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Plants vs. Mammals (Energy, Digestion, Broad Conceptual Explanations, and the Lion Diet)


This is not diet advice. I’m not a diet, nutrition or medical expert. And I’m not saying to stop eating plants. My guess is that a meat-only diet is a bad idea for most people. My article does not reach specific, actionable diet conclusions. These are incomplete, exploratory thoughts based partly on limited, initial research. I’m posting this primarily to allow for criticism or feedback, plus as an example of how to begin looking into an issue. This could also point people to some resources they could read which they might not have found otherwise. People should read resources from multiple sides of the debate, multiple perspectives, etc., before changing their diet. You should not try to use these ideas without doing your own research and forming your own opinions. I advise against making health-related decisions based on this article.


Why do we eat (and drink, breathe, and otherwise take external things into our bodies)? The high level answers is to get energy and mass.

Our bodies are made of atoms. We need to get atoms to grow as children. As adults, we need to build new cells, repair damage, and get some nutrients that we use in temporary ways (a bit like how cars need periodic oil changes).

In the abstract, we could eat anything with mass to get mass. Our actual eating is much more limited. We can’t turn stone into blood, bone or muscle. We can’t usefully eat dirt, wood or metal either (except some little bits here and there). To some extent, we need to eat the same atoms and molecules that our body is made with. And we need to eat things that we can digest. (We also get a bunch of mass from drinking water, and I don’t know how much from breathing.)

It’s hard to get a lot more specific, so let’s turn next to energy and see what we can figure out by thinking about energy.

Note that I’m not a scientist (nor historian, nor doctor). If someone knows of good sources of information from experts covering similar issues to what I discuss in this article, please share it. And if I got something wrong, please correct me. Thanks. What I am is a philosopher, so I know something about analyzing issues using conceptual explanations. I also know something about researching and learning about issues. So I’ve used those skills to hopefully figure out some useful explanations from a different perspective than other people bring.


Where does energy come from? The Big Bang. But that was in the distant past. The main sources of energy now are stars. Energy on Earth comes primarily from the sun that Earth orbits.

If you look at power plants we build, you can trace their energy back to the sun’s light shining on earth (with some exceptions like nuclear or geothermal).

Hydroelectric plants get power from the flow of rivers. That flow has energy. Why do rivers flow? They go down hill and the water is pulled by graviety. If they run down hill, why don’t they run dry? What replenishes them? What gets more water up to the top of the hill? Rain. Rain comes from clouds – a bunch of water in the sky. How does it get there? What makes the water go up into the sky? What lifts it against the force of gravity? The sun heats water (primarily from the oceans which are lower down than rivers) and evaporates it.

When we burn fossil fuels like coal or oil, the energy in them originally came from sunlight. The energy from burning wood or dung also came from the sun.

Solar power panels use sunlight directly.

Wind turbines rely on the sun to heat some air more than other air which leads to a flow of air. If there was no more energy coming from the sun, the air would calm down eventually stop moving around much (and after a very long time, stop entirely). For something to move around, there has to be an energy source.

So how can people get energy? The most obvious or direct answer is to get it from sunlight. That is what plants do. But we aren’t designed that way. We can’t just absorb the sunlight to power our bodies.

Since plants harness sunlight for energy, a second idea is to take energy from them. They can do photosynthesis and then we can eat them. This works, and we do it, but it has some drawbacks.

Plants vs. Animals

There has been an evolutionary battle for millennia between plants and animals (and let’s specifically focus on mammals).

Plants came first. They evolved to absorb energy from the sunlight. That powered them and let them grow. That is a good strategy for life. Plants also get mass from the air (carbon dioxide) and, secondarily, from the ground (water and nutrients). Carbon is one of the main things plants are made of, and many people don’t realize they get the majority of their mass from the air. That’s why you don’t get giant holes in the dirt where big trees grow. All that mass in the tree didn’t come from the dirt; only a little did. The tree got most of its mass from the air and rainwater (water provides hydrogen, and plants both use and excrete oxygen).

