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RHR: Micronutrient Density and Bioavailability, with Ty Beal


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Ty Beal, Research Advisor on the Knowledge Leadership team at the Global Alliance for Improved Nutrition, joins Chris Kresser in this episode of Revolution Health Radio to discuss nutrient density, bioavailability, and his recent study on global micronutrient deficiencies. Ty explains his approach to defining nutritional deficiencies and addresses common misconceptions and misunderstandings about which foods are the most nutrient-dense.

Revolution Health Radio podcast, Chris Kresser

In this episode, we discuss:

  • The Global Alliance for Improved Nutrition (GAIN)
  • The burden of undernutrition worldwide
  • The process and challenges of defining nutrient deficiencies
  • Ty’s recent study on global micronutrient deficiencies
  • The importance of considering nutrient bioavailability
  • Why micronutrients and protein from animal-sourced foods are unique
  • Misconceptions about dairy products
  • Why a mixed animal- and plant-based diet is ideal

Show notes:

Intro to Ty Beal

Hey, everybody, Chris Kresser here. Welcome to another episode of Revolution Health Radio. This week, I’m really excited to welcome Ty Beal as my guest.

He’s a research advisor on the knowledge leadership team at the Global Alliance for Improved Nutrition, where he generates evidence to guide programs and mobilize knowledge related to global nutrition and food systems. His research seeks to understand what people eat, why, how it impacts their health, and how to sustainably improve diets and human health. He holds a PhD from the University of California, Davis, where he was a National Science Foundation Graduate Research Fellow. I became aware of Ty’s work several years ago, and in this podcast, I particularly want to focus on a new study that he’s just published, which I think is a landmark study when it comes to looking at micronutrient density in foods and, really, I hope, is going to put to rest a lot of the misconceptions and misunderstandings in the nutrition community about which foods are most nutrient-dense, especially when we consider things like bioavailability.

I’ve talked a lot about these concepts on my appearances on [The Joe Rogan Experience] and in my articles, but this new study really fills in some of the missing gaps, again, particularly related to bioavailability and anti-nutrients, and what we can now reliably conclude from the research when it comes to [making] sure that people are getting enough of the essential nutrients that we need in our diet, both in the developing world and in developed countries like the [United States], the UK, Canada, Australia, etc. I think you’ll really enjoy this episode. So let’s dive in.

Chris Kresser:  Ty, welcome to the show. It’s such a pleasure to have you on.

Ty Beal:  It’s a pleasure to be here. Thanks for the invite.

Chris Kresser:  [I’m] just curious about your backstory. How did you get interested in this field that you’re working in now, understanding nutrition and how food sources of micronutrients, food supply, how that affects people both globally and in the [United States]? What drew you to this work?

Ty Beal:  I actually got interested in nutrition before I started going to school for it. And I started listening to different podcasts, including yours. [It was] one of the first ones I listened to back in 2012. And I changed my diet and had a lot of health issues resolved. Then family members, my parents, siblings, and also some friends changed their diet and saw some really big impacts. So I was pretty inspired to do something with nutrition if I could, but I didn’t have a major background in it. I was also at the same time interested in geography and agriculture and the diversity of environmental sustainability and food production and all of that. I had an organic garden for many years when I was younger, so I was always interested in that. So I ended up going to school at UC Davis for a PhD in geography and by chance, there happened to be a program there focused on global nutrition. And it wasn’t formally allowed for geography students because there hadn’t really been that interest. But I was the first; I applied for that program to be joined to the geography program, [and] I was actually the first student to graduate with what’s called a designated emphasis. So I had a mix of geography classes, ecology classes, and then a lot of nutrition epidemiology. My lab, interestingly, had a mix of ecology students, agronomy students, and geography students. So it was a really broad diversity of people.

Chris Kresser:  Yeah, that sounds like an amazing synthesis of disciplines, especially for what we need now and where we’re headed. This understanding of how food systems and ecology interact with micronutrient density of foods, and this is something where there’s more research happening from folks like you and Stephan van Vliet, and others who are really exploring this territory. And it’s great to see a more holistic approach, I think, to these topics because historically, as you know in academia, people can get really siloed in their particular area of specialization and not really see the forest. And it’s important to see the forest because, especially when it comes to food, there [are] so many factors that affect food quality. So it sounds like a really cool program.

Ty Beal:  Absolutely. I know a lot of people hated that diversity because there was sort of, “What do I focus on? Who’s going to be my advisor?” And I just loved it. So yeah. I think it’s needed. You’re absolutely right. The systems perspective in food systems is really important.

GAIN and the Burden of Undernutrition Worldwide

Chris Kresser:  Great. So tell us a little bit about your work at the Global Alliance for Improved Nutrition [(GAIN)]. I know you’ve focused a lot on undernutrition, the burden of undernutrition worldwide, particularly in the developing world. So maybe just give us a little background on GAIN, and set this up with some statistics on undernutrition worldwide and how that’s impacting people in the developing world.

Ty Beal:  Sure. GAIN is really focused on trying to improve access to safe nutritious foods in a sustainable way. And we do a lot of different programs in Africa and Asia. We do things like fortification of foods to improve salt, iodized salt, some important other nutrients, but we do a lot of work, actually, to try to improve the diversity of foods and improve the affordability of foods and how do you intervene to actually make changes in the market where you can improve access.

