title: Sources of phytoestrogen exposure among non-Asian women in California, USA.
abstract: OBJECTIVE
  We recently described the development of a comprehensive database for assessing phytoestrogen exposure in epidemiologic studies. This paper describes the first application of this database and the primary sources of phytoestrogen consumption in non-Asian women.
  
  
  METHODS
  Four hundred and forty-seven randomly selected African-American, Latina, and white women, ages 50-79 years, residing in California's San Francisco Bay Area and participating as controls in an ongoing population-based case-control study of breast cancer, were included in the present analysis. Average daily consumption of each of seven phytoestrogenic compounds was determined for each woman by combining the values from the new database with food consumption reported on a food-frequency questionnaire.
  
  
  RESULTS
  Phytoestrogens in the non-Asian Bay Area diet appear to come primarily from: (1) traditional soy-based foods (e.g. tofu and soy milk); (2) "hidden" sources of soy (e.g. foods containing added soy protein isolate, soy concentrate, or soy flour, e.g. many brands of doughnuts and white bread); and (3) a variety of foods which contain only low to moderate amounts of phytoestrogens per 100 grams but which are frequently consumed (e.g. coffee and orange juice).
  
  
  CONCLUSIONS
  In the absence of a comprehensive assessment of various phytoestrogens in a wide variety of foods, epidemiologic studies could suffer from the effects of uncontrolled confounding by unmeasured sources of phytoestrogen exposure potentially leading to biased estimates of effect and misinterpretation of findings.
authors.affiliation: Northern California Cancer Center, Union City 94587, USA. phornros@nccc.org
authors.forename: P L
authors.initials: PL
authors.lastname: Horn-Ross
authors.forename: M
authors.initials: M
authors.lastname: Lee
authors.forename: E M
authors.initials: EM
authors.lastname: John
authors.forename: J
authors.initials: J
authors.lastname: Koo
mesh_terms: D001741:Black or African American; D000368:Aged; D002140:California / Q000453:epidemiology; D019992:Databases as Topic; D004032:Diet / Q000706:statistics & numerical data*; D004968:Estrogens, Non-Steroidal / Q000032:analysis*; D005260:Female; D006630:Hispanic or Latino; D006801:Humans; D007529:Isoflavones; D008875:Middle Aged; D048789:Phytoestrogens; D028321:Plant Preparations; D010945:Plants, Edible; D011795:Surveys and Questionnaires; D044465:White People; D016387:Women's Health
chemical_list: D004968:Estrogens, Non-Steroidal; D007529:Isoflavones; D048789:Phytoestrogens; D028321:Plant Preparations