So plants replicate all over and use available resources (sunlight, air, water, dirt) to grow. Some plants also take advantage of other resources like wind or fire to help with some aspect of their life cycle (like spreading seeds to other locations).

Then, skipping some steps, along came mammals. What’s special about them? They don’t absorb sunlight directly. They can’t do photosynthesis. And they can move around. And they eat plants for energy.

Also, mammals live on land. The ocean is different because the water currents move things around without them having to move themselves. For everything I talk about, think of it happening on land not in the ocean (though a lot of it does apply in the ocean too).

The basic idea is, instead of getting sun energy, you eat plants. But if you can’t move, then you’d only be able to eat a couple plants before you run out of food. The strategy of eating plants has to be paired with moving around so you can eat plants in many locations.

Why don’t plants eat other plants? There aren’t enough plants to eat without being able to move. Plus growing a mouth and stomach is a lot of work.

Why don’t plants have legs to walk around? Legs take a lot of energy to grow and use. And it’s unnecessary. Plants don’t need to travel to get energy. Energy, in the from of sunlight, comes to them.

Wouldn’t it be nice for grass if it could run away from predators like cows to avoid being eaten? There’s an upside there. But the energy cost would be high. The grass would need legs and muscles. It’d need a brain to figure out when and where to run. It’d need eyes to see predators coming and see where it’s going. At that point, it’s sounding more like a rabbit than a blade of grass. Grass is really cheap and efficient, so it’s OK if some is eaten.

Why don’t rabbits do photosynthesis? They could run away from predators while having green backs and being powered by the sun. The problem is the sun doesn’t provide enough energy for that to work well. To support the rabbit lifestyle, more energy is needed.

The amount of energy you can get from the sun depends primarily on how large a surface you’re absorbing light from. If you harvest sun energy from a square foot, you’ll get way more energy than from a square inch.

Rabbits don’t have large enough backs to get enough energy. They can’t fit enough (organic, biological) solar panels on their backs.

To harvest the sunlight that falls on a larger area of land, rabbits can eat plants from a large area of land. They can use the plants as solar panels covering a whole e.g. square mile, then go around and collect that energy. Importantly, plants are also batteries. Eating a plant doesn’t just get you the sun energy from the last second. Plants still have some energy from sun that shined days ago (perhaps even years ago). So rabbits can get a lot of energy by eating plants covering a much larger surface area than their backs, and by letting the plants grow for a while (charge up their batteries) before eating them (they can eat one plant at a time while letting others grow).

So rabbits use a lot more energy than plants, but they also take in a lot more energy. The key elements of their strategy are being able to move around and being able to eat plants. So they need a way to travel (feet), a way to find plants (senses like sight and touch), their body to be in a portable bundle (skin), a way to take in plants (mouth) and a way to get energy from the plants (digestion – teeth, stomach, intestines).

Other mammals work broadly the same way as rabbits. Except predators. Another possible strategy, besides eating plants, is to eat rabbits. You can eat the things that eat the plants. The advantage is that they gathered a lot of energy in one place. The downside is they can move, so they’re harder to eat than stationary plants. Rabbits and other prey evolved many defense mechanisms including hiding and moving away from predators.

Humans can eat both plants and animals but not sunlight. What should we eat? What’s healthier or better, in broad terms?

People today broadly view eating plants as healthy, particularly fruit and vegetables. People seem somewhat more doubtful about whether meat is actually good for you or not, though most people enjoy eating meat and do eat it.

Plant Defenses

Rabbits don’t want to be eaten. They have defense mechanisms. So do plants. (That’s an approximation. Rabbits actually don’t want things. Their genes evolved under selection pressure to be good at replicating those genes. You can go read Richard Dawkins books if you want to know more about that. I’m not going to worry about being precise about evolution here.)

What do plants do to discourage being eaten?

Trees have armor called bark. I think it has other purposes too, but keeping stuff out of the middle of the tree is one purpose. That’s similar to how turtles and crabs have armor (shells).

