title: Equol-producing status, isoflavone intake, and breast density in a sample of U.S. Chinese women.
abstract: BACKGROUND
  Differences in ability to metabolize daidzein to equol might help explain inconsistent findings about isoflavones and breast cancer. We examined equol-producing status in relation to breast density, a marker of breast cancer risk, and evaluated whether an association of isoflavone intake with breast density differs by equol-producing status in a sample of Chinese immigrant women.
  
  
  METHODS
  Participants were 224 women, ages 36 to 58 years, enrolled in a study on diet and breast density. All women completed dietary recall interviews, underwent a soy challenge to assess equol-producing status, and received a mammogram assessed for breast density using a computer-assisted method.
  
  
  RESULTS
  In our sample, 30% were classified as equol producers. In adjusted linear regression models, equol producers had significantly lower mean dense tissue area (32.8 vs. 37.7 cm(2), P = 0.03) and lower mean percent breast density (32% vs. 35%, P = 0.03) than nonproducers. Significant inverse associations of isoflavone intake with dense area and percent density were apparent, but only in equol producers (interaction P = 0.05 for both).
  
  
  CONCLUSIONS
  These results support the possibility that equol-producing status affects breast density and that effects of isoflavones on breast density depend on ability to metabolize daidzein to equol.
  
  
  CONCLUSIONS
  Although these findings warrant confirmation in a larger sample, they offer a possible explanation for the inconsistent findings about soy intake and breast density and possibly breast cancer risk as well. The findings further suggest the importance of identifying factors that influence equol-producing status and exploring appropriate targeting of interventions.
authors.affiliation: Authors' Affiliations: Kinesiology Department, California Polytechnic State University, San Luis Obispo, California; Department of Preventive Medicine and Biometrics, Uniformed Services University of the Health Sciences, Bethesda, Maryland; Department of Food Science and Nutrition, University of Minnesota, Saint Paul, Minnesota; and Cancer Prevention & Control Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.
authors.forename: Marilyn
authors.initials: M
authors.lastname: Tseng
authors.forename: Celia
authors.initials: C
authors.lastname: Byrne
authors.forename: Mindy S
authors.initials: MS
authors.lastname: Kurzer
authors.forename: Carolyn Y
authors.initials: CY
authors.lastname: Fang
mesh_terms: D000328:Adult; D000368:Aged; D001940:Breast / Q000033:anatomy & histology / Q000378:metabolism*; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000209:etiology*; D002681:China / Q000208:ethnology; D015331:Cohort Studies; D004032:Diet; D060754:Equol / Q000096:biosynthesis* / Q000652:urine; D005260:Female; D006801:Humans; D007529:Isoflavones / Q000008:administration & dosage* / Q000493:pharmacokinetics* / Q000652:urine; D008137:Longitudinal Studies; D008875:Middle Aged; D011859:Radiography; D014481:United States
chemical_list: D007529:Isoflavones; D060754:Equol; C004742:daidzein
references.citation: J Natl Cancer Inst. 2006 Sep 20;98(18):1275-84
references.pmid: 16985246
references.citation: J Nutr. 2006 May;136(5):1347-51
references.pmid: 16614428
references.citation: Breast Cancer Res. 2008;10(2):R32
references.pmid: 18419813
references.citation: J Natl Cancer Inst. 2006 Apr 5;98(7):459-71
references.pmid: 16595782
references.citation: Breast Cancer Res. 2013 Jan 04;15(1):R1
references.pmid: 23289950
references.citation: Cancer Epidemiol Biomarkers Prev. 2005 Dec;14(12):2877-80
references.pmid: 16365004
references.citation: Breast Cancer Res Treat. 2009 Aug;116(3):587-94
references.pmid: 18821061
references.citation: Cancer Epidemiol Biomarkers Prev. 2008 Oct;17(10):2632-8
references.pmid: 18843004
references.citation: J Chromatogr B Analyt Technol Biomed Life Sci. 2002 Sep 25;777(1-2):45-59
references.pmid: 12270199
references.citation: Phys Med Biol. 1996 May;41(5):909-23
references.pmid: 8735257
references.citation: Am J Epidemiol. 1986 Jul;124(1):17-27
references.pmid: 3521261
references.citation: J Nutr. 2006 Aug;136(8):2188-93
references.pmid: 16857839
references.citation: Cancer Epidemiol Biomarkers Prev. 2008 Jan;17(1):33-42
references.pmid: 18199709
references.citation: Nutr Cancer. 2012 Aug;64(6):783-9
references.pmid: 22860715
references.citation: Cancer Epidemiol Biomarkers Prev. 1999 Jan;8(1):35-40
references.pmid: 9950237
references.citation: J Nutr Biochem. 2012 Jun;23(6):573-9
references.pmid: 21775122
references.citation: Breast Cancer Res Treat. 2007 Jul;104(1):47-56
references.pmid: 17009106
references.citation: Carcinogenesis. 2004 Jan;25(1):77-81
references.pmid: 14555615
references.citation: Cancer Epidemiol Biomarkers Prev. 2006 Apr;15(4):732-9
references.pmid: 16614116
references.citation: Epidemiol Rev. 1993;15(1):196-208
references.pmid: 8405204
references.citation: J Nutr. 2002 Dec;132(12):3577-84
references.pmid: 12468591
references.citation: Breast Cancer Res. 2001;3(2):134-41
references.pmid: 11250760
references.citation: J Natl Cancer Inst. 1997 Apr 16;89(8):531-3
references.pmid: 9106636
references.citation: Exp Biol Med (Maywood). 2005 Mar;230(3):155-70
references.pmid: 15734719
references.citation: Cancer Epidemiol Biomarkers Prev. 2002 Jul;11(7):608-13
references.pmid: 12101107
references.citation: J Nutr. 2010 Jul;140(7):1369S-72S
references.pmid: 20505018
references.citation: Lancet. 1997 Oct 4;350(9083):990-4
references.pmid: 9329514
references.citation: Cancer Prev Res (Phila). 2009 Oct;2(10):887-94
references.pmid: 19789300
references.citation: Cancer Epidemiol Biomarkers Prev. 2006 Jun;15(6):1159-69
references.pmid: 16775176
references.citation: Br J Nutr. 2012 Apr;107(8):1201-6
references.pmid: 21920062
references.citation: Eur J Med Res. 2005 Sep 12;10(9):389-94
references.pmid: 16183551
references.citation: Nutr Cancer. 2006;56(2):128-35
references.pmid: 17474857
references.citation: Cancer Epidemiol Biomarkers Prev. 2004 Jul;13(7):1156-62
references.pmid: 15247126
references.citation: Cancer Epidemiol Biomarkers Prev. 1998 Dec;7(12):1133-44
references.pmid: 9865433
references.citation: Hum Reprod Update. 2010 Nov-Dec;16(6):745-60
references.pmid: 20511398
references.citation: J Clin Oncol. 2007 Feb 20;25(6):648-55
references.pmid: 17200150
references.citation: Cancer Epidemiol Biomarkers Prev. 2002 Sep;11(9):815-21
references.pmid: 12223424
references.citation: Cancer Epidemiol Biomarkers Prev. 2008 Dec;17(12):3358-65
references.pmid: 19064551
references.citation: Phys Med Biol. 1994 Oct;39(10):1629-38
references.pmid: 15551535
references.citation: Cancer Epidemiol Biomarkers Prev. 2004 May;13(5):698-708
references.pmid: 15159299
references.citation: Int J Cancer. 2011 Jan 15;128(2):418-25
references.pmid: 20309943