Lifestyle  |  Nutrition

Soy and Breast Cancer

September 12, 2019  |  By: Whitney E. RD

There are numerous myths surrounding soy and breast cancer. Not only is soy harmless, but it has actually been shown to protect against cancer.

Have you heard the myth that soy causes breast cancer?

This gets me fired up. Namely, because of all the myths out there, this one has so so much evidence to the contrary that it just shocks me that people are still falling for this misconception.

So here are the facts – not only is there no scientific research showing that soy causes cancer (of any kind) it actually does the opposite! Soy consumption may be associated with reduced rates of hormone-dependent cancers like breast and prostate cancer.

Research suggests that eating soy foods may reduce breast cancer risk by a third. That’s huge.

This is because although soy contains phytochemicals known as isoflavones that are similar to our body’s estrogen, these phytochemicals behave differently in the body than our own body’s hormones.

Isoflavones are what we call “selective estrogen receptor modulators” and they selectively bind to different estrogen receptors in different tissues, which is what is believed to contribute to their anti-cancer effects in the breast.

Just look at Asian countries, where soy consumption is really high – historically, they have very low rates of breast cancer compared to countries like the US. If soy caused breast cancer, we’d see the opposite.

Now whenever I talk about this, I hear the argument, “Yeah, well in Asia they consume fermented soy” not the processed soy we eat here in the US.

Yeah, well, that’s just not true. In Japan and China, half of soy consumption comes from unfermented foods like tofu and soy milk.

Another concern I hear is whether soy is safe for breast cancer patients and survivors, especially those with estrogen receptor-positive cancer.

Again, since isoflavones seem to counteract our own bodies estrogen, they are perfectly safe, and again, probably beneficial.

One large meta-analysis showed that breast cancer survivors with high soy intake had a 16% reduced risk of mortality and a 26% reduced risk of cancer reoccurrence.

In fact, the American Institute for Cancer Research and the American Cancer Society both encourage soy consumption for breast cancer patients.

One final note – research shows that the earlier people start consuming soy the better. Some studies have shown a 60% decreased risk of breast cancer when women consumed 1-2 servings of soy foods a day, starting in childhood.

So if you’re a parent, make sure to include soy in your babe’s diet too! I recommend including 1-2 servings of soy a day – both fermented and unfermented products.

I usually have soy milk in my oatmeal in the morning and then tofu or tempeh with lunch or dinner. I also love to toss edamame in my salads or use miso to add an umami flavor to vegan cheese sauces.

And for more info on soy myths and facts, check out my three-part series on soy on my YouTube channel!

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Weigh in: What are your favorite soy foods? Have you heard this myth before?

*This post is sponsored by Soy Connection, but all opinions are my own. I thank you for your support of Whitney E. RD-approved partnerships that make this website possible.