Podcast Episode 273: Soy Foods: Navigating 4 Major Myths Using Research – Jill Castle & Karen Collins - Sound Bites RD (2024)

Speakers: Melissa Joy, Karen Collins, & Jill Castle

[Music Playing]

Voiceover (00:01):

Welcome to Sound Bites, hosted by registered dietitian nutritionist, Melissa Joy Dobbins. Let’s delve into the science, the psychology, and the strategies behind good food and nutrition.

Melissa Joy (00:22):

Hello, and welcome to the Sound Bites Podcast. I’m your host, Melissa Joy Dobbins, and-

Jill Castle (00:28):

The Nourish Child Podcast, hosted by me, Jill Castle.

Melissa Joy (00:31):

Today’s episode is a collaboration and a podcast swap with myself, Melissa, and Jill, and also, our esteemed colleague and guest, Karen Collins. We are three registered dietitian nutritionists, and our topic today is focused on myths about soy foods.

And just want to let our listeners know that this episode is not sponsored. And I’d like to start with just each one of us giving a short introduction of ourselves for those listeners who may not be familiar with one of us or all of us.

I am a registered dietitian and certified diabetes care education specialist. I am the CEO of Sound Bites Incorporated, which is a food and nutrition communications business.

And I’m the host of the Sound Bites Podcast, which I’ve been doing for over nine years, where I interview experts on a variety of topics and encourage and empower listeners to enjoy their food with health in mind.

Jill, I’ll turn it over to you.

Jill Castle (01:27):

Sure. I am a pediatric dietitian of over 30 years, and I am the founder and CEO of The Nourish Child, which is a parent education website, and a podcast as well since 2016.

I am also an author, just publishing my sixth book called Kids Thrive at Every Size: How to Nourish Your Big, Small, or In-Between Child for a Lifetime of Health and Happiness.

Melissa Joy (01:55):

And Karen.

Karen Collins (01:56):

I’m Karen Collins. I’m a registered dietitian nutritionist who focuses on translating nutrition research related to heart health cancer, and their intersection. I’m nutrition advisor to the American Institute for Cancer Research, and I write nutrition research summaries for various publications and for my website, karencollinsnutrition.com.

I love helping my fellow dietitians build their skills and confidence, translating research, which I do through my dietitian’s only membership, and as a provider of CDR-approved continuing professional education modules.

Melissa Joy (02:32):

Thank you both, and I’m so excited to have you both together on the podcast because I’ve had you both on my show recently, and I’m just excited to dig into these myths. So, I’m just going to list out the four myths that we’re going to cover, and then we’ll dig right in and share some science.

So, the four myths about soy foods are:

One, “Soy increases risk of breast cancer.”

Two, “Soy causes feminization.”

Three, “Seed oils are bad for your health.”

And four, “Processed soy foods do not provide as many health and nutrition benefits as traditional soy foods like tofu and tempeh.”

And Jill is going to start us off with the first myth, which is the one that I just read, the processed soy foods. We’re going to talk about the myths and some headlines and some insights, and some research and some takeaways.

So, I’ll turn it over to you, Jill.

Jill Castle (03:25):

Perfect, perfect, perfect. So, we’re going to start with “Processed soy foods do not provide as many health and nutrition benefits as traditional soy foods like tofu and tempeh.”

So, if you read the news, which I do, I’m always getting sort of the alerts for all the different topics that I’m interested in. I just want to read a few of these sort of headline news quotes, I guess, if you will, from all these different outlets. So, the first one:

“Ultra-processed foods — some more than others linked to early death.” This came out of Harvard.

A second one: “Here are the ultra-processed foods you most need to avoid according to a 30-year study.” That was published by CNN.

“Could ultra-processed foods be the new silent killer?” That came out of Florida Atlantic University.

And for the last one: “The riskiest of all processed foods: one of the most robust studies.” Yahoo just published that two days ago.

So, our job is to sort of present the research, and this is why we have Karen here because she is such a good analytical brain around research, and she’s going to keep us all on point with what the research is telling us about this. So, what do you think about this, Melissa?

Melissa Joy (04:52):

So, I’m going to share some insights before we dig into the research and then we’ll all share our thoughts and takeaways. But yeah, my head is already spinning from these sensational headlines that you’ve shared with us, Jill.

So, one of the insights that I pulled out that I’d like to share is from the 2024 Food and Health Survey by the International Food Information Council. I recently did a podcast episode on this survey, but one of the key findings in the executive summary of this year’s survey was most people say they avoid processed foods to some degree, but only one in three are familiar with the term “ultra-processed foods.”

Now, I will say that this is just about processed foods in general, not specifically related to soy. I do have a couple insights related to soy that I’ll share, but I also wanted to say in the 2023 Food and Health Survey by IFIC, when people were asked, “Do you consider whether the food is processed before purchasing the product?” Three in four, say they consider if a food is processed and 6 in 10, try to avoid it.

And also, when asked, “Which of the following terms best defines a healthy food to you?” 23% chose the phrase “minimal or no processing.” Not to confuse things, but back to the 2024 survey, basically 8 in 10 people surveyed consider if a food is processed prior to purchasing it.

