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120: Is Advice to Eat 30 Different Plants/Week Science-Backed?
2 Playsin 6 hours
In this episode of the Movement Logic Podcast, Laurel Beversdorf revisits the advice to eat 30 different plants per week and explains why it sounds scientific while resting on a much shakier foundation than it appears. She reflects on encountering the claim, why her and Sarah’s initial reaction was skepticism, and how listener feedback led to a closer look at where the idea came from and how it spread.
Laurel breaks down what the American Gut Project actually showed: an observational association between self reported plant variety and gut microbiome diversity in a specific, self selected, largely affluent cohort. She explains why this type of research cannot identify an optimal number of plants or justify turning a statistical cutoff into a universal lifestyle rule, especially given the limits of how plant intake was measured.
She then examines how the venture backed consumer health company Zoe translated this association into a prescriptive target and built products around it, arguing that the clarity and certainty of the message functions as marketing rather than sound, science backed health advice. Finally, Laurel zooms out to the emotional and social impact of this advice, explaining how moralized wellness claims turn health into a performance metric while ignoring access, instability, and other social determinants of health.
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RESOURCES
113: Debunking Menopause Grifters
118: How Should We Eat To Be Healthy? with Abby Langer, RD
102: Moralizing Movement
American Gut Project
McDonald, 2018; PMID: 29795809
Book: The Certainty Illusion, by Timothy Caulfield
Guardian Article: ‘Personalising stuff that doesn’t matter’: the trouble with the Zoe nutrition app
Zoe + Science + Nutrition interview with Prof. Tim Spector
Post: Dr. Lauren Colenso-Semple's infographic on scientific process
Post: What Peter Attia gets wrong
Post: Attia & 30 plants/week
Post: Doctor vs. Brand
Recommended
Transcript
Introduction to The Movement Logic Podcast
00:00:00
Speaker
I'm Laurel Biebersdorf, strength and conditioning coach. And I'm Dr. Sarah Court, physical therapist. With over 30 years of combined experience in fitness, movement, and physical therapy, we believe in strong opinions loosely held. Which means we're not here to hype outdated movement concepts.
00:00:15
Speaker
or to gatekeep or fearmonger strength training for women. For too long, women have been sidelined in strength training. Oh, you mean handed pink dumbbells and told to sculpt? Whatever that means, we're here to change that with tools, evidence, and ideas that center women's needs and voices. Let's dive in.
00:00:48
Speaker
Hey everyone, welcome to the Movement Logic Podcast. I'm your host, Laurel Beversdorf, and today I'm coming to you early in the morning before my family is awake with a little bit of a, and a lot of a rhinovirus. I have had this cold for, oh, going on three weeks, and my voice, you could probably hear it.
00:01:11
Speaker
It's on the mend though, so I'm hopeful that I will be all well and good in a couple days.
Is Eating 30 Different Plants Practical?
00:01:18
Speaker
So we're doing this episode because in previous episode, episode 113, debunking menopause grifters, which was all about Dr. Mary Claire Haver and Dr. Vonda Wright, captains of the menopause. Sarah and I talked about Mary Claire Haver's recommendation that women eat 30 different plants per week. And that recommendation came alongside her sketchy promotion of the Galveston diet as
00:01:46
Speaker
you know, somehow being a specially helpful diet for menopausal women. And so then when we heard this 30 plants advice, we frankly found it ridiculous. I think in our minds, it sounded ridiculous because tracking 30 different plants across an entire week sounded needlessly complex. I mean, we started wondering what even counts as a plant.
00:02:07
Speaker
Plant is an enormous category. And the only comparably large category I can think of is non-plant, which is not an official category, but if there were a non-plant category, of course, it would include animal-derived foods. And then, fun in fact, also fungi, which is actually a fungi fact. um Fungi aren't plants. They are their own biological kingdom. But I digress.
00:02:32
Speaker
Now we're getting into the weeds, although weeds are plants, but you get the point. We were wondering, what is a plant? Is flour a plant? Is corn a plant? I mean, of course they are, but what about highly processed flour or corn? Plants?
00:02:45
Speaker
Not plants. We also wondered if we even liked 30 different plants. And in retrospect, yes, I definitely do. But I think it was really the number itself that felt overwhelming. And then this idea that you would need to track that number of different plants across an entire week. So in this episode, we're going to talk about this piece of advice that we should be eating 30 different plants per week. We're going to talk about what its purported aim is in terms of health. We're going to talk about the research that's cited to support it.
00:03:18
Speaker
And then we're going to talk about who the originator of this advice is. And spoiler, it's not the scientists who worked on the research. And it's also not Mary Claire Haver.
00:03:31
Speaker
Then we'll talk about why this advice is shaky and how it misses the mark and who we think it's really designed to benefit. Before we talk about all this though, we wanna remind you that we have a mini course in the show notes, which is free, and it's all about how to use barbells.
00:03:52
Speaker
Barbell basics, Barbell 101. If you are barbell curious and you would like to learn form and technique for the deadlift, the back squat and the bench press, as well as modifications, and how to use the tools of strength training to progressively overload those exercises, but any exercise in strength training, head to the show notes, click the link, and sign up.
00:04:17
Speaker
If Sarah and I never heard the advice to eat 30 different plants per week, I'm pretty sure that many of you listening have probably also not heard this before. So let's back up.
00:04:28
Speaker
Quick disclaimer, I'm not a gut microbiome researcher, I'm not a dietician, and I'm not a nutrition scientist.
The Role of Plant Variety in Gut Health
00:04:35
Speaker
So everything I'm sharing in this episode comes from reading some research literature, listening to interviews with researchers who do study this stuff, and following how these ideas are discussed and marketed in public-facing health spaces. So this is more of a synthesis and critical thinking. It's definitely not an expert analysis, all right? So the idea behind eating 30 different plants per week is is rooted in research on the gut microbiome.
00:05:04
Speaker
Our gut microbiome refers to the trillions of bacteria and other microbes that live in our digestive tract, and these are known to play roles in digestion, immune function, inflammation regulation, and our metabolic health. This field on the microbiome is relatively new because advances in DNA sequencing have made it possible now to be able to see this full ecosystem with a lot more clarity than we used to be able to do. So just in the last 15 to 20 years, this has become an emerging field in science. And there are way more questions than answers.
