Dietary intake of phytoestrogens

The dietary intake of phytoestrogens supposedly influences a variety of diseases, both in terms of beneficial and adverse effects. This report describes current knowledge on dietary intakes of phytoestrogens in Western countries, and briefly summarizes the evidence for health effects. The predominant phytoestrogens in the Western diet are the isoflavones and the lignans. The consumer groups with the highest dietary intake of isoflavones are consumers taking dietary phytoestrogen containing supplements (± 40–100 mg/d), vegan consumers (± 75 mg/d), soy-based formula fed infants (± 40 mg/d) and consumers of a traditional South East Asian diet (± 25-100 mg/d). The dietary isoflavone intake of average Western (including Dutch) consumers and vegetarians is much lower (± <1–2 mg/d and ± 3-12 mg/d, respectively). The intake of lignans is less well-studied and is estimated at 1.1 mg/d for the average Dutch consumer. However, this is likely an underestimation. Evaluation of the health implications of phytoestrogens is very complex, mainly because of insufficient data. There is concern about the use of soy-based infant formulae in view of the potential inhibition of the thyroid function. In addition, hypothyroid individuals and women with oestrogen-dependent breast disease are of potential concern. Although adverse health effects of isoflavones in the latter two subgroups have not been reported in the published literature, more research is needed that addresses the toxicological properties of soy or isoflavones for these groups specifically. To date, the effects of lignans on human health are still being investigated. RIVM report 320103002 page 3 of 29