Do Soybeans Cause Breast Cancer?


Soybeans are one of the more controversial foods out there today. Some folks make soybeans a staple of their diet—especially vegetarians, who eat tofu as a major source of protein. And there are others who swear off everything soy, knowing that a number of the chemicals in soy mimic human hormones in unpredictable ways. And some have even said that soy can cause, or exacerbate, cancer—especially breast cancer. Today, I want to dispel one myth about soybeans. But don’t be mistaken—I’m not giving soybeans a clean bill of health. Rather, today I want to tell you what the true risks are, and what are false worries. Here’s a hint—it’s not what you think.

Cancer Cause Or Cancer Prevention?

Because soy contains chemicals, called isoflavones, that closely mimic estrogen, it’s long been feared that soybeans could increase the risk of estrogen-linked cancers.

Here, we’ve got good news. A few studies have concluded that eating soy doesn’t increase your risk of cancers like breast cancer.

In fact, it may just do the opposite—the evidence points to soy being a help in combating that particular form of cancer.

One study found that consuming soybeans actually decreased the amount of estrogen produced by the body of premenopausal women. That might, in the end, lower the risk of breast cancer—if only slightly. The effect is small, but beneficial.

What’s more, the phytoestrogens don’t appear to affect men’s reproductive organs, as once feared.

And another study, of breast cancer survivors, found that eating soy was actually mildly linked to an increase in lifespans. The finding was a small bump, but consistent.

And definitely not a negative. Many folks feared that soybeans could interfere with cancer drugs like tamoxifen. That doesn’t appear to be the case either.

Take it all together, and soybeans definitely don’t increase your risk of breast cancer. And, if you have a family history of breast cancer—or you’re a breast cancer survivor—soybeans could prove mildly beneficial.

Not Just Cancer Prevention

However, that doesn’t mean everyone should go out and start eating as much soy as they can.

We know it doesn’t hurt when it comes to breast cancer. And, in some cases, it can help just a bit.

But that’s about all we know.

But estrogen is involved in countless functions within your body.

And, frankly, we don’t know how the phytoestrogens in soybeans affect all these other processes.

If I had to guess, well, the human body is a finely tuned machine. When you start tinkering with important chemical systems, the odds are good something will get knocked off kilter.

Still, these effects are likely to be relatively minor. We’ve been eating soybeans for hundreds—thousands!—of years, after all.


You Are A Guinea Pig!

Not so fast.

The soy you’re eating today isn’t the same as that which your ancestor ate.

It’s not even the same plant your parents ate.

That’s because soybeans are one of the most genetically modified crops today. Something like 93% of all soy grown today is genetically modified.

That means it’s the vegetable equivalent of mystery meat.

GMOs—or genetically modified organisms—are one of the hot-button issues today. It’s not hard to find plenty of folks who will say they’re safe.

But it’s also not hard to find new foods that were prematurely declared safe, and weren’t.

In the early 1900s, lead was still used to thicken milk. There were red and orange food dyes that made children sick—but everyone was eating them because the regulatory bodies of the day said they were safe.

The truth is, whenever it comes to new foods that haven’t been properly tested in numerous settings, we just don’t know what they’ll do to us.

They might do nothing—plenty of the food dyes in 1900 were safe.

But they also could be very hazardous. Without testing, there’s no way to know.

When it comes to GMOs, I’m sure plenty will be found safe.

But I won’t be surprised if some are dangerous. And, until we have more experience with them and know what we’re doing, everyone eating GMOs is a guinea pig.

Who knows the long-term effects?

And that goes double for foods like soybeans, which we know contain hormone analogues like phytoestrogen. You don’t want to mess with hormones—and we simply don’t know how genetically modified soy will behave in your body.

Minimal Cancer Protection Isn’t Worth The Risk

Soy may not be bad for breast cancer.

It may even provide modest benefits, in terms of cutting down breast cancer risk and lengthening the lives of survivors.

But GMO-soy comes with a lot of other risks. We don’t even know what they are yet—just that you’re taking a step into the unknown, using your body as a test tube.

Unless you have specific reasons to worry about breast cancer, I recommend you treat soy with kid gloves. It probably won’t hurt you—but it might. It’s not worth finding out the answer to that question, using your own body as the lab.


Last Updated: August 16, 2018
Originally Published: June 12, 2017