DEBATE – Paul Saladino, M.D. and Alex Leaf, M.S. – Are Plant Foods Healthful or Harmful?

Alex: Yes, I guess I have two questions. One of them is a slight tangent which is that, Paul, do you think that consuming meat causes colon cancer?

Paul: No.

Alex: Why? Briefly, if possible.

Paul: I think about that from a number of perspectives, both evolutionary, mechanistically, epidemiologically if you compare Asian studies. There’s a lot of evidence in that opinion that there is–

Alex: Let’s ignore observational evidence because you made that clear that that’s not reliable, let’s ignore evolution because that’s not dealing with long-term health, that’s dealing with survival and reproduction. Let’s focus on mechanisms. Red meat is classified as a probable carcinogen and processed meat is a carcinogen by the World Health Organization and the International Association for Research on Cancer, the IARC based primarily on established mechanisms that show how meat and the compounds it contains cause cancer in your colon cells. If that mechanistic evidence exists, why do you not believe that the inclusion of meat is problematic because there’s a mechanistic possibility or there’s a mechanistic route through which it causes colon cancer?

Paul: I’ll show this study which I think is probably the best summary of this that I’ve read. It’s a review paper. The title is Red Meat and Colon Cancer, a review of mechanistic evidence for heme in the context of risk assessment methodology. If you look at this paper, what they elaborate on is that the working group cited mechanistic evidence for multiple meat components, including

those forms for meat processing, such as N-nitroso compounds, abbreviated as NOC, heterocyclic aromatic amines, and endogenous heme iron. In this paper, they make a great case for the fact that many of these, though there are hypothetical mechanisms, again, have been studied very poorly.

Animal studies utilized models that tested promotion of preneoplastic conditions, utilizing diets low in calcium, high in fat, combined with exaggerations of haem exposure that in many instances represented intakes that were orders of magnitude 10 to 100X above normal dietary consumption of red meat. Finally, clinical evidence suggest that the type of N-nitroso compounds found after ingestion of red meat in humans consists mainly of nitrosyl iron and nitrosophyls, products that have profoundly different chemistries from certain N-nitroso species which have been shown to be tumorigenic through the formation of DNA adducts.

I think that in response to your question, I would say that many of the mechanisms proposed for any of the compounds in meat being tumorigenic carcinogenic are something that need to be considered more carefully because there’s certainly a large amount of evidence that it doesn’t hold up to intense scrutiny, which makes a lot of sense evolutionarily. Different types of N-nitrosophyl compounds, heme iron being studied in animal models, which are calcium deficient, orders of magnitude higher, et cetera.

Alex: The context around they had a really crappy diet, they were deficient in calcium, et cetera. How is this criticism of the red meat cancer any different from you saying that these goitrogens are problematic in societies that have inadequate iodine intake or under certain circumstances where they’re consuming incredibly excessive amounts of these goitrogens in their diet or in animal models that use isolated goitrogens to show that it has a negative effect on thyroid? To me, it seems like you’re applying a double standard to one set of evidence and you’re not applying that same standard to the other side of evidence because I don’t think that there is.

Correct me if I’m wrong here. For example, if you look at soy, soy has goitrogens in it. When you look at studies that assess actual thyroid function in people that consume large amounts of soy, you find that thyroid function remains unaffected. In fact, the longest randomized controlled trial that we had, which followed 403 menopausal women for two years, reported that consuming 120 milligrams of soy isoflavones daily over that two-year period had no significant effect on thyroid function other than a trend for reduction in T4. That reduction was from 1.2 to 1.1, which isn’t clinically significant by any extent.

Why are you focusing on these mechanisms that oftentimes happen under unrealistic as opposed to hard outcome data that looks at things like actual thyroid function when eating what would be considered the upper end of reasonable quantities of these foods?

Paul: I think that that study that I showed illustrated pretty clearly that within the realm of normal consumption of those species of brassicas, there were compounds, specifically goitrogen, that pretty clearly affected radioiodine uptake and could be [crosstalk]–

Alex: I agree, it did, it affected uptake, but it didn’t affect thyroid function, did it? Was that assessed? Because iodine uptake in actual thyroid function, like the secretion of T4 and transformation to T3 are two totally separate outcomes. Iodine uptake is also affected by how much iodine you have in your diet. It could inhibit uptake, but if you have enough iodine to compensate, that seems to be a non-issue.

