Soy or not to soy – that is my dilemma.

I never been a huge soy consumer. Soy milk occasionally, miso soup every now and then and some tofu or tamari in stir fries.

After my breast cancer diagnosis in 2014, soy was totally off my menu.

I, like so many other women, had oestrogen positive breast cancer and after radiotherapy started on aromatase inhibitors (which stopped my body from producing oestrogen).

Is it ok for women with oestrogen positive breast cancer to consume soy?

Here is where I started to become totally confused.ļ»æ

Soy contains isoflavones (a weak form of oestrogen) which in theory could stimulate breast cancer growth. The soy isoflavones do lock on to oestrogen receptor B, where they can either block or stimulate growth.

Photo by Buenosia Carol on

Soy is a big part of the diet in many Asian countries, consumed from an early age. Women in these countries appear to have a lower incidence of breast cancer, possibly due to protective affects of soy throughout their lives. In the West, soy is not as widely consumed and for most, eaten in adult years, so it’s difficult to compare these populations and the risk of breast cancer/soy intake.

Like many women diagnosed with breast cancer, I’m pretty proactive with both my fitness, diet and overall positive outlook. I did a degree in nutritional medicine to try to understand what I should and shouldn’t eat.

Unfortunately, I didn’t get all the answers I was looking for.

I’ve attached below a couple of reference links to various papers discussing soy and inclusion in the diet of breast cancer survivors. Apparently a small amount of soy is ok (no supplemental soy). This is fine, however there is no strong evidence that soy consumption is ok for all breast cancer survivors.

I can’t seem to find any clinical trials, testing soy consumption and overall survival rates.

From the Australian Cancer Council the following excerpt:

“Women with current or past breast cancer should be aware of the risks of potential tumour growth when taking soy products.

There are no clinical trials available to definitively answer this question.”

Position statement Cancer Council 2009.

I know I’m not the only woman wanting answers regarding soy consumption and risks/benefits.

As the number of women diagnosed with breast cancer and those living after a diagnosis increase – there will be a lot of women out there like me – looking for answers supported by large scale clinical trials.

Why aren’t they being run? Is it because there is no drug being tested? No money to be recouped by pharmaceutical companies?

I guess my personal choice is continue to exclude soy from my diets until we have some answers. It may take a long time.


Eating Soy May Turn on Genes Linked to Cancer Growth,

POSITION STATEMENT, Soy, phyto-oestrogens and cancer prevention,

Is Soy Safe for Cancer Patients?,

10 thoughts on “Soy or not to soy – that is my dilemma.

    1. Hi Carol, thanks for reading and attaching the link. I had a look at the website and a lot of the studies look at the health affects within Asian populations who have consumed soy most of their lives. We, in the west have not and I’m not sure if we can compare the effects of soy in Western women. Still interesting though and hopefully over time there will be more information out there to help sort out the friend or foe status of soy.

      Liked by 1 person

      1. Yes I noticed that, Leonie although the Mayo clinic have completed some studies as well not sure if you have looked them up…I myself don’t eat soy based if I can help it because of the GM and I don’t really like it but many Thais do there are a lot of soy drinks etc and tofu is used a lot I just don’t really like tofu I have cooked with it but more to experiment and it was ok…Maybe I should persevere… If I see any western studies I will think of you. Food Forensics has some info Behind the Bean…by the Cornucopia Instutute and some orther info…I use this book as a reference quite a lot šŸ™‚ xx

        Liked by 1 person

    1. Thanks for reading and your comment. I checked out the link you provided, thanks. I agree there is a lot of confusion about negative vs positive effects of soy. There are phytoestrogens in many foods like flax, pulses and even vegetables and fruit contain some. Most health professionals do err on the side of caution and advise moderate amounts of soy are ok. I guess its a personal choice how to interpret “moderate”.


  1. This is a good topic! I also had estrogen-positive breast cancer and in 2017, I posed the soy question to a registered clinical dietician at my cancer center since I have been a vegetarian for many years and consumed a soy-heavy diet. She was of the mind that soy and phytoestrogens could not be definitively linked to breast cancer. My response has been to avoid the “fake meats” containing more processed soy and limit myself to tofu and tempeh, and even not rely on them so much for protein. I’m glad you’re bringing this up because it’s probably time to do another literature search and see what recent studies have shown.

    Liked by 1 person

    1. Thanks for reading my post and for your comment. There’s so much information out there on the web regarding soy, not sure if most of it is based on findings of scientific research. For my own peace of mind I will continue to avoid soy until I see the results of studies that involve western women and soy consumption. Let me know if you find anything interesting from your literature search.

      Liked by 1 person

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