What You Need to Know about Soy and Breast Cancer

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,

Kris Carr

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