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. 2001 Jun;4(3):837-46.
doi: 10.1079/phn2000113.

Using Isothiocyanate Excretion as a Biological Marker of Brassica Vegetable Consumption in Epidemiological Studies: Evaluating the Sources of Variability

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Using Isothiocyanate Excretion as a Biological Marker of Brassica Vegetable Consumption in Epidemiological Studies: Evaluating the Sources of Variability

J H Fowke et al. Public Health Nutr. .

Abstract

Objective: Brassica vegetable consumption (e.g. broccoli) leads to excretion of isothiocyanates (ITC) in urine. We evaluated the consistency of ITC as a biomarker for dietary Brassica vegetable consumption across the types of vegetables and methods of preparation used in Western societies, and across consumption levels.

Design: A single-armed behavioural intervention with duplicate baseline assessment and post-intervention assessment. Urinary ITC excretion and estrogen metabolites were measured from 24-hour urine samples. Dietary intake was measured by a 24-hour recall.

Setting: The behavioural intervention facilitated daily Brassica intake among participants by providing peer support, food preparation instruction, guided practice in a teaching kitchen, and other information.

Subjects: Thirty-four healthy free-living postmenopausal women who recently had a negative screening mammogram at the University of Massachusetts Medical Center.

Results: Urinary ITC excretion and total Brassica intake followed the same pattern over the intervention. The ITC biomarker significantly predicted Brassica intake when Brassica consumption averaged about 100 g day-1, but not when Brassica consumption averaged about 200 g day-1. Urinary ITC levels were somewhat higher when more raw vegetables were consumed as compared to lightly cooked vegetables, while the types of Brassica consumed appeared to have only a small, non-significant effect on urinary ITC levels.

Conclusion: Urinary ITC excretion would be a good exposure biomarker among populations regularly consuming a vegetable serving/day, but may be less accurate among populations with greater intake levels or a wide range of cooking practices.

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