I’ve always been really drawn to a foods-first approach because I think nutrition is very complex and being a little bit too reductionist, like you can miss a lot of the benefits of food. So I’ve tended to lean toward that in my own research in work at GAIN, but I really appreciate the balance that we need all sorts of approaches to try to improve nutrition. Especially for people who are living in poverty and don’t have access to really diverse diets. When you look at the burden of undernutrition worldwide, it’s quite staggering. A statistic I was just reading yesterday [is] 25,000 people die every day from hunger or undernutrition. And that’s including over 10,000 children. It’s pretty staggering. You think about the wars going on right now, which are devastating, but hunger is still one of the number one causes of death and suffering. So, particularly when you look at undernutrition for [women], beyond hunger, we see anemia in about 571 million women 15 to 49 years of age. And that has a lot of consequences on energy development; it can have severe consequences [on] quality of life. About 150 million children are stunted. [These] are children under five years of age. Stunting has a huge impact on economies; it has a huge impact, of course, on the children’s lives. There’s rapid development and growth that takes place in the early, especially 6 to 23 month, age[s] when complementary foods are first introduced. So stunting can have lifelong consequences. And really, there’s an intergenerational cycle where you have stunted parents who often are at greater risk of giving birth to preterm children or children who are at risk of stunting. So it’s really important to intervene during the maternal and child nutrition phase.

Another stat, I think, that many people maybe aren’t aware of is that a billion people are estimated to not consume enough protein. In the [United States] and other high-income countries, we think protein is not really an issue. And you can make that case. Protein deficiency isn’t an issue. There may be optimal amounts of protein that we’re not meeting. But in general, in much of the developing world, you actually see people not even getting enough protein. And then the people who do, children who get enough protein according to recommended intakes, are often deficient in certain essential amino acids. So the full story is not just protein, of course; it’s the quality of the protein.

And then lastly, I’ll say a statistic from a paper that we just finished writing. It’s under [Centers for Disease Control and Prevention] clearance, so we expect to submit this month in March. But we estimate that 1.6 billion children under five years and women 15 to 49 years [old] have at least one micronutrient deficiency. So that’s over half of children, [and] that’s about two in three women of reproductive age. And the surprising stat there [is] not that deficiencies are more common in low- and middle-income countries. In places like India, that can be as common as nine in 10 individuals have at least one deficiency, and often, there are several deficiencies coexisting. But in high-income countries, in the [United States], about one in three, so about 33 percent of women, have at least one deficiency. In the UK, it’s about one in two. And iron deficiency is pretty common, even in these contexts. Twenty percent or more in the [United States] and the UK. So I think that’s an important point to highlight. It’s not as big of an issue as it is in low- and middle-income countries. But certainly, undernutrition is not negligible in all contexts.

The Process and Challenges of Defining Nutrient Deficiencies

Chris Kresser:  I’d love to ask you a question about that, which I’ve often wondered about. How is deficiency being defined in this context? And what is deficiency? Is that according to the [Recommended Dietary Allowance] (RDA)? What are the metrics that you use in all those statistics and in the studies to define deficiency?

Ty Beal:  Sure. There are a lot of different ways to get at some measure of inadequacy in the diet. At the very highest level, it’s kind of a crude way of doing this, is looking at food supplies. So what is the food that’s available for people to consume, [and] you compare that to the average recommended intakes, and you can make some guesses about the inadequacies in the food supply. The next level is when you look at dietary intakes. So this is something like 24-hour recall, or individuals are asked to respond to the foods they’ve consumed in the past 24 hours that [are] quantitative. There you get an estimate of what’s called [the] prevalence of inadequacy or inadequate intake. And what we’ve done in this study is to look at micronutrient status biomarkers. So this is actually measuring different biomarkers in the body to understand what the level of deficiency [is]. And there are certainly a lot of uncertainties. There’s serum ferritin, there’s serum retinol, etc., these types of biomarkers. But it gives us a better sense of what the actual burden [is] in individuals because often, the dietary data [themselves don’t] always give us a full picture.

What we’re looking at is the micronutrient status biomarkers. But I think one thing that’s important to note is that we only have data on a few micronutrients. And we have pretty limited data at that. So if you think about [that], there are dozens of essential micronutrients, we’re only estimating for the data we have. The deficiency risk is actually probably quite a bit higher than we’re able to capture from the available data.

Chris Kresser:  And then even, just more of a 30,000-foot view question is, like, is deficiency defined as what will lead to acute symptoms? Chronic symptoms? Both? And how does that relate to what even might be an optimal intake? I assume those are all different things. You’ve got the level of vitamin C intake that’s required to prevent scurvy. But that’s not necessarily the same as the intake that’s required to promote optimal immune function and antioxidant status, right?

Ty Beal:  Yeah.

Chris Kresser:  I imagine this is incredibly complex and difficult. Because a lot of those optimal amounts haven’t even been necessarily quantified or at least accepted by mainstream science at this point.

Ty Beal:  Yeah, I think that’s a great point. We don’t have a lot of consensus. That’s the truth. And when you define, [or] when you talk about what a deficiency is, often, we think of these things or the [World Health Organization] (WHO) provides public health significance or public health guidance. We don’t have a lot of consensus on, “If a biomarker says this and X percent of the population has this, is that significant?” And you’re absolutely right, that what we’re looking at for the most part is some sort of consequence that’s significant. So it’s not always severe, like it’s going to be life-threatening right away. It can actually lead to a deficiency for a longer period of time. It can have consequences. So we’re trying to find a balance. We do our best to use cutoffs or thresholds that have some consensus, and we actually have an advisory panel.