00:05:47
Speaker
But one consistent finding in this research has been that diets higher in plant foods tend to be associated with greater microbial diversity. And this makes sense because humans and gut microbes have evolved together. So we kind of rely on each other, you know? Humans rely on microbes to break down plant fibers that we are not able to directly digest ourselves. And I learned about this researching for this episode, and I think it's pretty cool. So these microbes do us a solid, ah and they ferment these fibers that we can't digest directly. They do that for us. Thank you.
00:06:27
Speaker
When these microbes ferment these fibers for us, this ends up producing compounds that appear to support not only our gut health and function, but also really important system-wide processes. So they help us digest stuff we can't digest, and then what comes out of that is good for us, right? So the practical takeaway often coming out of this finding, this body of work, broadly speaking, is that when we eat a variety of plant foods, that may help support a more diverse
00:07:05
Speaker
gut microbiome, which is commonly framed as a marker of better gut health. So what do the current established nutrition guidelines actually say about eating plants?
00:07:19
Speaker
Okay, so the advice to eat 30 different plants per week is not a guideline from any major nutrition authority. The US dietary guidelines recommend five servings of fruits and vegetables per day with an emphasis on variety over time, but not fastidious tracking.
00:07:39
Speaker
Okay, so five per day feels more manageable to me than 30 per week. It's a smaller number, it's a shorter time period in which to be tracking, It doesn't require that I keep this running tally in my head all week long. The current guidelines also advise making at least half of all grain intake whole grains. They recommend a regular inclusion of legumes and making nuts and seeds a regular part of our dietary pattern. So these are broad,
00:08:09
Speaker
general, largely achievable, quite simple recommendations. So let's go back to the episode we mentioned this advice in initially. So Sarah encountered it in her research around Mary Claire Haver. And when I heard it on air for the first time, We both guffawed and we basically chalked it up to something that we see Mary Claire Haver and the menopause do frequently, which is she uses the language and aesthetics of evidence-based medicine along with her credentials as a board-certified OBGYN to deliver science-y sounding advice.
00:08:45
Speaker
with a very high level of certainty. But when you take a look at the science she's referencing or the medical guidelines that her advice frequently diverges from, you quickly realize that she either is inaccurately representing the science or that she's going against the guidelines. And she does this to millions of her followers. Sarah and I have both been blocked by her. So we don't know her current exact follower count, but the last time we checked it was around 1.5 million
00:09:19
Speaker
Now, after that episode, which we have linked in the show notes, I'm going to link everything I referenced in this episode in the show notes, by the way. After that episode, we heard from many listeners. And these were clearly regular listeners to the podcast who were very much on board with critical thinking,
00:09:35
Speaker
And they basically wrote us saying essentially, hey Sarah and Laurel, regular listener of the pod, love your work. But I heard you mention the 30 different plants per week recommendation and heads up, like this recommendation didn't come out of nowhere. It traces back to a legit study, the American Gut Project and an epidemiologist named Tim Spector.
00:10:00
Speaker
And then the Zoe app. And many of you wanted to reassure us that eating 30 plants a week is not that hard. And you pointed out that in the Zoe app, herbs and spices count toward the the total 30 count. And one listener even noted that coffee counts because they were obviously aware that Sarah and I love our coffee. And all of you who reached out were right about the origin of this claim. And you were right about the research and you were right about the folks propagating this claim And Sarah and I, up until that point, were not aware. So what we aim to entangle in this episode is the difference between what the study, the American Gut Project, actually showed, and then how many scientists, Tim Spector is one of them, and other influencers who work for ZOE, which is a venture capital company, how those scientists have shared
00:10:57
Speaker
the findings of this study. That's what we're getting into today. Now, if you don't know, as I said, Zoe's Venture-Backed, it's a consumer health company. It sells personalized nutrition advice and products based on microbiome and metabolic testing. It has, in our opinion, dubiously translated the observational research from the American Gut Project and other research that it conducts into app-based scores, recommendations, and a supplement. So media coverage of ZOE has estimated its valuation in the several hundred million dollar range. So we're talking about a big profitable company and
00:11:37
Speaker
about Tim Spector, who is, yes, an epidemiologist. He's a genetic epidemiologist. He was involved in the UK arm of the American Gut Project. He's co-founder of the ZOEAP, and he has since become one of the most visible public translators of the American Gut Project research. And he does this through his many media appearances, through his books. I've listened to several episodes in which he's interviewed, and I'm going to be frank which is that my spidey senses are up my hackles are raised i haven't listened to a ton of his messaging but i can say that the little that i have heard gives me pause aka his science communication is sketch and so we're going to talk a little bit more about this later so with this map in mind let's slow down let's look at what the american gut project the observational studies always cites to support
00:12:33
Speaker
Zoe's advice to eat 30 different plants per week. Let's look at what it actually set out to do and just as importantly, what it did not set out to do. Okay, so the American Gut Project was able to observe an association between self-reported plant variety and gut microbiome diversity in a very specific and self-selected population. The American Gut Project was not designed to determine an optimal number of plants that someone should eat for a diverse gut microbiome. It was not designed to test whether eating 30 different plants was physiologically special or at what point more plant variety suddenly became enough plant variety to evaluate whether changing someone's diet would lead to concrete health improvements. And it was not designed to generate prescriptive dietary targets for individuals.
00:13:27
Speaker
And this is important because what happened is that Zoe took this single observational finding from the American Gut Project and translated into a food target, which has basically become its brand message. Eat 30 different plants per week. And then of course, a lot of consumer products to help people be able to do
Limitations of the American Gut Project
00:13:51
Speaker
that.
00:13:51
Speaker
Okay, we're gonna get into the nitty gritty of the American Gut Project now. This is a genuinely interesting, very large for its kind observational study that found an association. So we're gonna bookmark that word because it's our word of the day. We're going to hear association a lot in this episode. It found an association between self-reported dietary plant diversity and participants' gut microbiome diversity association. Okay, so the study's stated aim was to look at how different people's gut microbiomes vary or are you know unique
00:14:28
Speaker
to each individual in real life, and it aimed to identify associations between that and not only self-reported diet, but lifestyle and health factors. And it did this in a very large real-world cohort. So this was a citizen science study. Citizen science means this is research where members of the public are not just study subjects whose scientists recruit and monitor and measure, but they actively carried out parts of the research themselves. So these are volunteers who around 2018, the time of the paper, paid 99 bucks to participate in this study. And so they signed up online, they paid their money, they completed a lengthy questionnaire, they collected their own stool samples at home, and they mailed that shit in.
