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The Natural Human Diet

When you see dead animals on the side of the road, are you tempted to stop and snack on them? Does the sight of a dead bird make you salivate? Do you daydream about killing cows with your bare hands and eating them raw? If you answered no to these questions, congratulations—like it or not, you’re an herbivore.

According to biologists and anthropologists who study our anatomy and our evolutionary history, humans are herbivores who are not well suited to eating meat. Humans lack both the physical characteristics of carnivores and the instinct that drives them to kill animals and devour their raw carcasses.

 Human Physiology

Although many humans choose to eat a wide variety of plant and animal foods, earning us the dubious title of “omnivore,” we’re anatomically herbivorous.

Teeth, Jaws, and Nails

Humans have short, soft fingernails and pathetically small “canine” teeth. In contrast, carnivores all have sharp claws and large canine teeth that are capable of tearing flesh.

Carnivores’ jaws move only up and down, requiring them to tear chunks of flesh from their prey and swallow them whole. Humans and other herbivores can move their jaws up and down and from side to side, allowing them to grind up fruit and vegetables with their back teeth. Like other herbivores’ teeth, humans’ back molars are flat for grinding fibrous plant foods. Carnivores lack these flat molars.

Dr. Richard Leakey, a renowned anthropologist, summarizes, “You can’t tear flesh by hand, you can’t tear hide by hand. Our anterior teeth are not suited for tearing flesh or hide. We don’t have large canine teeth, and we wouldn’t have been able to deal with food sources that require those large canines.”

Stomach Acidity

Carnivores swallow their food whole, relying on their extremely acidic stomach juices to break down flesh and kill the dangerous bacteria in meat that would otherwise sicken or kill them. Our stomach acids are much weaker in comparison because strong acids aren’t needed to digest pre-chewed fruits and vegetables.

Intestinal Length

Carnivores have short intestinal tracts and colons that allow meat to pass through the animal relatively quickly, before it can rot and cause illness. Humans’ intestinal tracts are much longer than those of carnivores of comparable size. Longer intestines allow the body more time to break down fiber and absorb the nutrients from plant-based foods, but they make it dangerous for humans to eat meat. The bacteria in meat have extra time to multiply during the long trip through the digestive system, increasing the risk of food poisoning. Meat actually begins to rot while it makes its way through human intestines, which increases the risk of colon cancer.

Read author John Robbins’ discussion of the anatomical differences between humans and carnivores or review Dr. Milton Mills’ entire article on the topic to learn more.

Human Psychology

Humans also lack the instinct that drives carnivores to kill animals and devour their raw carcasses. While carnivores take pleasure in killing animals and eating their raw flesh, any human who killed an animal with his or her bare hands and ate the raw corpse would be considered deranged. Carnivorous animals are excited by the scent of blood and the thrill of the chase. Most humans, on the other hand, are revolted by the sight of blood, intestines, and raw flesh and cannot tolerate hearing the screams of animals being ripped apart and killed. The bloody reality of eating animals is innately repulsive to us, another indication that we weren’t designed to eat meat.

If We Were Meant to Eat Meat, Why Is It Killing Us?

Carnivorous animals in the wild virtually never suffer from heart diseasecancerdiabetes, strokes, or obesity, ailments that are caused in humans in large part by the consumption of the saturated fat and cholesterol found in meat.

Fat and Cholesterol

Studies have shown that even when fed 200 times the amount of animal fat and cholesterol that the average human consumes each day, carnivores do not develop the hardening of the arteries that leads to heart disease and strokes in humans.

Human bodies, on the other hand, weren’t designed to process animal flesh, so all the excess fat and cholesterol from a meat-based diet makes us sick. Heart disease, for example, is the number one killer in the U.S., according to the American Heart Association, and medical experts agree that this ailment is largely the result of the consumption of animal products. Meat-eaters have a 32 percent higher risk of developing heart disease than vegetarians do!

Excess Protein

We consume twice as much protein as we need when we eat a meat-based diet, and this contributes to osteoporosis and kidney stones. According to peer-reviewed studies, animal protein raises the acid level in our blood, causing calcium to be excreted from the bones in order to restore the blood’s natural pH balance. This calcium depletion leads to osteoporosis, and the excreted calcium ends up in the kidneys, where it can form kidney stones or even trigger kidney disease.