Paul: My point is that there are many plants that contain chemicals that are clearly intended to have negative effects on animal-human physiology, whether it’s cassava, or goitrogenic compounds, and brassica vegetables. The question is, why would we eat those vegetables? Why would we even negatively affect thyroid function or any of the other potential issues with isothiocyanates when we could get all of the nutrients from those things from other foods like animal foods, animal meat, animal organs, et cetera? There’s a clear indication of the plant’s intention here and the intention is sinister.

There are plenty of good mechanistic studies as opposed to the poorly done mechanistic studies with red meat and cancer, or N-nitroso compounds, or heme iron that suggest that this is a mechanism that is damaging for humans so that we must ask the question, why would we include these things in our diet? To me, this is a really, really important conversation because there are literally hundreds of thousands, if not millions, hundreds of millions of people suffering with issues that are not resolved by Western medicine. We must ask these questions about whether all of these plants in their diets are completely benign.

Anecdotally, clinically, I see this over and over and over that people get better, whether it’s from a hypothyroid state, whether it’s from a GI issue state, inflammatory bowel disease, even irritable bowel syndrome when many of these brassica vegetables or other vegetables are removed from their diet. I think that it’s just beginning to ask the question about whether these plants are uniquely benign for humans because your position would be these plants are not harming you. I will tell you with complete certainty, Alex, that if you tell people that none of these plants are harming them, there are people who will not improve their quality of life because they will not consider this to be a possible negative influence on their health.

There are people that will continue to suffer. We must consider the fact that the intention of these plants is clear. These are negative compounds in our health. Are they going to affect everyone’s health negatively? No, certainly not. There are some people who may have enough iodine in their diet to be fine with it, but why would we eat plants, especially the most toxic defendant parts of plants that are not really improving our health as humans? This is the question I’m asking. I think that we have to be very careful to not forsake the people who are continuing to suffer.

We have to keep asking these questions. If someone is eating a diet containing kale or spinach, collard greens, and they’re thriving, who am I to tell them how to change their diet? I would never do that, but I think these discussions remain critically important for the people that are not well, that continue to suffer. I see it over and over and over that mechanistically, biochemically, there are so many of these defense chemicals, and that’s what I’m illustrating with that paper, that are not intended to be good for humans and that appear to have very negative effects for us.

Alex: Do you think instead of not being intended to be good for us, maybe that their effects are more accidental? The reason I say that is, again, if we go back to red and processed meats, there are compounds in there. Even though you say that that mechanistic data is of low quality, but other mechanistic data using similar conditions is not, which I don’t understand, but whatever. A lot of the stuff’s accidental, but why eat red meat? We can get all the nutrients we need in red meat from, for example, seafood and poultry. Why eat red meat and why risk consuming these nutrients that have a mechanistically plausible way of hurting us?

Paul: I got multiple questions there that I’ll answer in turn. I would disagree with you. There are many nutrients in red meat and organs that are not found in fish that are not found in chicken. Whether these be peptides that are unique to red meat, things like splenopentin or tuftsin or hepatic growth factor or BPC-157. It is simply an inaccurate statement to say that we can get everything that is found in red meat or ruminants in chicken or fish. I think it’s a splitting of hairs. I have no problem with people eating chicken and fish as long as the fish is not high in heavy metals, which usually is, not a huge fit for clear seafood consumption.

I think that if you look at the amounts of many nutrients, especially nutrients that we’re only now beginning to learn about, they’re not always evenly distributed and there are unique benefits to larger animals, specifically ruminants. That would be my answer to you. We can certainly discuss offline why the mechanistic studies with red meat are not accurate. I thought I discussed that clearly. I’m not sure what part of that you’re not understanding.

Ari: I think he’s more using it as a way of arguing rather than actually disagreeing, trying to argue that they’re harmful. He agrees with you.

Alex: I’m just using it to draw a parallel because a lot of the things you mentioned, low calcium intake, unrealistically high doses, those are the same conditions that are used with a lot of the mechanistic goitrogen studies.

Paul: Not the one that I showed.