This study was funded by USAID, so U.S. citizens’ tax dollars. And we actually had an advisory panel that provides these checks and balances where we met regularly and the experts say, “What’s the consensus? Which type of indicator? What type of adjustment for inflammation?”, etc. It [has many] different complexities to it. So we try to get at our best guess. But of course, there’s a lot of uncertainty. And I think, in large part, this effort is an advocacy piece because there really haven’t been any good estimates of the number of people deficient. There’s a number that was cited about 30 years ago in a WHO document, that 2 billion people are micronutrient deficient. And I’ve cited that, as well, in different contexts. But there’s no real evidence behind that other than anemia. That’s kind of the total number of people with anemia. So we set out to do this looking actually at micronutrient status biomarkers. And of course, the challenge there is we were only able to include children under five [years old] and women [aged] 15 to 49. So if you think about 1.6 billion, but that’s only maybe a quarter of the population, you’re looking at probably well up to 3 billion potentially with a deficiency. So it’s not a small issue.

Chris Kresser:  Not at all. And one of the myths is that this only affects people in the developing world, which I want to come back to in a moment. But I’ll just give an example of how complex this can be or maybe we can talk about a couple just to give people an idea. And I think it’s obviously a significant challenge from a research perspective because what might constitute adequacy in terms of blood level of a particular nutrient for one person might not be the same level for another person, depending on many other factors. And I think that makes this really [difficult], some of those factors being known and some of those factors maybe not even being fully known or understood at this point. And that might involve, “What’s their efficiency in converting a precursor nutrient to the active form of that nutrient?”, for example. And that can vary. In some cases, it’s as low as 1 to 3 percent [in someone] and could be up to 20 or 30 percent in somebody else. So you’re going to [find], with the given level of intake of something like beta carotene, one person is able to convert that into retinol at a sufficient level and then the next person is not, and they end up with a retinol deficiency or not enough retinol.

[Vitamin] B12 is something that’s been interesting to me. So I’m curious to know if you recall off the top of your head what the threshold range was. Because I’ve seen anywhere from 200 to 350 as the bottom end of the range, but I’ve also seen a ton of research suggesting that [at] levels of 200 to 400, you can start seeing some of the telltale signs of [vitamin] B12 deficiency even in terms of the impact that that has on DNA. So that’s an area where, when you look at studies on the impacts of [vitamin] B12 deficiency, it’s problematic because every study is using a different cutoff to define what deficiency actually is. So how did you approach things like that? Was it the panel that kind of decided what the cutoff was and what you defined as deficiency?

Ty Beal:  Yeah, absolutely. And this paper [is] going to be underwhelming in the sense that we’re not going to get into all those details for the individual nutrients, and the severity of the disease, and “What does this mean?” and all the uncertainties, just because we have limited space and ability to do that. But I think you’re absolutely right; there are a lot of questions. And [for vitamin] B12, I don’t know the thresholds that you’re referring to off the top of [my] head. We used thresholds that have been recommended in the latest literature and the panel agreed upon. But one thing I do know is that [you] usually aren’t able to absorb too much more than the recommended intakes. So, I think what you’re probably highlighting is that when you have inadequate intakes over an extended period of time, you can develop a deficiency that can have really severe consequences and actually is hard to correct. It’s not the same as just, “Okay, now just start eating vitamin B12, and you’ll be fine.” It’s like, your body missed out on this for years. So I think that’s a concern because it may be very subtle at first, and then by the time it’s severe, there may be consequences that are too late to reverse.

Chris Kresser:  This is my huge concern with vegan diets and children. Because some studies have shown that even when kids have later in their teens or adolescent years reintroduced animal sources of [vitamin] B12, which are really the only sources of B12, it has not corrected the issues that were caused by the extended lack of B12 in their diet. And it appears that some of those effects can be irreversible over the long term. So it is, I think, a very important thing for people to be aware of and whatever decision that they make, just to be sure that it’s coming from an informed place and not a plate. Because there’s so much misinformation out there about how you can meet these nutrient needs; it’s not backed up by scientific evidence. Yeah, go ahead.

Ty Beal:  I was just going to say I share your concern. I think when you have passionate vegans who are advocating [that] all you need to do is take the supplement or take the fortified food, I think it is possible to do that for [vitamin] B12 for many people. But I think it’s important to think about the population level. It’s not something that’s going to be easy for everybody to make sure [they do]. And it’s one thing if you have access to all the fortified foods or the supplements, and you can remember to do that regularly. The good thing about an omnivorous diet is you don’t have to think about it as much. If you consume diverse foods, you’re going to get a lot of your nutrient needs that way. And then the other thing is, in probably the majority of contexts worldwide, there is not really consistent access to fortified foods and supplements. So, right there, children, of course, are the most vulnerable because they don’t necessarily have a choice about it if their parents are going to be doing something. So I would be concerned about that, as well, and definitely advocate for if you’re going to do something like that, please, check with your doctor or check your micronutrient status and make sure you really are consuming enough nutrients.

Chris Kresser:  Yeah, and just like in the case of [vitamin] B12, there’s often an idea in the vegan community that you can just eat spirulina or algae because it does contain B12. But those are actually B12 analogs like cobinamide, which don’t have the same impact on B12 status that consuming B12 from an animal source would have or even a supplement source of adenosylcobalamin or methylcobalamin or hydroxocobalamin, which is going to be well absorbed. So there’s a lot of misunderstanding out there, and it’s so polarized, unfortunately, like everything else these days, that vegans are typically getting their information from vegan sources and ignoring anything that somebody like me might say, and vice versa. So it’s really hard for people to make sense of what is actually supported in the scientific literature.