Trees are mostly made of wood which is really stiff and hard to eat. Most mammals can’t digest wood, so we mostly leave trees alone. Their defenses work well. A lot of mammals do eat tree leaves, though humans mostly don’t.

Some plants put important or vulnerable parts in difficult to reach places. Trees put leaves high in the air where some animals can’t reach. In response, some animals evolved to climb trees to eat the leaves. Giraffes evolved long necks to eat high leaves. Birds can fly up to tree leaves, but I don’t know if any birds actually eat leaves.

Even putting things (e.g. fruit or berries) a little above the ground, like 12 inches, helps. From a human perspective that’s low, but for a mouse it’s pretty high and hard to reach.

Some plants have thorns to injure animals that try to eat them.

Some plants try to hide, e.g. with camouflage.

Some plants, like carrots, bury a lot of themselves underground. Some mammals can dig in order to eat underground plants, but that’s extra work, and not all mammals can do that.

And one of the big defense mechanisms plants have is being poisonous. Plants can contain toxins so that if you eat them you get sick. They can also be designed to be less nutritious for mammal digestion. The less benefit we can get from a plant, the less we’ll seek it out and eat it.

Caffeine is an insecticide. It evolved to discourage insects from eating coffee beans, cocoa beans, tea leaves, etc.

Some plants will kill humans if we eat them. A lot of plants will give us indigestion or otherwise make us mildly sick.

This issue of plants containing things that are bad to eat, as a defense mechanism, is a key concept for understanding what’s good to eat.

Broadly, plants have evolved for many thousands of years to be bad to eat! There is genetic selection pressure on them to be a bad food.

However, we have evolved to be good at eating plants. We’ve evolved countermeasures to let us digest plants well, to tolerate their toxins, etc.

In this evolutionary battle, we’re doing reasonably well. We can eat plants and survive. We haven’t lost. But it’s nothing like a paradise, utopia or garden of eden. Eating plants is hard. We don’t have a huge margin of error. We’re not winning in a landslide. Plant defenses affect us. They matter to us. Our digestion, immune system, ability to cook with fire, and other traits aren’t powerful enough to make plant toxins negligible. We have to avoid eating some plants entirely. We have to watch what we eat and put effort into choosing plants that work well for us.

Different people have different food sensitivities. In other words, for a lot of plants, the current human gene pool means that 90% of people (or some other amount) can eat that plant without a big problem, but not everyone. Fortunately, people tend to be sensitive to some plants but not others, so pretty much everyone has some plants that work well for them. But this illustrates how the battle against plant defenses, particularly toxins, is not just won and done. It’s not over. It’s ongoing. Plant defenses should still be respected and thought about. (Food sensitivities for some meats, like beef or chicken, are rare. Seafood sensitivity is more common.)

The FDA says 90% of food allergies are for just 8 foods, 4 of which are seeds. The foods are cow milk, eggs, tree nuts, peanuts, shellfish, wheat, soy and fish. (How allergies work is unclear, so they may not be from plant defenses.)

Some plant defenses, like caffeine, aren’t targeted at us. But they’re still bad for us. Why? Because we have a lot in common with insects. We share a lot of genetic code with insects. We have evolutionary history in common with them. We can somewhat tolerate caffeine, but it still harms us. (See my article Caffeine Is Bad.)

We have a lot more in common with mammals than insects. Plant defenses aimed at any mammal are more likely to be a larger problem for us.

Plant Parts

Plants have different parts. We can consider some broad categories like roots, stems, leaves, fruit and seeds.

Some plant parts are actually designed to be eaten. Those are fruit and sometimes seeds.

Roots, stems and leaves don’t want to be eaten. There’s no benefit to the plant when those are eaten. (There are probably some exceptions.)

Fruit and seeds are crucial to how plants replicate. Seeds are what can grow into more plants. The seeds need to be distributed to other locations that might be good for more plants to grow. But plants can’t walk so how will that work?

If a plan grows sideways a bit and then drops a seed, a new plant can grow with a different center point than the old plant. If seeds are light, wind or water can move them. Animals can move seeds around.

