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Why the Optimal Human Diet Includes Animal Protein


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Can athletes get enough protein on a vegan diet? In this episode of Revolution Health Radio, I talk about the major differences between plant protein and animal protein, and discuss the positive impact an ancestral diet (that includes animal protein) has on your overall health. Be sure to catch my upcoming appearance on The Joe Rogan Experience in November 2019.

Revolution Health Radio podcast, Chris Kresser

In this episode, we discuss:

  • My upcoming appearance on The Joe Rogan Experience
  • Why plant protein doesn’t measure up to animal protein
  • Where protein really comes from
  • How much protein athletes need
  • Protein intake for non-athletes
  • What protein quality is
  • Six nutrients that are missing from plant protein

Show notes:

Hey, everybody, Chris Kresser here. Welcome to another episode of Revolution Health Radio. I’m on the road this week, so apologies for the decline in recording quality. I should be back to my normal setup soon.

My Upcoming Appearance on The Joe Rogan Experience

So, this week, I wanted to do something a little bit different and talk about the recent film The Game Changers. You might have heard of this. It’s a new film advocating for the benefits of a plant-based diet for athletes. It’s on Netflix, and I think iTunes and maybe a few other channels, and it’s made quite a big splash. I’m going to be discussing the film in great depth on The Joe Rogan Experience on November 19 at 11 a.m. Pacific. So, definitely tune into that either live or [via] the recording, depending on when we end up releasing this episode, for the full details. But today, I wanted to talk just a little bit about one of the main claims in the film, which is that plant-based proteins are equivalent to animal proteins in terms of quality and as a basis for athletic performance. And, in fact, there are a few choice lines from the film that I want to comment on specifically. And then I’ll go into a little bit more detail about protein and why I believe that animal proteins are, in almost every case, superior to plant proteins, not only for athletes, but for people in general. And this is one of the main reasons that I have always argued that the optimal human diet contains both plant and animal foods.

Animal protein is necessary for an ancestral diet. Check out this episode of RHR to find out why, and don’t miss my upcoming appearance on The Joe Rogan Experience on Nov. 19 at 11 a.m. Pacific. #paleo #kressergamechangers #kresseronJRE

Why Plant Protein Doesn’t Measure up to Animal Protein

So let’s dive in starting with a comment that’s made by James Wilks, who’s the narrator and protagonist of the film pretty early on, where he says a peanut butter sandwich has about as much protein as three ounces of beef, or three large eggs. I was watching this film on a plane trip and I laughed out loud, and several people who were sitting around me looked at me wondering, I think, what I was watching. Probably had no idea that it was a documentary on a plant-based diet, the way that I was laughing. But this was, it was funny because for a peanut butter sandwich to have the same quantity of protein—not even addressing the quality of protein issue, which we will shortly—but just for a peanut butter sandwich to have the same amount of protein as three ounces of beef, which is a very small portion of beef, [because] most people eat more beef than that when they eat beef, or three eggs, you’d have to use five tablespoons of peanut butter. Okay?

So that’s a third of a cup of peanut butter. I don’t know about you, but I’ve never made a peanut butter sandwich with a third of a cup of peanut butter. And you know, for those of you that are tracking calories, that’s about a 500-calorie peanut butter sandwich. I mean, this is really disingenuous and it kind of sets the tone for the film because they play very fast and loose with the science and they make a lot of misleading statements, a lot of half-truths, a lot of things that, for the average person who doesn’t have a background in this stuff, might pass muster. But when you look into it, you quickly find that it’s just nonsense. It’s kind of like saying, “Yeah, you can get the same amount of calcium from spinach that you can get from milk.” Well, that’s true. If you eat 33 cups of baby spinach, you can get the same amount of calcium that you can get from drinking one eight-ounce glass of milk.