Alex: No, but the one that you showed just looked at iodine uptake. It didn’t look at actual thyroid function.

Paul: It’s just the intention [crosstalk]–

Alex: I can pull it up if you want, but I have a meta-analysis and the longest RCT that’s been conducted showing thyroid function remains essentially unaffected. That’s a hard outcome that we care about. Iodine uptake isn’t.

Paul: Like I said, if someone is eating these foods and has normal thyroid function and feels great, eat them, I have no problem with that, but in people who are suffering, the intention of plants is very clear here. You used the word accidental and I want to really clarify that. There’s no accident here. In the case of sulforaphane, the precursor molecule is glucoraphanin. I often ask people and I’ll ask you guys this, do you know how much sulforaphane is in a broccoli seed?

Alex: A lot.

Paul: Do you have any idea?

Alex: I think broccoli sprouts are like 1,000 milligrams per gram or something like that.

Paul: The answer is zero until [crosstalk]–

Ari: [inaudible] in the seed rather than the sprout.

Paul: No, it’s zero until the sprouts are chewed. It’s zero until the seeds are chewed. The intention of plants is very clear here. There is no sulforaphane in a broccoli seed until you chew it. The reason it is made when you chew it is because myrosinase combines with glucoraphanin. Those are separated in terms of cellular compartments. It is the mastication, it’s the chewing of the broccoli sprout seed plant that makes sulforaphane and other isothiocyanates. It’s the same thing with cassava and allyl isothiocyanate and hydrocyanic acid. These are defense mechanisms.

These are booby traps that are sprung when different cellular compartments in the plant are combined via mastication. The intention of the plant is quite clear here. The plants are now– and I’ve often heard it said that sulforaphane, many of these isothiocyanates are so reactive from an oxidative perspective that they would create oxidative stress in a broccoli plant. They’re not used. It’s not a molecule that’s in a broccoli plant. We know this in humans. That’s the reason sulforaphane triggers the Nrf2 Keap1 system. It’s because it is reactive oxidative molecule. There’s no question about that.

A Broccoli plant doesn’t contain sulforaphane until it is consumed by an animal. It’s no accident. I hope I’m understanding your position properly here, but these compounds are not accidental. These are compounds that the plants are actively using as booby traps to prevent or dissuade consumption. There’s no question that plants contain anti-nutrients and defense chemicals. The only question is how well adapted any individual is to eating these compounds. Certainly, there are systems in our body to deal with them, phase I and phase II detoxification in the liver, but there’s inter-individual variation in terms of how we do this.

I think for some people, they are pretty problematic and the corollary assertion that I’ve made throughout this is that I don’t see a benefit to excluding them from the diet. It seems like a much safer proposition that is evolutionarily consistent to me. I just wanted to respond to those points. There’s no accident here.

Alex: Yes, that makes sense to me and I would agree. I would agree plant secondary metabolites are defense mechanisms. I guess when I said accidental, I was thinking specifically of human consumption, but in the grander scheme of things, I completely agree with you that most phytochemicals are produced as a means of either promoting consumption or trying to circumvent it depending on what part of the plant. I also agree with you that I think the individual does need to be respected and that some people might do better limiting certain foods depending on their individual physiology and biochemistry.

I don’t want to get caught in the weeds of that individuality because we both agree on it. We both agree there’s always going to be exceptions to the rule, but I want to focus on the rule because some people should minimize their intake of high goitrogen-containing foods, just like some people need to minimize their intake maybe of phytoestrogens if they have an estrogen-sensitive breast cancer. There’s a lot of examples of it, but you get my point. Certain individuals need different things. Some people might need to exclude all plants to really feel amazing if they have inflammatory bowel disease because the flares are just killing them.

As a general rule of thumb, if we were to give population-level guidelines for how the optimal diet should be built, that’s what I want to focus on. I would not say that the glucoraphanin or a glucosinolate in broccoli that acts as a goitrogen is problematic for people, especially because over half of it’s reduced by simply boiling the broccoli for five minutes. That’s the case with a lot antinutrients is that cooking, if we get into others, most of them like lectins, cooking destroys a lot of them, which reduces their activity. Now, a lot of people eat plants raw. That could be even more problematic than cooked plants and I agree. That gets back to the individuality thing.

