Objective: To analyse 75 cereals and three soy flours commonly eaten in Europe for the phytoestrogens daidzein and genistein.
Design: The phytoestrogens daidzein and genistein were extracted from dried foods, and the two isoflavones quantified after hydrolytic removal of any conjugated carbohydrate. Completeness of extraction and any procedural losses of the isoflavones were accounted for using synthetic daidzin (7-O-glucosyl-4'-hydroxyisoflavone) and genistin (7-O-glucosyl-4'5-dihydroxyisoflavone) as internal standards.
Setting: Foods from the Cambridge UK area were purchased, prepared for eating, which included cooking if necessary, and freeze dried. Three stock soy flours were also analysed.
Results: Eighteen of the foods assayed contained trace or no detectable daidzein or genistein. The soy flours were rich sources, containing 1639-2117 mg/kg. The concentration of the two isoflavones in the remaining foods ranged from 33 to 11,873 micro g/kg.
Conclusion: These analyses will supply useful information to investigators determining the intake of phytoestrogens in cereal products in order to relate intakes to potential biological activities.
Sponsorship: This work was supported by the United Kingdom Medical Research Council, Ministry of Agriculture Fisheries and Food (contract FS2034) and the United States of America Army (contract DAMD 17-97-1-7028).