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The Light And Dark Sides Of Soy - How Soy Can Benefit Menopause Symptoms

Menopause is the official end of a woman’s menstrual cycle. Women can transition into menopause as early as their mid-30s, but the change typically happens around age 50. A diagnosis is made once 12 months have passed without a menstrual period.

Naturally declining estrogen levels will lead women to experience a number of uncomfortable menopause symptoms, including vaginal dryness, mood swings, reduced sex drive, fatigue, heart palpitations, osteoporosis, and more.

Hormone-replacement therapy (HRT), a popular treatment for easing symptoms, has been found to put great stress on the liver while also increasing the risk of blood clots; stroke; heart disease; urinary incontinence; dementia and memory loss; and cancers such as breast, lung, or colon cancer.

As a result, many women have stopped taking HRT and instead are searching for natural strategies, such as soy and soy isoflavones, to alleviate menopausal symptoms.


Can Soy Help Menopause Symptoms?

Isoflavones are chemical compounds found in soy and other plants that are phytoestrogens, or plant-derived estrogens. They have a chemical structure that is similar to the estrogens naturally produced by the body, but their effectiveness as an estrogen has been estimated to be much lower than true estrogens. Two types of isoflavones, genistein and daidzein, are found in soy beans, chick peas, and lentils, and are considered to be the most potent estrogens of the phytoestrogens. Still, the estrogen potency of phytoestrogens is estimated to be only 1/1000 to 1/100,000 of that of estradiol, natural estrogen.

Some studies have shown that these compounds can help relieve the symptoms of menopause, and many women do use soy products to help control the symptoms of menopause. In particular, women who have had breast cancer and do not want to take hormone therapy (HT) with estrogen sometimes use soy products for relief of menopausal symptoms. However, some phytoestrogens can actually have anti-estrogenic properties in certain situations, and the overall risks of these preparations have not yet been determined. For example, researchers have shown that long-term use of phytoestrogens in postmenopausal women led to an increase in endometrial hyperplasia (overgrowth of the tissues lining the uterus) which can be a precursor to cancer. Further research is needed to fully characterize the safety and potential risks of phytoestrogens.There is also a perception among many women that these products are "natural" and therefore safer than HT, but this has never been proven scientifically.


The Light And Dark Sides Of Soy


Today, it's all but impossible to find a health-related magazine or TV show that doesn't shout out the benefits of soy foods for the prevention of menopause symptoms, breast and other cancers, heart disease and osteoporosis. In the past decade, the soy industry has poured hundreds of millions of dollars into the research, marketing and advertising of soy foods, and it has been well rewarded for its efforts. However, while we agree that certain soy foods, eaten in moderation, can be a healthy addition to the diet, we believe that women who are eating soy with every meal, or even every day, may be damaging their health. 

Are you a woman who eats soy, drinks soy milk, munches edamame or takes soy isoflavones as a supplement thinking it will help you with hot flashes, night sweats and other inconvenient and uncomfortable menopausal or perimenopausal symptoms?
As it turns out, the risks of soy to hormone health are significant. It is not the middle aged health panacea for women that is is promoted to be! If your doctor is harping on the benefits of soy to alleviate your discomfort, find a new doctor!

Studies show that even small amounts of unfermented soy has the potential to disrupt female hormonal balance. This amount is only 45 mg isoflavones – a bit more than a single cup of soymilk!

Studies Showing That Soy Messes Up Your Hormones


  • A 1991 study found that eating only 2 TBL/day of roasted and pickled soybeans for 3 months to healthy adults who were receiving adequate iodine in their diet caused thyroid suppression with symptoms of malaise, constipation, sleepiness, and goiters (Nippon Naibunpi Gakkai Zasshi 1991, 767: 622-629)!Still think munching on edamame is a healthy habit?

  • Six premenopausal women with normal menstrual cycles were given 45 mg of soy isoflavones per day.  This is equivalent to only 1-2 cups of soy milk or 1/2 cup of soy flour!   After only one month, all of the women experienced delayed menstruation with the effects similar to tamoxifen, the anti-estrogen drug given to women with breast cancer (American Journal of Clinical Nutrition 1994 Sep;60(3):333-340).

