Soy & Breast Cancer Prevention

by | Oct 12, 2020 | Articles, Cancer, Conditions, Nutrition, Prevention, Women's Health

One of the most important elements in breast cancer prevention, and in applying safe methods for hormone replacement therapy (HRT), is understanding the role of estrogen receptors and the different types of estrogen in the body.  Soy food products have a lead role in this area.

Estrogen Receptors

There are two estrogen receptors subtypes, estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ), and they are found in most every organ system in the body of both men and women.   Cancers are always involved with ERα.  Estrogens and similar chemicals will bind to ERα and stimulate tissue proliferation and growth, whereas ERβ will inhibit proliferation and prevent cancer.

Types of Estrogen

There are three types of estrogen in the body; estrone (E1), estradiol (E2) and estriol (E3).  E2 will equally bind and activate ERα and ERβ, while E1 strongly binds to ERα at a 5:1 ratio, thus causing significantly increased proliferation of breast tissue.  E3 will bind to ERβ at a 3:1 ratio thus having potential for breast cancer prevention.

Prior to menopause, women have equal ERα and ERβ expression, whereas after menopause the ratio changes showing increased ERα sites.  Furthermore, E3 is the most prevalent estrogen prior to menopause, but is replaced by E1 as the dominant estrogen after menopause.  Thus, one can appreciate that the conditions for breast cancer increase after menopause due to increased ERα expression and the increased ratio of E1.

I recommend the use of E3 when replacing women’s hormones.  The safe and effective use of E3 for treating the symptoms of menopause has been established in many studies, going back over 30 years.  There are no accounts of increased breast cancer associated with the use of E3 and in fact there are studies that show it reduces the development of breast cancer equal to that of one of the leading oncology drugs, tamoxifen, but without the side effects of tamoxifen.

E3 may act as an estrogen and an anti-estrogen.  It will bind to ERα but only for a short time and does not stimulate the cellular response like E1 and E2.  Thus, is effectively blocks E1 and E2 binding, limiting genetic transcription and preventing breast proliferation.  This is what is called a “selective estrogen blocker”.

When prescribing HRT the inclusion of E3 is a critical part of creating a safe and effective hormone balance.  At the behest of Wyeth, the pharmaceutical giant and maker of the non-bioidentical drugs premarin and provera, the FDA has tried to remove E3 from the marketplace.  This type of back-door politics between government and big business is creating a less-safe situation for women trying to safely replace their hormones, and is considered criminal by many experts in the field of HRT.

Benefits of Soy

Soy can also play a huge role in the prevention of breast cancer, but it is a misunderstood food source that needs clarification.  Soy is a phytoestrogen, which is a plant-derived chemical that is similar to estrogen.  Soy phytoestrogens are selective estrogen blockers that bind to ERβ with a 20:1 affinity over ERα and in addition they will increase the number of ERβ and decrease the ERα in cells.  More ERβ sites equal less cancer!

When talking about the benefits of soy, I am referring only to FERMENTED forms of soy, which include:

  • Tempeh a fermented soybean cake with a firm texture and nutty, mushroom-like flavor
  • Miso, a fermented soybean paste with a salty, buttery texture
  • Natto, fermented soybeans with a sticky texture and strong, cheese-like flavor
  • Soy sauce, which is traditionally made by fermenting soybeans, salt and enzymes

Fermented soy will improve estrogen metabolism by decreasing the amount of cancer promoting metabolites.  It will also increase the P53 tumor suppressor gene expression, increase the BRCA1 and BRCA2 gene expressions and decrease the HER2 gene expressions.  Women with low BRCA1 and BRCA2 gene activity have a higher rate of breast cancer, and decreasing the HER2 gene expression will slow breast cancer growth.

Older men are prone to prostate cancer, have higher estrogen levels than women of the same age, and increased ERα sites on prostate cells.  This leads to more cancer.  Again, soy will increase the ERβ sites on tumor cells in prostate as well as breast and even ovarian cancers.

Unfermented soy products, including tofu, and processed soy products like soy milk, soy cheese, soy burgers and soy ice cream, are NOT healthy.  There are thousands of studies showing unfermented soy is linked to digestive disturbances, immune dysfunction, thyroid disorders, hormone disruption and more!  The billion dollar soy industry has a million dollar disguise in the advertising designed promote the health benefits of soy.

Learn about fermented soy.  Tempeh is like a “meat substitute”, similar to the more commonly known tofu, typically cut into cubes and sautéed, baked or fried.  Miso is usually found in miso soups, often paired with rice, and is also used in marinades and sauces.  Natto is usually paired with rice and veggies, and flavored with everything from soy sauce to sugar.  Natto has the benefits of soy, mentioned above, plus it has a positive blood thinning effect, and is high in Vitamin K which helps build strong bones.

Cooking with fermented soy is not hard, but it is not well known in our culture.  The next time you shop, try something different and improve you health – add some fermented soy products to your list!


Scott Rollins, MD, is Board Certified with the American Board of Family Practice and the American Board of Anti-Aging and Regenerative Medicine.  He specializes in bioidentical hormone replacement for men and women, thyroid and adrenal disorders, fibromyalgia and other complex medical conditions.  He is founder and medical director of the Integrative Medicine Center of Western Colorado ( and Bellezza Laser Aesthetics (   Call (970) 245-6911 for an appointment or more information.

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