Original Communication
European Journal of Clinical Nutrition (2005) 59, 369–375. doi:10.1038/sj.ejcn.1602083 Published online 3 November 2004
Urinary isoflavone excretion as a compliance measure in a soy intervention among young girls: a pilot study
Guarantor: G Maskarinec.
Contributors: GM conceived the idea for the study and directed the project, the analysis, and the manuscript preparation; CO developed the nutritional education strategy; CO and YM prepared the first draft; YM performed the statistical analysis; SH coordinated the project and wrote part of the methods; RN provided nutritional consultation; AAF participated in the planning and was responsible for the analytical work; all authors reviewed the final manuscript.
G Maskarinec1, C Oshiro2, Y Morimoto1, S Hebshi1, R Novotny2 and A A Franke1
- 1Cancer Research Center of Hawaii, Honolulu, HI, USA
- 2Human Nutrition, Food and Animal Sciences, University of Hawaii at Manoa, Honolulu, HI, USA
Correspondence: G Maskarinec, Cancer Research Center of Hawaii, 1236 Lauhala St., Honolulu, HI 96813, USA. E-mail: Gertraud@crch.hawaii.edu
Received 2 June 2004; Revised 2 September 2004; Accepted 27 September 2004; Published online 3 November 2004.
Abstract
Objective:
To investigate the compliance of young girls with a soy intervention.
Design:
An 8-week dietary intervention and urine sample collection.
Setting:
Free-living girls.
Subjects:
A convenience sample of 8- to 14-y-old girls (20 started and 17 finished the study) recruited through flyers distributed to staff members and previous study participants.
Intervention:
The girls consumed one daily serving of soymilk, soy nuts, or tofu, completed 3-day food records, kept daily soy intake logs, and collected weekly urine samples.
Main outcome measures:
Compliance with the intervention was evaluated by daily soy intake logs, 3-day food records analyzed by the center's Food Composition and Food Groups Servings Databases, and weekly urinary isoflavone excretion using high-pressure liquid chromatography. The statistical analysis included paired t-tests, analysis of variance, and Spearman's rank-order correlation coefficients.
Results:
Daily soy intake logs indicated a mean intake of 6.28 servings out of a maximum of 7.0 servings per week. The food records revealed a six-fold increase in isoflavone intake during the study period (P<0.01) which was confirmed by an increase in urinary isoflavone excretion of similar magnitude (23.3–142.1 nmol/mg creatinine, P=0.02).
Conclusions:
This study demonstrated the ability of young girls to consume one daily soy serving and the usefulness of urinary isoflavones as a primary compliance measure. The high urinary isoflavone excretion levels detected in girls as compared to adult women suggest less intestinal degradation and/or greater absorption of isoflavones in nonadult populations. This finding requires further investigations into the pharmacokinetics of isoflavones.
Keywords:
nutrition, intervention, soy foods, girls, phytoestrogens, compliance