Variability of phytoestrogen content in foods from different sources

Phytoestrogens are a group of non-steroidal polyphenolic plant metabolites and can mimic or modulate the action of endogenous estrogens. Phytoestrogens are considered to be beneficial for a variety of conditions, for example hormone-related cancers like breast and prostate cancer; however, epidemiological data are inconclusive and more information on exposure is required. To assess the exposure of larger cohorts or the general public, reliable data on the phytoestrogen content of food is necessary, however, this is made difficult by the variability of phytoestrogen content depending on variety, environmental factors, growth, harvesting and processing. Only limited data is available and most investigations have been conducted on soya beans in which a fourfold variation has been found. We have analysed nine different types of foods from different sources and countries of origin for their phytoestrogen content. The average detected range of phytoestrogen content between samples was threefold (95% confidence interval: 2.4; 3.4) with an average CV for isoflavones of 37% and lignans of 33%.