But the peanut butter sandwich example completely ignores the issue of protein quality, too. So, protein quality is a function of amino acid profile and bioavailability. So, what specific mix of amino acids does the particular protein contain? And how bioavailable is it? Which means how readily can we digest, absorb, and utilize that protein? So, scientists now use a scale called the digestible indispensable amino acids score, or DS, to rate proteins using the amino acid profile and bioavailability criteria. And higher is better on the scale. So, the DS score for eggs is 1.13, which is excellent. One of the highest scoring proteins on the scale. Beef score is 1.10, also very high scoring. And peanut butter is 0.46, one of the lowest scoring proteins on the scale. The DS score for whole wheat is 0.2, which is at the very bottom. For oats, [it] is 0.43, also at the bottom. So, what this scale is telling us is that animal proteins are much higher quality than plant proteins. And that’s actually true. For every animal protein that’s on the scale, the DS scale is higher than every other plant protein.

So, even if you did make a peanut butter sandwich with a third of a cup of peanut butter, which is just absurd, the quality of the protein you’d get from that would be far inferior to what you would get from eating beef and eggs. And I’ll talk a little more about protein quality in a moment.

There’s another comment from the film about protein and muscle mass, and they refer to a peer-reviewed study. And the quote is:

“And when it comes to gaining strength and muscle mass, research comparing plant and animal protein has shown that as long as the proper amount of amino acids are consumed, the source is irrelevant.”

Now, I actually don’t disagree with that statement. But there’s a huge caveat, which is that consuming the proper amount of amino acids when you’re eating only plant foods is not easy, especially if you’re not including protein powders. Also, if you go and look at the full text of that study, which they know that virtually nobody who watched the film will do (only people like me would actually do that), it says in that same study:

“As a group, vegetarians have lower mean muscle creatine concentrations than do omnivores. And this may affect super maximal exercise performance.”

So the very study that they reference in the film to support the idea that plant-based proteins can be equivalent itself says that vegetarians have lower muscle creatine levels and that can lead to poor exercise performance. So, I mentioned earlier they play fast and loose with the science; they often reference studies that either don’t say what they’re saying, and they say or tell only part of the story of what the study is saying in the film. And this is a pattern that we see all throughout the film.

Where Protein Really Comes From

So here’s another claim from, again, Wilks.

“I was surprised to learn that all protein originates in plants. Cows, pigs, and chickens, it turns out, are just the middleman.”

Well, I was surprised to learn that, too, because, in fact, all proteins come from bacteria, not plants. Bacteria take up nitrogen from the atmosphere, and are consumed by plant roots when they feed on carbon. Bacteria also die and their necromass provides free amino acids that are also taken up by plants. Bacteria in cattle’s rumen, which is a chamber in the stomach, convert carbs to short-chain fatty acids, which the animals then use for energy. Bacteria die in the rumen and are also consumed for energy. So cattle and other ruminants get their protein from bacteria. And this explains why the levels of amino acids, which are the building blocks of protein, are so much higher in meats than they are in plants.

And yeah, I would say I would agree with James’ statement that animals are the middlemen, but I wouldn’t say they’re just the middlemen. Because it’s amazing that animals can convert nutrients in plants that are inedible to humans, like grasses and forbs, into highly bioavailable and concentrated sources of protein that our bodies thrive on. That is exactly the point of eating animals because they are extremely efficient middlemen that convert inedible nutrients to highly bioavailable nutrients. That is why animal products are an important part of the diet. And they don’t just do this for protein, they do it for other nutrients. For example, animals convert a portion of the beta-carotene that they get from eating grass into retinol, which is the active form of vitamin A. While humans can convert some beta-carotene from plant foods into retinol ourselves, that conversion is limited, especially for some people who have a certain genetic profile [for which] conversion may not happen much at all.

So, for example, if you’ve seen someone who did, like, a carrot juice cleanse or fast, or is drinking a lot of carrot juice, and the palms of their hands are turning kind of yellow or orange, that’s a person who’s not able to convert much beta-carotene into retinol. And this explains the results of studies, which have shown that dietary retinol decreases the risk of hip fractures in women, but dietary beta-carotene did not. So that’s a sign in those people that they’re not able to convert the beta-carotene into retinol. And it’s retinol, the active form of vitamin A, that really performs the most essential functions of that nutrient. And retinol is really only found in the meat, milk, and organs of animals.

