Plant Estrogens

The popular press has played up the use of plant estrogens, called phytohormones, in the treatment of menopausal symptoms.


What is a bioflavonoid?

Bioflavonoids are naturally occurring plant substances found in many brightly colored fruits and vegetables, such as cherries, oranges and other citrus, grapes, leafy vegetables, wine, and some types of red clover. Researchers are studying bioflavonoids for the treatment of a number of conditions, including the control of bleeding, hemorrhoids, and varicose veins.

Understanding Plant Hormones

So how can a plant or herb compound relieve the symptoms of hormone depletion and imbalance? The answer to that question lies in the chemical makeup of certain plants that contain phytohormones — natural substances found in some herbs and other plants that help to regulate the plant's growth. Though plant and human hormones are very different substances, phytohormones (some types are referred to as phytoestrogens) can bind to the human body's estrogen receptors; phytoestrogens may act like an estrogen on the body or like an anti-estrogen, depending upon the particular type and dosage.

Two of the most popular types of phytoestrogens used in menopausal supplements today are isoflavones (a class of bioflavonoids) and lignans. Isoflavones occur in soybeans, red clover, and (in much lower quantities) green tea, peas, pinto beans, lentils, and other legumes. Lignans occur in flaxseeds (though flaxseed oil contains only small amounts).

Natural estrogen can be extracted from some foods, such as soy; and plant hormones from the wild yam have been extracted to create a progesterone-like cream. Some tests have shown that certain plant estrogens offer some relief from hot flashes of perimenopause and menopause, if the symptoms are mild. They are the subject of a great deal of ongoing research, as the medical community continues to test the safety and efficacy of these substances and to learn how their use compares with the effectiveness of traditional MHT in the treatment of symptoms of women with diminishing levels of hormone production.


Studies are constantly changing our understanding of these natural alternatives to MHT. To stay current on the uses of these substances, read information by researchers and clinicians. Use the information you gain in this chapter as a foundation for your own research and discussions with your health care professional.

Soy and Isoflavones

Soy is a major source of a number of important vitamins and nutrients, and it is one of the primary sources for isoflavones — a type of plant estrogen. The North American Menopause Society (NAMS) has reported on a number of studies of the use of isoflavones and their role in managing menopausal health (see Appendix C). Though some of the studies have been inconclusive and work continues in this area, many health and nutrition experts believe that soy has major benefits for treating some symptoms of menopause:

  • The isoflavones in soy may help reduce LDL (“bad”) cholesterol and triglycerides while increasing HDL (“good”) cholesterol levels.

  • Many women find that soy reduces the occurrences and the severity of hot flashes.

  • One study, reported in 2001, found that women who included whole soy foods in their diet had reductions in some of the key indicators for the onset of osteoporosis. (You can read this study online at under abstract 85384 or see Appendix C for its print source in the NAMS journal.)

  • Some women report that an increased intake of soy isoflavones helps alleviate their symptoms of vaginal dryness, though no long-term study has confirmed this.

Keep in mind that the type of soy you consume has a huge impact on the amount of symptom relief you may be able to expect. For example, raw, green soybeans contain the most isoflavones — as much as 150 milligrams per 100 grams of food — whereas soy hot dogs or breakfast sausage may contain only 3 or 4 milligrams. Most medical experts recommend that if you're using soy to manage menopause symptoms that you consume at least 100 milligrams per day (for 25 to 50 milligrams of isoflavones). In the Scheiber NAMS Fellowship study mentioned earlier, the participants ate whole soy foods containing 60 mg/d every day.

Soy products aren't calorie-free, but they tend to be low in fat, high in dietary fiber, and full of vitamins and minerals. Soy milk, tofu, tempeh, and imitation meat products such as burgers, sausage, and “unchicken” cutlets are some of the readily available sources of soy. Soy sprouts, soy flour, and roasted soybeans are also rich sources of soy isoflavones.


Asian women, who often eat a diet rich in soy products, have exceptionally low rates of hip and spine fractures and endometrial, breast, and ovarian cancers. Although the Asian diet is also low in red meat and saturated animal fats, researchers are tracking down possible connections between the consumption of soy isoflavones and the low rate of hormone-related conditions.

Red clover is the second richest source of isoflavones. Though some herbal teas and compounds include red clover, it's more commonly taken as a plant extract. There is no clear evidence that red clover is effective in relieving menopausal symptoms, including hot flashes, but the studies do not report serious side effects either. Some animal studies have raised the question about red clover's effect on hormone sensitive tissues such as breast and uterine tissue, but no human studies have looked at this.


Scientists are still not clear about how the plant estrogens (phytoestrogens) found in soy and red clover operate in a woman's body. If you have had (or at high risk for) uterine, breast, or ovarian cancer, endometriosis, uterine fibroids, or if you are on hormone therapy, cancer drugs or designer estrogens (SERMs), do not use these substances without first having a serious discussion with your health care provider.

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