Kris Carr

Kris Carr

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What You Need to Know about Soy and Breast Cancer

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Hiya Gorgeous!

To eat soy or not to eat soy? Breast cancer and soy have had an “it’s complicated” type of relationship over the years, even though most minimally processed organic soy foods are considered safe and healthy to eat. Luckily, there’s growing research filled with great news! Today I’d like to walk you through it (and link you to it!) so you can take a look for yourself.

I want to unpack this research specifically for breast cancer thrivers—both current patients and anyone who is post-treatment—and then uncover what this means for breast cancer prevention too. If you’re curious about whether or not you should consume soy, then this is for you—knowledge is power, my friend!

Personally, I’ve made the choice to keep and enjoy organic soy in my diet. If you take a peek in my fridge, you’ll find a variety of whole and minimally-processed organic soy foods, such as edamame, tempeh, miso and tofu. These foods land on my plate 2-3 times per week. I made this choice because I’ve taken the time to understand the benefits of soy, I see they’re working for me, and my medical team has given me the green light. I’m also vegan and including organic, minimally processed soy in my diet (not the processed crap) provides more variety and protein options. There’s also just so many great dishes and recipes you can make that include healthy soy options!

Exploring the research and debunking common misconceptions can help you decide whether or not minimally-processed, organic soy is a good fit for you. As always, it’s important to follow your doctor’s advice. But if you’re wanting to include some soy in your world and your MD has given it the kibosh, you might want to alert your medical team to this soy and breast cancer research (check it out below!) Just because your doctor is a fabulous smarty pants, doesn’t always mean that he or she is up on all the nutrition studies. So let’s dig into these beautiful findings, thriving and prevention…

Breast Cancer Thriving and Soy

If you’re currently a breast cancer thriver, you may be feeling some confusion around soy. Many oncologists have been on the fence about whether or not women who have had breast cancer should consume soy foods. To play it safe, they’ve discouraged breast cancer thrivers from consuming soy.

The reason behind this is that soybeans contain weak estrogens, and these estrogen-like properties have raised concerns of potentially making the cancer grow in women with breast cancer. This is because in hormone receptor-positive cancer—the most common form of breast cancer—there are some worries that high estrogen levels help cancer cells grow and spread. But this remains very controversial. Oddly enough, most people are more fearful of soy than they are of dairy, which doesn’t have protective phytoestrogens and contains estrogen (with full-fat dairy products having the most estrogen).

In 2012, researchers took a look at the diets of nearly 10,000 breast cancer patients and what they found was worth noting—the women who consumed the most organic soy (at least ½ cup of edamame per day) had a 25 percent less chance of having a cancer recurrence compared to women who consumed little or no soy (study). But people and oncologists have still been on the fence….

Enter another study blessing soy for breast cancer thrivers

This study on soy and breast cancer (study abstract) included 6,235 American and Canadian breast cancer patients from the Breast Cancer Family Registry, a National Cancer Institute-funded program that has collected clinical and questionnaire data on participants since 1995. By looking at this diverse population of over 6,000 breast cancer patients, the researchers specifically analyzed their soy intake. And the results were pretty amazing. Here’s a summary of the top takeaways…

Higher Survival Rates

Eating foods rich in isoflavones (the specific phytoestrogens in soy foods) is associated with reduced all-cause mortality. More specifically, the researchers found a 21% decreased risk of death among women with the highest versus the lowest intake of soy foods. This was especially true in women with hormone-receptor-negative breast cancer (which is typically the more aggressive kind) and women not treated with hormone therapy.

Women in North America could benefit from increased organic soy consumption

Even though women living in North America had an overall low consumption of soy in their diet, they may still benefit from increasing their isoflavone intake to a higher level. This benefit may be for those thrivers who are not currently receiving hormone therapy, but there’s also no negative impact shown for those who are.

Increasing soy may increase survival rate after a cancer diagnosis

Here’s the absolute BEST news: recent diet is important! If you’ve been diagnosed with ER-negative breast cancer, soy may play a significant role in your survival, and may even matter more if you start eating it now than if you ate it way back when. So not only did this study find that soy wasn’t harmful for survival, but it actually may improve it. And while this study only found these specific perks for ER-negative survivors, previous research has found soy to be beneficial for ER-positive survivors and for both users and nonusers of hormone therapy (study). Happy dance!