How can a plant recruit an animal’s help? How can it get animals to distribute its seeds to other locations? That’s what fruit is for. Fruit is meant to be eaten. It attracts animals on purpose.

Inside the fruit are the seeds. Seeds can have two different strategies. They either don’t want to be eaten, or they want to be eaten but not digested. If an animal eats seeds but poops them out whole, that’s a success for the plant. And plants can make a lot of seeds, so if some get chewed up but some other seeds survive, that can be good enough.

How can seeds avoid being eaten when the fruit is eaten? For example, peach pits are really hard to eat. Apple cores are not great to eat either. So we might just eat the apple fruit (flesh), then drop the core with the seeds on the ground.

So, broadly, as a first approximation, fruit is safe and good to eat. Some seeds are safe to swallow whole and don’t digest them, but that isn’t useful (you have to digest stuff to get energy). Many seeds contain toxins if you chew them up. Seeds really need to discourage being digested because if they all get eaten then the plant can’t replicate. And stems, leaves and roots also may contain toxins. But there are many other defense strategies that plants use, so they don’t always have dangerous toxins.

Another defense strategy plants use is just replicating so much that it’s hard to eat all of them. That strategy is harmless for us. Similarly, a tree might create a lot of leaves, so it’s OK if some are eaten. It’s the same for seeds and roots. Having extra stems is less common, so stems are probably worse to eat on average.


So plants contain energy and nutrients. They are good to eat. But they also contain toxins and antinutrients (things that have a negative nutritional value for us). They’re also partly bad to eat.

We have a powerful digestion system that’s good at eating plants, but it’s imperfect so we still need to watch out some. Different people have different food sensitivities.

Our ability to tolerate bad things from plants is limited not unlimited, so eating a variety of plants can help. That way we don’t get too much of any one bad thing. Different types of plants tend to have different toxins or antinutrients, though some plants share some of the same ones. Eating a variety of plants also helps us get all the different good things we need from plants. If we only ate one or two plants, we’d probably become deficient in some important nutrients.

The modern, industrial western diet means people average getting around two thirds of their calories (energy) from just four plants: wheat, corn, soy and rice. (I have not fact checked this statistic.)

That’s not enough variety. And all four of those plants are fairly similar to each other. Three are grains and one is a bean. All four are seeds. All of them have some antinutrients. For example, wheat contains lectins, which are bad to eat (everything else being equal). In general, eating seeds always has some downsides.

One way to look at plant variety is color. There is advice to eat a variety of colors of plants. E.g. you can eat some green, red, orange, yellow, blue and white. You might try to have some of each color every week. (Eating a balanced diet on the timespan of a single meal or day is totally unnecessary. There is some bad advance floating around about that. I don’t know the optimal timespan to balance your diet for. Maybe it’s 5 days or 18 days or 42 days. I couldn’t tell you. And actually it’s complicated. It varies by nutrient – you need some more frequently than others. So any single time period will just be an approximation.)

Wheat, corn, soy and rice don’t have good color variety. They’re basically white, yellow and brown. There’s no green, red, orange or blue.

Why do we eat so much of just a few plants? Because we figured out how to mass produce them. We got good at growing a lot of them. They’re cheaper and enable a large number of human beings to be alive and fed. There are major positives. But we didn’t choose to eat so much of these few seeds for health reasons (besides getting enough calories being a health issue). We didn’t think they were especially nutritious. We didn’t think that we’ll have fewer illnesses if we eat this diet.

There are a lot of other diet common modern choices that also weren’t made for optimal health, such as eating lots of cow milk or chicken. I’m not saying cow milk or chicken are unhealthy to eat, but they were not optimized for being healthy, and they do have downsides. There’s also a lot of stuff done with processed foods for reasons other than optimizing health.

We selectively bred animals like dairy cows and chickens to optimize for things like getting a lot of milk or meat. We didn’t breed them to be as nutritious as we could. We tried to avoid obvious downsides but we didn’t do much to avoid subtle downsides.

