Phytoestrogens: What You May Not Know

Phytoestrogens are not actually estrogen, in contrast to a common belief. They are chemicals found in many plants that, when eaten in our food, may provide health-promoting effects. This is in contrast to xenoestrogens—plastics, industrial chemicals, herbicides, pesticides and others—that are hormone disruptors even in small amounts. Phytoestrogens in our diet have been associated with heart healthanti-viral effectsreduced incidence for certain types of cancer, and more.  That said, I’m not a huge fan of taking purified phyotestrogen supplements. As with many things, more isn’t necessarily better.

How Estrogen Works

To make sense of what phytoestrogens do in people, it’s important to have a sense of what estrogen itself does and how it does it. First, estrogen is made not just in the ovaries, but in many other places in the body, too. And there are three types of estrogen: Estradiol (involved in the menstrual cycle), estriol (functions during pregnancy) and estrone (the predominant estrogen after menopause).  I’m just going to refer to “estrogen” generally in the article to keep it simple.

Most folks know that estrogen is key in reproductive health and function, but did you know that estrogen also influences the immune system? That women are more likely than men to have an autoimmune disorder is possibly due to higher estrogen levels.  Estrogen is also important for the health of muscles, bone, heart, and blood vessels.  Estrogen even influences brain function!  A very busy hormone…

Estrogen controls certain cellular functions throughout the body by binding to and activating estrogen receptors inside the cells.  For example, estrogen may tell a cell to divide and produce more cells, as happens normally with the uterine lining or abnormally with certain forms of cancer. The estrogen receptor involved in stimulating cell growth is called “ER-alpha”.  There is another estrogen receptor called “ER-beta” that opposes ER-alpha activation, telling cells not to grow and inhibiting other functions of the more “aggressive” ER-alpha.  These two estrogen receptors have many other activities and are found along with lesser characterized estrogen receptors throughout the body.

What do phytoestrogens do?

Back to phytoestrogens. What do they actually do? Some influence metabolism of our own estrogens in a beneficial way, for instance, by reducing production of damaging estrogen breakdown products that are associated with unregulated cell growth. Some phytoestrogens actually decrease our own estrogen levels. Some bind to ER-alpha without turning it on or only activating it weakly. This may effectively reduce the binding of our own strong estrogens to the receptor—hence, an “anti-estrogenic” effect by certain phytoestrogens. Other phytoestrogens bind to ER-beta and activate its cellular growth suppressing activities and other of its functions. As mentioned, these estrogen receptors are all over the body, so you can see how phytoestrogens can potentially have broad effects! Phytoestrogens also do things not related to estrogen, for example reducing inflammation and free radical load.

There is a whole slew of phytoestrogens. Here are some of the better-known categories:

  • Isoflavones—Found in beans, peas, lentils, and other legumes, especially soy.  Genistein is an example. It binds to and activates ER-beta, the more “protective” estrogen receptor.  Isoflavones are also antioxidants and may inhibit tumor growth in various ways.
  • Lignans—High levels in flax and sesame seeds. Also in black and green tea, whole grains, legumes, nuts, and certain vegetables and fruits.  Lignans, like other phytoestrogens, have activities related to as well as independent from the estrogen receptors. They’ve been associated with heart health. A high intake of lignan-containing foods may result in a modest reduction of hormone dependent breast cancer in menopausal women.
  • Stilbenes—Found in grapes, mulberries, peanuts, and other plants.  Stillbenes are both antioxidant and anti-inflammatory.  Resveratrol, a well-known antioxidant from grape skins, is an example. It’s being studied for use related to cancer.
  • Coumestans—Found in alfalfa, soy, clover, legume sprouts and, to some extent, in other beans, broccoli, and spinach. An example is coumestrol, which supports nerve cell health in studies. Coumestans are being studied for potential anti-cancer benefits.


A note to the more science-y folks out there:  When looking at studies that say a phytoestrogen is “estrogenic,” check to see whether this was determined in a cell culture dish or test tube or in an actual living being.  The first two “in vitro” types of study often don’t correlate with what actually happens in us humans!