Consuming animal protein has also been linked to cancer of the colon, breast, prostate, and pancreas. According to nutrition expert T. Colin Campbell, the director of the Cornell-China-Oxford Project on Nutrition, Health, and Environment, “In the next ten years, one of the things you’re bound to hear is that animal protein … is one of the most toxic nutrients of all that can be considered.”

Eating meat can also have negative consequences for stamina and sexual potency. One Danish study indicated that “[m]en peddling on a stationary bicycle until muscle failure lasted an average of 114 minutes on a mixed meat and vegetable diet, 57 minutes on a high-meat diet, and a whopping 167 minutes on a strict vegetarian diet.” Besides having increased physical endurance, vegan men are also less likely to suffer from impotence.

Food Poisoning

Since we don’t have strong stomach acids like carnivores to kill all the bacteria in meat, dining on animal flesh can also give us food poisoning. According to the U.S. Department of Agriculture, meat is a significant cause of foodborne illnesses in the U.S. because it’s often contaminated with dangerous bacteria such as E. coli, listeria, and campylobacter. Every year in the U.S. alone, food poisoning sickens more than 48 million people and kills more than 3,000.

Dr. William C. Roberts, editor of the authoritative American Journal of Cardiology, sums it up this way: “[A]lthough we think we are one and we act as if we are one, human beings are not natural carnivores. When we kill animals to eat them, they end up killing us because their flesh, which contains cholesterol and saturated fat, was never intended for human beings, who are natural herbivores.” Learn more about how meat damages human health.

Human Evolution and the Rise of Meat-Heavy Diets

If it’s so unhealthy and unnatural for humans to eat meat, why did our ancestors sometimes turn to flesh for sustenance?

During most of our evolutionary history, we were largely vegetarian: Plant foods, such as yams, made up the bulk of our ancestors’ diet. The more frequent addition of modest amounts of meat to the early human diet came with the discovery of fire, which allowed us to lower the risk of being sickened or killed by parasites in meat. This practice didn’t turn our ancestors into carnivores but rather allowed early humans to survive during periods in which plant foods were unavailable.

Modern Humans

Until recently, only the wealthiest people could afford to feed, raise, and slaughter animals for meat, and less wealthy and poor people ate mostly plant foods. Consequently, prior to the 20th century, only the rich were plagued routinely with diseases such as heart disease and obesity.

Since 1950, the per capita consumption of meat has almost doubled. Now that animal flesh has become relatively cheap and is easily available (thanks to the cruel, cost-cutting practices of factory farming), deadly ailments such as heart disease, strokes, cancer, and obesity have spread to people across the socio-economic spectrum. And as the Western lifestyle spills over into less developed areas in Asia and Africa, people there, too, have begun to suffer and die from diseases associated with meat-based diets.

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  • Pro-Vegan says:

    In response to “I’m not a vegetarian hater; I just hate bogus arguments” Chimpanzees do NOT hunt down and consume other small animals, besides bugs like ants and fleas. While yes, humans were never meant to be strictly vegan, they were certainly not meant to eat pigs, or cows. Why do you think we cook and spice our meat? We cook our meet to avoid meat-borne diseases that carnivores and some omnivores are naturally resistant to, and so that we can actually chew and digest it. We spice and flavor our food so that the taste appeals to us. Also we don’t “salivate at the thought of grass and control our “instinctive” urge to eat every bush and plant they pass when walking down the street” because those aren’t plants that humans would consume naturally in the wild, but I would have to control the “urge” to eat a mango, for instance. And animals in the wild aren’t obese because they have a reason to get up and work out, while most humans don’t. Wild animals also don’t have the abundance of food that we do. In fact the reason we love sugars so much is that they are good and essential for us in the right amount, but scarce in the wild, so we have an instinct to eat them when available. the same goes for fats and oils found in potato chips. Humans are omnivores, but only to the point of our ability to eat certain bugs and worms, which is by standard, gross, and not something I, or anyone else considered “normal” would ever do unless forced.

  • BVB says:

    I’m with Erik on this.
    We’re not meant to eat EVERY kind of plant. Observe our evolutionary relatives; chimps. They eat a range of plants, roots, fruits and nuts etc, without the need to eat everything. We can survive on the same thing they do without becoming ill. Plant-based diet means things from plants, not just the plant itself.

    No, not everyone should be vegan, but just take a moment to think compassionately. Find the source of your food, was it free-range or cooped up in a tiny cage? Learn a bit of self-responsibility and make the world a little bit better.