00:15:15
Speaker
Now this study design, the way they did this, as a citizen science study, this was both this study's strength and this study's limitation. It was a strength because it allowed researchers to study gut microbiomes at an unprecedented scale.
00:15:32
Speaker
using this modern DNA sequencing. But it was a limitation because it also meant that the sample of over 10,000 people was not representative of the general population. And the authors were very explicit about this. This cohort skewed wealthier. They skewed more educated. They skewed less likely to smoke, less likely to be obese. And It underrepresented Hispanic and African-American participants. So in practical terms, this was a self-selected group with a disposable income, right? So they probably had stable housing, internet access, time, and obviously an interest in gut health.
00:16:12
Speaker
Okay, let's talk about a really big part of this research. So one big part was the DNA sequencing, but another really big part, equally big, was this survey that everybody filled out who participated. And this survey is where scientists determined how many different plants per week these people were eating.
00:16:33
Speaker
And we gotta talk about this because from my perspective, Zoe's entire reason for existence hinges on what this survey found from a single self-reported question on this 150 plus question survey which asks participants how many different plants do you eat in an average week okay so this questionnaire from the american gut project was quite long. And when I say 150 plus question survey, it's because questions had multiple parts.
00:17:02
Speaker
So that's on the low end of how you would count up these questions. Participants were asked an enormous range of questions about their bodies, lives, and habits, basic demographics, height, weight, birthplace, where they live, how often they've moved, living situations, things about roommates, pets, indoor, outdoor pets, travel history, and you know international travel history. They were asked about details about their lifestyle, their education level, whether they exercise, smoke, use alcohol, the type of alcohol, the frequency with which they drink. They were asked about their sleep, swimming pools.
00:17:40
Speaker
surfing, nail biting, oral hygiene, deodorant use, and they were asked about fabric softener, which You know, all these little details are very interesting. These things affect the microbiome, apparently, right? Surfing probably because of like regular exposure to the ocean, right? Anyway, then health history. You want to know about your bowel habits, recent antibiotic use, vaccinations, birth control, pregnancy, weight changes, childhood feeding, tonsils, appendix, acne medications, prescription and over-the-counter drugs, mode of birth, stuff about breast milk versus formula, okay? Then there was an extensive diagnostic section about asthma, ADHD, autism, autoimmune disease, diabetes, heart disease, migraines, thyroid and kidney disease, mental health, allergies, food intolerances, epilepsy, dementia, vivid dreams, right? And more.
00:18:34
Speaker
And then only after all of that do participants reach the detailed section about their diet. So here participants are being asked to estimate how often they cook, how often they eat restaurant food, how often they eat grains, fruit, vegetables, dairy, meat, seafood, snacks, sweets. soda, diet drinks, water, olive oil, eggs, fermented food. So almost everything is framed as frequency categories across a typical week. Not how much, but how frequently do you eat this stuff? And then embedded in all of this is one question that looks deceptively simple, and it's in an average week, how many different plants do you eat?
00:19:16
Speaker
Do you eat less than five, six to 10, 11 to 20, 21 30, more than 30? twenty one to thirty more than thirty and plants, right? So like I said, big category, little amorphous. So a brief example is given, and the example is soup with carrots, potatoes, and onions counts as three plants. Multigrain bread counts as multiple plants. Fruit counts, stuff like that.
00:19:40
Speaker
But that's it. There's no definition of what counts as a plant beyond that. No guidance about herbs versus spices. No help with mixed dishes, sauces, condiments, or processed food beyond ah the single soup example. Now imagine answering this honestly and accurately after you've clicked through dozens of questions about your medical history and hygiene and pets and bowel habits and travel. I think that would be cognitively hard. And in this situation, of course, estimation error is probably quite likely. So when we hear clean sounding headlines about how people who eat more than 30 plants per week have this more diverse gut microbiome, it's probably worth remembering the circumstances in which that number 30 was obtained and what that number actually represents.
00:20:35
Speaker
which is a rough self-reported estimate shaped by memory, loose interpretation and wishful thinking. People aren't always honest on surveys. They're not always honest with themselves, um but who knows? We don't know.
00:20:50
Speaker
All this to say, this is not a precise or objective measure of what these people actually ate. Importantly also, at no point did this survey capture the plant quantity people who were eating. There wasn't a single question about how much by weight, volume, servings, how much plant food was eaten, it only captured variety, not dosage. And because the study never measured how much of any kind of food people ate, including plant food, it can't tell us whether the variety itself mattered or whether variety was simply a stand-in for having higher overall diet quality. Eating more plants overall or having more time, money, stability, and health-supporting behaviors that might be associated with a person who marks down on a survey that they eat more than 30 plants per week. All of these could also easily, plausibly explain the observed differences in gut microbiome diversity observed in this cohort. By the way, if you want to read the study,
00:21:56
Speaker
It's linked in the show notes, it's open access. The survey is in the supplementary materials and it is the only docx file. So you can go ahead and look at that survey yourself. You just have to scroll down and see it. Okay, so all these people are wealthy enough to pay $99 to volunteer to participate in the study. But even within this paid self-selected cohort of over 10,000 people, there's going to be a lot of differences that still exist between people, right? differences in education, work schedules, stress, healthy behaviors, and this is represented in the American Gut Project data, which showed a wide variation in BMI, in antibiotic use, in smoking, in exercise, and in health conditions. So even in a perfect world where everyone answered that single survey question accurately, anyone's ability to eat or inability to eat a wide variety of plants would still be sensitive to factors like access, wealth, and more. All of these confounders that I've just named, all of these details that would interfere with this neat finding of people who eat more plants have more diversity of their microbiome, these confounders, they are rarely acknowledged lodgeed in Zoe's own messaging.
00:23:09
Speaker
So let's zoom out and review. Using people's stool samples, scientists measured gut microbial diversity with DNA sequencing. But plant diversity intake was estimated using one memory-based question in a series of about 150 plus unique questions.
00:23:28
Speaker
Now, why 30? So why that number? That is actually from the research, but it doesn't mean what Zoe implies that it means. So researchers, once they had all this data, they grouped participants into categories.
