Soy contains compounds that are very similar to human estrogen. Some see that as a bonus, other warn against. What’s the science say?
On this episode we'll talk about phytoestrogens in soybeans, and whether they have estrogen-like effects in women—for better or for worse.
Nutrition Diva is hosted by Monica Reinagel. A transcript is available at Simplecast.
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Welcome to the Nutrition Diva podcast, a show where we take a closer look at nutrition trends and headlines, explain how the latest research applies to you, and answer your questions. I’m your host, Monica Reinagel, and today I want to talk about phytoestrogens in soybeans, and whether they have estrogen-like effects in women—for better or for worse.
But first, a question came up in the comments section of a post that I wrote on my blog at NutritionOverEasy.com on whether protein powder is too processed to be considered a healthy food.
The post was in response to a question from Catherine, who wrote: “Virtually everyone says to cut down on processed foods. It’s one of the few things everyone from different camps generally agrees on. Yet a large number of nutrition influencers recommend smoothies that include protein powder. How the heck are those not processed?”
Catherine is right: There’s a lot of talk these days about the harms of ultra-processed foods. But this designation turns out to be problematic. Some of the foods in this category are exactly the ones you might expect—things like Red Bull, Cheetos, and Pop-Tarts. But the category also includes foods that we generally think of as healthy (or, maybe, healthier) choices, such as almond milk, soy burgers, cholesterol-reducing spreads like Benecol, high-fiber breakfast cereal, baby formula and, yes, protein powder.
Rather than painting all processed foods with the same brush, it’s worth considering what the purpose of the processing is. Is it to concentrate the sugar, increase the intensity of the flavor, or otherwise create a product that hyper-stimulates the reward centers of the brain? Is it to increase the profit margin of a cheap ingredient?
Or does it serve to extend shelf life, increase the nutritional value of a food, improve its digestibility, or make a nutritious food safer or more convenient to prepare? Obviously, the processing required to turn peas or whey into protein powder serves a different purpose than the processing required to turn an ear of corn into a bag of Cool Ranch Doritos.
I also think we need to consider what role or function that processed food plays in our diets. A Pop-Tart, for example, is at best a source of empty calories. At worst, it could be displacing a healthier breakfast choice. Protein powder, on the other hand, can really only be used to increase the protein content of other foods. In that case, the benefit may well justify the use of an ultra-processed ingredient like protein powder.
But another controversy unspooled in the comments section for this post, where a reader warned against any protein powder that wasn’t cold-processed, because heat processing would denature the protein.
Denatured protein sounds very bad, doesn’t it? But if you’ve ever eaten a scrambled egg, you’ve eaten denatured proteins. All “denatured” means is that the protein molecule has been twisted into a different shape. It still contains the same amount of protein, the same amino acids, and, when digested and metabolized, will have the same benefits.
Good thing, too, because proteins consumed in their raw state will quickly be denatured by stomach acid. Our ability to make use of the protein we eat does not depend on the shape of the protein molecules. One less thing to worry about!
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And now, I want to turn to Stacey’s question, about the phytoestrogens in soybeans.
“Is edamame safe for women to consume regularly? I actually became interested in eating it because I read that it may help perimenopause symptoms, but other articles warn against the estrogen. What’s your take?”
Soy contains isoflavones, compounds that happen to be shaped very similarly to the human hormone estrogen. In fact, they’re close enough that they can actually fit into estrogen receptors in human cells.
Osteoporosis, hot flashes, and breast cancer are all closely linked to estrogen activity in the body—either too much or too little. Initially, it was thought that the weaker plant estrogens (or, phytoestrogens) in soy might protect you from either scenario. If estrogen levels were low, isoflavones might provide just enough estrogenic activity to prevent bone loss or hot flashes.
On the other hand, if estrogen levels are too high, which might increase your risk of breast cancer, phytoestrogens could help block excess estrogen from entering your cells by occupying the estrogen receptors and causing your cells to turn on the “No Vacancy” sign.
Newer research suggests that it’s not quite what we thought. The estrogenic activity of soy doesn’t seem to depend as much on how much estrogen you do or don’t have in circulation. Apparently, it’s more complicated than that.
Nutrition research often progresses along parallel tracks. On one track, scientists attempt to understand the mechanisms for how foods and nutrients interact with our biology. On another track, researchers are gathering data on clinical outcomes—meaning, what happens to people when they eat more or less of a given food or nutrient.
On that second track, studies have found that eating soy reduces hot flashes in some women but not others. (Incidentally, it seems to be much more effective in reducing hot flashes if you also exercise.)
It's also important to note that the studies that did observe a benefit involved consuming pretty high amounts of soy, or taking higher dosages of isoflavone supplements. The best we can say is that high soy or isoflavone consumption combined with a healthy lifestyle might have a modest beneficial impact. Or it might have no impact at all.
Here’s the thing. Hot flashes are hard to miss. It’s not like you need a blood test or bone scan or something like that to know whether or not you’re experiencing them. So you could try adding edamame or other soy foods to your diet and see if it seems to help. At worst, it’s some protein and fiber. At best, it brings a little relief.
But, as Stacey found, some have warned against soy for the very same reason that others recommend it—namely, that it might have estrogenic effects in the body. Specifically, the concern is that phytoestrogens in soy foods might promote the growth of estrogen-sensitive cancer cells.
Up until pretty recently, breast cancer patients were often advised to avoid soy food out of an abundance of caution. However, there is now compelling evidence to show that eating soy foods poses no risk to breast cancer survivors. If anything, it appears to be beneficial, reducing the risk of recurrence of both estrogen-receptor positive and negative breast cancers.
In fact, the researchers on Track One (the mechanistic track) are starting to question whether the benefits of soy on things like hot flashes, or its protective effects against breast cancer, aren’t really about estrogenic activity at all, but due to other mechanisms. Either way, there doesn’t seem to be any reason to avoid soy for fear of its harmful effects on estrogen-sensitive tissues.
And, either way, edamame makes a great snack!
This is Monica Reinagel, the Nutrition Diva. If you have a nutrition question you'd like me to answer, you can email me at nutrition@quickanddirtytips.com. You can also leave me a message at 443-961-6206.
If your question is more on the subject of habits and behavior change, please check out my other podcast, the Change Academy, where we talk about how to convert our good intentions into sustainable healthy habits. You’ll find it wherever you listen.
Nutrition Diva is a Quick and Dirty Tips podcast and is supported by a fantastic team, which includes our Director of podcasts, Adam Cecil, audio engineer Nathan Semmes, Davina Tomlin runs our marketing and publicity, Holly Hutchings is our Digital Operations Specialist and Morgan Christianson is our Podcast Operations and Advertising Specialist.
Thanks for listening!