Phyto-oestrogen intake in Scottish men: use of serum to validate a self-administered food-frequency questionnaire in older men.
OBJECTIVE
To study dietary intake and serum concentrations of isoflavones in order to provide relative validation of isoflavone intake estimates from the Scottish Collaborative Group - Food-Frequency Questionnaire (SCG-FFQ).


METHODS
Validation study.


METHODS
Southern Scotland.


METHODS
Dietary intake of isoflavones was estimated using the semiquantitative SCG-FFQ and rank correlation and Kappa statistics were used for the relative validation of intakes against serum isoflavone concentrations in 203 male participants who were population controls in a case-control study of diet and prostate cancer.


RESULTS
The median intake of isoflavones (daidzein and genistein) was 1.0mg/day (l-QR 0.6-1.8). The median serum concentration of genistein was 33.79 nmol/l (I-QR 14.12-64.93), nearly twice that of daidzein (18.00 nmol/l, I-QR 8.26-29.45). Equol was detected in 49% of subjects; in these subjects the median was 0.67 nmol/l (I-QR 0.34-1.51). Isoflavone intake was significantly correlated with serum concentrations of daidzein (p = 0.24, P = 0.001), genistein (p = 0.26, P < 0.001) and total isoflavonoids (sum of daidzein, genistein and equol) ( p = 0.27, P < 0.001). Whereas values for weighted Kappa ranged from 0.16 (P = 0.002) for daidzein and equol combined to 0.22 (P < 0.001) for genistein.


CONCLUSIONS
These results demonstrate the suitability of the SCG-FFQ to rank usual isoflavone intakes in older Scottish men, a population observed to have low consumption of soy foods.
Heald
C L
CL
Public Health Sciences, University of Edinburgh, Medical School, Teviot Place, Edinburgh, UK. charlotte.heald@ed.ac.uk
Bolton-Smith
C
C
Ritchie
M R
MR
Morton
M S
MS
Alexander
F E
FE
D000368:Aged; D015415:Biomarkers / Q000097:blood; D003430:Cross-Sectional Studies; D004034:Diet Surveys; D060754:Equol; D019833:Genistein / Q000008:administration & dosage / Q000097:blood; D006801:Humans; D007529:Isoflavones / Q000008:administration & dosage* / Q000097:blood*; D008297:Male; D008875:Middle Aged; D048789:Phytoestrogens / Q000008:administration & dosage / Q000097:blood; D015203:Reproducibility of Results; D012606:Scotland; D013025:Glycine max / Q000737:chemistry; D011795:Surveys and Questionnaires / Q000592:standards*
C007610:4',7-dihydroxy-3,4-dihydroisoflavone; D015415:Biomarkers; D007529:Isoflavones; D048789:Phytoestrogens; D060754:Equol; C004742:daidzein; D019833:Genistein