00:23:43
Speaker
They group them into categories of those reporting 10 or fewer plants per week on that one question, those reporting 30 or more, and then a middle group in between. And this kind of grouping is common in observational research. But here's something important to know. That number 30 does not represent a biological threshold of some kind, like this is the point at which the gut microbiome achieves an optimal diversity. No, no, no. This was a statistically convenient cutoff for comparing higher and lower ends of the distribution. So this study, and we're going to talk more about this, was not designed to test
00:24:23
Speaker
something like, is 30 physiologically special? ok What the study found was an association. There's that word again. So people reporting higher plant diversity tended to have more diverse microbiomes. And another important thing, the outcome was microbial diversity, not symptoms, disease risk, health. The study did not test whether eating 30 plants improves health, gut health, right?
00:24:51
Speaker
Let's talk about association versus
Understanding Observational Studies
00:24:54
Speaker
causation. So this was an observational study. And observational studies are great at showing patterns and identifying areas for future research. They're a really important part of the scientific process. They're an early part of the scientific process. Observational studies can tell us that when X is present, we often see y but they cannot tell us that X caused Y. For that, we need a randomized control trial.
00:25:23
Speaker
Observational studies are an important early step in the scientific process. Randomized control trials happen later, and these are where causal recommendations can come from.
00:25:35
Speaker
Now let's root this in an example some of you might be familiar with. And I'm going to link a post by Dr. Lauren Colenzo-Simple, expert in female physiology, in our show notes. We also interviewed her, so we're going to link that as well. So in this link that I'm sharing, she shares an infographic on her social media, on her Instagram page, that spells out what I'm about to tell you in very crystal clear terms. So check it out. Give her a follow on social media as well. She's always posting really helpful, super clear educational content. Let's take the belief that menopause hormone therapy prevents muscle loss in postmenopausal women.
00:26:13
Speaker
I think I used to believe this. It seems legit, right? It seems plausible. Estrogen is an anabolic hormone. Menopause hormone therapy increases estrogen levels in estrogen depleted women.
00:26:26
Speaker
And so not only is this biologically plausible, but this idea began with observational findings that showed that postmenopausal women indeed tended to have less muscle mass than premenopausal women. So estrogen depleted, muscle depleted. That was the connection. However, while this was a real pattern or association, connection, link, when we see X, we tend to see Y.
00:26:53
Speaker
that these observational studies identified. It doesn't show that menopause or estrogen loss causes this decrease in muscle mass. So then, animal studies were conducted, another really important part of the scientific process.
00:27:09
Speaker
And these animal studies explored possible mechanisms. And these showed that when estrogen was removed from rodents, there were effects to their muscle. Okay, but here's the deal. Rodent data is frequently an unreliable proxy for human data. Almost always an unreliable proxy for human data because human lives are a lot longer longer.
00:27:32
Speaker
and their lives and behaviors are a lot more complex than that of rodents. Okay, so then, when estrogen therapy was finally tested in human randomized controlled trials, study after study showed it did not.
00:27:47
Speaker
prevent muscle loss. So while this association was real, postmenopausal women tended to have less muscle mass than premenopausal women or estrogen depleted women tended to have less muscle mass than women who are not estrogen depleted, right? The assumed cause of this reduced muscle mass and solution for this reduced muscle mass, right? Menopause hormone therapy, these were wrong.
00:28:10
Speaker
Now, the reasons postmenopausal women had less muscle mass than premenopausal women is likely due to the fact that postmenopausal women are typically older than premenopausal women, right? Muscle mass declines with age and and they frequently move less and lift less overall, okay? It's not because losing estrogen directly causes their muscles to shrink. Research consistently shows that postmenopausal women who strength train can maintain or increase muscle mass and strength despite their lower estrogen levels. So moral of the story, we cannot take an association from an observational study and treat it as causal. Lower estrogen levels don't appear to directly cause muscle loss.
00:28:53
Speaker
If they did, menopause hormone therapy would reliably prevent it, and it doesn't. Likewise, we don't actually know why the American Gut Project found that people who reported eating more than 30 plants per week tended to have more diverse gut microbiomes. And until we do, we should be cautious about prescribing 30 different plants per week as a causal strategy for improving gut microbiome diversity.
00:29:22
Speaker
Here's another quick example. Say we conduct an observational study on productivity and coffee consumption. I happen to be being productive at the moment, creating a podcast episode and drinking coffee. So we conduct this observational study and we might notice that the most productive workers also drink the most coffee. And it'd be really tempting to conclude that coffee causes productivity, right? But a more likely explanation is a third factor.
00:29:52
Speaker
workload. People with heavier workloads may drink more coffee and also get more done. so Coffee is not a cause of productivity in this case, it's a response to workload. So to test causation, in this case, we would need a randomized controlled trial. So if we wanted to run a randomized controlled trial to test this hypothesis that coffee consumption increases people's productivity, we'd need to randomly assign similar workers to coffee or no coffee. We'd need to hold everything else as constant as possible. And then we'd need some systematic way to measure productivity. And only then could we say whether coffee itself made a difference.
00:30:33
Speaker
So back to the gut microbiome. Features of the gut microbiome may be a marker, a signal of broader lifestyle patterns, may be associated with broader lifestyle patterns, right? Patterns like overall diet quality, stress. healthcare access, work schedules, stability, not the direct results of eating a specific number of different plants per week. So observational studies are valuable for spotting patterns, but it's irresponsible and incorrect to turn them into lifestyle rules, especially if you should know better not to do that.
00:31:15
Speaker
Observational findings are best used to guide further research. And if they're used to guide guidance, that guidance should be broad and flexible, like the current established guidelines.
Critique of the Zoe App and Marketing Tactics
00:31:27
Speaker
Try to get variety. Try to incorporate grains and legumes and nuts, right? This is broad and flexible.
00:31:37
Speaker
It definitely should not be a prescriptive checklist. Try to get at least 30 or more different plants per week. Okay, let's talk about the Zoe app. As we've already noted, the eat 30 different plants per week message is not coming from public health guidelines. It's not coming from clinicians at large. It's not coming from registered dieticians at large. It's not coming from the scientific community at large. It's coming primarily from a company called Zoe and then people who've encountered this company and its claims and are parroting it like Mary Claire Haver.
00:32:13
Speaker
As noted earlier in the episode, Zoe was co-founded in 2017 by Tim Spector, the epidemiologist, and Jonathan Wolff, a technology entrepreneur. It sells at-home testing, mail-in fecal testing, app access with proprietary scoring systems, and a supplement.
