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.
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.
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, https://www.breastcancer.org/research-news/soy-may-turn-on-genes-linked-to-cancer
POSITION STATEMENT, Soy, phyto-oestrogens and cancer prevention, https://www.cancer.org.au/content/pdf/CancerControlPolicy/PositionStatements/PS_Soy_phyto-oestrogens_and_cancer_September_2006_update_August_2009.pdf
Is Soy Safe for Cancer Patients?, https://www.cancernutrition.org/is-soy-safe-for-cancer-patients/