  • Dietary estrogens in the form of soy foods were found to have the potential to disrupt the endocrine system with the effects in women similar to taking the breast cancer drug tamoxifen (Proceedings of the Society for Experimental Biology and Medicine 1995 Jan;208(1):51-9).

  • Estrogens consumed in the diet even at low concentrations were found to stimulate breast cells. The effect is much like the pesticide DDT which increases enzymatic activity leading to breast cancer. (Environmental Health Perspectives 1997 Apr;105 (Suppl 3):633-636).

  • The soy isoflavones genistein and daidzein appear to stimulate existing breast cancer growth indicating risk in consuming soy products if a woman has breast cancer. (Annals of Pharmacotherapy 2001 Sep;35(9):118-21).


Benefits of Soy Isoflavones for Menopause


Studies also show that whole soy products are safe for women who had estrogen-receptor positive breast cancer. Soy isoflavones have also been found to play a role in bone formation.

A study published in the Journal of Hygiene Research in 2010 found that menopausal symptoms and estrogen were improved in women during pre-menopause with a daily dosage of 120 mg of soy isoflavones. In the long-term, this might also reduce the risk of cancer.

A 1990 study of 25 menopausal women published in the British Medical Journal found that vaginal maturation value (MV) increased after two weeks of a soy-rich diet, but not from other phytoestrogen-rich foods like red clover or linseed.

The MV is a method used to measure the estrogenization of the vaginal epithelium, which includes factors like vaginal pH, vaginal moisture, vaginal mucosa, vaginal elasticity, and vaginal fluid volume.

Another study published in Climacteric: The Journal of International Menopause Society in 1998 suggests that phytoestrogens in soy may be used to alleviate some menopausal symptoms. That being said, the rate of hot flashes did not change in this experiment.

However, a 2007 study published in the Journal of Women’s Health discovered that consumption of roasted soybeans three to four times daily would reduce hot flashes and improve menopausal symptoms in general.

For the eight-week study, 60 women with menopause changed their diet to include a half-cup of roasted soybeans divided into three or four portions spaced throughout the day with a total of 25 g of soy protein and 101 mg of aglycone isoflavones.

A review published in the Cochrane Database of Systematic Reviews in 2013 concluded that supplements with mostly genistein would significantly reduce hot flash frequency; however, the same was not true in studies that featured soy isoflavone extracts, dietary soy, or red clover extracts.

At the same time, a systematic review published in the journal Menopause in 2012 found that 30 mg to 80 mg daily of supplemental soy isoflavone extract for six weeks to one year resulted in a 17.4% reduction in hot flash frequency in 13 placebo-controlled trials that featured 1,196 menopausal women.

Some researchers have concluded that since studies have shown conflicting results in a small number of studies, the efficacy of soy-based foods for menopausal symptoms is still unclear.


Soy Isoflavones May Benefit Postmenopausal Health Issues


  • Osteoporosis
    Short-term studies have found that increasing soy intake through soy isoflavones can improve markers of bone formation and resorption or attenuated bone loss in postmenopausal women.

    Some researchers believe that the effect of soy isoflavones on bone health may be dependent on whether the person is able to produce the daidzein metabolite equol. But a study published in the American Journal of Clinical Nutrition in 2015 found that soy isoflavone supplementation could increase calcium retention capacity in postmenopausal women regardless of equol-producing capacity.

  • Cardiovascular Disease
    Soy isoflavones might also reduce the risk of cardiovascular disease, including stroke, heart attacks, and coronary heart disease.

    A study published in the journal Circulation in 2007 found that soy isoflavone intake was associated with a 65% decreased risk of ischemic stroke and 63% lower risk of heart attack in Japanese women between the ages 40 to 59 years old.

    A meta-analysis of 64,915 Chinese women between ages 40 and 70 years old published in the Journal of Nutrition in 2003 found a relationship between soy food consumption and a reduced risk of coronary heart disease after a 2.5-year follow-up.

  • Dementia
    A study published in the journal Menopause in 2015 found that isoflavone intake was associated with better scores in a processing speed test, but worse scores in a verbal memory test in late pre-menopausal and postmenopausal Asian women.

    A meta-analysis of 10 randomized controlled trials also published in the journal Menopause in 2015 found a significant improvement in the pooled summary of cognitive function tests in postmenopausal women who supplemented with 60 mg to 160 mg of soy isoflavones daily for six to 30 months.