00:32:34
Speaker
And it sells all of this to its likely health-conscious app. affluent consumer base. So again, ZOE and the people representing ZOE are responsible for taking a single observational finding from the American Gut Project and translating it into prescriptive lifestyle advice. Okay, so whereas in the study, researchers grouped people by higher and lower ends of a distribution, ZOE took that statistical comparison and reframed it as a behavioral target. Eat 30 different plants per week. That target then becomes a well-defined, seemingly science-supported problem, and then Zoe builds products designed to help users solve it. This pattern isn't unique to Zoe.
00:33:19
Speaker
We see it all the time. In the wellness and consumer health space, Peter Atiyah regularly takes observational data linking higher VO2 max, greater grip strength, and higher muscle mass with lower mortality risk, and then he translates those associations into very specific exercise benchmarks or prescriptions that he says everyone needs to hit.
00:33:46
Speaker
I'm going to link a post Sarah made in the show notes about Atiyah, a breakdown of the issues with Atiyah, and we're going to be doing an episode about him in the coming season. Okay, but because Atiyah an MD, saying what he's saying, right? He's a doctor. It feels serious and official.
00:34:05
Speaker
Similarly, in Tim Spector's case, this is an epidemiologist. This is a scientist, legit scientist. So his advice lands kind of similarly. In many podcast interviews, it's Zoe's scientists speaking for Zoe. These are legit scientists. They're representatives of Zoe, the company. And when they say eating 30 different plants per week is important for gut health, that advice feels really objective and science-based and credible. Add to that our growing public awareness that gut health is important, that fiber is really important, that plants are really important, right? Listen to our interview with registered dietician Abby Langer a few episodes back. We'll link it in the show notes. We talk about lots of different topics around food and food myths, but we talk quite a bit about the importance of fiber and gut health.
00:34:48
Speaker
Right? Plants matter. We've got scientists saying this and we know that gut health is really important to many different aspects of our health. So suddenly this message to eat 30 different plants per week, it doesn't just feel scientific, it feels urgent.
00:35:03
Speaker
Now, to be clear, eating a variety of plants is good for you. So the issue that I'm pointing out is not about these behaviors. The issue is that these doctor marketers and scientist marketers are misleading people.
00:35:19
Speaker
They're turning observational signals into rigid protocols that don't align with the guidelines, and they're doing it in ways that conveniently serve their own purposes.
00:35:31
Speaker
Let's talk about marketing for a second. So unlike scientists, marketing has a much lower ethical bar, right? Don't lie outright, don't commit fraud, what we call false advertising.
00:35:43
Speaker
Okay, so within these bounds, marketers have a lot of wiggle room, and they are heavily incentivized to bend the truth, to create the illusion of objectivity, scientific inevitability.
00:35:57
Speaker
And when that illusion gets attached to a product that helps people feel like they're investing in their health, doing something smart, proactive, good. It's a goldmine.
00:36:09
Speaker
Let's put ourselves in the shoes of the consumer. We're all consumers, right? How does this advice land to us? I guess it depends, right? You hear this advice to eat 30 different plants per week. Sarah and I laughed, but I can see how hearing this advice on a podcast you trust, right? Reading it in a blog post from an influencer you trust hearing scientists say it, hearing your friends talk about it, right? you You care about your health. You care about your family's health. You have some disposable income. You're learning that gut health connects to seemingly every aspect of your health. And then this message comes along and it
00:36:48
Speaker
just slots so neatly into what already feels important to you. So to you, suddenly this advice doesn't seem ridiculous. And then also investing in an app to help you track your plants doesn't seem ridiculous. And seems like a small price to pay, right To take on this extra healthy lifestyle.
00:37:08
Speaker
And then maybe the supplement starts to seem like pretty reasonable. a small price to pay to solve this newly discovered significant problem you have that you didn't even know you had.
00:37:19
Speaker
All the while, the original data these scientists are citing doesn't actually support the certainty of the advice they're giving or the products they're selling you.
00:37:32
Speaker
Let's talk about Zoe's plant scoring system. So we know Zoe's advice is to get 30 different plants per week or more, And to help consumers do this, they have this app that helps you track your 30 plants. So for Zoe's plant counting system, there are rules. And here's some curiosities of this plant scoring system that I was able to find out.
00:37:53
Speaker
Whole plant foods count as one point, regardless of portion size. Regardless of portion size. So this means that a single chia seed counts the same as a whole scoop of chia seeds. A single chia seed.
00:38:07
Speaker
A single lentil counts the same as a whole bowl of lentils. According to Zoe's point system, herbs and spices are typically weighted as fractions, as a quarter fraction.
00:38:19
Speaker
So you get a quarter fraction of a point towards your 30 if you spice your food with dried oregano, but a single lentil counts four times that as one whole number.
00:38:30
Speaker
Highly processed foods, couldn't quite figure this one out, but they may count less or not at all. I think it depends on how it's processed, how much it's processed. There are some guidelines around it, and they appear to be not entirely clear.
00:38:44
Speaker
Importantly, these scoring rules do not come from the American Gut Project. They are not biological thresholds that have been validated with research. They are, as far as I can tell, untested in any scientifically meaningful way. These rules are based on Zoe's proprietary model. They were choices made by Zoe to make a workable consumer product.
00:39:07
Speaker
It's important to remember that when someone representing Zoe says spices count as a quarter point toward 30 plants, that's not science. That's how Zoe chooses to weight spices in its app.
00:39:19
Speaker
Let's talk about Zoe's supplement. It's just so predictable, isn't it? So Zoe sells a supplement. They say it's designed to help users hit this 30 plant target. It's called the Daily 30 Plus and it costs $220 for four month supply. So that's $55 a month. My membership at my gym costs $80 a month for my entire family.
00:39:43
Speaker
Okay, this supplement is powdered, it's plant-based, it has dried legumes, grains, seeds, vegetables, herbs, and spices in it, and it's marketed as a quote, prebiotic shortcut.
00:39:57
Speaker
This is so poetic because this is literally word salad. So this quote prebiotic shortcut, ah AKA marketing garnish, they say will add 30 plants to your diet by, according to Zoe, feeding your gut microbes fermentable fibers. So for $55 per month, you get to feel like you're doing something objectively, scientifically health improving for yourself.