From our conversation on goitrogens, yes, I agree that they are problematic in certain contexts. I disagree that the evidence supports a widespread problem of including more goitrogen-rich foods in the diet because I haven’t seen and you haven’t shared any data that shows that it actually has a negative effect on thyroid function outside of very specific circumstances such as insufficient iodine intake, consumption of maybe excessive amounts in that circumstance. It’s been a lot of mechanistic reasoning that is logical, it makes sense, but it doesn’t play out in the grand scheme of things because there’s a lot of other factors that come into play in our biology. Iodine intake’s one of those.

Ari: I have a devil’s advocate question for both of you. Paul, are you okay with me asking you a devil’s advocate question?

Paul: Can I just respond to that?

Ari: Sure.

Alex: Yes.

Ari: I’m just trying to ask a question here, but go ahead.

Paul: No, I think I agree with you, Alex. I think that it’s just important to consider that when we’re designing an optimal diet for humans, we need to have this consideration of plants as on a toxicity spectrum. For me, the question remains, why would we include these foods in our diet? Why would we include– Again, we’re getting to the point I think we may have to do a part two or something for this discussion because I think that nobody listens beyond this point. I wanted to keep it a little more succinct than this. I think that the question becomes, why would we include kale?

Why would we include brassica vegetables in the diet if they don’t have a unique benefit and there’s a potential mechanistically for harm? If we are going to design an optimal ideal diet for humans within those guidelines, we must have the caveat that, hey, many people feel better when they remove these foods from their diet. Many people feel better when they get these things out of their diet. There are plenty of instances of these things triggering people in very negative ways. There’s mechanistic science behind it, there’s interventional studies that are, again, with salmon, shrimp, and salmon eggs. on uptake rather than end thyroid outcomes suggesting the intention of plants as a defense chemical.

What I fear is that when we try and create a diet for everyone, we were making broad strokes that are often much too broad and that don’t serve individuals. How do we create then an idea of a framework of a diet for humans that also includes a very clear message that the exclusion of many of these foods, specifically what I might consider to be the most toxic plants, can be very helpful for people who are continuing to suffer? I think that’s what gets left out of these broad strokes conversations about human health.

I think that if the majority of people in the United States, in the world, ate a paleolithic type diet with organs and meat and animal fat and vegetables, human health would improve massively. It’s like you said in the beginning that if people ate an animal-based diet or a carnivore diet, I think the human health would improve massively as well. I think in either of those contexts, we have to have the discussion. This is what I believe has been left out and maybe the importance of this conversation. We must have the asterisk. We must have the consideration of the fact that these plants do not serve all humans very well.

That’s a statement that gets left out often because people will say, “Look at this data, look at this observational data. These are clearly beneficial for humans.” I feel like one of the unique aspects of the position that I’m taking here is to say, “Hey, this is not great for everyone.” Like I’ve said throughout this discussion, if somebody is thriving, doing well, don’t change your diet, but I want people to know when they are suffering, that these things are not uniquely beneficial for humans and this is why because this is where the plants are coming from and these compounds are clearly intended to be negative for us. I’ll let you respond to that if you want, or I’m happy to answer your question, Ari.

Alex: It would be your brief response Ari, 30 seconds.

Ari: Go for it.

Alex: I guess in my head though, when you mentioned that there are certain chemicals like bioactive peptides in animal foods that we can’t get in plants, I would make the analogist argument that a lot of the phytochemicals in plants we can’t get in animal foods. Even though we could get some, no doubt, we can’t get the majority and that even though the majority might have weak evidence behind them, I think you would also have to concede that a lot of these up-and-coming bioactive peptides would also have equivalently weak evidence, possibly even weaker.

It comes back to something you brought up earlier, which is that we need better data, and that’s something I wholeheartedly agree with. While I don’t think that this type of thing would be done ever, it would be cool to start seeing some studies that actually look at primarily carnivorous diets and compare them to equivalently quality diets that were richer in plant foods because that would answer a lot of questions. That would really help isolate all of these phytochemicals without the unrealistic scenario of looking at them in isolated high dose concentrations.