How Much Protein Do Athletes Need?

So here’s another claim from Wilks:

“In fact, the largest study to compare the nutrient intake of meat eaters with plant eaters showed that the average plant eater not only gets enough protein, but 70 percent more protein than they need.”

So this one’s going to require quite a bit of unpacking. So, first, what is Wilks referring to when he says enough protein? The study that he referenced in the film measured protein intake and compared it against the RDA, which is the recommended daily allowance. The RDA for protein is currently 0.8 grams per kilogram. However, a more recent and thorough statistical analysis of the data that were used to determine the RDA suggested that it should actually be one gram per kilogram of body weight. Also, the RDA does not represent the optimal protein intake, it’s merely the amount that we need to eat to avoid malnutrition.

In other words, it’s the bare minimum of protein that we need. Another issue is that the RDA was determined using outdated nitrogen balance studies, which underestimate dietary protein requirements. A newer method called the indicator amino acid oxidation, or IAAO, technique provides a much more accurate estimation of protein needs. So, if you use that IAAO technique, it gives you 1.2 grams per kilogram of body weight as a more appropriate RDA for healthy young men, older men, and women. Now let’s go back to the film in the study that Wilks was referring to. The median protein intake in that study for strict vegetarians was 70 grams per day. Assuming a minimum necessary intake from the IAAO studies that I just mentioned of 1.2 grams per kilogram in a sedentary healthy person—this is not an athlete, just a sedentary healthy person—70 grams per day would only be enough protein for an adult that weighs 130 pounds or less. So right there, we can see that his claim that vegetarians are getting 70 percent more protein than they need is false. If you weigh more than 130 pounds, and/or if you’re an athlete who requires more protein, which is what this film is all about, and/or if you’re trying to lose weight or improve cardiometabolic risk factors, all of which require higher protein intakes, or if you’re a pregnant woman or if you’re elderly, a vegetarian diet won’t provide enough according to this study that the film itself referenced.

But Wilks does at least acknowledge in passing that athletes need more protein than the RDA. “But athletes need more protein than most people do.” Unfortunately, he fails to explain just how much more protein athletes do need, and it turns out to be a lot more. The American College of Sports Medicine, the Academy of Nutrition and Dietetics, the Dietitians of Canada, and the International Society of Sports Nutrition all recommend a range of 1.2 to 2.0 grams per kilogram of protein to optimize recovery from training and to promote the growth and maintenance of lean mass when caloric intake is sufficient. What’s more, a lot of studies suggest that higher amounts of protein are more effective for muscle building. The most thorough meta-analysis on this topic to date found that the average amount of protein required to maximize lean mass is about 1.6 grams per kilogram, and some people need upwards of 2.2 grams per kilogram.

When you look at studies that use the newer IAAO method in athletes, they found different numbers on training days.

  • Female athletes required 1.4 to 1.7 grams per kilogram the day following a regular training session.
  • Male endurance athletes required 2.1 to 2.7 grams per kilogram.
  • Two days after their last resistance training session, amateur male bodybuilders required 1.7 to 2.2 grams per kilogram.

So this puts the range of protein intake for the most effective muscle gain and recovery for athletes at 1.4 to 2.7 grams per kilogram, with the best results at the higher end of that range. So, if we just take a median number of 2.1 grams per kilogram of body weight, that’s about one gram per pound of body weight. So, for a 200-pound athlete, that’s 200 grams of protein a day. And this is much harder to obtain on a plant-based diet unless you use protein powders extensively, which many athletes who are following a plant-based diet end up doing. It’s also worth pointing out that studies have shown that if an athlete is trying to bulk up and maximize muscle gain, eating even higher amounts of protein of up to 3.3 grams per kilogram won’t increase muscle protein synthesis above what they can get with 2.7 grams per kilogram. But it can help them to minimize the fat gain that typically occurs on a hypercaloric diet. So it’s a way that athletes can bulk up and increase muscle protein synthesis without gaining fat while they’re doing that.