Recent Study on Global Micronutrient Deficiencies

Chris Kresser:  I want to turn our attention to the paper you recently published with a colleague. Is that Flaminia Ortenzi, am I saying that right?

Ty Beal:  Yeah, that’s it.

Chris Kresser:  Okay. So the paper is called “Priority Micronutrient Density in Foods.” Give us a brief summary of what you set out to study in this paper.

Ty Beal:  I think I want to just say [that in] this paper, we did not have any preconceived ideas or objectives about trying to make certain foods look better or worse. We are interested in improving undernutrition in people’s lives. And our goal [was] built on some work that I had been involved with for a few years. I led a project, at least on the GAIN side with UNICEF, to look at the micronutrient gaps in young children’s diets—and this is children 6 to 23 months [of age]—and the affordability of those foods when you look at nutrient density as opposed to just the price per kilogram or price per calorie. And from that work, over all these different work extremes, [the] inadequacy of diets, micronutrient deficiencies, all these different datasets, we looked at “what are the most common nutrient deficiencies and inadequacies in sub-Saharan Africa and South Asia, etc.?” And what we found [is] it’s highly dependent on what data you have available, but iron [is] very common, zinc deficiency, folate, calcium, [vitamin] B12, and vitamin A. And there are others, of course, but there [are] limited data on others. And it’s also an issue of trying to quantify that properly in food for other nutrients.

So we stuck to these nutrients. And the other reason [that] these were the focal point is that in the food composition databases—these are database[s] that look at the nutrients in food—we wanted to go beyond the [U.S. Department of Agriculture] (USDA) database, which is very U.S.-centric. It’s a great database; it’s amazing. But we also wanted to try to capture a diversity of foods because we’re interested globally in populations that don’t have diverse diets and who are really suffering from this burden of micronutrient malnutrition. So we just wanted to get a global overview of which foods are the top sources of these different nutrients. We wanted to know per nutrient because sometimes there are programs to [address] vitamin A supplementation or iron deficiency, [or] whichever nutrient may be a focused priority in a country. We wanted to get a sense [of] overall nutrient density because foods are often not quantified like that. We think about people say[ing], “Oh, nutritious foods, eat whole grains, eat a diversity of fruits and vegetables.” Now, those can be healthy foods and contribute to healthy diets. But there’s actually quite a range of nutrient density when you look at foods and try to account for bioavailability and really look at the nutrients that are of greatest public health concern, particularly in our case in low- and middle-income countries.

So we combined a bunch of different databases from Latin America, Africa, and Asia, as well as the USDA database to say, “Here’s the median or the average density for various food groups.” We tried to be pretty comprehensive, but we stuck with minimally processed or unprocessed foods. And we present the results in two different ways. We present the portion size in grams required to meet an average of a third of the requirements across these nutrients or the portion size in calories. And then we use an algorithm to try to account for the fact that if a food requires too much mass, like a pound of salad, for example, it’s not going to be easy to consume, and if it requires too many calories to provide the nutrients, it’s also not going to be dense enough. So we rate different foods by this rating overall and then we also do this for individual nutrients.

What we found, just the high-level overview, is that unsurprisingly, organs like liver, spleen, kidney, [and] heart are the top sources across most of these nutrients. Also, small dried fish. These are very common in many countries in Africa and Asia. Small canned fish are good, as well. Dark leafy greens, so things like kale, moringa, etc. Shellfish and particularly the bivalves—so clams, mussels, [and] oysters—but also crustaceans, and then ruminant meat like beef and goat, and mutton and lamb, and eggs, dairy, and then fish, particularly with the bones consumed. So that was the high-level takeaway. We did a lot of analysis by population groups so that you can say, “Okay, if you’re a woman 15 to 49 years of age, here’s the density targets you should be looking for, for these foods. If you’re an average adult 25 years or older, here are the foods you should aim for.”

Chris Kresser:  So [there] is so much to unpack here, and [it’s] really fascinating. I just want to point out a few things that I took away from looking at these charts. First of all is consistency with some of the previous studies, like the Milo, I’m not sure how you pronounce his name, French name study, which I’ve referred to a few different times. And even though those studies didn’t consider bioavailability as this study did, which I want to come back to in a second, they still largely found that organ meats were at the top of the list when it comes to nutrient density. And of course, this is a drum I’ve been beating on for a very long time, and I’m struck by the fact that four out of the six top foods on your list are organs. It’s pretty remarkable. Liver, you have to eat 11 calories of liver. What is that? Like licking a piece of liver or something? I mean, a tiny, tiny little piece this big.

Ty Beal:  Right. It’s not much at all, right? It’s tiny.

Chris Kresser:  And I just want to put this in perspective for people who are not looking at the chart right now. You have to eat 11 calories of liver to reach a third of the recommended intakes of vitamin A, folate, [vitamin] B12, calcium, iron, and zinc for women of reproductive age. In comparison, you have to eat 380 calories of other vegetables. That’s not a reason not to eat vegetables, and I have more to say about that; I’ll come back to that. You have to eat 1,100 calories of chicken, and you have to eat over 4,000 plus of refined grains. And I imagine the plus means that they’re devoid of certain nutrients. So you could eat almost as much as you can handle, and you’re still not going to reach those targets.

Ty Beal:  I had to cut it off somewhere, so I just cut it off. There is a portion size, but I don’t think it’s very realistic to consume.

Chris Kresser:  Right. Something bad is going to happen.

Ty Beal:  Something else bad is going to happen if you reach that.