Eating Animals

So, eating plants have lots of upsides but also downsides. Other than the fruit, they tend to contain some things that are bad for us, which were evolved to discourage animals (sometimes specifically mammals) from eating them.

How else can we get energy? We can’t absorb sunlight for energy. We can’t burn fuels to power our bodies. We can’t eat oil. Besides eating plants, our main alternative is eating animals.

What are animals? Basically big bundles of digested plants. (A few of them ate other animals, so they are more indirectly a bunch of digested plants. Ultimately animal energy and mass basically just comes from plants, air and water. There’s also a little bit of mineral and metal, e.g. salt. The plant part is really important and is where the energy/calories comes from.)

What are the upsides of eating animals? They have different defense mechanisms than plants. They run away. They have teeth and claws. But they don’t generally have a bunch of toxins in their flesh. Animals rely less on being poisonous to eat than plants do.

It’d be hard for animals to contain anti-animal toxins in their bodies because they’d poison themselves. Plants can contain anti-animal toxins more easily because plants are different than animals and are affected by different toxins.

Some animals have poisons in a particular part of their body, e.g. rattlesnakes have some venom. But they don’t just have the venom running through their veins, muscles, organs and whole body. It’s kept in a container. We can eat the other parts of an animal and throw away the poisonous parts.

Animals digest plants for us. Whatever toxins or antinutrients those plants had, the animals may have already dealt with the problem for us by the time we eat the animal.

Some animals may be better at digesting certain things than we are. Cows can eat grass effectively but we can’t. Eating cows lets us indirectly eat grass. Otherwise the grass would go to waste.

Suppose an animal eats some plants and processes antinutrient A in a safe way but ends up with a bunch of antinutrient B in its body because its digestion is bad at handling B. Then we eat the animal and our digestion handles B well. This way of eating will work well for us even if we couldn’t digest A well ourselves.

What animals are the best eaters, which can best digest plants and handle the antinutrients? The short answer is the animals with multiple stomachs. They are better at eating than we our with our one stomach. Their bodies are designed to be more focused on digestion and they put more resources into being good at digestion.

What animals have multiple stomaches? Cows. Also sheep (lamb), goats, bison, deer and some other related animals. These are called the ruminant animals. They’re the super-eaters with the best digestion. They’re good at eating grass and leaves that we aren’t. They’re better than us at extracting nutrient value (and neutralizing antinutrients and toxins) in their food than we are. It’s their speciality.

So beef is a particular good, nutritious, safe meat. Chickens and pigs only have one stomach, so they’re not as good.

Cows are also something humans have domesticated and eaten for thousands of years. Chickens and pigs have worse histories. Pigs were a source of disease which is why Judaism and Islam say not to eat them. Chickens were much smaller than today and hard to feed (they don’t eat grass and leaves; if they eat grain that is taking away food that people could eat). Eating chicken became a lot more prominent after 1900.

Fish are another animal that we’ve eaten successfully for thousands of years, so that’s another promising candidate thing to eat that’s probably especially compatible with our digestion. There are some potential downsides including heavy metals (the more fish you eat, the more of an issue that is, so it could be bad if you designed a diet primarily based on fish). And there are some problems with farmed fish.

Any kind of traditional diet that people in a region ate for thousands of years probably works pretty well. Modern western eating changed how we eat significantly without enough understanding of what we’re doing and how nutrition works, so there have been downsides.

Note that we’ve bred our main plants and animals to be significantly different than the old wild varieties. So the fruit, berries, meat, etc., that’s in our grocery stores is different than what people traditionally ate even if it has the same name like “apple” or “banana”.

As a quick aside, what about foods other than eating plants or animals? Dairy is problematic because over 50% of people alive are lactose intolerant and casein (a milk protein) is hard to digest. Some dairy products like cheese have less lactose (hard cheeses have very little). Butter has very little lactose or milk protein. Dairy is designed for young cows not adult humans. (Human breast milk isn’t available in large quantities for adults to drink, and even if it was it still wouldn’t be designed for adults.) Lactose intolerance started becoming less frequent after we domesticated cows (around 10,000 years ago). And eggs, like dairy, are are a common food sensitivity. So there are some concerns with dairy and eggs, though they could be good foods for people who don’t react poorly to them. As to fungi, I’d expect them to have some of the same defenses as plants, and a lot of mushrooms are poisonous, but maybe some are good for humans to eat. I don’t know much about eating insects except that it hasn’t been a large part of our historical diet.

