Phytoestrogen content of fruits and vegetables commonly consumed in the UK based on LC–MS and 13C-labelled standards

Phytoestrogens are a group of non-steroidal secondary plant metabolites with structural and functional similarity to 17β-oestradiol. Urinary and plasma phytoestrogens have been used as biomarkers for dietary intake, however, this is often not possible in large epidemiological studies or to assess general exposure in free-living individuals. Accurate information about dietary phytoestrogens is therefore important but there is very limited data concerning food contents. In this study, we analysed the phytoestrogen (isoflavone, lignan and coumestrol) content in more than 240 different foods based on fresh and processed fruits and vegetables using a newly developed sensitive method based on LC–MS incorporating 13C3-labelled standards. Phytoestrogens were detected in all foods analysed with a median content of 20 μg/100 g wet weight (isoflavones: 2 μg/100 g; lignans 12 μg/100 g). Most foods contained less than 100 μg/100 g, however, 5% of foods analysed contained more than 400 μg/100 g, in particular soya-based foods and other legumes. The results published here will contribute to databases of dietary phytoestrogen content and allow the more accurate determination of phytoestrogen exposure in free-living individuals.