So, we’re seeing people being aware of this term and perceiving it in a negative connotation. There was also a survey or insights by a company called Reputation Leaders, this is an online survey. In May of 2023, they asked people, “Do you have any concerns that prevent you from purchasing or consuming soy-based products?” And 24% said, “I worry about soy-based products being ultra-processed.”

So, just a few of the insights there related to this topic, and I don’t want to jump ahead, but I think part of the problem is people are hearing this term more, but what does it mean? So, I guess I’ll just tease that, and I’ll turn it over to Karen for some research tidbits.

Karen Collins (07:05):

Yeah, some very interesting findings you both just shared, and especially the quote that 80% of people was it, are looking for less processed foods, is kind of in contrast with the fact that surveys show that on average, U.S. adults get 57% of their calories from ultra-processed foods, and children get 67% from these foods.

So, there is clearly a whole lot of mix up. If they are looking for non-processed foods, they’re clearly not doing a very good job. But maybe that’s a good thing because actually, this whole issue of what’s processed, what’s ultra-processed, and does it matter is really important. So, let’s just clarify a little bit of that.

In the research, the kinds of things that Jill was just sharing, usually, the studies define ultra-processed foods using a system called NOVA. There are a few others, but most of the research uses that. And what’s really important to know is that the foods are categorized as ultra-processed based on the type and the amount of processing, not the nutrient content. So, it does not say anything about nutrients just being labeled ultra-processed.

Now, many of the most common ultra-processed foods, the things people are eating most are concentrated in calories. They tend to be lower in fiber, lower in nutrients and so forth, but not always. That’s a blanket statement that doesn’t apply to them all. What matters in terms of whether it’s ultra-processed or not, is what’s on the ingredient list, not the number of ingredients.

Virtually, all the evidence about ultra-processed foods and health risks is from observational studies. That’s research that shows things that are associated with each other without showing that one causes the other.

So, what we can say is that as a whole, people who consume more ultra-processed foods do show a higher risk of obesity, type two diabetes, cardiovascular disease, and possibly, some cancers. But there are three key points that we’ve got to keep in mind when we hear about these headlines.

First, the quality and the credibility of the evidence of these studies is graded generally as low. This can reflect in precision in identifying how much ultra-processed food someone consumes. It’s not as clear cut as it sounds: whole grain bread, peanut butter, raisins, even brown rice can be minimally processed, processed, or ultra-processed with just very small differences.

And most people, dietitians know it’s hard to get an accurate dietary assessment from anybody just on general foods, much less the minute differences in what kind of whole grain bread they buy, for example. So, we really have to look at these studies with some concern.

And there are inconsistencies, and this is where watching the headlines comes in because what you’ll see is the headlines or the news stories will highlight what ultra-processed foods were related to an increased risk.

But in almost all those studies, there’s something else they weren’t related to, but that doesn’t make it into the stories. So, it’ll say related to this, some cancer but not other cancer. And then different studies show opposite things.

So, how we translate this research is also not clear cut. So, point number two to think about is the problem is grouping all ultra-processed foods together.

Now, studies show that when we look at people who consume high amounts of ultra-processed foods, generally, what they’re eating more of, there’s more sugar sweetened beverages, more French fries, fast food, desserts like candy, cookies, cakes, more processed meats, more packaged salty snack foods, and ready-to-eat or eat meals.

So, when we see the relationship to health associations remember that those are the foods they’re eating. So, that doesn’t necessarily mean that other foods that are ultra-processed, like a whole grain cereal or a veggie burger or an unsweetened soy milk — they are technically defined as ultra-processed, but that is not what those people are generally consuming a lot of who are showing health risks.

Third, we have to consider confounders, other things that are part of these diets. So, what is a diet like that’s high in ultra-processed foods? Are they controlling for calories because the ultra-processed foods that most people are choosing may be higher in calories.

Now, some studies, they do it as a percent of calories, but it is important to consider that. We have to look at diet quality. If you’re eating more of these major ultra-processed foods that are what people are consuming, what are they not eating? What is it replacing?

Generally, the diets that are high in ultra-processed foods are low in vegetables, lower in fruits, lower in whole grains than is recommended for health.

And we have to ask, is it the foods that are the problem, or is it that many of these are very accessible, and having many of these types of ultra-processed foods, the snack food kinds of things around all day, is it promoting all day snacking and basic overeating? That’s all part of the dietary pattern that goes with high ultra-processed food consumption.

Jill Castle (12:35):

Can I ask you a question, Karen, and Melissa you too — so, NHANES does these data among youth in terms of consumption of ultra-processed foods has shown that 67% of total energy intake is coming from ultra-processed foods. This is NHANES cycle data.

And when we think about the way we classify ultra-processed foods in that that can in and of itself be a little problematic to interpreting this information, I mean, what’s your sense of that? Because these massive organizations are doing this retrospective analytical analysis and basing it on NOVA classification, presumably. Correct?

Karen Collins (13:22):

Most of them do, and they generally will say in this study, most of them do use NOVA, and that’s kind of what I was getting at when talking about the inaccuracies of dietary assessment. There are some foods that if I ask you how often you consume — potato chips, for example, that is ultra-processed foods, and there’s really not any question like, “Ooh, I don’t know the nuances if it’s baked or fried or what oil they’re using.” It’s an ultra-processed food.