00:40:25
Speaker
ZOE points to a single ZOE-funded pre-print randomized controlled trial that has not yet been peer reviewed to support this claim, that its supplement improves gut health, digestion, and energy, and that might still on the surface sound compelling, but this kind of evidence should be considered weak as a support for a product level health claim.
00:40:48
Speaker
Let's talk about stool testing. As a part of its program, ZOE asks subscribers to collect stool samples at home and mail them into a partner lab for DNA sequencing. And the stated purpose is to analyze the composition of their gut microbiome and use that information to generate personalized food scores and recommendations inside the app. But here's the issue with this.
00:41:15
Speaker
And I'm going to link an article in The Guardian in the show notes that did some reporting on this. Scientists emphasize that there is no clear definition of a healthy microbiome. And Abby Langer, in our interview with her, she alluded to this as well. There's no universal good or bad gut bacteria and substantial variability.
00:41:36
Speaker
in laboratory reliability. So as a result, stool test findings often lack clear clinical meaning, right? They can't be cleanly mapped to health outcomes and dietary prescriptions. It also highlights a broader tension, which the article in The Guardian reported on, which is that Zoe simultaneously operates as a research project and a consumer wellness product. So it offers advice based on developing science. Experts argue this is an ethical gray zone because users are paying to generate data that fuels ongoing research while receiving guidance that has not been robustly validated. Earlier versions of Zoe's programming also encourage continuous glucose monitoring for people without diabetes. And this is a move that many clinicians have criticized. It promotes unnecessary surveillance. It's a lot of noise, not a lot of signal, creates unnecessary behavior change, and... you know
00:42:38
Speaker
probably neuroses. and Zoe has publicly acknowledged that continuous glucose monitoring data in non-diabetic populations lacks clear clinical meaning and should not be interpreted as diagnostic. And from what I can tell, they've stopped encouraging it, which is positive.
00:42:54
Speaker
Additionally, many users have reported that Zoe has functioned to increase their anxiety and rigidity around food, which is not surprising, right? So rather than improving their relationship with eating, it's made it worse. And finally, we got to talk about the representatives of Zoe, their broader issue of sketchy science communication. So Zoe markets itself as science first, but many of the most visible voices promoting its ideas are Zoe paid scientists representing Zoe.
00:43:23
Speaker
Now to be clear, that doesn't automatically invalidate these scientists' expertise. It certainly doesn't mean everything they say is wrong. But it should set off alarm bells when while listening to these Zoe scientists connecting findings from the American Gut Project to Zoe's claims and extolling the benefits of taking Zoe's 30 different plans per week advice,
00:43:45
Speaker
It should make you go, hmm, when you notice what they're conveniently not saying, which is little to nothing about the American Gut Project's limitations in terms of what it could show and the connection or lack thereof to information.
00:44:01
Speaker
Zoe's advice and products. In podcast appearances and media interviews, Zoe's representatives often present the eat 30 different plans per week idea as central and inevitable for gut health. They speak with high confidence and enthusiasm, but what's rarely foregrounded are the constraints of the single study they cite. The American Gut Project, this single self-reported survey question within that study, the popsicle sticks supporting their claim, and then also the absence of plant dosage data. The fact that this was a self-selected
00:44:38
Speaker
paying cohort, so likely affluent, not representative of the population at large. The fact that 30 was a statistical cutoff, not a physiological meaningful threshold.
00:44:49
Speaker
The fact that the finding regarding variety was associative rather than causal. Instead, they'll frame plant variety as a universal imperative. They won't frame it as it really is, which is one signal among many that were observed in this very specific cohort. Scientists engaging in sound science communication would be transparent about these limitations and about the bias, the obvious bias, which is Zoe's incentives for making these claims. And there was another consistent and problematic rhetorical move that I have been picking up on.
00:45:28
Speaker
Not in every interview, but I've noticed at times that the scientists representing Zoe tend to paint institutional guidelines as outdated or insufficient or they cast the government of the countries in which these guidelines exist as having completely failed the citizens of that country They cast certain foods as villains without qualification, without any nuance.
00:46:00
Speaker
So in an interview on a recent Zoe Science Plus Nutrition podcast, which we'll link in the show notes, Tim Spector is being interviewed, and he claims that diet soda is bad for the microbiome, and that it was falsely marketed as a health drink, and that it doesn't in fact cause weight loss, and that it it actually increases cravings for sweetness via the brain, and it disrupts gut microbes, and it causes metabolic problems because artificial sweeteners are, quote, chemicals the body isn't used to.
Tim Spector's Selective Health Advice
00:46:37
Speaker
and some are derived from petroleum, which gut microbes, quote, haven't evolved to deal with. And almost every part of that chain of logic overstates the evidence.
00:46:49
Speaker
Almost every single part. So first, it's true that diet soda is not a weight loss intervention on its own, and know who's saying that. But also, randomized controlled trials consistently show that replacing sugar-sweetened beverages with diet soda leads to neutral or modestly beneficial effects on weight and metabolic health, especially compared to continuing to drink sugary beverages. The claim that diet soda is metabolically harmful relative to sugar sodas is not supported by randomized control trials. Second, the idea that artificial sweeteners broadly disrupt the microbiome
00:47:29
Speaker
and cause metabolic problems relies largely on animal studies and observational associations. In humans, findings are inconsistent, often small, and highly individual.
00:47:41
Speaker
So there is no strong causal evidence that diet soda consumption causes metabolic problems in otherwise healthy people. Third, arguments about artificial sweeteners being unnatural from petroleum or something gut microbes quote haven't evolved to handle.
00:48:00
Speaker
These are not evidence-based claims. They're not evidence of harm. Many substances humans consume safely are not from nature. They're synthesized, they're refined, or they're chemically identical to compounds that do occur in nature. Something being evolutionarily unfamiliar is not toxicity. None of this makes diet soda a health food, okay? But it does mean that confident claims about gut damage and metabolic dysfunction from Spectre go well beyond what human evidence can support. And what made this demonization of diet soda particularly striking was an inconsistency I noticed. Because in the same media ecosystem, maybe even in the same episode, red wine is framed as beneficial for gut for gut health because it contains polyphenols, which These used to be called antioxidants.