Breast Cancer Prevention and Soy

In addition to all these wonderful findings for breast cancer thrivers, here’s some more good news for prevention! Eating soy can help prevent breast cancer in women of all ages. In a meta-analysis (that’s a study analyzing all the research on a particular topic—in this case soy consumption and breast cancer prevention), researchers found that soy consumption cut breast cancer risk by 41 percent among Asian populations (study). But here’s the catch—it can’t be just any type of soy.

Most of us actually consume lots of soy, but unfortunately, most of it is highly processed—which isn’t good for our health and doesn’t allow us to reap the benefits of prevention. To eat soy for its preventative benefits, it has to be the less processed versions, such as tempeh, miso, edamame, tofu and soymilk (always organic and non-GMO too!).

Now, this is where things get really interesting: prevention is also linked to how long you’ve been eating minimally processed soy. For instance, Asian populations typically eat minimally processed soy, like tofu, miso, tempeh and edamame throughout their lives. And Asian women have the lowest incidence of breast cancer, most likely from eating soy during puberty when breast tissue was forming. While this might explain why Asian women in general have less cancer, it could be worthwhile to add some unprocessed soy foods to your diet, even if you’re past puberty.

It’s ultimately your choice whether you decide to incorporate soy into your diet. Do whatever feels right for you and don’t forget to check with your doctor—and let your MD team know about all the research on soy and breast cancer. Hopefully you’ll be able to make a more-informed choice with this insight. Also, keep in mind that this article is not geared toward people with soy allergies. If that’s you, then soy may still not be the right choice. But a plant-based diet without soy can still be very beneficial. Knowledge is power, baby!

Peace and happy thriving,

Add a comment
  1. Thanks for sharing such a awesome info. I would love to share it with my friends. Thanks Again.

  2. mavras says:

    Breast cancer is highly common in women. After treatment still women have e chance of getting another breast cancer. read it and be saved.

  3. Marie says:

    Hi Jen Reilly where are you and Kris located?

  4. wow, That’s good to know.
    Actually, I don’t really know the relationship between soy and breast cancer but my mom and my friends often say soy is good for your breast, it makes your breast becomes more bigger lol. But whatever it is, I love soy <3
    My mom used to make soy milk when I still lived with my family. We've used soy in daily meals. It's just so good and delish.

    Now I know more about its benefits so Yay, I will eat soy more xD Thanks for sharing!! 🙂

  5. Elaine says:

    Hi Kris,
    Thank you for the article. Dr. Michael Greger (book: How Not To Die, documentary: Cowspiracy, documentary: What the Health) has done some wonderful reviews of the science behind eating soy and breast cancer and I agree with both of you. Minimal processing, always organic, and variety. Thank you again for this article.

  6. Kathy says:

    Hi Kris, Thank you for the great info! I am a two year BC thriver and this topic has certainly been on my mind. I’m curious if you have done any research on Maca? The little research I’ve done says this superfood is not recommend for those post BC. Thanks to you and your team!!

  7. Dominique says:

    Thank you for this very informative article. I’m a breast cancer thriver and am also confused about chick peas and sesame seeds as being possibly high in phyto estrogens. I’m vegan and cannot live without hummus and tahini salad dressings. Thoughts?

  8. Sheila says:

    Thank you for providing the information….. I’m also a breast cancer survivor and have been wondering about the soy connection since coming off dairy and looking for a new coffee creamer that is dairy free!! My only advise, that you didn’t ask for, is that all studies quoted be within 5 years. I am an Oncology RN, and I know it can be hard to find recent studies sometimes, but for me I probably would not make a change in lifestyle or professional practice based on 1 study, or on only studies that were from more than 5years ago. So thank you for providing several studies, including a meta analysis, you just shortened my research time!! Thanks, blessings!