And so, for most people, because of the choices, again, what we’re seeing, a lot of the studies don’t show what foods people were selecting, but some studies in the supplemental data, you can go and you can see what ultra-processed foods were they eating.

And almost inherently, most of them, it’s high sugar sweetened beverages. It’s the packaged sweet or salty snack foods. It’s those kinds of products. And so, in that sense, they probably are capturing the people who are eating the most ultra-processed foods.

There’s a few foods that are vague. So, for example, some of those examples I gave you of whole grain bread or peanut butter, which could be ultra-processed, could not be … but for most people, that’s going to be a smaller part of their diet.

So, I mean, you can niggle over whether it’s exactly 57% of calories or whether it’s 45 or 60%, but we probably are seeing that in general, people whose diets are high in these kinds of ultra-processed foods.

Again, is it the ultra-processed? Is it that it’s high calorie? Is it that it’s low nutrients? Is it a dietary pattern? Which I think we really have to emphasize, is what are you not eating because you’re choosing ultra-processed foods.

And in general, those dietary patterns are exactly the opposite of what’s recommended for health, which is more fruits, vegetables, whole grains.

Melissa Joy (15:24):

Nutrient-dense foods.

Karen Collins (15:25):

Yeah, exactly.

Melissa Joy (15:26):

Yeah, and I think the definition or lack thereof is a big issue. Even though many of the research studies are using NOVA, not all of them are. So, then it’s kind of like comparing apples and oranges or apple juice and orange juice. I just made that up.

Jill Castle (15:42):

That was a good one.

Melissa Joy (15:43):

There you go. But also, with regard to the amount of processed foods that people are currently consuming, that makes me think of the research paper published in the Journal of Nutrition by Julie Hess, where the purpose was to determine the feasibility of building a menu that aligns with the recommendations for the healthy dietary pattern from the 2020 dietary guidelines and includes 80% or more of the calories from ultra-processed foods as defined by NOVA.

And what they concluded, long story short, was that healthy dietary patterns can include most of their energy from ultra-processed foods and still receive a high diet quality score higher than what Americans are currently getting, and contain adequate amounts of most macro and micronutrients.

I keep coming back to the lack of the definition, but also that not all processed and ultra-processed foods are created equal. Again, reiterating some of the foods that Karen already mentioned: fruit flavored yogurt, soy milk, canned greens, packaged whole wheat bread, and tofu can be considered ultra-processed.

Jill Castle (16:47):

Yeah, and I mean, I think about when I look at this, and I know my parents out there are listening, hear that two thirds of the energy their kids are consuming are from ultra-processed foods — that doesn’t feel right because I know they’re eating peanut butter sandwiches.

Peanut butter sandwich would be considered ultra-processed by these definitions. And so, that nuance around the nutrient content is very important, I think.

Melissa Joy (17:11):

I agree. A lot of these “ultra-processed” foods like this peanut butter sandwich, they’re providing nutrients of public health concern.

Karen Collins (17:21):

And the flip side, Julie Hess that you just mentioned, did a flip side study just published where she took the opposite side and did what’s called a Western dietary pattern, which is associated in general, it’s a high in red meats, refined grains, sweets and so forth, and it’s associated with greater risk of all the chronic diseases: type two diabetes, cardiovascular disease, and cancer.

And she said, what if we took that western diet and differed whether we constructed it out of ultra-processed foods or minimally processed foods. And yeah, you can have a western diet largely made out of minimally processed foods, and it’s still going to be an unhealthy pattern. It’s just going to cost more and have a lower, shorter shelf life.

So, this idea that everybody wants to simplify it. Give me a simple way to eat healthy. And unfortunately, the idea that just avoiding ultra-processed foods as a whole category is the way to do it is not an accurate way to identify healthy eating.

Melissa Joy (18:24):

Good point. And that makes me think of the health equity lens that we do look at things through as dietitians. And the unintended consequences could be the increased food costs, decreased accessibility, increased food prep time, the food guilt of course (I’m the guilt-free RD), so I don’t like any of that food guilt, and just the confusion and the negative messaging and the fear-mongering.

Karen Collins (18:45):

So, for me, the takeaway that I share with people is that we need to differentiate between ultra-processed foods that are nutrient-dense, sometimes because they have fortification versus those that are high in added calories, added sugars, and unhealthy fats, but low in nutrients.

And the food choices that may be best for one person may be different than the best options for someone else. So, as dietitians, we can help people consider what barriers are keeping them from a diet that supports good health, and make choices by asking if a food is going to move them closer to or further from that kind of dietary pattern.

And for people who would benefit from reducing ultra-processed foods, make sure to clarify what alternatives, what replaces those ultra-processed foods that will work for people. What about you guys?

Jill Castle (19:36):

For me, I think let’s bring common sense back into the picture. I think parents out there inherently know which foods are nourishing their children and which are not nourishing their children well. And so, put your thinking cap on and use your common sense.

There are nuances, but our job as registered dietitians and healthcare providers is to split the hairs and look at the research and the nuances. But as a parent out there who is trying to navigate all of this, a peanut butter sandwich is going to nourish your child well, it’s going to provide nutrients. And so, look at food through a nutrient lens is usually my advice. Does what you’re offering your child offer a good source of nutrients?