  • Erik says:

    In regards to almost every pro-meat argument ever, NO. Being a vegan/vegetarian has NOTHING to do with eating grass, or bushes, or just any form of plant life. Of course we don’t have multiple stomachs, and of course we can’t digest certain plant materials, because we weren’t made to eat everything that happens to be edible to other animals. We are physiologically omnivorous because humans are designed to be opportunistic. (I could get into humans being opportunistic not just with diet, but in basically all other aspects as well, but that discussion doesn’t belong here, so just think about it for yourself.) Meat can be accepted into our diet, because it is conveniently rich in a lot of important nutrients (fat, iron, protein, b-vitamins, zinc…). We have evolved into technological predators, not physical predators. Given that, it should be pretty obvious that our bodies are not meant for such a significant amount of meat. Eating meat is not the problem, it’s having meat as such an important part of your diet that is. We don’t need every human being to go vegan, but if we all significantly reduced our reliance on animals and animal products in our diets, the entire planet would become a much healthier place to live.

  • Chintha Yatawatte says:

    I am a total vegetarian. Being a Buddhist realizing is quite easy. Life is a life!!! Can not spread loving kindness/compassion etc… without being a VEGAN!

  • I'm not a vegetarian hater; I just hate bogus arguments says:

    With that argument vegetarians and vegans would have to salivate at the thought of grass and control their “instinctive” urge to eat every bush and plant they pass when walking down the street. The entire article argues that humans aren’t carnivorous because of all the anatomical and physiological “proof” , but obviously humans aren’t strictly carnivores, we’re omnivores. So yes, our teeth and digestive systems should be different from those of lions and other carnivores. Also, if we look to chimpanzees, our evolutionary relatives, they have soft nails and not claws and very similar anatomy to humans and they themselves are omnivores. It’s very common for chimpanzees to hunt and consume other smaller animals. And very few, if any, wild animals have obesity problems- carnivores, omnivores, or herbivores. Animals don’t splurge and eat until their obese in the wild. Fitness is incredibly important to animals in the wild, otherwise natural selection will just kill them off.

  • Paul says:

    If I’m a herbivore, why don’t I have a 4 chambered stomach that allows me to digest cellulose, like cows do? Why are there plant molecules that I can’t digest, effectively lowering the amounts of energy i can pull out of eating grass? Why does cooking increase the bioavailability of plant nutrients? Why is my digestive system incapable of using up plant resources to the full?

  • Queso Grande says:

    If humans are herbivores, why does my nose and tongue tell me how amazing bacon smells and tastes while at the same time telling me how bland and joyless lettuce and rolled oats can be? Does this have to do with “desensitized” taste buds and if so, is there a way to “resensitize” them? Rolled are much cheaper than bacon and might have a wonderful flavor with “resensitized” taste buds but then with “resensitized” taste buds how much more amazing would the bacon taste? It is quite a conundrum.

  • Jupi says:

    I wish everyone in the world would read this with an open mind! Sometimes when people see animal cruelty, rather than back up and wonder why they should keep on eating meat, instead they try to justify the cruelty. That makes the world a worse place for the animals *and* the people who begin to believe that cruelty is okay. If only every person was a vegetarian! Whenever I try to prove to my friends that humans are herbivores, they make the stupid argument that we have canine teeth. Um, hello? You mean you’re supposed to tear open raw carcasses with those puny things? I think it’s about time I started memorizing some of these facts. If I can get just one person to hear me out with an open heart, and so much as eat one less burger a day, my existence won’t have been a waste.

  • Slav says:

    We have small canine teeth and an omnivorous physique that suggests we should eat meat. Yet red meat is unhealthy and we generally shouldn’t eat it, plus we have no typical carnivorous weapons to bring down prey. How do we explain this contradiction?

    Simple: humans ARE NOT supposed to kill and eat large pray by nature. Hunting is an invention, not a natural thing. What humans ARE supposed to eat is small prey that they can catch/steal/gather with their long arms and opposable thumbs, with soft skin and shells that our delicate fingernails and weak teeth are capable of dealing with: prey like fish that we catch in a stream, clams and crabs we catch and gather along the shore, eggs and honey we steal from the trees. Incidentally, these foods are healthy and easily digested in a raw natural state while red meat isn’t. Also incidentally, in the wilderness humans can only catch small amounts of such prey in a day, and small amounts of such prey in a day is EXACTLY how much essential amino acids and vitamin B12 our body needs in addition to a few pieces of fruit and a few pieces of vegetable for a healthy diet.

