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Listen to this siteWednesday 14 July 2004
This research project aims develop an improved analytical method to quantify phytoestrogens in foods, and to determine how human exposure to dietary phytoestrogens is affected by gut microflora (bacteria).
Study Duration : April 1999 to September 2001
Contractor : Veterinary Laboratories Agency
Two main problems have hindered attempts to accurately determine human exposure to dietary phytoestrogens by measuring their levels in food. Firstly, microflora (bacteria) in the gut convert plant-derived phytoestrogens in food into alternative compounds, although these also have oestrogenic activity. Secondly, current methods to quantify plant-derived phytoestrogens in food require their release by hydrolysis of the food, usually under acidic conditions. This brings into question the extent to which the amounts of released phytoestrogens analysed are representative of the amounts of phytoestrogens available to the body after digestion of foods.
This project will investigate one group of phytoestrogens, the lignans. The oestrogenic/anti-oestrogenic activity of selected plant- and microflora-derived lignans will be examined. The production of lignans by gut microflora will also be investigated. Additionally, an improved analytical method (involving liquid chromatography with tandem mass spectrometry (LC-MS/MS)) will be developed and validated. The method will then be used to measure the concentration of lignans in a range of foods and in the milk of cattle fed a lignan-rich diet. The project will also compare the amount of lignans released from food samples by gut microflora and by acid hydrolysis.
The plant lignans secoisolariciresinol (SIL) and matairesinol (MIR) are converted in the body to the metabolites, enterolactone (EL) and enterodiol (ED). All of these compounds were found to have low oestrogenic or anti-oestrogenic potency. Lignans may therefore act only very weakly on processes involving oestrogen within the body, although it is possible that they may act through other mechanisms (e.g. as antioxidants).
Human faecal microflora were found to convert SIL to ED, and to convert MIR to a complex range of unidentified metabolites.
For all foods tested, digestion with microflora released either an equivalent or greater amount of total lignans than acid hydrolysis, which is normally used to extract lignans from food prior to analysis. Release of lignans from foods by microfloral digestion was considered to provide a more accurate representation of total lignans likely to be released from food in the gut.
An improved LC-MS-MS method for the analysis of phytoestrogens was developed and validated. Analysis of 13 types of food showed that their lignan content ranged widely, as follows: linseed (~6,000 µg/g) > > Burgen bread (~400 µg/g) > > leaf tea > rye bread > carrot, banana, red wine, lentils, cheese > full fat cream, skimmed milk, yoghurt (0.04 ng/ml).
Milk from cattle fed linseed-rich diets was found to contain similar amounts of lignans to milk from cattle fed standard diets, indicating that transfer of lignans to milk is inefficient.
The results of this project were evaluated by the Committee on Toxicity (COT) as part of its review on phytoestrogens and health .
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
Coldham, N.G. and Sauer, M.J. (2001). Identification, quantification and biological cactivity of phytoestrogens in a dietary supplement for breast enhancement. Food and Chemical Toxicology 39 , 1211-1224.
Presentations
Sauer, M.J. et al (2001). The lignan content of milk from cattle fed a linseed enriched diet, as determined by LC-MS/MS. Research in Veterinary Science 70 , Supplement A, 39 (abstract 117).
Sauer, M.J. and Coldham, N.G. (2001). Phytoestrogen content and oestrogenic activity of a hop-containing food supplement. Annual meeting of the Society for the Study of Fertility, Cambridge. Abstract series 27, p15, abstract 30.
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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