title: A semiquantitative food frequency questionnaire is a valid indicator of the usual intake of phytoestrogens by south Asian women in the UK relative to multiple 24-h dietary recalls and multiple plasma samples.
abstract: We investigated the relative validity of an interview-administered FFQ to estimate phytoestrogen intake among South Asian women in the UK. A population-based sample of 108 healthy South Asian women completed random repeated monthly 24-h recalls [with a subsample (n = 58) also providing multiple plasma samples] over a period of 1 y followed by administration of the FFQ. The FFQ produced slightly higher estimates of phytoestrogen intake than the 24-h recalls, but the percentage of women classified into the same +/- 1 quartile by the 2 methods was high for all phytoestrogens (from 81 to 94%) with only a small percentage (<5%) being misclassified into extreme opposite quartiles. Energy-adjusted Spearman correlations coefficients between the estimates obtained by the FFQ and the 24-h recalls were 0.55 for genistein, 0.60 for daidzein, 0.70 for secoisolariciresinol, and 0.63 for matairesinol (all P < 0.001). Spearman correlation coefficients between the FFQ estimates and plasma levels were 0.21 (P = 0.12) for genistein, 0.32 (P = 0.02) for daidzein and 0.10 (P = 0.43) for enterolactone; the corresponding values for the 24-h recalls compared with plasma levels were 0.43 (P < 0.001), 0.40 (P = 0.002), and 0.08 (P = 0.50), respectively. The method of triads was used to estimate the validity coefficients (VCs) between the estimates provided by each assessment method and "true intake." The FFQ had the highest VC for lignans (0.91 vs. 0.73 for 24-h recalls and 0.11 for plasma samples) and satisfactory VCs for both genistein (0.46 vs. 0.95 and 0.45, respectively) and daidzein (0.67 vs. 0.83 and 0.45, respectively). This FFQ is thus a relatively valid tool with which to estimate phytoestrogen intake among South Asian women in the UK.
authors.affiliation: Department of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK.
authors.forename: Dee
authors.initials: D
authors.lastname: Bhakta
authors.forename: Isabel
authors.initials: I
authors.lastname: dos Santos Silva
authors.forename: Craig
authors.initials: C
authors.lastname: Higgins
authors.forename: Leena
authors.initials: L
authors.lastname: Sevak
authors.forename: Tashmin
authors.initials: T
authors.lastname: Kassam-Khamis
authors.forename: Punam
authors.initials: P
authors.lastname: Mangtani
authors.forename: Herman
authors.initials: H
authors.lastname: Adlercreutz
authors.forename: Anthony
authors.initials: A
authors.lastname: McMichael
mesh_terms: D001210:Asia, Southeastern; D044466:Asian People; D001774:Blood Chemical Analysis; D049628:Body Size; D016022:Case-Control Studies; D003431:Cross-Cultural Comparison; D015930:Diet Records; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D008568:Memory; D008875:Middle Aged; D048789:Phytoestrogens / Q000032:analysis*; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D006113:United Kingdom
chemical_list: D048789:Phytoestrogens