Urine accurately reflects circulating isoflavonoids and ascertains compliance during soy intervention.
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.
Franke
Adrian A
AA
Cancer Research Center of Hawaii, 1236 Lauhala Street, Honolulu, HI 96813, USA. adrian@crch.hawaii.edu
Hebshi
Sandra M
SM
Pagano
Ian
I
Kono
Naoko
N
Mack
Wendy J
WJ
Hodis
Howard N
HN
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
D007529:Isoflavones; D008894:Milk Proteins; D010919:Placebos; D030262:Soybean Proteins