  • Cancer
    High consumption of soy isoflavones in Asian countries may contribute to the reduction of breast cancer risk. However, observational studies in Western populations found that the average soy isoflavone intake was low, and therefore not associated with a reduced breast cancer risk.

    Research published in the journal Nutrition and Cancer in 2009 shows that lifelong isoflavone exposure may be needed to reduce the risk of developing breast cancer later in life.

    A meta-analysis of 9,514 breast cancer survivors followed for 7.4 years, published in the American Journal of Clinical Nutrition in 2014, found that high soy intake was linked with a significant 25% reduction in recurrence of breast tumors in postmenopausal women.

    That being said, not all of the research is positive.

    For instance, lower circulating estrogen concentrations have been linked to a reduced breast cancer risk in postmenopausal women. However, a meta-analysis published in the journal Advances in Experimental Medicine and Biology in 2009 found no beneficial effect of soy isoflavone supplementation on circulating concentrations of estrogenic hormones, estrone, estradiol, and sex hormone-binding globulin.
    As for other cancers, a meta-analysis and systematic review published in the journal Medicine in 2015 also suggests that greater consumption of isoflavone foods is linked with a 19% decreased risk of uterine cancer in postmenopausal women.

    Research published in the Journal of National Cancer Institute in 2012 also found that isoflavones were linked with a 34% lower risk of uterine cancer.

Amount of Soy Isoflavones to Take for Menopause

What’s the correct dosage of soy isoflavones to take for menopausal symptoms and postmenopausal health issues?

  • 40 mg to 80 mg daily to lower hot flashes
  • 50 mg daily for bone health
  • 40 mg to 80 mg daily to strengthen blood vessels and improve blood pressure
  • 50 mg daily for cholesterol reduction


Soy Side Effects: 


Although there are some benefits of soy and soy isoflavones, there are also some precautions to consider before consuming them.

For starters, soy is one of the most common genetically modified foods in the world, and that is why certified GMO-free and organic soy products are best. The phytoestrogens in soy products like tofu can have an estrogen-like effect on the body that blocks normal estrogen production, and this is linked to breast cancer.

Soy also contains goitrogenic compounds like the soy isoflavone genistein, which is considered a thyroid hormone blocker that can interfere with thyroid hormone production and cause hypothyroidism.

Soy products are also high in anti-nutrients like phytates, which can block mineral absorption and cause deficiencies in zinc, iron, and calcium. Other soy anti-nutrients include saponins, lectins, oligosaccharides, oxalates, and protease inhibitors.

Soy has also been negatively linked to dementia and Alzheimer’s disease. Research shows that people who ate tofu in mid-life had reduced cognitive function during later stages of their lives.

A study published in the journal Dementia and Geriatric Cognitive Disorders in 2008 found that eating high amounts of tofu was linked with worse memory, while consumption of higher amounts of tempeh was shown to improve memory.

The B12 analogs in soy resemble vitamin B12, which is why soy foods like tofu can lead to vitamin B12 deficiency, especially in vegans and vegetarians. Soy products also contain strong enzyme inhibitors, which can block the activity of pancreatic enzyme trypsin and other proteolytic enzymes needed for protein digestion.

Although some studies support soy for heart health, research published in the Journal of Clinical Investigation in 2006 suggests that a soy-rich diet has negative effects on heart health.

The study found that mice fed a soy-based diet exhibited significantly worse hypertrophic cardiomyopathy (HCM) than mice given a soy-free diet. HCM is a condition where the heart muscle becomes thick, making it more difficult for the heart to pump blood.

Soy is also one of the top allergic foods. The phytoestrogens in soy may also interfere with breast cancer drugs tamoxifen (“Nolvadex”) and raloxifene (“Evista”), which are used to prevent and treat osteoporosis in postmenopausal women.

Furthermore, soy may interact with estrogen medications and other hormonal drugs. The food should also be avoided in people taking antidepressants like MAOIs (monoamine oxidase inhibitors) tranylcypromine (“Parnate”) and phenelzine (“Nardil”).

Soy may also increase bleeding, especially if you are on blood thinners like clopidogrel (“Plavix”) or warfarin (“Coumadin”).

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