People with Big but Vague Health Problems

Humans are pretty robust and resilient. Do you have to think a bunch about what you eat? If you’re doing fine, then maybe not. Trying to understand food better and eat in a more healthy way shouldn’t be everyone’s priority. I think it’s interesting though.

What if you have health problems that conventional medicine is failing to help with? Like chronic fatigue, anxiety or “depression”? Changing your diet, even drastically, is probably less risky than taking psychiatric medications.

Your problem might be some antinutrients and toxins from your food.

So you might consider the Lion Diet which focuses on eating ruminant animals (the super-eaters with multiple stomaches), salt and water. It’s meant as a temporary diet to heal you and help you figure out which foods are hurting you. If you can fix your problems, then you can reintroduce foods one at a time to figure out which ones are OK for you and which aren’t.

You may have a leaky gut where some foods harm your gut and then it starts leaking other foods into places they shouldn’t be. Then your immune system sees stuff that shouldn’t be there and tries to fight it. This can cause autoimmune disorders.

If you heal your leaky gut, you may be able to tolerate a lot of foods. It could be that a few foods really hurt your gut and cause it to leak, and then if it’s leaky a lot of foods cause you problems. So after doing the Lion Diet for a while, you may only need to avoid a few foods. But just avoiding those few foods right away might not work, even if you knew which ones they are. You might need to avoid a bunch of extra foods temporarily, then a few foods permanently.

What are some of the main candidate foods that may be hurting you?

Gluten, soy, and dairy. After that, more candidate foods are other grains and seeds, plus sugar (which may lead to too much of the wrong bacteria growing in your gut). The sugar issue makes eating a lot of fruit potentially problematic. After that, what could be cut next is more or all plants, plus animals that are less safe/healthy. The extreme conclusion is the Lion Diet of ruminant animals, salt and water.

So there are some big, broad conceptual reasons why the lion diet, or a milder approximation of it (which is suitable for people without major health problems) makes sense. By contrast, some other diets have no good conceptual explanations behind them (that’s particularly true of most diets aimed at weight loss not health).

Also, vegan and vegetarian diets are motivated primarily by ethical concerns, not health-based reasoning. Basically everything that vegans say about how healthy plants are is said because they want to save animals from being eaten, not because of an unbiased, objective study of nutrition. It’s like how you can’t trust environmentalists, who care a lot about global warming, who then try to tell you about how electric cars are superior to gas cars for transportation. They start with a predetermined conclusion (electric cars are better) with a predetermined reason (to help the environment), and whatever they say about transportation is designed to support their agenda.

A milder approximation of the lion diet could mean cutting gluten, soy and dairy, limiting grains/beans/seeds and sugar, and eating more meat particularly beef and lamb. There are some arguments that gluten and soy are just plain bad for everyone (in a somewhat mild way that doesn’t kill you), but I haven’t researched it enough to say. Another thing that generally helps is eating whole foods instead of parts, juices or extracts.

Modern society has a lot of stuff that’s very good for our health. We don’t starve. We have antibiotics. These huge improvements can mask downsides and problems, and make it less obvious if some major parts of our food supply are actually bad for us.

Also, because I think it’s relevant to my serious fans who intend to learn from me for years to come: I do not have a major health problem. That’s not why I researched and wrote this.


The final section of this article is some quotes I found notable when reading about nutrition and downsides of plants:

From Does Meat Rot In Your Colon? No. What Does? Beans, Grains, and Vegetables!:

Most of the edible part of a plant is cellulose, a polysaccharide (i.e. a very long chain of sugars) that is very difficult to break down. In fact, no digestive enzyme, in any animal, is capable of breaking down cellulose!