Paul: That actually makes me think of a question that I have for both of you. I don’t know if you were saying this, we didn’t really talk about this earlier in this detail. There are clearly compounds in animal foods that you cannot get in plant foods, B12, creatine, carnitine, choline, anserine, taurine, vitamin K2. There’s really not a lot of riboflavin in plant foods. This is really not even a topic for discussion to understand. There are many unique things that are necessary for optimal human health in animal foods.

Now, I think that it’s much more difficult to make the corresponding argument though your point is well taken that we would have to consider are these phytochemicals really valuable for humans, and do we really know which of them show up in animal foods and which of them don’t. The paper that I showed might suggest that maybe the ones that are beneficial for humans, a significant amount of them might actually show up in animal foods. I think that would be something that’s a topic for further discussion.

Ari: [inaudible] give example of that as well, showing up in salmon and shrimp and salmon eggs.

Alex: Yes.

Paul: Yes.

Ari: That is primarily [crosstalk] sources of that as well, unless you go seek out that algae, which I’m not aware of any human society that does that.

Alex: The closest I could think of would be spirulina, but that’s technically not an algae. It’s a cyanobacteria. The natives off of Lake Chad in Africa and Tanzania and Central America have that as a staple of their diet. Interestingly enough, it’s also a bioavailable source of vitamin B12 that is usable by humans in quantities that could satisfy B12 requirements. Although no study I’m aware of has actually looked at if it could prevent a deficiency because that would take a really long time. It contains the cobalamin molecule.

Paul: Interesting. It seems like it’d be much easier to just eat animal foods.

Alex: I agree.

Ari: Do you guys want to do fiber or are we going to end?

Paul: I think we should wrap it up. We can’t do fiber, it just gets to be [crosstalk]–

Alex: I think fiber would be a cool one to do within a follow-up.

Paul: Can I ask you guys a question?

Ari: Go for it.

Paul: Have either of you ever done a carnivore diet or an animal-based type diet?

Ari: Animal-based? Yes, certainly, not to the exclusion of plants.

Paul: By animal-based, I mean the way that I’ve talked about it with the exclusion of nut seeds, grains, legumes, leafy greens, stems, and roots. Have you done that, Ari, just meat and fruit and organs?

Ari: When I was doing heavy meat, it was more of an extreme low-carb keto approach, so no fruit and honey.

Paul: Were you including any organs in your diet?

Ari: Yes.

Paul: You were?

Ari: Yes. Liver and heart.

Paul: Cool. What about you, Alex?

Alex: Yes. I don’t know. This might have been back in 2014, I think. My diet was based around meat, like chicken, bison, chicken hearts, beef liver, eggs, and cheese. Then the primary plants in my diet were potatoes for starch, a big salad at lunch, and coconut.

Ari: Why do you ask?

Paul: I’m just curious because I think that personal experience is valuable. I have my own story of basically eating a paleolithic diet and having pretty bad eczema and then excluding the majority of plant foods and having that improve. I wasn’t sure if either of you had experimented with something like that to see how your body reacted.

Ari: I’ve done probably every extreme diet than you can imagine in my teens and 20s. I agree completely with what you said. I’ve done vegan, I’ve even done raw vegan for a [unintelligible]. I can’t say those experiments ended well at all, but my low-carb keto, heavy animal food diets also didn’t end great, especially just as an athlete. Notable decrements in performance for sure. Other than that, I can’t say I noticed much of an effect. Alex, do you want to jump in with your experiences?

Alex: The whole reason I got into nutrition was because I did a decade of competitive wrestling that gave me an eating disorder. I’ve always just been able to push my way through any diet I’ve been on with willpower. I probably feel best where I’m at now, which is just a mix of plants for starches, probably less fibrous vegetables than I’ve eaten historically. Then continue to eat high-quality lean meats. Most of my fat comes from plant sources, all of my fiber from plants, then resistant starches from cooked and cold starches, but meat provides half my nutrients and all of my protein.

Paul: I will say, Ari, that a lot of people experience that on ketogenic or low-carb diets and that’s one of the reasons that I re-incorporated carbohydrates in my diet from sources that seem to work both for me. That’s why I think that there should be a consideration of those macronutrients a little bit.

