title: Urine accurately reflects circulating isoflavonoids and ascertains compliance during soy intervention.
abstract: BACKGROUND
  Isoflavonoids (IFL) may protect against chronic diseases, including cancer. IFL exposure is traditionally measured from plasma (PL), but the reliability of urine is uncertain. We assessed whether IFL excretion in overnight urine (OU) or spot urine (SU) reliably reflects IFLs in PL and the usefulness of the three matrices to determine soy intake compliance.
  
  
  METHODS
  In a randomized, double-blind, placebo-controlled soy intervention trial with 350 postmenopausal women, IFLs (daidzein, genistein, glycitein, equol, O-desmethylangolensin, dihydrodaidzein, dihydrogenistein) were analyzed by liquid chromatography/mass spectrometry in OU, SU, and PL collected at baseline and every 6 months over 2.5 years.
  
  
  RESULTS
  High between-subject intraclass correlations between all three matrices (median, 0.94) and high between-subject Pearson correlations (median r(OU-PL) = 0.80; median r(SU-PL) = 0.80; median r(OU-SU) = 0.92) allowed the development of equations to predict IFL values from any of the three matrices. Equations developed from a randomly selected 87% of all available data were valid because high correlations were found on the residual 13% of data between equation-generated and measured IFL values (median r(OU-PL) = 0.86; median r(SU-PL) = 0.78; median r(OU-SU) = 0.84); median absolute IFL differences for OU-PL, SU-PL, and OU-SU were 8.8 nmol/L, 10.3 nmol/L, and 0.28 nmol/mg, respectively. All three matrices showed highly significant IFL differences between the placebo and soy intervention group at study end (P < 0.0001) and highly significant correlations between IFL values and counted soy doses in the intervention group.
  
  
  CONCLUSIONS
  OU and SU IFL excretion reflect circulating PL IFL levels in healthy postmenopausal women accurately.
  
  
  CONCLUSIONS
  Noninvasively-collected urine can be used to reliably determine systemic IFL exposure and soy intake compliance.
authors.affiliation: Cancer Research Center of Hawaii, 1236 Lauhala Street, Honolulu, HI 96813, USA. adrian@crch.hawaii.edu
authors.forename: Adrian A
authors.initials: AA
authors.lastname: Franke
authors.forename: Sandra M
authors.initials: SM
authors.lastname: Hebshi
authors.forename: Ian
authors.initials: I
authors.lastname: Pagano
authors.forename: Naoko
authors.initials: N
authors.lastname: Kono
authors.forename: Wendy J
authors.initials: WJ
authors.lastname: Mack
authors.forename: Howard N
authors.initials: HN
authors.lastname: Hodis
mesh_terms: D000328:Adult; D000368:Aged; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007529:Isoflavones / Q000008:administration & dosage / Q000097:blood* / Q000652:urine*; D008875:Middle Aged; D008894:Milk Proteins / Q000008:administration & dosage; D009369:Neoplasms / Q000517:prevention & control; D010349:Patient Compliance; D010919:Placebos; D017698:Postmenopause / Q000097:blood / Q000652:urine; D030262:Soybean Proteins / Q000008:administration & dosage
chemical_list: D007529:Isoflavones; D008894:Milk Proteins; D010919:Placebos; D030262:Soybean Proteins