Chris Kresser:  Yeah, exactly. So that’s just remarkable. We’re talking about a 400-fold difference in nutrient density with these particular nutrients between liver and refined grains. We’re talking about even a 100-fold difference between liver and chicken and like a 20-fold difference or a 30-fold difference between liver and vegetables and even vitamin A-rich fruits and vegetables. So it’s pretty incredible to me to see how this actually shakes out in a visual way. It’s highly … I’m not sure if this paper is going to be open access. Do you know?

Ty Beal:  It’ll be open access, and it’s going to come out on March 7. So that’s this Monday coming up.

Chris Kresser:  Great. So yeah, there’s the saying [that] a picture is worth a thousand words, and I think just visually seeing the tables or the charts in the paper itself is very powerful. It really gives a sense of how much more nutrient-dense those foods are on the top of the list than foods that are often promoted as being very nutrient-dense by certain communities. You’ve got a lot of foods that are [at the] bottom of the list, [which] are things like quinoa, fruits, millet, roots, tubers, plantains, whole grains, and [also] nuts were at the very bottom of the list along with refined grain products and refined grains. So I think that will surprise a lot of people because there’s a saying, “Healthy whole grains” that we hear thrown around [a lot]. But in reality, at least when we’re talking about these specific nutrients, they are not anywhere close to things like organ meats and shellfish and dark leafy green vegetables and ruminant meat and dairy products.

The Importance of Considering Nutrient Bioavailability

Chris Kresser: I want to come back to bioavailability because we were chatting about this before we started recording. I’ve been on [The Joe Rogan Experience] several times, almost always to discuss the difference in nutrient content between an omnivorous diet or mixed diet and vegan and vegetarian diets. I’ve had debates about this. And often, in the context of those debates, I would be referring to the existing scientific literature on this topic, which had various scales for assessing nutrient density in these foods. But none of those attempts, [well], I don’t know about none, but very few of them actually considered bioavailability. And the importance of that, for people [who] aren’t familiar with that term, is when you look at an analysis of the amount of a nutrient in a given food. Let’s just take calcium in spinach as an example. You can look at a cup of spinach and say, wow, there’s actually quite a bit of calcium in there. But then you realize that spinach also contains phytic acid, which inhibits the absorption of minerals like calcium. And there have been studies that have shown that you need, I think, something like eight cups of spinach in order to get the same bioavailable amount of calcium that you get from drinking one glass of milk.

How do we know which foods are the most nutrient dense? How much does bioavailability matter? In this episode of Revolution Health Radio, Ty Beal and I discuss how to approach nutritional deficiencies and tackle some common misconceptions. #chriskresser #nutrition

So in practice, in reality, somebody could be misled by the food label, or looking up nutrition data and seeing how much calcium spinach has, and they might make the assumption that if they eat that spinach, they’re going to get that amount of calcium. But it never works out to be 100 percent. Even with foods where the bioavailability is higher, like calcium in milk, you’re not getting 100 percent. You’re getting a lower percentage, but it’s much higher than you get from eating spinach. I’ve always been frustrated by the fact that these kinds of studies haven’t considered bioavailability even though I know how hard that is, because there [are] so many different things to consider. Tell us a little bit about how you did that and what led to making that. How did you pull it off, given that this really hasn’t been done in a paper like this before?

Ty Beal:  Bioavailability is a really important piece of this to consider, because like you say, there are very different levels of bioavailability of nutrients. There are anti-nutrients like phytic acid, oxalates, etc., that can bind to the minerals and prevent absorption. [For] some of the nutrients, the recommended intakes are actually designed to account for this. So if you look at vitamin A, there’s something called a retinol activity equivalent, which assumes about a 12-1 ratio of carotenoids to retinol. That’s the average, and there are certainly people who are poor converters. So for them, getting it from animal sources is more important. But there’s a large variation. So if you look at vitamin A, there’s a study that showed if you have raw carrots, it’s like 77-1; if you have cooked carrots with fat, it’s much closer to 12-1. If you have something like red palm oil, which is fat, it’s actually closer to 2-1. So I think there’s a lot of nuance in there. We can’t always assume just because you’re getting the average [that it’s sufficient]. And of course, [there are] a lot of individual factors.

I want to just mention calcium. I went into this not really knowing what to do about calcium. And I looked into it because, as you point out, there is actually a study that shows the absorption from spinach—and this is spinach in the [United States]—is very low. I think it was something like 5 percent. We, of course, were looking at countries all over the world. So I reviewed data from Kenya, from India, and there are actually studies that looked at the bioavailability of dark green leafy vegetables overall and very specific varieties. And what we found is that the absorption is actually relatively similar, on average, if you’re looking at all dark, leafy greens. So I think there’s probably something, I don’t exactly know [what], but there’s probably something with spinach, or at least spinach in the [United States], that has less absorption. But I think it’s an important point. We don’t always know about the bioavailability.

Now the two big nutrients people do not adjust for in individual foods because they’re not actually in the requirement is iron and zinc. So if you look at a package that says percent of RDA and it’s black beans versus a steak, it’s going to show you something that’s not really reflecting the true bioavailability. And I think that’s kind of confusing to consumers. So what we did for iron [is] we looked at the amount of heme iron in each food. In ruminant meat, it’s the highest. Close to two-thirds of the [iron in meat] is heme iron, and heme iron is much more bioavailable than non-heme iron. You look at different foods; there’s a range. So we calculated a few different estimates based on averages of different foods, and then we gave a 10 percent absorption estimate for plant foods. And the reason for that is that we don’t really have a way to estimate the individual absorption precisely because it depends on how much phytate is in the overall diet. It depends on how much vitamin C is in the diet. It depends on how much animal protein is in the diet, how much heme iron, etc. But we do our best to get at what would be the average scenario here. So there’s actually a difference.