  • Maria says:

    Wars for oil are proof of human values. Cromagnon Homo sapiens sapiens eat even their own kin since thousands of years. If meat eaters turn vegan just for health sake, when a pandemy arrives Cromagnons at heart will survive and this will last forever.

  • chris says:

    Animal eating animals have 30 times more acidity in their stomachs than a human being. Our’s by nature is alkaline, although we produce a small amount of acid in the stomach could this be to combat disease? A healthy immune system is alkaline.

  • Nat Freeman says:

    First, maybe I can clear up a couple of errors postulated above. One, humans do NOT have canine teeth, we have incisors as do most mammals. Our incisors are short, whereas a carnivores incisors are long in order to grasp and hold, as well as, tear the flesh of its prey. Second, humans are NOT herbivores, as we do not have multiple stomachs like true herbivores do. If we try to eat a diet of stems and bark we die just as those in the Batan Death March learned during the Second World War. Those that chewed the fibrous plants and spit out the pulp survived even though they did not have that full stomach feeling. “Diet Tribe” an interesting play on words, conveniently forgets to remember human physiology whenever it suits his point. He or she thinks he/she is a dog and in fact compares himself to other four legged animals of which humans are distinctly apart from having only two legs among many other differences. He avoids thinking and simply reacts, as most of us do when one of our cherished myths is challenged. Yet, he does not challenge the idea that if we humans were truly flesh eaters, then why do we not start to salivate at the site of a fresh kill. Even my father, who was an active hunter of small animals, mostly rabbits, and would routinely gut on the spot the animals he shot could not stomach the site of a slaughter house killing. As I remember that he once visited such a place and could not eat the flesh of an animal for many days thereafter. Such was the degree of his revulsion to what he saw. Mr. play on words is correct on one point and that is that he will not be swayed by mere logic alone unless he first has the desire to know and experience what it is to be truly human and humane. We are among the primates, the most evolved vegetarians. We function best on an all vegetable diet. At 68 years young, all of my friends suffer from a host of disease symptoms, have had many operations, take many daily medications and still have no clue as to why I do not share in drug habits or in their misery.

  • Diet Tribe says:

    Why is it that in the carnivores vs herbivores debate everyone ignores a) Omnivores and b) Scavengers.
    Humans have far more in common with Hyenas than they do with wolves or goats (actually, we have the most in common with Pigs, who are also opportunistic carnivores with a high-plant diet).
    We aren’t carnivores, our teeth prove that, our intestines aren’t specialized, and (past a certain point) corruption of food bothers us (although some of that is cultural, ask a meat eater about ‘aged beef’ sometime).
    However, we are decidedly NOT herbivores, who never have canines, even if we “…don’t have large canines…” we DO have them (much like Hyenas and Pigs), also we don’t have organs for the digestion of cellulose, a key adaptation for herbivores.
    The solution to the tooth thing? Scavengers. I said we don’t like ‘corrupted’ meat – but we do like our meat dead, the freshest steak tar tare and sushi are long past rigor mortise.
    Humans crave salt, fat, and protein – even to the point of doing ourselves harm by eating far too much if its made available to us. This is an instinct from an eon before Restaurants and Supermarkets, to encourage us to be opportunists, when the opportunity presented itself to eat meat. In the ‘wild’ nobody would be able to support the average American’s ratio of meat in their diet – but since you’d have grown up in a world without Iphones and Twitter you’d have taken whatever food you could get your hands on and not worried at the morality of anything other than sharing with the people you lived with (a lone human in the wild is a dead human, all apologies to Mr. Rice-Burroughs).
    I’ve been looking for information about the evolution of human digestion and all I’ve found is articles like this one and those on the other end of the spectrum, and frankly I resent people grossly editing data and actively ignoring the scientific method to present their own perspectives. I put to you that you will not convince anyone who doesn’t already agree with you, and will frankly offend the people who might be trying to make up their minds, much as Prohibition, Abstinence Only, and the ‘War on Drugs’ only produce results in the negative. Some ‘food for thought’.

