Isoflavones for Menopause Relief – What You Need To Know

What is an isoflavone?

In order to understand how and why isoflavones are used for symptoms of menopausal relief it is useful to understand why plants make isoflavones in the first place. Though many different types of plants produce isoflavones one family of plants in particular, the bean or Fabaceae family, produces isoflavones in the highest amounts. 1 The Fabaceae family includes plants such as:

  • Soybean
  • Green bean
  • Alfalfa
  • Mung bean
  • Red clover
  • Kudzu
  • Chick pea
  • Peanut

These plants produce isoflavones as protective growth factors to interfere with the growth of harmful fungi and bacteria as well as to encourage the growth of certain types of beneficial soil micro-organisms which the bean family plants require to thrive and grow. 2 Fortunately for us humans two of these isoflavones in particular, genistein and daidzein, have very similar structures to certain human hormones and can act on some of our important enzyme systems and our human sex hormone metabolism. 3 The isoflavones genistein and daidzein are found in highest amounts in the most commonly consumed source of isoflavones for humans on the planet: soybeans.

Benefits of soy isoflavones for menopause relief

The isoflavones genistein and daidzein from soybeans have been fairly well studied for a number of different hormone conditions in humans. However, most of the research has been done on the potential benefits of soy isoflavones for menopause for two reasons.

First, scientists noticed a few decades ago that women of Asian countries, particularly those who ate large amounts of soy, tended to have far fewer symptoms of menopause and had a much lower incidence of breast cancer compared to women in the USA and Western European countries.

Second, the isoflavones genistein and daidzein are chemically most similar to the female hormone estrogen (you can read more about estrogen here and here).

While no single study has ever shown conclusively that soy isoflavones can be statistically beneficial for any symptom or effect of menopausal changes, claims have been made that soy isoflavones could potentially be benefit any of the following:

  • Hot flashes
  • Night sweats
  • Hormonal headaches
  • Joint pain
  • Memory loss
  • Mood improvement
  • Osteoporosis
  • Breast cancer

The theory on how these soy isoflavones may provide benefit for menopausal symptoms is based on their ability to act as Selective Estrogen Receptor Modulators (SERMs). 4 In basic terms this means that depending on the specific tissue the isoflavones are interacting with in the body, the isoflavones may either inhibit or stimulate estrogen-like activity. As such, they are sometimes referred to as phytoestrogens. Therefore in cases of estrogen deficiency, such as menopause, these isoflavone phytoestrogens may act as weak estrogens to improve the symptoms.

Soy isoflavones vs other herbal medicines for menopause relief

One advantage of soy isoflavones over other herbal medicines is that because of their popularity of use, the soy isoflavones genistein and daidzein have had more scientific studies conducted on them for safety and efficacy than most other herbal preparations for menopause. Another advantage of soy isoflavones over other herbal medicines for menopause relief is that, at least as food, humans in many cultures have been consuming large quantities of isoflavones for centuries with an excellent track record for safety. While there have been some studies conducted on soy isoflavones which show significant effectiveness in treating some menopausal symptoms, other studies have shown other herbal or nutrient preparations more effective than soy isoflavones. 5 Furthermore, one study has shown that while soy isoflavones are a popular remedy in the public for menopause relief, women who use them tend to report they are less effective than other complementary and alternative medicines for menopause symptoms. 6

What is the appropriate dose to take for menopausal symptoms?

As is true for all medications and supplements, the appropriate dose for any single individual will depend upon a person’s size, severity of menopausal symptoms, other health conditions, and possible other medications and supplements which the person is taking. The average daily ingestion of soy isoflavones in the female Japanese diet is around 50mg per day. 7 In general, for the average sized otherwise healthy female with moderate menopausal symptoms the daily dose most practitioners recommend is in the range of 100-200mg per day of total (genistein and daidzein) soy isoflavones. However, scientists point out that high doses of soy isoflavones (>100mg per day) are not recommended without further study to evaluate the safety in females with breast cancer. 8

Is it safe to take soy isoflavones for during menopause and what are the potential side effects?

Numerous studies have indicated that consumption of soy isoflavones in the form of food appears to be safe even in the cases of breast and prostate cancer. 9 It also appears safe for the vast majority of women who choose to take soy isoflavones in the form of supplements for menopause relief. 10 The exception would be in cases of high dose supplementation (>100mg) in breast cancer patients. Side effects, if any are experienced, tend to be very mild. At normal recommended doses, the only typical side effects tend to be intestinal such as bloating, diarrhea, or constipation. 11 These isoflavones do not seem to increase any risk for abnormal uterine growth or cancer. 12 Potentially, patients with kidney disease or those who are prone to kidney disease should avoid large amounts of soy products because soy contains high amounts of oxalates which can cause problems for those patients. Finally, there is a small amount of evidence that soy products could negatively impact the thyroid gland so patients with thyroid problems should talk to their doctor before supplementation. 13 In summary, soy isoflavones are very safe but talk to your doctor if you have any of the following:

  • Cancer
  • Kidney disease
  • Thyroid disease
  • Food allergies

Are there any new scientific studies on soy isoflavones for menopause?

Though there have been hundreds of scientific studies on soy isoflavones for menopause relief, most of them unfortunately show either no or a very small benefit for relieving menopausal symptoms. Large scientific reviews of hundreds of individual studies on soy isoflavones show conflicting results. 14 When scientists initially looked at these conflicting results compared to the very well known lower incidence of menopausal symptoms in Asian cultures which consume high amounts of soy isoflavones they were confused. Recently there have been studies conducted which are bringing new insight to this confusion.

It seems there is a certain kind of naturally occurring bacteria which grows in the intestines of some humans which metabolize the soy isoflavones genistein and daidzein when taken orally into a much more potent and active substance in the body called S-equol. It seems to be this S-equol which determines whether or not soy isoflavone supplementation is effective in relieving menopausal symptoms. While most Asian women do have this bacteria growing in their intestines, only 1/3 of women in the USA and Western Europe have this bacteria. 15 This of course begs the question, “Could we supplement women with this bacteria to in turn make soy isoflavone supplementation more effective?” Research has not yet been performed to answer this important question. Some early studies have indicated that supplementing with the soy isoflavone metabolite S-equol directly may be beneficial for relieving menopausal symptoms such as hot flashes and joint stiffness. 16

What are the views of expert menopause clinicians about soy isoflavones?

With the exceptions indicated above for safety concerns, the vast majority of practitioners who utilize complementary and alternative remedies in the treatment of menopause consider soy isoflavones to be very safe. These isoflavones are commonly included in comprehensive approaches to treat menopause. While the comprehensive treatment protocols are effective in providing menopause relief, it is not clear how much of this benefit are through the soy isoflavones alone.


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