Expert Views :: Phytoestrogens in Human Health
Jennifer E. Fox,

The importance of phytoestrogens in human health has been the focus of much research in our Environmental Endocrinology Laboratory as well as in many others laboratories in recent years. While most studies have concentrated on the effects of phytoestrogens on human and animal endocrine function, little is known about how humans and synthetic chemicals in the environment may affect plants and phytoestrogens. Many chemicals in the environment are able to affect estrogen signaling and exposed animals, laboratory cell lines, and humans; these chemicals are termed endocrine disrupting chemicals (EDCs). For more information on the background of EDC research visit our website Environmental Estrogens and Other Hormones. Included in the EDC category are many organochlorine pesticides such as DDT, herbicides, plastics by-products, and polychlorinated biphenyls (PCBs).

Although humans may use phytochemicals from soy or alfalfa for medicinal or health purposes, plants produce these chemicals for their own benefit. For example, many phytochemicals are necessary for producing color in fruits or warding off predatory insects. Leguminous plants such as soybeans and alfalfa use phytochemicals to signal to soil bacteria, which are able to then inhabit their roots and fix atmospheric nitrogen into a useable fertilizer for the plants. This interaction is called symbiotic nitrogen fixation and is crucial to leguminous plants. Phytochemicals, produced by soybeans and alfalfa, are used to communicate with and attract beneficial soil bacteria. If these phytochemicals are not recognized by the soil bacteria, nitrogen fixation will not take place.

My research has focused on the effects of EDCs on phytochemical signaling between these leguminous plants and nitrogen-fixing soil bacteria. Since phytoestrogens are able to disrupt or affect estrogen signaling in vertebrates and EDCs are also able to disrupt estrogenic signaling, I have hypothesized that these same EDCs may disrupt phytochemical signaling from the plant to the soil bacteria. I have tested many different types of EDCs and found that some do interrupt bacterial recognition and response to phytochemical agonists produced by their host plant. My latest findings, Nature, 413,  127-128 (2001), have shown that many EDCs inhibit soil bacterial response to phytochemicals in a concentration dependent manner. My future research focuses on the impact of this interruption of phytochemical-bacterial communication on the actual plant and nitrogen fixation within treated plants.