  9. audrey says:

    I am Asian and I had breast cancer. And surrounding me are Asian ladies who have had breast cancer or who are doing treatments for it. So it’s not entirely true that eating soy products for us help prevent it. I strongly feel the rate of breast cancer among us Asians are on the rise! I ate soy products since young such as tofu, bean curd (the firmer ones), soy dessert, bean curd skin, bean curd puff, soya beans itself in soups, miso soup (Japanese source) but admittedly it’s not a daily affair that I eat them. I had hormone negative breast cancer and my oncologist says that is worse than hormone positive as it is further more mutated than the normal breast cells as compared to the hormone positive cancer. Anyway, I am staying clear of soy for now, as I journey to find healing for me body. There are lots of other good whole foods available for me. Cancer is really a multi-factored disease. x

  10. Pauline says:

    Great article, thnx!!! I like to eat some soy yoghurt sometimes, what’s your opinion on that?

  11. My naturopath didn’t want me to consume soy at my age of 72 because it acts like a hormone. Is she correct? I also have am hypothyroid and take 30 mg of Nature Throid daily. It says in a book I have about thyroid issues to avoid beans, peanuts, kale, spinach, any cruciferous veggies unless they are cooked. I am a little confused. I probably should do what my Naturopath advises but I keep reading how healthy they are.

  12. anne says:

    thanks for sharing this! I have long eaten unprocessed soy and love it! have never understood how western docs could say NO SOY, because of breast cancer, when Asian women have the lowest incidence of cancers……….(kind of like wine, breast cancer, and the French women………)

    • audrey says:

      I am Asian and I had breast cancer. And surrounding me are Asian ladies who have had breast cancer or who are doing treatments for it. So it’s not entirely true that eating soy products for us help prevent it. I strongly feel the rate of breast cancer among us Asians are on the rise! I ate soy products since young such as tofu, bean curd (the firmer ones), soy dessert, bean curd skin, bean curd puff, soya beans itself in soups, miso soup (Japanese source) but admittedly it’s not a daily affair that I eat them. I had hormone negative breast cancer and my oncologist says that is worse than hormone positive as it is further more mutated than the normal breast cells as compared to the hormone positive cancer. Anyway, I am staying clear of soy for now, as I journey to find healing for me body. There are lots of other good whole foods available for me. Cancer is really a multi-factored disease. x

  13. Ruth Fryman says:

    I ate soya products for years but I still got breast cancer, so not convinced about its preventative properties. I have been breast cancer free for 8 years now and I’m not jeopardising it by eating soy products

  14. J says:

    Thank you Kris! As a breast cancer survivor, this information is so appreciated!

  15. Tasma says:

    Thanks so much for sharing this. I went against my oncologists wishes, after doing a lot of research myself, and ever since my diagnosis and treatment for breast cancer (5 years ago now!) I regularly include tempeh, edamame, miso and tofu into my diet. At the end of the day ‘you’ need to be comfortable in the decision regarding what ‘you’ are putting into your body. I will never be able to thank you enough for the impact you have had on my life Kris, I have learned so much from you and I feel amazing and thankful every day 🙂 xx

  16. Anne says:

    Thanks, I never understood or used soy foods…this article explained what they are and benefits. I will be able to research them more now and maybe incorporate them a bit more.

  17. Lisa brott says:

    Thank you for this informative article. I am a semi vegetarian and do consume some soy products. I will always stick for to the unprocessed and organic. I do think there are many other reasons for lower cancers in asians and Americans who consume soy including less saturated animal fats, Asians move more and have little obesity. Americans who eat soy also eat more veggies, watch their weight, exercise more, less smoking rates, etc. almost impossible to find cause and affect for one food type such as soy. That’s the complicated frustrating part.

    • Jen Reilly, RD says:

      Hi Lisa! I’m the nutrition director here at Crazy Sexy Wellness so I’ll chime in for Kris. Nutrition research studies typically adjust for all those possible factors that may make (in this case) soy look good. This particular study adjusted for confounding factors including age, study site, total caloric intake, race/ethnicity, education, total fiber intake, Healthy Eating Index (HEI)-2010, treatment type, recent recreational physical activity, BMI, usual alcohol consumption, and cigarette smoking status. These adjustments help determine cause and effect for what’s really being tested. Hopefully that helps you feel more confident about the results. xo!

  18. I have been eating organic soy for over 35 years and enjoy excellent heath at the age of 83+years young. My late husband Gunter Pfaff and I produced Betsy’s Tempeh in Mich. for 9 1/2 years and people loved our product. So yes organic soy has been part of my life and will continue to be so until I no longer exist.