00:48:52
Speaker
Now they're called polyphenols. um This is despite alcohol being known as a gut irritant and a carcinogen. Research is showing that no amount of alcohol is considered beneficial to the human body. So you can't confidently demonize diet soda while uncritically promoting red wine, unless you're applying very different standards of evidence to each claim. And this is just the tip of the iceberg with Tim Spector.
00:49:20
Speaker
and Zoe at large. We might do another episode on Spectre and Zoe down the line, but I have a feeling that this is going to be a pattern that shows up again and again and again. But man, are these people really excellent at marketing.
00:49:34
Speaker
Is marketing gold? I'd like to design an app. I'll call it Zappy. and an accuracy tracking platform for science communicators.
00:49:46
Speaker
Every time a science communicator makes a claim that exceeds the evidence, Zappi delivers a small corrective shock in real time. Zappi's scientific evidence-based proprietary bullshit detector is calibrated to spot mechanistic overreach and marketing-driven certainty in an instant.
00:50:05
Speaker
When triggered, Zappi delivers immediate feedback to help the user to recalibrate their claims back to what the data actually supports. Subscribers will also receive an empty reusable bag for collecting their bullshit, which is a well-known nutritive supplement for their vegetable gardens.
00:50:20
Speaker
Free 99 for an endless supply, Zappi. Better claims are coming soon.
00:50:27
Speaker
Guys, I created both an app and a sponsor for the podcast. Okay, jokes aside, let's talk about how this advice to eat 30 different plants per week lands
Moralization of Health Advice
00:50:38
Speaker
emotionally. Most of you listening are women.
00:50:40
Speaker
Many of you are caretakers. You cook, you plan meals, you think about food daily as a real logistical and emotional responsibility. And you're already health conscious.
00:50:53
Speaker
You're already trying in this regard. You already know that eating plants is good. So the emotional undercurrent from Zoe's claim that you should be eating 30 different plants per week and other similar wellness claims, the undercurrent there is pressure.
00:51:10
Speaker
It's pressure to do health the right way, even better than you are, and to not miss something that is important. This type of pressure is exactly what author Timothy Caulfield describes in The Certainty Illusion, which I highly recommend reading, and I will link it in the show notes. In the book, Caulfield lays out the central problem with our misinformation crisis that we currently all find ourselves in.
00:51:40
Speaker
And one of the problems he lays out is that humans are drawn to health, wellness, and science claims that sound really clear, decisive, and certain, even when the underlying evidence for them is weak or uncertain. Confident influencers, some of whom have some serious credentials, will often create the illusion that complex biological systems can be controlled if we just follow the right protocol. Stacey Sims, Andrew Huberman, Peter Atiyah, Mary Claire Haver,
00:52:13
Speaker
Fonder right. And those are just the people that we have been talking about. Caulfield shows how this certainty illusion is amplified by the media influencers, all of whom have commercial interests, especially in areas like nutrition, supplements, longevity, and personalized health. So the result of all this is that uncertainty, nuance, and the limitations of the evidence being used to support these claims all get stripped away while speculation around observational findings gets presented as settled fact.
00:52:47
Speaker
There's a tension that exists between science and marketing. Science advances, ironically, through uncertainty and then through revision.
00:52:58
Speaker
But for marketing purposes, certainty sells. And when certainty oversells, it misleads people. It distorts their decision-making processes. And it doesn't actually lead to the better health choices or outcomes that certainty seemingly supports.
00:53:16
Speaker
Eat 30 different plants per week. These rules become, in a sense, moralized. So the idea there, the pressure there is that if you follow them, you're being good.
00:53:28
Speaker
If you miss them, you're a failure. In the Certainty Illusion, Caulfield describes goodness as one of the three psychological hooks that make shaky health claims like this eat 30 plants per week claim.
00:53:43
Speaker
This hook of goodness makes that claim feel irresistible. And by goodness, he means that health advice gets framed as a moral signal, not just information, but rather following this rule means you are being responsible, you are being disciplined, you are being smart, you are enlightened, and you are good. While ignoring it implies you're lazy, you're ignorant, you're not doing health the right way, you're not taking it seriously, you're a failure.
00:54:13
Speaker
In episode 102 the Movement Logic podcast, I talk about this problem with moralization around moralizing movement. And this is before I read Timothy Caulfield's book. So when I read Timothy Caulfield's book, I just felt like all the pieces were coming together in terms of what I was picking up on. For those of you who don't know, Timothy Caulfield is a prominent science communicator and a law and public health professor at the University of Alberta. He's been a leading voice against misinformation and for better media literacy. So check out his book, linked in the show notes, The Certainty Illusion. So once a claim is moralized, something shuts off in our brain. We stop asking whether the claim is actually true or well-supported, and the question shifts from does this actually work
00:55:06
Speaker
to what kind of person am I if I don't do this? And Caulfield's point is that goodness is especially dangerous in health science because it turns uncertain evolving evidence into a character test, a sticky, evidence resistant, and sometimes socially enforced character test.
00:55:27
Speaker
So goodness kind of hijacks our brain It hijacks our skepticism, critical thinking, and our willingness to investigate the claim. This past Monday, I posted about a thought
Impact of Social Determinants on Health
00:55:40
Speaker
experiment. The advice, eat 30 different plants a week, doesn't come from Peter Atiyah, but in the real, I asked how Peter Atiyah and the advice to eat 30 different plants per week is connected. And then I...
00:55:50
Speaker
went off about the observational associations turning into protocols and how Atiyah does that and how this advice is basically that. And then at the end of the post, I asked, what gets lost when gut health becomes a lifestyle performance metric sold to affluent audience, trackable with a beautiful paid app from a company?
00:56:07
Speaker
who sells supplements instead of a public health discussion about who actually has access to 30 different plans per week, okay? And someone commented, and I'm paraphrasing here, the US dietary guidelines have sucked for decades and I'm not gonna live my life based on what everyone else has access to. And they went on to say that focusing on accessibility is socialist and that we live in the greatest country on earth where choice is an option. Choice is an option.
00:56:35
Speaker
Like choice is a choice. Is a choice is a choice is choice. Anyway, so yeah, my response was essentially, ah how do we know the guidelines suck if very few people actually follow them? Abby Langer made that point in our interview with her, which is a very good point.
00:56:48
Speaker
And then I also made the point that my pointing out the absence of any discussion around the social determinants of health from people like Atiyah or Zoe, this is not telling everyone how to live their life. Okay. Massive red herring, massive false equivalency, massive straw man, just so much wrong with that leap in logic.