Protein Intake for Non-Athletes

So the film doesn’t talk a lot about this because it’s mostly focused on athletes, but optimum protein intakes are higher for fat loss. For those who desire fat loss as well, the range for that is somewhere between 1.2 and 1.5. grams per kilogram per day. As I mentioned earlier, elderly adults also need more protein. Sarcopenia, which is impairment of physical function, is the primary cause of age-related frailty in the elderly. You might have heard the saying, “You break your hip, [you] die of pneumonia.” This refers to the fact that many elderly people, if they break a bone or experience some other age-related frailty condition, and then they’re immobilized, they can often develop pneumonia, which can be very dangerous and life-threatening. It’s actually a way that a lot of people over a certain age do end up dying. So preserving muscle mass is absolutely critical to reducing morbidity and mortality in the elderly. And low protein intake is associated with frailty and worse physical function.

So most research suggests a range of 1.2 to 1.5 grams per kilogram as a target for the elderly. For pregnant women, there’s new evidence using the more current IAAO method, which I mentioned earlier, that the RDA for pregnant women should be about 1.7 grams per kilogram during the early gestation from weeks 11 to 20, and then go up to 1.77 or 1.8 grams per kilogram during the later stage of pregnancy between weeks 32 through 38. And a meta-analysis of 16 studies found that increasing protein beyond the RDA during pregnancy led to a 34 percent lower risk of low gestational weight, a 32 percent lower risk of low birth weight, and a 36 percent lower risk of stillbirth. So these are not small changes that come from increasing the protein intake.

What Is Protein Quality?

So I referred earlier to the issue of protein quality. And this is what Wilks has to say. He does acknowledge the importance of it, but it goes a little bit off the rails after that. So he says:

“But what about the quality of the protein? I’d always heard that plant-based protein was inferior.”

And then Dr. James Loomis, who’s one of the plant-based physician experts in the film, says:

“Proteins are strings of amino acids, and there’s some amino acids our bodies can’t make. Those are the essential amino acids, so we have to get them from food. And one of the arguments about animal-based proteins being superior is that plant-based proteins aren’t complete. So you’re not going to get all the amino acids. And that’s a fallacy as well.”

So, again, these statements are misleading half-truths. Protein quality, as I mentioned, is a function of amino acid profile and bioavailability, and plant proteins are inferior to animal proteins on both counts. This is not controversial. It’s well-established in the scientific literature and it’s accepted by major health and governmental organizations around the world. And it’s reflected in protein quality scales like the PDCAAS [protein digestibility-corrected amino acid score], which was the scale used previously, and it’s now being replaced by the DS scale that we talked about earlier. Loomis’ statement is a strawman fallacy. No credible person has ever argued that plant proteins are inferior because they don’t contain all of the essential amino acids. The claim, which is backed by science, is that plant proteins have lower amounts of the essential amino acids that are important for building muscle.

Essential Amino Acids

Proteins and food are made up of a combination of 20 amino acids, and our bodies can manufacture 11 of these, which means we don’t have to get them from food. These are referred to as nonessential amino acids. The other nine can’t be made in the body and have to be consumed in diet, and they’re referred to as essential amino acids, or EAAs. The muscle protein synthesis depends on all 20 amino acids, but the EAAs play a disproportionately important role. In particular, the EAA leucine is thought to more strongly activate anabolic signaling and muscle protein synthesis. In addition to having lower amounts of leucine, many plant proteins have limiting amino acids. So this means that the levels of certain amino acids are so low that they can interfere with protein synthesis. So an example is that lysine is a limiting amino acid in grains like wheat and rice, and methionine and cysteine tend to be limiting amino acids in legumes.

So, if you look at charts that compare the essential amino acid profile in a food like beef, to other plant proteins like beans, peas, and rice, what you’ll see is that beef is higher in every essential amino acid than any of the other plant proteins, with the single exception that soybeans are slightly higher in tryptophan than beef. You also see that a single serving of beef meets the RDA for three of the nine amino acids, whereas none of the plant proteins get even close to that.