  19. Ruth says:

    HI Kris, as always your information is intelligent, helpful and encouraging thank you! I’d like to offer a thought about soy. While I mostly agree with all of the science here, the elephant in the room for me is the reality that it’s nearly impossible to find soy that hasn’t been contaminated with genetically modified organisms. The herbicides – glyphosate being one of the biggest culprits – are devastating to us short term and long term. Not only do they destroy our gut bacteria even if the exposure is small, but important information is coming out everyday from reliable sources (and being suppressed by the organizations who should be protecting us but that’s another subject) showing that most modern day epidemics – diabetes, obesity, cancers, autism, heart-disease – have risen in exact proportion to the prevalence of genetically modified seeds, practices, herbicides. Anyway, you do a lot more research than I do and I trust your thinking and information but wanted to raise this issue because I think it should be a key player in any food choice large and small.

    • Penny Norris says:

      Hello Ruth. I have been using a low processed, non GMO, NSF certified dairy free vegan shake mix for the last 4 years. It has been clinically studied at MD Anderson for ovarian cancer survivors!

  20. Lucy Schratz says:

    Hi Chris–I too, still have major concerns with soy. I realize the article pertains to breast cancer but what about soy’s effects on those with autoimmune disorders? I have a 17-year-old daughter with Graves disease and in my quest to heal some of her symptoms with nutrition, most all of the literature points to all soy as a major no-no. Since we are mostly plant based, I have spent the last month coming up with soy alternatives. I agree with you that everyone is different and you have to make decisions based on your specific needs. Thank you for sharing the article and your continued passion for health. You continue to be an inspiration for us!

    • Jen Reilly, RD says:

      Hi Lucy! I’m the nutrition director here at Crazy Sexy Wellness so I’ll chime in for Kris. Soy isolates (found in some veggie burgers, powders, supplements, and processed foods) may decrease the effectiveness of thyroid medications in people with hypothyroidism. But, I’ve not found any convincing research to support the theories that soy foods can stimulate a harmful immune response in people with autoimmune thyroid disease. It’s possible, however, that if someone with thyroid disease is deficient in iodine, the isoflavones in soy (and compounds in cruciferous vegetables) may have a goitrogenic effect. Obviously if you feel more comfortable skipping soy for your daughter, that’s ok. Just wanted to help explain some of the info out there and encourage you to keep looking into the research, especially if you are missing soy. xo!

  21. beverly says:

    Morning, Kris,
    When you read the JAMA article on soy, there’s some fine print that reads to me like the jury is still out… I realize that this is a 2009 study; however, it still speaks to me to be careful with soy.

    “Consumption of soy food has been inversely related to the risk of breast cancer in many epidemiological studies.4- 6 However, genistein, a major form of isoflavone, has been shown to enhance the proliferation of breast cancer cells in vitro and to promote estrogen-dependent mammary tumor growth in ovariectomized rats.3,7 In addition, breast cancer treatments often lead to a decrease in the endogenous estrogen supply of survivors, and a concern has been raised as to whether soy isoflavones may exert their estrogenic effects, promote cancer recurrence, and, thus, negatively influence overall survival.7,8Furthermore, both in vivo and in vitro studies have suggested that soy isoflavones may interact with tamoxifen, although both synergistic and antagonistic interactions have been reported.3,9- 13 “

    • Jen Reilly, RD says:

      Hi Beverly! I’m the nutrition director here at Crazy Sexy Wellness so I’ll chime in for Kris. That portion of the JAMA study is from the Introduction where the researchers are outlining their reasons for doing this research. If you scroll down to the Comments (Discussion) section, you’ll see them explain their statistically significant results. This text specifically:

      “In our comprehensive evaluation of soy food consumption and breast cancer outcomes using data from a large, population-based cohort study, we found that soy food intake was inversely associated with mortality and recurrence. The inverse association did not appear to vary by menopausal status and was evident for women with ER-positive and ER-negative cancers and early and late-stage cancers.

      Among the many constituents of soy food, soy isoflavones are the most intensively studied phytochemicals for their health-related effects. It has been shown that soy isoflavones compete with endogenous estrogens in the binding of estrogen receptors, increase the synthesis of sex hormone–binding globulin (thus lowering the biological availability of sex hormones), inhibit 17β-hydroxysteroid dehydrogenases (thus reducing estrogen synthesis), and increase clearance of steroids from the circulation.2,3 These antiestrogenic effects may be one of the underlying mechanisms through which soy food consumption is associated with better breast cancer outcomes.”