And you can see that on the package, you can look at the nutrition facts labels. And if it’s not the a package, you’re probably more likely to get nutrients from those foods.

Melissa Joy (20:29):

I would agree with both of you. And I would just also add, we definitely need to keep in mind the access to nutrient-rich foods and not shame foods if they’re in a box or a can, and whether it’s a person with food insecurity or just the cost of groceries these days, or for people who follow traditional cultural diets — we just need to have that sensitivity and that, like you said, common sense. I love it.

Jill Castle (20:54):

So, do we have some resources we might want to offer our listeners if they’d like to dive into this topic a little bit more?

Karen Collins (21:03):

Well, I really like the fact sheet that the Soy Nutrition Institute Global has put together called Navigating the Nuances of Ultra-Processed Foods. It’s super brief. So, whether it’s for the general public, like if my sister’s listening, this would be a good one for you, or for dietitians who want to have something they can hand out that’s super simple, I like that one.

And just a pitch, if you haven’t heard for the dietitians out there, I am offering CDR-approved continuing education now, and my first module is ultra-processed foods. What is the research on cardiovascular health and cancer, and how do we translate that into practical advice?

Jill Castle (21:44):

I’ll just add, I interviewed Julie Hess as well on the Nourish Child, and so you can go and listen to that episode. It’s called Can Ultra-Processed Foods be Nutritious?

Melissa Joy (21:54):

Excellent.

Karen Collins (21:55):

And Melissa, you have some podcasts too, don’t you?

Melissa Joy (21:58):

Yeah, I have two kind of related podcasts, one with Dr. Mark Messina, Ultra-Processed Foods and Hyper Palatability, which is an interesting topic that we don’t have time to cover today, so I encourage people to check that out. It’s episode 205.

And also, I interviewed Dr. Joanne Slavin about ultra-processed foods and the dietary guidance and where the research is to date. We’ll have links to all of these resources and everything that we talk about today in the show notes at soundbitesrd.com.

Jill Castle (22:28):

And at thenourishedchild.com.

Melissa Joy (22:29):

Excellent.

Jill Castle (22:30):

Let’s go on to the next myth. Myth number two is seed oils are bad for your health. So, here are some of the leading headlines out there.

“Seed oils — is your canola oil killing you?” That’s from Gimlet.

“Widely consumed vegetable oil leads to an unhealthy gut.” That was put out by UC Riverside.

And the third one: “Why everyone on the internet suddenly hates seed oil.” And Salon put that out.

I’ve got four or five more, but we’ll start with those.

Oh boy, seed oil, seed oils, the bad boy of nutrition. Melissa, what insights do you have on this myth?

Melissa Joy (23:20):

I have a few to share, one from the reputation leaders that I mentioned before on their plant protein research in August of 2023, concerns about soy-based products.

23% of the people surveyed said, “I worry that seed oils including soybean oil are unhealthy.”

There was another survey called Social Media Listening. This was done January 1st, 2022 through January 31st, 2023, and basically, shows that traditional media coverage of seed oils had increased 62% from 2022 to 2023.

And when we were looking at the negative associations of seed oils on Twitter, this is the laundry list of the negative associations that people were making with seed oils. One was obesity, the second one was inflammation, the third one was heart disease, the fourth one was diabetes, fifth was cancer, and the sixth was testosterone.

Jill Castle (24:26):

Everything causes obesity today, right?

Karen Collins (24:28):

See, for me, this is a classic example of what I don’t like about having so much information on the internet.

Jill Castle (24:37):

Yeah.

Karen Collins (24:37):

What happens is something comes out years and years ago, it’s debunked by sound science, but once it’s out on the internet, it just goes round and round and round, and you have it picked up by people who don’t know nutrition science and keep circulating it thinking they’re doing good stuff. And it’s really unfortunate because this is very outdated information that’s being circulated.

These fears that omega-6 fatty acids, a lot of it involves the fears that they promote inflammation, so let’s just dive into that. It’s coming from the fact that these omega-6 fatty acids are high in linoleic acid, an essential omega-6 PUFA or polyunsaturated fat.

And yes, if we look at a metabolic pathway, we can see that it can form gamma-linolenic acid and then arachidonic acid, and arachidonic acid is the bad boy in these headlines that can give rise to a range of compounds, including some that are considered to be pro-inflammatory.

But that is looking at one tiny piece of a thousand-piece jigsaw puzzle. Here are three points that I think are really important on this that often get overlooked.

First, stable isotope studies in controlled trials in humans (not just in a lab, but in humans) show that increasing linoleic acid, that omega-6 fatty acid in the diet actually has very limited effects on changing the levels of arachidonic acid, the one that’s stated to be scary on changing body levels of that. So, it’s not as simple as just looking at what pathway it could have.

Secondly, this arachidonic acid that’s labeled as the bad boy does not only form inflammatory metabolites, it’s also the precursor to important anti-inflammatory metabolites and mediators that resolve inflammation.

And so, third, we always then look to human trials what happens, and in randomized control trials and prospective observational studies, higher intake of these omega-6 PUFAs and linoleic acid are not associated with higher levels of biomarkers of inflammation like one called CRP, which is the most well-known.