So, given all this, is it possible to get enough essential amino acids from plant foods for a regular person or a competitive athlete? It is possible to combine different plant proteins with different amino acid profiles to achieve a more complete protein. Beans and rice is a classic example. Rice is poor in lysine, while soybeans are poor in methionine. So, if you combine soy and rice, they’re better than one or the other. Similarly, the amino acid profile of 70/30 blend, so 70 percent pea and 30 percent rice protein powder blend will give you an essential amino acid mix that’s similar to animal proteins. But now you’re getting into highly processed protein powders versus real whole foods. So there’s the protein quantity issue, like an eight-ounce top sirloin steak has about 50 grams of protein, whereas one cup of cooked unsalted white beans contains about 17 grams of protein. So that’s just an enormous difference in the quantity. But the amino acid, essential amino acid profile of that beef will be complete and superior for muscle protein synthesis compared to the cup of beans on its own. Unless you add another protein source to that. But again, you’re going to have to eat pretty enormous amounts of the beans and the rice in order to match the quantity of protein that you would get from just the eight ounces of steak, and even then, the quality won’t be as good for muscle protein synthesis.

Animals concentrate essential amino acids, so you get a lot more of them in a smaller amount of food. And this is why many vegan athletes, including some of those who are featured in the film, use a ton of protein powder. There are some videos on YouTube from Patrik Baboumian, who’s the vegan strong man in the film, where he shares a typical day of his diet. And you see that he has at least four massive soy protein powder shakes with a lot of powdered supplements in order to get to the protein intake that he needs to maintain his strength. So that’s not ideal. Protein powders isolate plant proteins, and to do that, they have to take out the fats, the phytates, the oligosaccharides, and the fiber from the peas or wheat or soy beans or other sources of plant proteins. And that process usually involves hexane-based solvents or alkali extraction, isoelectric precipitation, salt extraction, dialysis, and micellar precipitation. And the processes might also include chemical solutions like sodium hydroxide, which is also known as caustic lye, centrifuging, freeze-drying, and ultrafiltration. And if your head is spinning, you don’t know what any of these processes are; that’s kind of the point. They’re not natural at all. These are highly ultra-processed foods, these protein powders, and they don’t contain any of the other essential nutrients, the vitamins, and minerals that a steak or another type of animal protein contains.


So that’s the essential amino acid profile. The other aspect that’s important to protein quality is bioavailability, which is how much of it is digested and absorbed. We talked about the DS scale earlier, which is being used now because it does take bioavailability into account. And when you look at that scale, every animal protein is higher than every other plant protein. The beef, again, is 1.1, eggs are 1.13, and chicken breast is 1.08. The highest growing unprocessed plant food is chickpeas at 0.83. And then the lowest growing animal food is chicken breast at 1.08. So there’s quite a big difference even between the lowest scoring animal food and the highest scoring plant food. And this might surprise you, especially for those who are under the impression that dairy products are unhealthy. Whole milk, which is definitely maligned in the film, and in the vegan world, in general, blows away every plant protein, and, in fact, every animal protein, too, with a score of 1.32. So this is why milk and then whey are used as protein powders by bodybuilders because of their superior amino acid profile and bioavailability.

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Six Nutrients that Are Missing from Plant Protein

But there are some other issues with plant proteins that aren’t addressed in the film. Proteins aren’t just protein. If you eat a whole food with protein, it doesn’t just have protein; it has other nutrients. And a lot of the plant-based proteins don’t have these nutrients in as high levels as you would find them in animal protein. So an example of this would be creatine, which I referred to earlier. Studies have shown that vegans have lower levels of muscle creatine, which is a nonessential nutrient that’s supplied by meat and contributes to strength and power. One study showed that giving vegetarians creatine supplements during a strength training routine increases their strength more than supplemented omnivores, which suggests that vegetarian diet can limit strength potential. Vegetarian athletes also have lower levels of muscle carnosine. Carnosine helps maintain a normal pH in muscles by buffering the hydrogen ions created when muscles generate energy.