      I hope that helps ease your mind. xo!

  22. Daniel says:

    Well Soy might be ok for women, but Soy is Toxic Kryptonite for Me! The only Soy I consume has been fermented, Only!

  23. Michelle says:

    I’m still leery of soy, especially soymilk. My friend who is male used soy milk when he made his protein shakes. He got breast cancer with no link to it in his family. After researching and going through his diet they contribute it to the soy milk he used every day. He has taken soy out of his diet.

    • Jen Reilly, RD says:

      Hi Michelle! Thanks so much for your comment. I’m the nutrition director here at Crazy Sexy Wellness so I’ll jump in for Kris. I’m sorry that your friend was challenged with breast cancer. It’s very hard to pinpoint the cause of breast cancer unless a genetic link is found. And for men, there’s very little research on diet and breast cancer. We do know, however, that soy foods may help prevent prostate cancer in men. The good news is that a plant-based diet without soy can still be incredibly healthy, and there are tons of delicous and nutrient-rich non-dairy, soy-free milks available. xo!

  24. Sherrie says:

    Thank you! Thank You!
    All your blog post have been so very helpful…I am a survivor and this one subject I have been struggling with for some time now. I will be sharing with my Thrivers group!


  25. Carole Audet says:

    Can you please list brands of minimally processed organic soy, Thank you.

    • Jen Reilly, RD says:

      Hi Carole! I’m the nutrition director here at Crazy Sexy Wellness so I’ll chime in for Kris. There are so many brands of soy products out there, that beyond the ones we’re familiar with (Nasoya, Eden Foods, Silk, Pacific Foods, etc.), it would be hard to make a complete list. Just keep in mind that you should always look for organic, non-GMO, and check the ingredients for as few items as possible without artifiical additives and preservations. Edamame beans, soy nuts, tempeh, and miso are the most unprocessed soy foods with soymilk and tofu coming in at a close second (and still considered minimally processed). The more processed soy foods which have been manipulated enough that we’re unsure of their benefits include the various meat and dairy substitutes like soy dogs and soy cream cheese. Hope that helps! xo

  26. Sheryl says:

    Thank you once again for your research. A whole generation of thrivers are so thankful for you!

  27. Marlane says:

    Thank you for this information which backs up my conclusions about soy. And yes always organic and non GMO. WHAT I REALLY WOULD LIKE TO SEE ON OUR STORE SHELVES IS PRODUCTS FRON SOY THAT HAS BEEN GROWN AND PROCESSED IN CANADA AND THE USA.

  28. Kat says:

    Asian women’s diet is also very rich in iodine which is known to be great for breast cancer prevention.

  29. Kris thanks so much for putting this informative post together. This is such a sensitive topic and even I find it hard to encourage soy when there is so much fear around it. I am sharing this article everywhere and on my blog. Really appreciate all the time you put into this. You’re a freakin’ queen!!!!!

  30. Thanks for clarifying this. I get asked a lot about this in my work, this is a great article to direct them too.

  31. Ellen says:

    I love soy milk, but I’ve heard that it is a more processed soy product. I currently drink Silk, which is non-gmo but has more ingredients than I’d prefer. Do you have an organic and non-gmo brand you recommend? Thank you!

    • Jen Reilly, RD says:

      Hi Ellen! I’m a dietitian and the nutrition director here at Crazy Sexy Wellness, so I’ll jump in for Kris. Silk has an organic, non-GMO line which only includes the organic soybeans, water, sea salt, natural flavor and gellan gum for thickness (plus the vitamins and minerals added for fortification). The unsweetened is great and I love that it gives you a nice dose of protein compared to the other plant milks:

      Hope that helps! xo

    • Gretchen Harder says:

      Westsoy organic soy milk is sold at my Kroger store (Fred Meyer in WA), where the shelf stable nut milks are located. The only ingredients are filtered water and whole organic soybeans. It is Non GMO Project Verified, and USDA Organic. There is also a Vanilla one, that just has the addition of vanilla – no sugar or other additives.

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