In our modeling, we consider ruminants [as] having the highest amount, about 20 percent absorption versus 10 percent. So it’s about double the absorption. Now for zinc, there are recommended nutrient intakes at the global level that have been worked on by [the] WHO and [Food and Agriculture Organization] and others that say, “If you have an unrefined diet,” so this is like [if] you have all whole foods, whole grains, there’s no type of refinement to the flours, “then your absorption is this amount. And if you have a semi-refined [diet, then your absorption is this amount].” All the way to [places] like the [United States] where you have an unrefined diet, they assume there’s hardly any [absorption], which really is kind of the case. Most grains in the [United States] are refined. And that estimate is supposed to be about 300 milligrams of phytate.

Why Micronutrients and Protein from Animal-Sourced Foods Are Unique

Ty Beal:  Now what’s really interesting is if you look at the phytate content of a diet that is largely plant-based. Like, we looked at the EAT-Lancet diet, [which] has about 2,000 to 2,500 milligrams of phytate. And the highest level of phytate for a kind of penalizing bioavailability of zinc is 1,200 milligrams. So it’s off the charts. We don’t really know what the impact is. You basically have to assume the recommended intakes at what’s called the unrefined level. [Meaning] when the diet is considered to have 1,200 milligrams. So we did our best to do an estimate of what [this would] be on average for individual foods, assuming that people are trying to have a diverse diet and not too high in phytate. But I think these are actually pretty conservative estimates. So it’s definitely possible that we’re actually under-appreciating the bioavailability in animal-sourced foods. I would say this is a pretty fair balance. If we made an error on either side, it would probably be to favor plant-sourced foods.

Chris Kresser:  Yeah. That’s a fantastic point. And everything you just said points directly to the complexity of this issue and why it’s been so difficult for researchers like yourself to try to quantify this in a paper. There are so many considerations, like I said before, some of which are known and established but still hard to quantify for the reasons that you mentioned. Like the data might not even be there in the database, or in the case of [how] you mentioned the top level of phytate coming out at 1,200 when it’s actually much, much higher in someone who’s eating a whole foods, plant-based diet. And then there are factors that we probably don’t even fully understand yet in terms of bioavailability. But I think you did a great job, and, just based on my years and years of researching this, and also years and years of treating patients who are making different dietary choices and coming to me with that history, I would concur with the guess that this is probably, if anything, an underestimate of how important bioavailability of animal foods [is]. Because that’s certainly what I see.

Most of the patients who come to me who’ve been following a plant-based type of diet are not eating refined grains all the time. They’re eating whole grains, and they’re doing a pretty good job of following that approach. I became alarmed at the level of how quickly some people would develop clear signs of nutrient deficiency as validated by laboratory assessments that I was doing and also all the telltale signs and symptoms that go along with that deficiency. And I think that’s probably a result of the pretty significant differences of bioavailability that we’re not even fully aware of.

While we’re on this topic of bioavailability, let’s talk a little bit about protein. It seems to me that this has been a little bit easier to quantify, and there [have] been more efforts in this direction like the [Protein Digestibility-Corrected Amino Acid Score] (PDCAAS) scale, which actually looks at not only how complete a protein is—the full amino acid profile—but also the digestibility of the protein—how much of it has been absorbed by the time it reaches the terminal ileum—which gives us more information than just looking at the amino acid profile. So talk a little bit about the difference between animal and plant foods in your study from that perspective, or in previous research that you’ve done.

Ty Beal:  That’s a great point, and my expertise is not in protein, so I will probably say limited things about this, but l will point to that. We also recently put out a paper, and this one has, I think you had Stephan van Vliet on your show. He was a co-author on this one. It was talking about this sort of reductionist approach to nutrition in a specific case of animal protein. Because it’s very common in policy spheres to say, “Let’s try to change from animal protein to plant-based protein.” And it’s sort of equivocate. It’s like, “This is the same; you just need to produce a kilogram of whatever plant-based food.” And there are differences. There are two differences. There’s one, of course, on the amino acid completeness and content and then, of course, bioavailability.

So in general, animal sources are superior. I think soy is a great option for a plant-sourced food. But in general, from what I understand, if you consume enough protein, this becomes less of an issue. It’s really for if you’re consuming, let’s say you consume the RDA, which is the amount to generally prevent deficiencies. But what I’ve heard from experts in this, like Stuart Phillips and others, [is] that once you consume about 1.6 grams of protein per kilogram of body weight per day, it’s less important to make sure you get it from animal-sourced foods. But most people aren’t consuming that much. And I think, especially when you look at the low- and middle-income countries, this is where we see it in children. A recent study looked at this. It’s like children were meeting the targets for recommended intakes of protein. But the biomarkers of amino acids were actually low. And that actually has an impact on their growth and development.

So it’s a real issue, and I don’t think we can dismiss the issue of protein quality, even though in the West, it’s much less of an issue. And if you consume a lot of protein, you don’t have to worry about it too much.

Chris Kresser:  Yeah, I think that’s a really important point where, just to reiterate, you can meet the recommended amount of protein on paper, but if the amino acid distribution is not optimal, you’re still going to suffer from the relative effects of protein deficiency. And I think there [are] some examples of other nutrients where that’s possible, as well.