And then long-term studies show no increase in cardiovascular disease risks, and if anything, lower risk of cardiovascular disease, cancer, and all cause mortality with higher levels of linoleic acid, whether that’s based on an assessment of consumption in the diet, or based on actual levels of linoleic acid in body fat or in the blood.

So again, those old myths are just taking metabolic pathways and completely overlooking all research that has totally debunked that has occurred since.

Some people get hung up on the issue of the omega-6/omega-3 ratio, even though that’s really no longer supported. Melissa, you covered this in one of your podcast episodes, didn’t you?

Melissa Joy (27:55):

I did, and I found this to be very compelling because it’s again, one of those things that is definitely persisting and I feel like as a health professional, I thought that this was still a thing. So, I asked my guest, Martha Belury, to educate me on this.

So, the fact is that seed oils have a high omega-6 to omega-3 ratio. At one point, the scientific consensus was that a high dietary omega-6 to omega-3 fatty acid ratio was harmful. However, current understanding does not support the broad characterizations that omega-6 polyunsaturated fatty acids are pro-inflammatory, and that omega-3 polyunsaturated fatty acids are anti-inflammatory.

So, the population studies often show that higher linoleic acid intake and biomarkers of intake are associated with reduced rather than increased inflammation. I would also just say that this is kind of interesting too, is that the inflammation is not caused by the high ratio, but by the low intake of the long chain omega-3 PUFAs. So, I thought that was interesting as well to add.

Karen Collins (29:07):

I think that’s a really important takeaway. And just think logically, going back to what Jill said earlier about, put your thinking cap on — if the ratio is what’s important, that would suggest that lowering the ratio, whether it was by reducing omega-6 or increasing omega-3s would have the same effects. And that is clearly not true.

Because we see that higher omega-6, in fact, is associated with lower risk of these conditions that we were mentioning. The problem is that we don’t consume enough omega-3s, and we can’t fix that by cutting back on omega-6s.

Melissa Joy (29:45):

And I’ll just add that there are many authoritative health organizations such as the Academy of Nutrition and Dietetics, and the American Heart Association that recommend intake of vegetable oils including seed or omega-6 PUFA containing oils as part of healthy dietary patterns.

Karen Collins (30:01):

Absolutely. So, when I think about the key takeaways, this is circling back again so that we have to focus on overall diet quality based on what specific foods you are choosing and what they would be replacing. Some studies that allegedly link omega-6 fatty acids to negative health outcomes don’t consider the overall dietary pattern.

So, where are you getting your omega-6 fatty acids if you’re eating a lot of high calorie low-nutrient snack foods? Yeah, it’s not the fault of the omega-6s, it’s the foods that you are getting them from. So, don’t be afraid of the oils, look at overall diet quality and what that food is giving you, and what you could replace it with that might be doing more for your health.

What about you guys? How do you see the takeaways for your people?

Jill Castle (30:54):

For parents, I know kids don’t get enough omega-3 fatty acids and they’re uber important for brain development and function. And so, introducing fish at an early age, really using other sources of omega-3 oils like olive oil are really helpful in this neck of the woods, and possibly, even supplementation because just a lot of kids aren’t meeting that need at all.

Melissa Joy (31:23):

And I’ll just add that the practical takeaway is literally when you go to the store, what oils do you buy and how do you use them? And I did a podcast interview with Wendy Bazillian on seed oils and she shared a lot of practical takeaways about it’s more than just smoke point.

So, something like soybean oil is great for sauteing or grilling vegetables, creating dressings for salads and sandwiches, even baking. Other oils that have a lower smoke point, you would be more careful about how you’re using those.

Karen Collins (31:57):

Melissa’s got those excellent — Sound Bite Podcast, we’ll have those in the show notes, I’m sure. For the dietitians here who are looking for a handout that they could use to counter this information with their clients, we’ll also have a link to an infographic from the American Heart Association, which is called 4 Ways to Get Good Fats, and that includes putting all this in perspective. And I think that in a simple one-page handout could be really helpful.

Melissa Joy (32:26):

And I’ll just add some of my podcasts offer free continuing education, and I forgot to check if the ones that I’m referring to, I think almost all of the ones that I’m mentioning today do offer continuing education opportunities for dietitians.

Jill Castle (32:39):

Alright, myth number three: “Soy increases the risk of breast cancer.”

Now, when I look at the headlines around soy and breast cancer, there are a lot and they keep coming out and coming out, but they are very favorable or neutral about the role of soy.

But as you pointed out, Karen, when we were pre-planning this, the interesting point here is that even though a Google search will show headlines that are generally neutral on soy, there are still tons of fear and information being passed along, calling for caution or avoidance, particularly after ER positive breast cancer, which you’re going to talk about a little bit.

But here are some of the headlines that are popping up:

“Does soy affect breast cancer risk?” That’s out from Cleveland Clinic

“For breast cancer survivors, eating soy is tied to a longevity boost.” That’s out of NPR.

And then just picked this one up today: “Does breast cancer feed off of soy?” That’s out of Nebraska medicine.

So again, these headlines can alert us to what people are thinking and what the trends are, but also convey the fear and misinformation that’s out there. So, Melissa, you were going to share some insights about this.

