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Listen to this siteWednesday 22 October 2003
This research project aims to measure the absorption and metabolism of one group of phytoestrogens (the isoflavones) in humans.
Study Duration : July 1998 to July 2003
Contractor : University of Surrey
This project aims to measure the absorption and metabolism of one group of phytoestrogens (i.e. the isoflavones) in humans, and to determine whether these processes are affected by age, gender or food composition. The findings of this project will improve understanding of the fate of phytoestrogens within the human body, and will aid the design of future studies.
This project will be divided into two stages. The first stage will determine the relationship between the amount of isoflavones consumed and their levels in the blood and urine of 13 healthy pre-menopausal women. The second stage will investigate the possible effects age, gender and food composition (e.g. liquid and solid) may have on the levels of isoflavones in blood and urine following isoflavone consumption by 17 postmenopausal women and 20 men.
Isoflavones were readily absorbed from the gastrointestinal tract and reached maximal concentrations in blood within a few hours of consuming soya foods. Blood and urine levels of phytoestrogens appeared to increase in a non-linear fashion with increased consumption, suggesting that high levels of intake of soya foods may not necessarily result in an equivalent increase of blood and urine phytoestrogen levels.
The food matrix affected the absorption of phytoestrogens. They appeared to be absorbed more slowly from solid food (textured vegetable protein) than liquid food (soymilk). In addition, unconjugated phytoestrogens were more bioavailable than conjugated forms.
Some gender effects on absorption of phytoestrogens were seen, but the size of this study was not sufficient to establish if these were real differences. No effects of age on phytoestrogen absorption were observed.
It was found that there was good correlation between peak blood levels and 24-hour urine levels (urine collected over a period of 24 hours) but poor correlation between �spot� urine levels (a single urine sample) and blood levels. This is important for future clinical studies, which will require collection of 24-hour urines to monitor isoflavone intake.
The final report is available from the Agency's Information Centre.
To obtain a copy, please contact the Enquiry Desk, Information Services, Food Standards Agency (tel: 020 7276 8181/8182 or email:
infocentre@foodstandards.gsi.gov.uk
)
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