Phytoestrogens - An Exciting Alternative
Phytoestrogen seems to be the new buzzword these days when discussion turns to menopause and alternatives to hormone replacement therapy, but what are phytoestrogens and how do they affect us? The word, phytoestrogen, comes from "phyto", meaning plant, and "estrogen" due to their ability to affect estrogenic activity in the body. It is important to know that although phytoestrogens may have some similar actions to estrogens, they are not true estrogens as our bodies produce. Phytoestrogens are a group of compounds found in plants that influence our own estrogen activity. There are several types of phytoestrogens found in plants and although most are non-steroidal, some plants do contain minute amounts of steroidal estrogens that match those produced in our bodies. The following plants contain steroidal estrogens (estradiol, estrone, or estriol) in small amounts: French bean, pomegranate seed, apple seed, date palm, licorice, and rice. Most non-steroidal phytoestrogens belong to the family of compounds called phenolics. These include the flavones, flavanones, flavanols, isoflavones, lignans, and coumestans, which are found in numerous plant sources. Isoflavones, such as those in Revival Soy Protein, are especially prevalent in legumes, like soybeans, and plants such as red clover.
Phytoestrogens can either act as weak estrogens, or provide precursors to substances that affect our estrogen activity. To understand how phytoestrogens work, it is important to understand a little about how our hormones work in general.
Viewed simplistically, hormones are typically manufactured and released by various glands, organs, and tissues into our blood stream where they can then travel to target tissues. These target tissues contain receptor sites that are specific to certain hormones. When the hormones bind to the receptor sites, they can initiate an effect on the target tissue.
For example, estradiol, our body's strongest estrogen, can be released from the ovary and travel to any number of target tissues, including the breast and the uterus. At the breast, estradiol can bind to receptor sites and increase cell division; at the uterus, estradiol can cause the endometrial lining to thicken. These receptor sites are not so specific that other substances can't bind to them. However, just because a substance can bind to a receptor site doesn't mean it will have a positive effect on the target tissue. Such is the case with Tamoxifen®, a drug that is used as a treatment for breast cancer. Tamoxifen® can bind to estrogen receptors in the breast without causing an increase in cell division as an estrogen would, thereby acting as an estrogen "blocker." At the same time, it can bind to receptors in the uterus and cause proliferation (growth) of the endometrium. In other words, Tamoxifen® can have an anti-estrogenic effect on the breast, but have a pro-estrogenic effect on the uterus.
Phytoestrogens, such as Revival Soy Protein, can bind to estrogen receptors in our
bodies and have either pro-estrogenic effects, or anti-estrogenic effects on the target tissues. How it affects the tissues depends in part on how much estrogen our bodies are already producing and how saturated our receptor sites are. If our estrogen levels are low, as in menopause, empty estrogen receptor sites can be filled with phytoestrogens, which can exert a weak pro-estrogenic effect (Phytoestrogens may be anywhere from 1/100th to 1/1000th the strength of estradiol.). If our estrogen levels are high, as in some women who suffer from PMS and endometriosis, then phytoestrogens can compete with our own estrogens for binding to receptors. When the phytoestrogens are successful, they decrease overall estrogenic activity because their effect on the target tissues is less than if estradiol had been allowed to bind.
Other factors that can affect phytoestrogen activity, besides the ability to bind to receptor sites, include:
- how long a phytoestrogen remains bound to the receptor
- how rapidly it is broken down and removed from the bloodstream
- how it affects other aspects of estrogen load, such as levels of sex steroid hormone binding globulin (SHBG).
SHBG binds to hormones in the bloodstream and acts as a regulator of protein-bound, or inactive hormones.
There are hundreds of plants that contain phytoestrogens. Some of the more well known include red clover, licorice, soybeans, flaxseeds, black cohosh, and alfalfa. Historically, many of these plants have been used to regulate hormones and control fertility. Even animals have been known to graze selectively on plants to enhance or diminish fertility. Much of the early research on phytoestrogens was done with animals and interest was likely sparked by the observation that sheep that grazed too much on clover became temporarily infertile.
Recently, there has been a resurgence of phytoestrogen research as more women have demanded options to conventional hormone replacement therapy.
Some studies report positive findings on the reduction of bone loss in women supplementing with soy phytoestrogens. Other research points to a reduction of cardiovascular disease risk similar to that seen with estrogen replacement therapy (ERT). Furthermore, epidemiological studies comparing native Asian women to other cultures have suggested that the high phytoestrogen content of their diets may be responsible in part for their low rate of breast cancer, and the ease with which Asian women pass through menopause.
Certainly, more studies on women using phytoestrogens need to be done to establish both benefits and risks. However, given the bulk of information available, phytoestrogen use can be considered a relatively safe method of affecting estrogen activity given the options currently in practice.
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By power-surge.netntributor: Dr. Deborah Moskowitz
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