It turns out that pepsintrypsinchymotrypsin, and our other proteases do a fine job of breaking down meat protein, and bile salts and lipase do a fine job of breaking down animal fat. In other words, meat is digested by enzymes produced by our own bodies. The primary reason we need our gut bacteria is to digest the sugars, starches, and fiber—found in grains, beans, and vegetables—that our digestive enzymes can’t break down.

rabbits run their food through twice: they eat their own poop in order to get more food value out of the plant matter they eat.

But wait! There’s another punchline! Whenever we eat grains, beans, and vegetables, we’re not digesting and absorbing much of the plant matter…we’re actually absorbing bacterial waste products. Rephrased less diplomatically:

You’re not eating plants: you’re eating BACTERIA POOP.

Eating bacteria poop is not as bad as your intuitive reaction says. It might sound awful but it’s actually pretty OK. It’s interesting and relevant to various nutrition stuff.

And from Health Dangers of a Plant-Based Diet:

Plants produce these chemicals to defend themselves. And it’s not just one or two plants that have this super power. It’s all of them.

In fact, 99.99% of all pesticides in our diet are natural chemicals plants produce to deter predators.

They produce toxins to protect themselves from fungi, insects, and animal predators. There are tens of thousands of these natural pesticides. And every species of every plant contains its own set of toxins. Different parts of each plant contain different toxins in different amounts.

Some parts of the plant are more vital for the success of the species than others.

Seeds are critical. Because they are so important plants take extra care to protect them and lace them with potent toxins to deter predators.

Grains, nuts, and beans are all seeds. These are the plant’s babies. And messing with a mother’s offspring often has dire consequences. The parent plant wants to protect them and ensure their offspring’s survival. The plant isn’t concerned about the health, nutrition, or survival of humans. Quite the contrary.

What are seeds?

Of all plant parts, seeds tend to be the most tricky. Grasses, trees, and legumes are plants and have seeds that we call different things.

Grains are the seeds of grasses which include wheat, corn, oats, and rice. Walnuts, hazelnuts, and pecans are all nuts, which are the seeds of trees. And legumes like peas, lentils, soybeans, and chickpeas have seeds called beans.

Some weapons like tannins are bitter. Others like phytates interfere with nutrient absorption aiming to malnourish the predator. Similarly, enzyme inhibitors disrupt a predator’s food processing. From the plant’s perspective, if they are going to get eaten, they are at least going to cause negative consequences for the predator to discourage their consumption in the future.

The article goes into more detail on lectins, how they attack our digestion, and how they can cause leaky gut. Lectins, like gluten, are one of the major defenses of seeds. Then it talks about phytic acid from nuts (which reduces our ability to absorb nutrients like iron from the plants we eat). It also covers soy and more.

Animals like cows and sheep have bacteria in their guts that break down phytates. Their guts are designed for plant-based diets. Humans guts aren’t designed to handle phytic acid.

Soybeans are rich in antinutrients like phytic acid and tannins as well as trypsin inhibitors which deter predation.

The high antinutrient concentrations in soy are a health concern to humans and livestock.

In order to limit their damage, food processors do the best they can to reduce the damaging chemicals. Soybeans are soaked which can reduce tannin levels by about half, but it doesn’t do much to decrease phytic acid or trypsin inhibitors. [r]

Then they are often boiled and/or roasted to try and reduce antinutrients further. Fermenting with fungi and bacteria can help too.

But all this processing also comes at a cost. It can damage essential amino acids making it difficult or impossible to digest and assimilate. [r]

So food manufacturers are tasked with the impossible: cook soybean enough to reduce the antinutrients but not too much. An impossible balancing act.

An interesting perspective is that there is a really high incidence of soy allergy. Many peoples’ bodies go on an all-out attack when consumed.

Not only that, but raw soybeans are toxic to all monogastric animals – and we humans are monogastric.

Evidence suggest that we are not designed to eat soybeans – and enzyme inhibitors, endocrine disruption, and saponins are just a few reasons why.

