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Listen to this siteWednesday 14 July 2004
This research project aims to measure the amounts of phytoestrogens consumed in typical vegetarian and non-vegetarian UK diets.
Study Duration : May 1997 to February 2001
Contractor : Central Science Laboratory
Phytoestrogens can be divided into a number of different groups, including the isoflavones (e.g. genistein), coumestans (i.e. coumestrol), the prenyl flavonoids (e.g. the prenylnaringenins) and the lignans. Accurate assessment of the consumption of these phytoestrogens by the UK population requires analysis of their levels in the diet.
This project will be divided into three stages. The first will analyse the levels of phytoestrogens in the diets of 101 vegetarians. The second will investigate the phytoestrogen content of a range of foods by analysing 195 Total Diet Study samples, 10 real ales and 14 additional fish samples. The third will attempt to identify components of the UK diet containing novel conjugates of the phytoestrogen genistein. Analysis will involve liquid chromatography with ultraviolet detection and mass spectrometry (LC-UV-MS).
The results of the three stages of analysis undertaken are as follows:
Stage 1 (Vegetarian diets)
The average (mean) total isoflavone content of the vegetarian diets was 5.4 mg/kg wet weight of food. This was similar in the summer and winter. Most of the diets were based on soya, which contains high levels of isoflavones. However, some of the diets were not soya-based, and these contained isoflavones from other dietary sources.
Coumestrol was not detected in any of the vegetarian diets. This indicates that the diets contained little or no legume sprouts (e.g. clover and alfalfa).
Stage 2 (Total Diet Study samples)
195 Total Diet Study Samples were analysed, which included foods such as fruit, vegetables, dairy products, meat products, cereals and bread. Important sources of isoflavones were meat products and bread, which contained up to 22 and 52 mg/kg wet weight respectively.
All of the real ale samples contained at least one isoflavone, as well as relatively high levels of prenylnaringenins (e.g. mean concentrations of 210 µg/l of 6-prenylnaringinen and 61 µg/l of 8-prenylnaringenin). This suggests that for some individuals, real ales may be a significant dietary source of one type of phytoestrogen.
Isoflavones were not detected in farmed or ocean fish fillets. However, some fish-based products were found to contain isoflavones (up to 8 mg/kg wet weight), possibly as a result of the addition of isoflavone-containing ingredients during manufacture. For example, the presence of isoflavones in seafood sticks may have been due to inclusion of soya.
Stage 3 (Novel genistein conjugates)
Chilli powder, curry powder, crushed chilli peppers, tandoori powder and garam masala were identified as significant dietary sources of unusual genistein conjugates.
A number of genistein conjugates were detected in food for the first time. One of the vegetarian diets contained genistein-4'- O -glucoside. Chilli extract contained genistein-'4'-(6"- O -acetylglucose).
Final report is available from the FSA Library and Information centre.
To obtain a copy, please contact the Enquiry Desk, Dr Elsie Widdowson Library and Information Services, Food Standards Agency tel: 020 7276 8181/8182 or email:
library&info@foodstandards.gsi.gov.uk
.
Publications
Clarke, D.B. and Lloyd, A.S. (2004). Dietary exposure estimates of isoflavones from the 1998 UK Total Diet Study. Food Addit Contam. 21, 305-316.
Contact
: For any enquiries concerning this research project, please contact the relevant Programme contact or email:
science@foodstandards.gsi.gov.uk
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