Recently I learned that new studies are suggesting that soy might not be as bad as I thought it was in promoting breast cancer. Earlier on in my research, the studies were showing that the isoflavones in soy are phytoestrogens, properties that mimic estrogen and its effect in the body, specifically in attaching themselves to estrogen positive receptors, thereby increasing the amount of estrogen in the body which can cause estrogen positive breast cancers (ER+). Any studies countering this idea were based on Asian cultures where breast cancer incidents are low. My concern in these studies was that they were comparing apples to oranges, there are so many other factors to be considered when looking at Asian cultures vs American cultures, such as environment and lifestyle. I asked that a study be done on Asian Americans and all other Americans and also looking at when they started eating soy and what type of soy they were eating since the majority of American soy products are GMO and processed.
Someone must have heard my call. New recent studies are comparing the risk of breast cancer in Asian Americans and others and looking at when they started eating soy and what impact that may have. They also looked at the source of the soy products.
It would seem, based on these newer studies, that soy in its fermented state like miso and tempeh, is not linked with an increased risk of breast cancer in any Americans studied. Furthermore, for those who started eating soy at a young age, typically in the Asian cultures, it may even have a protective effect against cancer. However, for those who started eating soy in their later years (beyond the teen age years) no benefit has been shown.
Non GMO fermented soy and even non-fermented soy foods, eaten in moderation, do not seem to have enough dietary nutrition to impact breast cancer either way. However, soy based protein powders and bars that isolate the soy isoflavones and thereby provide it in higher concentrations may be linked to increased risks of breast cancer still because of its higher nutrition content of the phytoestrogenic properties. More studies need to be done.
I am still undecided and will continue to research this. As an ER+ breast cancer thriver who ate a ton of soy products before my first breast cancer diagnosis, I am not ready to hop on board the soy wagon. Since my children are allergic to soy, it won’t be back in my kitchen any time soon. For those who are ready to rejoin the world of soy, please eat soy in its natural, non-GMO, non processed, preferably fermented, form.
For those taking Tamoxifen, please note that some studies show that the soy isoflavone known as genistein can actually weaken the effects of Tamoxifen.
*Update: Listening to a podcast with Elizabeth Rider, health coach and chef, she mentioned that there is just as much evidence against soy as there is supporting soy. She too believes that it is based on geneology. If your ancestors have been eating soy for years, your body knows what it is and will handle it well, but if you have not, your body won’t. And again, fermented soy is really the best type of soy that should be eaten, definitely not GMO soy or processed soy like soy lecithin, soybean oil, or soy isolates.