I want to talk a little bit about the long-chain omega-3 fats because there are a variety of nutrients that are either only obtainable from animal foods or are mostly obtainable [only from animal foods]. There might be one or two plant sources, but they’re not commonly consumed plant foods, particularly in the American diet. And retinol—preformed vitamin A—is something that stands out there. Heme iron, of course, is only found in animal foods. [Vitamin] B12 and vitamin D are only found in significant amounts in their bioavailable absorbable forms in animal foods. Then you have [eicosapentaenoic acid] (EPA) and [docosahexaenoic acid] (DHA), which you can get some DHA from marine algae, and that’s indeed what I recommend for vegans as a way of supplementing. [But] I don’t know a lot of people who are eating marine algae regularly in the [United States] or even sea vegetables in general. So animal foods become a really vital source of EPA and DHA, particularly if someone’s not eating much seafood, which is also not uncommon in the developed world.

Ty Beal:  Yeah, absolutely. And I think your point is right. There are ways to get plant sources of omega-3s that are DHA and EPA, but it’s not like they’re widely available, or will be anytime soon, right? So I think we should keep pursuing that, of course. Let’s produce and find ways for people to eat more sea vegetables. They’re actually really nutrient-dense.

Chris Kresser:  I love them.

Ty Beal:  So consuming lots of seaweed, go for it. It’s going to be great. But the important point is that when you look at the actual amount that’s converted from plant sources, like flax or hemp seeds, or all these different types of plant sources of omega-3s, they’re at best 10-1. And honestly, this is like a best-case scenario. It may be quite a bit lower. So if you assume that it’s 10-1, it’s not like it’s going to be easy. First of all, seeds are not easy to eat tons of, and people don’t regularly consume that much. So it’s a big dietary change. Whereas if you eat a little bit of fatty fish, it’s going to be a much better source. So, absolutely. And especially when you look at low- and middle-income countries, this nutrient is going to be much more problematic. And that has protective factors for [non-communicable disease] risk factors, so there [are] non-communicable disease [factors], and it’s really important for brain growth.

Chris Kresser:  Brain health and inflammation, yeah. And here’s another example of how complex this gets and where I think we’re often underestimating the impact of these factors determining bioavailability. In order for that conversion of alpha-linolenic acid to EPA and DHA to take place, other cofactors and enzymes have to be present. And those enzymes that are in that biological pathway of the conversion from [alpha-linolenic acid] to EPA and DHA require nutrients like iron or zinc, or the exact kind[s] of nutrients you would expect to be at a higher risk of deficiency on a plant-based diet.

So you have a double whammy effect there where someone on a plant-based diet is not only going to be at risk just like everybody would [be] if they’re only getting those precursor omega-3s and being able to convert those into the longer forms, but they will be at increased risk, as well, because of lower levels of the nutrients that are required to make that conversion in the pathway. I don’t think there are many studies that are considering things at that level because it’s just so complex and difficult to quantify.

Ty Beal:  Yeah, it’s a great point. When you look at metabolomic studies, it’s really pretty clear. There are tens of thousands of compounds in foods, and we don’t really understand how they impact metabolism and health, and the food matrix plays a major role. This is the same thing in eggs. Even protein digestibility can be improved by consuming the full egg as opposed to just the egg whites. So there’s definitely a point about synergistic nutrients, and I think this is my perspective and some colleagues of mine that this nutritionism reductionist approach can often oversimplify, and it can be unhelpful and problematic in some cases because you’re not really considering all the cofactors and food matrix.

Chris Kresser:  I love that term “nutritionism.” That’s from Gyorgy Scrinis, right?

Ty Beal:  Yeah.

Chris Kresser:  Are you in contact with him? Do you have a relationship with him?

Ty Beal:  I have an informal relationship with him. I’ve exchanged a few emails. I think we share a lot of similar perspectives on diet quality. So yeah, he’s great.

Chris Kresser:  I’m going to follow up with you. I’d love to get him on the show. When I first read his paper about nutritionism, it was like, “Yes, yes, this is exactly.” It was exciting for me in a geeky nerdy way because I think he really hit the nail on the head in terms of the problems with that kind of reductionist approach.

Ty Beal:  Absolutely.

Misconceptions About Dairy Products

Chris Kresser:  I want to talk briefly about dairy products because this is another area of a lot of controversy and misunderstanding, both in the vegan world and also even in what I might label a conventional healthy diet world. Dairy gets really demonized. Everything from spurious arguments like, “We’re the only animal that drinks the milk of another animal.” Okay, well, we’re the only animal that uses iPhones, too, and flies on airplanes. That’s not necessarily a reason to [not] do it. [From that] to milk is not a nutrient-dense food and doesn’t have really significant levels of any nutrients. Yet it appeared pretty high on your list in the study. So what are dairy products rich in? Why should people consider, if they tolerate them and if they don’ have an allergy or an intolerance to dairy, why should they consider including dairy products in their diet?

Ty Beal:  Dairy is similar to eggs in that it provides a decent amount of lots of different nutrients. It’s not like it’s high in just one source. But of course, calcium is one of those nutrients and other nutrients like zinc and vitamin A. But there’s a lot of things that dairy provides.

When you think about it in my field of global nutrition, it’s easy for young children to eat yogurt, for example. So it’s a really good first food [for] introducing food. I know [with] both of my girls, that was one of the easiest ways to get a lot of nutrients into them, so dairy is great. I think, with your point, dairy is very mixed. What people think of dairy is all over the map. If you think of the Global Burden of Disease study, they consider dairy a positive. Milk is a positive nutrient or ingredient. But [in] something like the recent Food Compass by Tufts, they consider milk kind of negative. Yogurt is the only dairy that’s sort of considered positive. But cheese and milk [are] scored pretty lowly.

