiph.umu.se
authors.forename: Kerstin
authors.initials: K
authors.lastname: Hultén
authors.forename: Anna
authors.initials: A
authors.lastname: Winkvist
authors.forename: Per
authors.initials: P
authors.lastname: Lenner
authors.forename: Robert
authors.initials: R
authors.lastname: Johansson
authors.forename: Herman
authors.initials: H
authors.lastname: Adlercreutz
authors.forename: Göran
authors.initials: G
authors.lastname: Hallmans
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000097:blood*; D000375:Aging; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000517:prevention & control; D015331:Cohort Studies; D004043:Dietary Fiber / Q000008:administration & dosage; D005260:Female; D006801:Humans; D017705:Lignans / Q000097:blood*; D012016:Reference Values; D012307:Risk Factors; D011795:Surveys and Questionnaires
chemical_list: D004043:Dietary Fiber; D017705:Lignans; D015107:4-Butyrolactone; C029497:2,3-bis(3'-hydroxybenzyl)butyrolactone