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Soy and Equol: How Soy Reduces Breast Cancer Risk

soy consumption and breast cancer

Metastatic Breast Cancer reduced by soy in some. Why not others?

Research from Harvard University and Korea’s National Cancer Control Institute has confirmed that not only can soy consumption significantly decrease the risk of breast cancer: It can also reduce the risk of breast cancer among those with a genetic mutation that increases their likelihood of breast cancer.

The question remains whether this effect is only upon Asian women.

Cancer Study from Korea

An ongoing research project that has been studying 1,967 breast cancer patients since 2007 is called the Korean Hereditary Breast Cancer Study (KOHBRA). The KOHBRA study has confirmed in the past few years that the BRCA1 and BRCA2 gene mutation significantly increases the risk of breast cancer.

They have found that almost a quarter of breast cancer cases with a family history have the BRCA mutation, and 22 percent of those with bilateral breast cancer have the gene mutation. Furthermore, about a third of those patients who contract both breast and ovarian cancer have the genetic mutation.

Soy Consumption reduces risk of genetic version too

Previous research has confirmed that increased soy consumption significantly reduces breast cancer. But this study aimed to see whether soy consumption would also decrease the risk of breast cancer among carriers of the gene mutation as well.

The research found that increased soy consumption reduced the risk of breast cancer among BRCA carriers by over 60 percent. Furthermore, increased meat consumption doubled the risk of breast cancer among both BRCA carriers and non-BRCA carriers alike.

The researchers concluded:

“Our study suggests that soy product consumption is associated with lower breast cancer risk and it had an interaction with BRCA mutation.”

Other studies confirm these findings – but only among Asians?

As mentioned, the association between soy consumption and decreased breast cancer risk has also been found in other studies.

For example, in a U.S. National Cancer Institute study of 1,563 adult American women of Chinese, Japanese and Filipino descent, researchers found that those with greater soy consumption reduced the risk of breast cancer.

They found that more childhood consumption of soy decreased breast cancer incidence by 60 percent, and more adult consumption decreased breast cancer risk by 24 percent.

However, this effect appears to be limited to Asian women. In a study of almost 3,000 non-Asian women of different descents from the Northern California Cancer Center, increased soy consumption did not have any effect upon the breast cancer risk of women.

Soy and Equol Producers

The assumption that soy is only preventative among Asian women does not reveal the real issue. The real issue is related to the production of equol. For example, research from Australia found that those women with the highest levels of equol in the blood had reduced cancer risk by nearly 75 percent.

Other research found that soy’s (and other isoflavone containing foods) ability to reduce breast cancer risk was significantly greater among women who produce more equol.

And more recent research has found that increased soy consumption does not reduce breast cancer risk without increased equol production.

This difference was illustrated clearly in a study from the Italian National Cancer Institute. This study identified equol producers among 325 women who underwent mammograms. The study found that 30% of the women were equol producers and 19% of the women regularly ate soy or a soy supplement.

The research found that equol producers who ate soy had significantly reduced mammogram densities (average 31% compared to 39%), while increased soy intake among non-equol producers resulted in a higher average mammogram density than those who ate less soy.

This means, at least among Western women, that one must be a equol producer in order to gain the advantages of eating soy.

How to increase equol production

And the key to equol production? Probiotics. It is our intestinal bacteria that produce equol in the presence of isoflavones, notably diadzein.

This may well also explain the reason why Asian women – who may have a different microbiome likely because Western medicine has pushed the use of antibiotics ahead of Asian countries. Western medicine has led the charge in antibiotic medicine and this has significantly affected our microbiome.

Certainly this conclusion has yet to be fully authenticated – and would be very difficult to do so without a time machine – but there is evidence illustrating this.

Research also shows that probiotics affect our production of equol.

Learn how to boost probiotics while supporting this ad-free website.


Ko KP, Kim SW, Ma SH, Park B, Ahn Y, Lee JW, Lee MH, Kang E, Kim LS, Jung Y, Cho YU, Lee B, Lin JH, Park SK. Dietary intake and breast cancer among carriers and noncarriers of BRCA mutations in the Korean Hereditary Breast Cancer Study. Am J Clin Nutr. 2013 Dec;98(6):1493-501. doi: 10.3945/ajcn.112.057760.

Han SA, Park SK, Ahn SH, Lee MH, Noh DY, Kim LS, Noh WC, Jung Y, Kim KS, Kim SW; Korean Breast Cancer Study Group. The Korean Hereditary Breast Cancer (KOHBRA) study: protocols and interim report. Clin Oncol (R Coll Radiol). 2011 Sep;23(7):434-41. doi: 10.1016/j.clon.2010.11.007.

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Fuhrman BJ, Teter BE, Barba M, Byrne C, Cavalleri A, Grant BJ, Horvath PJ, Morelli D, Venturelli E, Muti PC. Equol status modifies the association of soy intake and mammographic density in a sample of postmenopausal women. Cancer Epidemiol Biomarkers Prev. 2008 Jan;17(1):33-42. doi: 10.1158/1055-9965.EPI-07-0193.


  • California Naturopath, Ph.D. in Natural Health Sciences, Doctorate in Integrative Health Sciences, Board Certified Alternative Medicine Practitioner. Diplomas in Blood Chemistry, Clinical Nutritional Counseling, Homeopathy, Aromatherapy, Colon Hydrotherapy, certificates in Pain Management and Case Management/Contact Tracing. Has authored more than 30 books and hundreds of periodical articles on natural medicine. Recreational activities include surfing, sailing, running, biking, swimming, SUPing, hiking. Contact: case(at)caseadams(dot)com.

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