Ari: I applaud you for not being so dogmatic in that belief system, especially being an author of a book on that subject. It’s, I think, easy to lock ourselves into our belief system where we become inflexible and unable to adapt. I know I’ve been there many times with different extreme diets where I’ve been so convinced of that diet being the ultimate truth that– It basically created an eating disorder as far as inflexibility of being willing to deviate from that. If you guys are cool with it, I’d like to ask one devil’s advocate question to wrap up.

Paul: I’ll just mention in response to your statement, Ari, that as I said in the beginning, even when I wrote the book, I don’t think it was dogmatic or extreme, there were considerations that allowed for some flexibility. I just want to make that very clear because you seem to continually try and paint me differently.

Ari: I’m always happy to give you the opportunity to clarify. Apologies if you feel I’m misrepresenting. Alex, I would like to ask you if, and to this point, Paul, if you feel I’m misrepresenting things please correct. I would like to ask you, Alex, if you think it’s possible that this whole body of nutritional epidemiology for the last 70 years and the thousands of studies on that that have pointed towards plant-based diets being the key to health. I would say if there’s one point of agreement that historically everybody on the different dietary spectrum has agreed upon it’s that the vegetables are healthy.

In this podcast that’s been debated. Do you think it’s possible that mainstream thinking around nutrition for many, many decades just we could have gotten that badly wrong and all of the studies that have pointed in that direction could be flawed?

Alex: I think it’s possible that eating a diet with little to no plant food could be healthy. I don’t think we have data to support that and I think what data we do have looking at meat-heavy diets is heavily confounded by unhealthy user bias and also by the types of meats being consumed. However, I would hypothesize based on what evidence we do have available that a meat-heavy diet that perhaps reduced its meat and replaced much of it with plant foods, not just any plant foods, but specifically replaced it with fruits, fibers, vegetables, and legumes, would be probably much healthier.

That will get into hopefully a follow-up discussion we had about fiber. I also do think that there isn’t sufficient data to support a detriment of anti-nutrients such lectins, phytates, goitrogens, phytoestrogens, or phytoestrogens in certain plant foods when it comes to actual hard outcomes in humans, even if there is mechanistic plausibility, especially under the context of a nutrient-sufficient diet. I think there’s more possibility that a plant-heavy diet is detrimental under conditions of, for example, poor socio-economic status or developing countries where they’re not getting a lot of these bioavailable nutrients that are supplied by animal foods.

Therefore, these anti-nutrients wreak even greater havoc. We go back to that goitrogenic example, low iodine intake with high intake of goitrogenic foods, bad case of goiter. I think under nutrient adequacy supplied by a combination of plant and animal foods, I don’t think that these anti-nutrients I don’t think they are detrimental to our health and I think that there is a good body of evidence supporting the beneficial effects, even if we haven’t figured out every single mechanistic reason why of a lot of these secondary plant metabolites that go outside of just the vitamins and minerals that they provide.

Just like, I think, that there’s a lot of benefits from certain zoonutrients that are present in animal products, things you can’t get in plants, like carnitine, creatine, taurine. I think a lot of these bioactive peptides, bioactive amines, that type of thing, also have benefits and we can’t get those from plants.

Ari: Excellent. Paul, my question to you is, correct me if I’m misrepresenting, if plants are, let’s say, a net negative, is that agreeable, or in the majority of people that high plant food consumption is net harmful rather than net positive?

Paul: What’s your question, Ari? I’m not understanding why you’re [crosstalk]–

Ari: That’s okay.

Paul: No, we’ll see.

Ari: If that is the case, how could so many studies, epidemiological, flawed as they may be, healthy user bias incorporated, but given that many of these studies try to control as much as possible for a lot of those confounding variables like smoking and exercise habits, how could so many point in that direction and how could there be so many anecdotes of, let’s say vegan. Remember, I’m not a vegan or an advocate of veganism, but how could there be so many vegans who go entirely plant-based where their whole diet is composed of things that you’re saying have sinister intentions and yet report such positive health effects and reversal of diseases and so on?

Paul: I believe you’re asking me multiple questions. I will answer the vegan one first. I think that, again, the devil’s in the details. This is the problem with considering the weight of the evidence, but if you look at these instances, again, we don’t have specific vegans here to ask about the improvements in their health, but I think it’s pretty clear that the main offender, as we said from the beginning, is processed sugar and seed oils and the processing of food. Despite the inclusion of anti-nutrients in their diet, moving from a diet containing more toxic things to a diet containing relatively less toxic things could lead to health improvements.