The human genus transitioned from tree-dwelling herbivore to bipedal meat eater.

isotope studies of fossils [from ~50,000 years ago] reveal a human diet nearly indistinguishable from carnivores.

grains come from wild grasses. Naturally, in the wild, these grains are small with just a few seeds per plant. And they readily fall and disperse. Humans would have basically never eaten these.

our guts had transformed [by evolution] beyond recognition to that of our early herbivore primate ancestors. Our transformed gut was now optimized for the efficient absorption of meat that was dense in energy as was required to fuel our gigantic brains; it was no longer equipped for grazing 7 hours/day and using a microbiome to turn plant fiber into useable energy.

The article says that thanks to the Agricultural Revolution we started eating far more plant toxins and this has had major downsides. And then things got a lot worse, in this regard, with the Industrial Revolution. It concludes that the biggest four dangers are grains, vegetable oils, sugar and soy, and it recommends eating more meat.

The article also talked about how much people eat plants without realizing what they’re eating and how plant-based their diet is. (Hint: If it’s not meat/seafood/dairy/egg, then you’re probably eating plants!) In general, I think people don’t recognize all the different forms of wheat they eat and see them as repetitively eating the same plant over and over. They don’t have a good intuitive or automatic understanding of the ingredients in their foods.


I also wrote a shorter previous article called Understanding Food. And after writing this article, but before publishing, I found the book The Plant Paradox: The Hidden Dangers in "Healthy" Foods That Cause Disease and Weight Gain. It warns about toxins and antinutrients in plants, particularly lectins. Chapter 1 is titled “The War Between Plants and Animals” and it covers some of the same themes as this article. (The quotes section above was also based on reading done after writing the prior text.)

My main goal here was to think about plants and mammals using conceptual explanations. I started with mass and energy, then proceeded to the evolutionary war between plants and mammals.

Most mammals are plant predators. Plants have defense mechanisms against mammals, including toxins and antinutrients. There are evolutionary reasons for seeds to be equipped with especially powerful defenses to discourage eating them. Seeds, which include grains, beans and nuts, are like the eggs or babies of plants. We have some scientific understanding of defenses like lectins and phytic acid.

Plants shouldn’t be thought of as an obviously safe, nutritious food. We don’t live in a paradise where the plants are designed for us to eat. Plants have evolved to be bad for us to eat, but our own digestion has evolved to let us eat plants anyway. It’s a battle where we’re doing pretty well overall, but it’s not surprising that many people do poorly when eating at least a few plants. Most people’s digestion is weak against at least a few plant defenses, and some people have problems with many plants. We also using other methods to overcome plant defenses, like cooking, soaking, fermenting and sprouting.

There are broad conceptual reasons to expect, on average, for non-seeds to be safer plant foods than seeds and for fruit to be the safest part of plants. This doesn’t mean to stop eating plants; it’s just bringing up a problem.

Other foods besides plants have potential problems too. The overall safest food, for the most people, may be meat from ruminant animals. Ruminants like cows, sheep and goats primarily eat grass and leaves, not seeds. And they have the most powerful digestion systems, including multiple stomachs, to deal with plant toxins and antinutrients.

If you remember one thing, remember that plants are evolved to be bad food sources. If you’re familiar with evolution, it makes sense when you stop to think about it, yet there’s a widespread misconception that plants naturally grow to be healthy food for us. But evolution favors plants that avoid becoming food.

Disclaimer: This is not diet advice. I’m not a diet, nutrition or medical expert. And I’m not saying to stop eating plants. My guess is that a meat-only diet is a bad idea for most people. My article does not reach specific, actionable diet conclusions. These are incomplete, exploratory thoughts based partly on limited, initial research. I’m posting this primarily to allow for criticism or feedback, plus as an example of how to begin looking into an issue. This could also point people to some resources they could read which they might not have found otherwise. People should read resources from multiple sides of the debate, multiple perspectives, etc., before changing their diet. You should not try to use these ideas without doing your own research and forming your own opinions. I advise against making health-related decisions based on this article.

Elliot Temple on July 24, 2022


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