I think there’s a lot of perspectives on this, and I think, of course, we don’t know everything. But one thing that we know is that the food matrix really plays a role in the health effects of dairy, as well. Dairy can be demonized or targeted because of the saturated fat content. But in general, what I think we’ve seen from the evidence is that when you have a whole food matrix, like a naturally fermented whole milk yogurt, it’s not problematic. It’s usually associated with beneficial outcomes. And the other thing to keep in mind is that whenever there are some potential negative risks being considered, it’s really important to consider the positives. And I think this is done all the time with red meat and with other foods. They’re sort of targeted, because, “Oh, if you consume too much in a certain population, you may increase your risk of this.” But there’s very little consideration of all the benefits. I think you need to consider holistically to say, “What are the potential risks, [and] what are the potential benefits?” And in general, for people who tolerate dairy, it’s an excellent source of nutrients and protein. So I think it’s important, of course, to consider allergies, intolerances, etc. But in general, I think dairy is a really, really healthful food. And you’re right, it came out really high in our study. And dairy is not something that’s commonly consumed all over the world. So there’s actually a lot of room for increasing it where there’s [a] desire to do so. And my organization, GAIN, does have some programs where we look to increase dairy production.

Why a Mixed Plant- and Animal-Based Diet Is Ideal

Chris Kresser:  Nice. So I want to end by bringing this full circle perhaps and mentioning that your study, I think appropriately so, focused on essential micronutrients, like iron and zinc and [vitamin] B12 and calcium, folate. These are nutrients that cannot be synthesized endogenously, meaning we can’t make them on our own. So we have to obtain them from food sources, and they are also nutrients that we know from decades, if not a century of research, are absolutely critical to human health and well-being. And if we develop a deficiency, really bad stuff can happen from the lack of these nutrients. But that doesn’t mean that there aren’t other nutrients that are important. I just want to make that clear here, that [these] were not studied and include things like carotenoids, diallyl sulfides, polyphenols, flavonoids, lignans, plant sterols and stanols, [and] prebiotic fibers. These are nutrients that you would get by eating plant foods. There’s an increasing amount of research pointing to the benefits of these foods above and beyond just those essential nutrients. And this is why I’ve always argued that, at least as far as we can tell [by] looking at three different legs of evidence at what ancestral populations have eaten—archaeological evidence, and then modern clinical observational research as well as experimental evidence—that most humans do best on a mix of both plant and animal foods because those different categories of foods provide different categories of nutrients. Would you agree with that?

Ty Beal:  A hundred percent. You look at the nutrient profiles of plant- and animal-sourced foods and they are very complementary. So the nutrients that we didn’t talk about, often these can be of really big importance in Western countries like the [United States]. Magnesium, potassium, vitamin C, vitamin E, and even folate [are] more commonly found in plant-based foods. So I think that’s a really important point. Some like to take this study and the figure and say, “Look, we all need to be carnivores.”

Chris Kresser:  Carnivore, carnivore. Yeah. I know that will happen; 100 percent.

Ty Beal:  Sure, it’s going to happen, and I can’t do anything about it. But I will just say, again, I’m not advocating for a carnivore diet for anybody. It’s just that there really is a push to reduce or eliminate animal-sourced foods. And when we look at this objectively, we find there’s a big role for animal-sourced foods. It doesn’t mean that they need to [be] the majority of your diet, but they really should be included for optimal health. And if you choose not to consume them, that’s great. There are a lot of reasons why people don’t. Let’s just try to understand the evidence in a balanced way and focus on the nutrients that you need to [get] if you’re not going to consume animal-sourced foods.

Chris Kresser:  Absolutely, couldn’t agree more. I’ve had many patients who are vegans and vegetarians over the years. I myself, as most of my listeners know, was a macrobiotic vegan for a couple of years. So I don’t come at this with any kind of moral judgment or rigid viewpoint. I just want to provide information that will help people make informed choices so that they’re not thinking, “Oh, I’m getting plenty of this nutrient from this food,” when in fact, that’s not the case because of either issues with bioavailability or the form of that nutrient being not the right form, like cobinamide being an analog of [vitamin] B12 but not true B12 in something like algae. So that’s really what it’s all about. And I appreciate that about you, Ty, and your work. It’s really about helping people meet these nutrient needs and reduce their risk of disease and just live a healthier and happier life.

So I appreciate the work you’ve been doing. I’ve been following you on Twitter for quite a while now, and I’ve really enjoyed this paper and all your previous work and look forward to what’s to come. Where can people learn more about your work and stay [up-to-date] with what you’re doing? Like I said, I follow you on Twitter. But what are the best places?

Ty Beal:  Yeah, I think Twitter’s the best place just because I’m most active there. It’s Ty R. Beal, T-y-r-b-e-a-l. That’s my handle. And I’ll post a lot of research that I find interesting, or anything that I’m working on. Sometimes I’ll even post some sneak peeks of things that haven’t been published. So yeah, definitely check it out, and I’ll keep updating there.

Chris Kresser:  Awesome. Well, [I] look forward to future research that I know you’re working on. And I’d love to have you back on the show when some of those papers are published. In the meantime, keep up the good work.

Ty Beal:  Thanks so much, Chris. I’d love to come back, and keep up the good work, as well.

Chris Kresser:  All right, thanks, everyone, for listening. Send your questions to ChrisKresser.com/podcastquestion, and we’ll see you next time.

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