Melissa Joy (34:05):

Yes. So, going back to the reputation leaders survey on plant protein research from 2023, when people were asked about concerns about soy-based products, 26% said, “I worry about the risk of breast cancer.” And 24% said, “I worry about soy’s estrogen mimicking effects.”

There’s another survey conducted by Soy Connection that looked at soy related concerns professionals hear from their clients. And when it came to breast cancer, they were comparing the concerns from 2022 to 2023, and they saw a significant increase in concern.

So, in 2022, 34% of health professionals said that they’re hearing soy-related concerns from their clients. In 2023, it was up to 47%. And again, that was a significant increase from year to year.

Karen Collins (35:00):

For sure. So much fear. And yeah, for many people in the population by what you saw in the Google search, Jill, this may not resonate. But I can tell you as nutrition advisor to the American Institute for Cancer Research, for people who feel that they’re at risk of breast cancer or who have had a diagnosis of breast cancer, or health professionals who work with people who have had breast cancer, there is a huge amount of concern and a whole lot of misinformation.

The first and most important thing to understand based … all this is stemming from the concept that soy foods have natural plant compounds called isoflavones, and they have been categorized as phytoestrogens, plant estrogens because they have a chemical structure that’s similar to human estrogen.

But honestly, if you do one thing, please stop using the term phytoestrogen. Technically, that’s true. Their structure is somewhat similar, but they don’t act like estrogen in the body. They function very differently. And just using that term is what sends the red lights flashing and the fear going for people. So, let’s look behind the headlines on three fears related to this.

First, where did all this even start? The fears started with rodent studies where breast cancer cells were implanted in mice, and then when they were exposed to isoflavones, that tended to fuel the growth of those cells.

Well, what we didn’t realize at the time, this was decades ago, rodents don’t metabolize isoflavones like humans do. So, this resulted in blood levels way beyond what humans would get from consuming soy foods. And at the time, we didn’t have human studies.

Now, we have human randomized control studies and soy protein powder or soy isoflavone supplements. Often, the studies use isolated soy isoflavone so that they can have exactly controlled equivalent doses provided. And these show absolutely no effect on markers of breast cancer risk like hormone levels, like markers of breast cell growth or breast density.

So, there’s no evidence, in other words from humans that soy promotes breast cancer risk, but that leaves us still a lingering fear for people after a breast cancer diagnosis.

And here, we have several forms of evidence. Population studies consistently show no increased risk for breast cancer survivors who consume soy foods. And in fact, the 2023 AICR/WCRF, American Institute for Cancer Research, CUP Global Report on breast cancer survivors rated evidence limited suggestive that soy food consumption is associated with greater survival and decrease recurrence. And that includes in women who had estrogen receptor positive cancer.

And what’s really interesting is that the link to overall survival — so it was associated with lower breast cancer mortality, but also lower overall mortality, and that lower overall mortality may reflect a role for soy foods and eating habits to benefit heart health, because for people living with and beyond breast cancer, heart health is actually a very big concern.

And soy foods, as we’ve said, provide unsaturated fat, which reduces LDL cholesterol when it replaces saturated fat. It’s a way to have plant protein as people cut back on red and processed meats, and may help lower LDL cholesterol. So, it’s not — the evidence does not (let me say this again), is not strong enough to support advocating including soy foods to reduce the risk of recurrence or mortality.

The evidence graded limited suggestive is a call for more research, not a call for recommendations, but it does allay the fears that there’s increased risk.

So, we’ve talked about risk of breast cancer, we’ve talked about outcomes after breast cancer, and the third aspect of these fears is, “Yeah, okay, so tofu and tempeh are okay, but what about those foods with soy protein or soy fiber added, these isolated pieces?”

Here, I think the concern is that people are assuming that these isolates concentrate isoflavones. So, they’re picturing getting massive doses of isoflavone beyond what’s identified as safe. What they don’t know is actually, it’s just the opposite. The isoflavone content of isolated soy protein or fiber is dramatically lower than whole soy foods.

So, if you see a protein bar or a cereal or something like that, that has these isolated bits of soy added, it will be lower in isoflavones than a serving of traditional soy foods like tofu or soy milk or something.

So, the key point is that whole soy foods, when we look at things like tofu and tempeh and edamame and soy milk, contain a whole variety of nutrients and many phyto compounds, not just isoflavones, and dietary fiber in many of them.

And as a whole, these combine to contribute to health. Just remember that when you pull out only protein or only fiber, that boosts the protein or the fiber in that food either for nutrient or maybe it’s just there for food texture benefits.

So, it doesn’t bring the whole range of nutrients found in soy foods. So, watch for the health halo. So, it’s not a risk, but you do have to look at, as we’ve been saying, throughout our conversation today, what is the overall nutrition content of that food? Is it working for you or not so much?

Jill Castle (41:09):

That’s great. I think of my audience and obviously, we’re talking about mothers who might have some of these fears, and I think you did a really good job of allaying some of these issues that are out there, and common fears that women have in general.

But I know moms are really busy and they don’t always get the information that they need when they need it. And so, I think it was very helpful, Karen, the way that you just kind of went through each of these major fears and debunked some of them and provided the information that’s needed to continue to operate in life.

