Risks: Nutritional and toxicological considerations of phytoestrogens

Abstract

The term „phytoestrogens (PE)“ defines a structurally diverse class of natural compounds that possess the ability to alter various components of the endocrine system (e.g. receptors, metabolizing enzymes, transporters) and potentially induce adverse health effects in exposed individuals and populations. Particularly nuclear receptors which include steroid receptors are known to bind many of such substances mimicking or antagonizing the effects of estrogens or androgens and this may have substantial impacts for female and male fertility. By the example of the isoflavone genistein (Gen) a risk assessment with focus on fertility and hormone dependent cancer is performed. Soy products contain significant amounts of Gen. Those products are used to improve health. i.e. they are consumed as drugs to ameliorate for example psycho-vegative climacteric complaints or even to prevent cancer. Another exposure to Gen results from the intake of processed soy products which often are supplemented with isoflavones. An increasing number of babies are fed with industrially-prepared formula milk or vegetable based puree, however the effects of PEs contained in these products on babies' health remain unclear. Data from animal experiments provide convincing evidence that a prepubertal exposure to PEs may not affect the onset of reproductive function but reduces fertility outcome and accelerates reproductive ageing. In contrast to these adverse effects of PEs prepubertal exposure followed by a life-long intake of PEs at concentrations, naturally present in vegetarian food, reduces the risk of steroid dependent cancer. Taken together, to perform a reliable assessment of the magnitude of any adverse effect of PEs on the health of individuals or populations improved experimental and epidemiological approaches are required to model demographic effects of PEs on fertility and the risk of cancer.