00:57:08
Speaker
But it's clear to me that this person is just kind of shutting down the possibility that our social structure plays any role in people's access. Right. But what struck me most was just like how quickly the conversation jumped to socialism like somewhere along the line stating something fairly obvious right that wealth and access and stability in adulthood often reflects luck luck first and foremost in that person's starting conditions like how they started out right like being born on third base doesn't mean you hit a triple right I think that used to be something people would say about George W. Bush And people who grew up socioeconomically disadvantaged are presented with a different set of choices than people who grew up in more socioeconomically advantaged circumstances.
00:58:02
Speaker
And these beginnings don't always, but they often affect what happens next in the person's life. This is common sense. This is so obvious. This is not even to mention the fact that many people experience economic hardship due to events completely outside of their control, like that had nothing to do with choices they made. But somehow this common sense reality, like facing it, is anti-American because it's reframed as a political threat.
00:58:34
Speaker
Socialism. To me, this just speaks to how successfully the political right has been in convincing ordinary people to act against their own interests, to vote against social safety nets, to vote in favor of corporate interests, almost, in effect, turning these people into unpaid brand ambassadors for corporate greed. And if you can get people like this woman in the comment section who started her comment by saying, like, I love the stuff you guys do, but socialism, right? If you can get a woman like that, who's on board with us, it's like not just trolling us, right? To yell socialism. Anytime someone asks who's benefiting from advice from a corporation that's leaving out any mention of the social determinants of health, socialism, right? They never have to even consider the question, let alone the obvious answer.
00:59:29
Speaker
I grew up in the poorest county in Wisconsin, but relative to where we lived, my family was actually pretty well off. My dad was a school administrator. My mom was a high school English teacher. We had financial stability. We had access to healthcare, nutritive food, lots of free time. Many kids I went to school with, their parents did not have this. These kids relied heavily on the public school for their sustenance and even their safety. So for these kids, my peers, If they lacked plant variety in their diet and all of the other actually much more important things they needed to start their lives, that wasn't a choice they were failing to make.
01:00:06
Speaker
And certainly for a lot of them, the choices that they had, the options they had to choose between going forward were different than the ones I had simply because of who our parents were and who their parents were and it goes on and on and on. These were not choices they failed to make, all of them. These were choices they simply didn't have available to them.
01:00:27
Speaker
And yes, to state another obvious point, of course personal responsibility matters. And of course it is probably the primary reason for why a lot of people aren't healthy, okay?
01:00:41
Speaker
It's not the only reason though. It may not even be the biggest one. Social conditions and personal responsibility both matter. People make choices, their choices affect their health. In adulthood, what you eat, how much you move, these are daily decisions we all make. But for a socioeconomically disadvantaged versus advantage person, the decisions being made are being made in a very different reality. A single parent working two jobs, an elderly person on a fixed income, somebody who lives far away from a grocery store or lives in a neighborhood surrounded by bodegas and gas stations and no grocery stores in sight.
01:01:20
Speaker
right These folks are often choosing between entirely different food options than someone with, say, flexible work, a disposable income, a full kitchen, who lives in proximity to grocery stores, who has time to plan, to cook, to track their food in an app even. right These are just not the same decision landscapes.
01:01:39
Speaker
The wellness marketplace loves to focus on individual responsibility, choice, because it's so easy to sell. You can monetize supplements, apps, but you can't monetize food access. You can't monetize stable housing. You can't monetize affordable or free childcare, predictable work schedules. These factors disappear because they're not marketable.
01:02:01
Speaker
But another common sense reality is that health is doesn't exist in isolation. Food access, housing costs, work schedules, stress, and health care shape everyone's health. So even if you personally feel buffered from these obstacles to health and nutrition some people face, you're still living inside the systems that created those obstacles, that support those obstacles, and that fail to fix them.
01:02:26
Speaker
So when gut health gets framed as a personal performance metric, eat more plants, 30, buy the right supplement, ours, track the right score with our app, it turns an access problem for a huge portion of the population of the United States into an individual protocol. And in our minds, a challenge to be either a success, a good person, or a failure at reaching it. And that's a really convenient framing. That's a really convenient way to live inside our heads.
01:02:54
Speaker
for the people selling us and profiting enormously from the story, from the problem, and from the solution they sell. It's much less useful for improving gut health, yours or anyone else's.
01:03:07
Speaker
Logistically, we made this episode because many thoughtful listeners pushed us
Episode Conclusion and Reflections
01:03:11
Speaker
to look closer. While, in my opinion, our initial gut reaction to the advice we encountered to eat 30 different plants per week was appropriate, we definitely did not yet have all the background that we do now. So thanks to you, we dug deeper into the American Gut Project, the Zoe Company, Tim Spector, and that was valuable.
01:03:29
Speaker
I am now less dumb. Ethically, we made this episode because this pattern shows up everywhere in wellness. Observational data gets turned into prescriptive advice that this observational data was never designed to support.
01:03:46
Speaker
Profit-driven companies tend to prioritize brand clarity over scientific nuance. Sarah created a post, it went a little viral, talking about the difference between doctors versus brands. I'll link it in the show notes. Check it out if you haven't seen it. These profit-driven companies, these profit-driven brands, they turn this observational data into prescriptive advice and they don't do this to help you.
01:04:09
Speaker
They do it to help themselves. I know most of you listening care about science literacy. You care about media literacy. A big part of that is knowing generally what a study can and cannot tell us because this can help you notice when a study is cited and certain claims are being made with a high level of enthusiasm, certainty, evangelism. Maybe it aligns with the brand of the person making them, right? When certainty around those claims show up around observational data, just know that Actually, there should be quite a bit of uncertainty predominating the message. Caution. Humility. But that's just not sexy.
01:04:45
Speaker
Unless you recognize it for what it actually is. In science communication, or just really as a person, right? It's intellectual humility. It's honesty. It's accuracy. And that shit is sexy as fuck.
01:04:58
Speaker
All right, everybody. Thanks for listening. Thanks to those of you who wrote in. If you found this helpful, please... give us a rating. If you want to go deeper on strength, barbells, check out our Bone Density Mini Course linked in the show notes.
01:05:12
Speaker
If you're on Instagram and you don't follow Movement Logic Tutorials, give us follow. We'll link that in the show notes as well. All right, everybody. Thanks for listening. We'll see you in two weeks.