So, those who are listening, make sure you share this episode with your other mother friends because other moms are concerned about these issues. Breast cancer is a big issue, it runs in families.

I don’t want to over speak here, but if it has been in your family, your fears may be heightened. And so, Karen has just provided some really amazing information around where the research stands on these issues.

Melissa Joy (42:14):

And I’ll just add my audience is a mix of health professionals, mostly dietitians, but also the general public. And I think this is a perfect example of how I feel many times and many of my dietitian listeners feel like. I know I shouldn’t worry about this, but I don’t know how to communicate that to my patients in the public.

Thank you, Karen, for helping us with that. And that’s something I try to do in my podcast, is bring on experts who know the science and know how to, okay, beyond not worrying about it, how do I help spread that good positive communication?

Karen Collins (42:50):

And I think we really have to lean into the fact that there is so much misinformation and behind that misinformation is fear. So, whether you are just someone who’s interested in nutrition or a health professional, I urge you to check out the resources in our show notes here because you’ll find a very short piece from the American Institute for Cancer Research blog that pulls together what is the current information on these myths and misconceptions about soy and breast cancer. It’s a short read and easy read that you can refer anyone to.

For health professionals who’d like a deeper dive in understanding why these fears aren’t justified, I do have a more in-depth review of the research on my website at Karen Collins Nutrition, and we will have the link to that in the show notes.

And if you want to hear from a panel of experts, the Soy Nutrition Institute Global actually did a webinar. I was one of the speakers along with two other experts including Larry Kushi from the Pathways study, which has got some fabulous data, and we’ll share the link to that in the show notes too.

Jill Castle (44:02):

Awesome, thank you. Alright, we’re going to head into our fourth and final myth, which is: “Soy causes male feminization.”

And I have a personal story about this because when I took my son for his 11-year-old checkup, he had breast buds and I was like, “What is this?” And the pediatrician was like, “This is completely normal. It’s called gynecomastia, and it is a condition that oftentimes happens in puberty.”

But I had a freak out moment at that time. And just as a follow-up, if you see my son walking around, no, he doesn’t have man boobs, it all resolved with time. But this myth is out there and the headlines that keep perseverating things like, “Are soy boys real?” That came out from the Daily Mail.

“Why men are afraid soy will turn them into women.” That came out of The Atlantic, some nutty things.

Out of the Washington Post: “Does drinking soy milk cause men’s breasts to grow bigger?”

So, you can see some of these headlines are so, ugh, they just get you, they tap right into your fear.

Karen Collins (45:20):

Talk about clickbait headline, wow.

Jill Castle (45:22):

A hundred percent. So, Melissa, what kind of insights do you have on this topic of soy causes male feminization?

Melissa Joy (45:31):

Yeah, I just have one quick one. It’s by that same Soy Connection survey that I mentioned last time with the breast cancer. And the question was regarding hormonal effects in males, and again, this is soy-related concerns that professionals hear from their clients.

In 2022, 12% reported that they’re hearing questions about hormonal effects in males. And in 2023, 14%, so a little bit of an increase, not a significant difference, not nearly as high as the breast cancer concerns.

Jill Castle (46:01):

So, we know, and I’ll just lead in before Karen, you’re going to share the research as you know it — but in terms of puberty and boys, we know that there can be an imbalance between estrogen and androgen activity during puberty. This is very, very common. It’s typically transient, it resolves within several months, and it can be caused by other conditions that your child might have.

So, it’s not something that you want to ignore. If you’re noticing it, you should talk to your pediatrician about it and just make sure there aren’t any other endocrine diseases or disorders that are occurring. But for the most part, between the ages of 12 and 16, about half of boys will experience gynecomastia in one or both of their breasts.

Karen Collins (46:50):

Interesting. I mean, that’s great background for us, Jill, about gynecomastia and adolescent health. But listen to those headlines, they were talking to adult men who are afraid of it, talk about way off kilter. So, not only is it not related to gynecomastia, it’s also off topic thinking about it.

So, I think everything that we said about isoflavones not being phytoestrogens in terms of breast cancer is circled around to exactly what we need to consider here. Isoflavones are not estrogens, they don’t act like estrogens in the body. And we have, again, kind of I’ll break it down into three sort of fears people might have on this ground.

First, they might because they’re tying isoflavones and estrogens, think of it raising hormone levels in the body. And yet we have a meta-analysis of 41 different clinical trials, mostly from Western populations, and they found no effects of soy or isoflavone consumption on levels of reproductive hormones in men. So, it’s not going to change male hormones.

Secondly, there’s two placebo controlled clinical trials that evaluated the effects of isoflavones on breast tissue in men, and neither of them found evidence of gynecomastia. So, don’t look there.

And then well, what about circling back to the whole hormonal milieu, is it somehow affecting hormonal effects? And although research is limited, it suggests that soy does not exert any hormonal effects in children or affect pubertal development. And for the adult men out there who are thinking it’s somehow going to affect their fertility, in studies of men that were undergoing in vitro fertilization, intake of soy foods or isoflavones was not related to fertilizations rates or other fertility measures.