Beta-alanine is a rate-limiting precursor to forming carnosine, which is primarily found in animal foods like meat, fish, and poultry. Vegans may need to supplement with beta-alanine to maintain sufficient muscle carnosine levels. Taurine is a sulfur-containing amino acid that reduces muscle damage and improves recovery after exercise. Vegans have been shown to consume almost no taurine in the diet. And while taurine is not an essential amino acid because it can be synthesized in the body from cysteine and methionine in the presence of [vitamin] B6, vegans tend to have lower levels of B6 than omnivores and lower levels of cysteine and methionine as well, which makes taurine deficiency more likely. Vegans also consume less calcium than omnivores and other vegetarians. A study of Canadian vegans showed that vegans consumed only an average of 578 milligrams per day of calcium compared with 950 milligrams per day for omnivores, and 875 milligrams per day for ovolactovegetarians who are eating dairy products. And this explains why studies have shown that vegans are at a higher risk of fracture.

Zinc is important for cell growth and repair, protein metabolism, exercise, recovery, and hormone production, including testosterone. And although zinc is found in many plant foods, as is the case with calcium, the plant foods that contain zinc also contain nutrient inhibitors that reduce zinc absorption. So, this explains why the Institute of Medicine has suggested that vegetarians might need to consume up to 50 percent more zinc than non-vegetarians, and a meta-analysis showed that vegetarians and vegans have significantly lower zinc intakes and blood levels.

So we could go on, but I think you get the point. Food isn’t just an isolated nutrient like protein; it contains a whole bunch of other nutrients that work in a synergistic way. And you know, whether you’re looking at the quantity of protein or the quality of protein, there’s really not much of a comparison between animal proteins and plant proteins. Animal proteins are superior in all of those respects. And it is possible, as I mentioned, too, if you’re really on the ball and paying close attention, and if you’re willing to use protein powders to get adequate protein if you’re an athlete on a completely plant-based diet vegetarian, certainly, it’s much easier because you can use dairy products and eggs. But as a vegan, it’s still possible using, like, a 70 percent/30 percent pea/rice protein powder blend and just being very careful of how you combine foods. But it’s not easy to do. And even if it’s done correctly, you’re still going to be missing out on many other nutrients, which Patrik Baboumian seemed to be aware of when he was adding those to his four protein powder smoothies a day. He was adding creatine and beta-alanine, which you can see on the YouTube video. So it’s possible, but you often have to use a lot of supplements and you need to be very careful. And you need to often eat an enormous quantity of foods like beans and grains, which can be pretty hard on the digestive tract in the quantities that you might need to eat them and depending on the person.

Okay, so I’m going to stop there. There’s much more that I could say, and that I will say on The Joe Rogan Experience. I think we’ll probably end up talking about it for a few hours. There’s a lot of other claims in the film that are pretty outrageous and false, that aren’t related to protein directly. And I’m looking forward to breaking that all down on Joe Rogan’s show. So I hope this was helpful. And I just want to point out, I should have made this clear at the beginning: this is not an attack against any vegans. I was a vegan myself. In fact, a macrobiotic vegan, which is even more restrictive, and a raw food vegan for a period of time. I think many of you know my story. And I have many friends who are vegan, and I respect people’s right to choose their own dietary approach. What I take issue with is a film that completely misrepresents the science on this topic, and doesn’t provide any experts in the film that have an opposing point of view, and really just tells one side of the story and doesn’t tell it accurately or well at all. So that’s why I’m recording this podcast. And that’s why I’m going on The Joe Rogan Experience just to set the record straight.

So thanks again for listening. Send in your questions to ChrisKresser.com/podcastquestion. Even though we haven’t been doing Q&A episodes lately, I do look over your questions. They help inform what guests I have on the show and there’s always a chance we might return to that Q&A format. I periodically do that when I take breaks from guests, and sometimes I can answer your questions in other formats like written articles. Okay, everybody, thanks for listening. Take care.

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