What are Phytoestrogens?

Phytoestrogens sometimes called "dietary estrogens" are a diverse group of naturally occurring non steroidal plant compounds that because of their structural similarity with estradiol (17β-estradiol), have the ability to cause estrogenic or/and antiestrogenic effects. Most common phytoestrogens found in plants. The similarities, at molecular level, of estrogens and phytoestrogens, allow them to mildly mimic and sometimes act as antagonists to estrogen. Evidence is accruing that phytoestrogens may have protective action against diverse health disorders such as prostate, breast, bowel, and other cancers, cardiovascular disease, brain function disorders, menopausal symptoms and osteoporosis.

The key structural elements crucial for the estradiol-like effects are:

The phenolic ring that is indispensable for binding to estrogen receptors (ERs)

The ring of isoflavones mimicking a ring of estrogens at the receptors binding site

Low molecular weight similar to estrogens (MW=272)

Distance between two hydroxyl groups at the isoflavones nucleus similar to the occurring in estradiol

Optimal hydroxylation pattern

In addition to interaction with ERs, phytoestrogens may also modulate the concentration of endogenous estrogens by binding or inactivating some enzymes and may effect the bioavailability of sex hormones by binding or stimulating the synthesis of sex hormone binding globuline (SHBG).

In human beings, phytoestrogens are readily absorbed, circulate in plasma and are excreted in the urine. Metabolic influence is different from that of grazing animals due to the differences between ruminant versus monogastric digestive systems.

Because phytoestrogens may mimic endogenous estrogens, there has been some unsubstantiated speculation that this similarity and the consumption of high quantities of phytoestrogens may result in hormonal imbalances. However, the scientific studies which have been done do not support these concerns. The main reason why the dietary consumption of phytoestrogens is not considered a risk factor is that phytoestrogens do not appear to bioaccumulate. In some countries, phytoestrogenic plants have been used for centuries in the treatment of menstrual and menopausal problems as well as for fertility problems. The plants most used have been those that have later shown higher content of phytoestrogens i.e. Pueraria mirifica, Angelica, fennel and anise.(Source: Wikipedia.org)