So, it doesn’t change your hormones, it doesn’t lead to gynecomastia, and it doesn’t change your fertility. For me, the takeaways here are that we need to lean into the best available science and not just the quick answer of oh, phytoestrogens. Make decisions based on what you think makes sense in healthy eating, not based on isolated compound fears.

Melissa, Jill, what do you think is the most important message to allay these unfounded fears?

Jill Castle (49:34):

I mean, I think for children in puberty, their bodies are changing so rapidly and immensely. Just check in with your pediatrician. They know what’s normal, what’s not. Certainly, if you are a parent of a child with a larger body, I know in girls, you can enter puberty earlier as a result of carrying extra body fat. That has not been shown to my knowledge to be proven in boys.

But I think that sometimes if you are carrying extra body fat, it can show up in the breast area, boys or girls. And so, again, check in with your healthcare provider and have a conversation about it if you’re concerned

There’s a great resource out from the Pediatric Endocrine Society. It’s a PDF download, we’ll include it in the show notes, but it does go through puberty and gynecomastia, so really gives you what the norms are, and when it’s not normal, so you can sort of do a check with your pediatrician and figure out if what you’re seeing is normal and transient, or if it’s something more involved, but it does not appear to be diet-related.

Karen Collins (50:45):

Jill, you had an episode of The Nourished Child Podcast about body image issues in boys too, didn’t you?

Jill Castle (50:51):

I did, I did. I talked with Charlotte Markey, who is the author of the book called The Body Image Book for Boys. Certainly, if boys are experiencing gynecomastia, they may also have some body dissatisfaction and body image challenges. And so, this is a good resource for parents to listen in and with some concrete action steps they can take if their child is experiencing this.

Karen Collins (51:20):

And for the health professionals out there, there is a reference guide for health professionals. We’ll include the link in the show notes called The Health Effects of Soy: A Reference Guide, it published in Frontiers in Nutrition in 2022. And that goes through a whole lot of these different concerns about health and soy, that it summarizes the research. I think for health professionals out there, you might find it really helpful.

Melissa Joy (51:44):

And I don’t have much to add, so I guess we should just wrap up this conversation. Maybe each one of us could share a bottom-line takeaway for our listeners and our respective audiences or what people should do, or what they should be aware of. And of course, we’ll have where people can find more information. But Jill, how about some parting thoughts from you?

Jill Castle (52:07):

Yeah, so parents out there, don’t believe everything you read in the headlines. Number one, seek out your registered dietitians, your trusted healthcare professionals to really help you navigate any fears or concerns you have around your child’s growth, development, puberty, eating habits, eating patterns, nutrient-density of their diet.

There’s so much we can help you with and get to the root of the science. I think that is probably one of the biggest take home messages I can give you.

Melissa Joy (52:39):

Great. And my add on to that would be, be skeptical of those sensational headlines and those social posts. I encourage my listeners, whether you are the general public or a health professional, to really improve critical thinking skills.

I think as health professionals, we need to continually work on improving our critical thinking skills and helping our patients in the public do the same. And I have some resources for that. I have a sound science toolkit that talks about things like confirmation bias that’s all free and accessible on my website at soundbitesrd.com. But ultimately, I just want people to be informed and unafraid. Karen?

Karen Collins (53:16):

Yeah, I think in all these areas, it is important to get, as we said, certainly beyond the headline that you see in the media because that is written specifically to get you to click. That is not a way to get your nutrition information.

The nuances of the research are important to being able to identify what actually makes sense. Dietitians are the trusted translators of nutrition science, and we need to help people stop to consider what kind of research is behind these claims that they hear and how the claims line up with overall research, not looking at individual compounds in isolated lab studies.

Melissa Joy (53:57):

Great. Well, as I’ve said, all the resources will be in my show notes at soundbitesrd.com, but also at Jill’s show notes at thenourishedchild.com.

Jill Castle (54:08):

Yes.

Melissa Joy (54:08):

And I mentioned my sound science toolkit, Karen, I think we’ve shared a lot of resources, but was there anyone in particular that you also wanted to kind of highlight as we are parting ways here?

Karen Collins (54:19):

Well, I’d love for listeners to subscribe to my news list. You can go to my website, karencollinsnutrition.com, and check out any of the research reviews on topics that interest you. And then if you sign up for my newsletter, you’ll be the first to hear when new reviews are published, and for those dietitians out there, you’ll be the first to hear when additional CPE modules become available, and when doors open again to my dietitians-only membership.

Melissa Joy (54:46):

Yes. And I encourage everybody to follow all of us on social. Sign up for all of our newsletters, go to our websites. Don’t forget about Karen’s continuing education opportunities and mine as well. Jill’s new book, her sixth book, Kids Thrive at Every Size.

Thank you again for tuning into this episode. If you liked it, share it with a friend or a family member, tell a coworker about the podcast, both of the podcasts, and as always, enjoy your food with health in mind. Until next time.

Jill Castle (55:19):

And remember, give that child in your life a loving squeeze today. Bye for now.

[Music Playing]

Voiceover (55:26):

For more information, visit soundbitesrd.com. This podcast does not provide medical advice. It is for informational purposes only. Please see a registered dietitian for individualized advice.

Music by Dave Birk, produced by JAG in Detroit Podcasts.

Copyright: Sound Bites, Inc. All Rights Reserved.

ur transcript here…