Now, interestingly, as I touched on earlier, if you look at long-term vegan nutrient adequacy, it’s abysmal. I think that that is an indication of lower bioavailability and overall content or overall presence of antinutrients, or at least digestive enzyme inhibitors, things that block absorption of nutrients on an entirely plant-based diet. To bring good old Joel back into this conversation, long-term vegan diets are a nutritional nightmare for humans without massive amounts of supplementation because plant foods simply do not contain adequate nutrition for human beings. That is very difficult to argue. I feel very strongly about that.

Though people may improve in the short term, they ultimately have just a flaming crash of the airplane later on when they run into all sorts of health problems with these diets. You could improve a fast, you could eat no food and see an improvement. You mentioned this earlier with regard to the potato diet and other diets. It’s really important to consider that many of the studies with vegan vegetarian diets are calorie-restricted as was the Twinkie diet, as are these potato diets because you simply cannot eat enough calories from potatoes.

Anyone with metabolic dysfunction is going to see an improvement in their overall health in insulin sensitivity when they have calorie-restricted diets. Even if those calorie-restricted diets are composed of some of the least bio-available nutrients or foods that are what I would consider to be less optimal for humans, they’re going to see an improvement at least in the short term, but I think long-term studies bear out the fact that there are problems with these foods both in the absolute amounts and bioavailability of nutrients.

I would suggest from the perspective of the fact that many of these nutrients are much harder to absorb, or these antinutrients like phytic acids or oxalates, like we discussed with the zinc study, can impair the absorption of minerals from other foods that might even be animal containing. That’s the answer to your first question. Well, that was the second question you asked. The first question you asked which was, why do so many observational studies point to a benefit with these plants? I think we discussed that earlier pretty in-depth, having to do with healthy user bias with unhealthy user bias. I’m not sure we really need to go into that in detail.

Ari: [crosstalk] the second part.

Paul: You and I discussed this a little bit in our previous meeting. I think that there are no good studies that have been done looking at high vegetable and low vegetable populations from an observational perspective and it just doesn’t exist. When we look at these studies, they’re generally all of the people in them are eating vegetables at moderate amounts. It’s hard to see a signal of epidemiology and as we talked about in this podcast, I think that this may be one of the cases where we have to think about whether we lose the individual, and individuals continue to suffer when we consider that other research as a primary means of making the decision.

Ari: Guys, thank you so much for all of the time. This has been a lot of fun. Thank you for also being so polite and respectful and being willing to agree when you actually agree on certain things. This was awesome. Paul, thank you for being brave enough to come on after we met in-person and had a brief scuffle, so you knew we had some disagreements going into this. I know you’re a bit wary of a two-on-one dynamic. I did my best to leave out most of my commentary of this. I know you got mad at me a couple times there, but hopefully, I was good enough to be relatively unbiased in moderating this discussion. Guys, thank you so much. This was awesome and, hopefully, we can do it again.

Alex: I would like a follow-up on fiber because I think that’s just a fun topic to talk about and I really like fiber. As a discussion topic, I think it’s interesting because there is a lot we actually don’t know. I think that it would be interesting to see what agreements me and Paul could come to on that, just like we did here.

Ari: Paul.

Paul: I appreciate you guys. Thanks for coming on, Alex. I enjoyed it. I think it’s fun, and we should keep sharing ideas. I think this is what moves things forward and it’s what we need to do more of. I appreciate you hosting, Ari. It’s good to have a moderator, though as I said, I think it’s important the moderator remains– [chuckles]

Ari: Trust me when I tell you there was about 500 times I wanted to interrupt you and say certain things and I restrained myself.

Paul: Appreciated that.

Ari: I did the best I could on that front given that we are humans; we all have our own biases. Thank you, guys, again. To all the listeners, I guess the debate lives on. You have to decide which arguments you felt were more compelling around plant foods being helpful, or harmful, or benign, and where you fall on that. Thank you, guys, again. This was a pleasure. I hope to talk to you both again in near future.

Alex: Yes.

Paul: Thanks, man.

Alex: Later.

Ari: See you guys.