  • Lewy jackson says:

    Very good presentation mate! Spot on. I’m very happy to see many people coming together and sticking up for this. It’s a fact of nature, she provides all er children with the diet they need already to eat, no preparation (cookin or burning) needed. Of course our ‘big powerful brains’ allowed us to use meat in times of lack of superior nutrients. We developed the habit and desensitized our taste buds. Now we are sticking up for it and making assumptions on how it’s right trying to justify it but the truth is quite obvious if you open your mind.

  • Neutral Nutrition says:

    In this reply I will touch on every BOLD category to the best of my independent research in human physiology and dietary habits, As well as some other great apes of our family Hominidae.

    Although we are more suited to eat plant fibers, we are not true herbivores because not all of are teeth are specialized for grinding plant material. Us humans also posses the canines and sharp teeth in the front of are mouths for ripping stronger material(I.E. meat). In addition, our eyes are oriented towards the front of our line of sight to allow us to have better depth perception instead of field of view, a key evolutionary attribute in predators.

    As stated in the article, we do not posses the teeth best suited for eating meat, but as our chimpanzee brothers they do not either. while the chimpanzee(our closes genetic relative) is mostly a forager/ herbivore, the too also eat meat. It could be as a source of protein or indulgence, regardless they are capable of killing other animals and eating their carcasses.

    blah blah blah, i don’t know why I bother, humans should eat mostly plants, and some meat. Humans should not feel bad about killing animals for food, we have been doing it since before any of your families had a last name.

  • John says:

    “The more frequent addition of modest amounts of meat to the early human diet came with the discovery of fire, which allowed us to lower the risk of being sickened or killed by parasites in meat. This practice did not turn our ancestors into carnivores but rather allowed early humans to survive in periods when plant foods were unavailable.”

    Seems like early humans spent a massive amount of time developing weapons and hunting strategies for something they only ate when it was absolutely necessary. Plus, a purely carnivorous animal is sickened by plant matter, and vice versa. So the fact that humans can eat a predominantly grain and meat diet without being physically ill as many do suggests that we are in fact adapted to the omnivore diet.

    I’m a vegetarian. But this article doesn’t make sense, there are entirely too many bias influenced pseudo-facts which have no logical support.

  • Colin Proctor says:

    I think people eat far too much meat and should err on the side of vegetarianism. I have cut down on meat a lot in the last few years. Aside from the fact that it literally costs the earth to “grow” meat just look at what it does to your health – both mental and physical. And if they didn’t use so many hormones and drugs it would not be as bad, but eating little or no meat solves so many problems in one fell swoop. If you see a really fat person, chances are they are a veggie, if not then they are a veggie that eats too much refined food. Drink some apple juice and eat a steak and see what happens – I rest my case!

  • Meadyaon says:

    If humans are herbivores as some saw we are then were are multiple stomachs or stomach chambers of a herbivore. We do not but instead have only one stomach. Humans can’t digest the cellulose

    Carnivorous fish doe not have claws.

    Nails allow humans to manipulate objects more easily..

    Humans: no sharp front teeth, but have sharp front teeth for tearing, and flat rough, jagged rear molars for grinding

    Eating meat drove the evolution of our big, powerful brain

  • sanjoz says:

    The best thing to do, for those that seek the truth, is to educate yourselves. Remember, what was ‘fact’ yesterday can be incorrect today. It wasn’t that long ago we thought the only source of Omega was fish oils, we now know better. Harvard and Cornell Universities state the amount of meat required for a healthy human diet is precisely zero. Just because we used to think we were omnivores, doesn’t mean we are. It is only our addiction to meat that causes us to continue down that road, as we don’t know where we will get our next ‘fix’ from! If meat was eradicated from all our diets today, would we all suddenly become weak? Frail? Hungry? Actually, no, quite the opposite, we would be healthier, fitter and stronger. Don’t let the meat industry lie to you anymore the way the tobacco industry did to smokers in the sixties and seventies. They have something to lose.

    Whilst man developed tools to hunt, our physiology did not change and as such we are, and always were suited to a vegetarian (more precisely, a vegan) diet. There is ample evidence, medically and physiologically to support this fact. That is not to say humans cannot eat small quantities of meat and ‘get away with it’, we are simply not suited to consume flesh.

    Look at any TRUE omnivore on the planet, they are different to us. A true omnivore cannot just survive, but THRIVE on EITHER a carnivorous diet or a herbivorous diet for sustained periods of time. As a human, try surviving on a PURE carnivorous diet for a sustained period of time, and you will not be around to have this debate!

    Our teeth are not adapted for meat consumption. Our facial muscles are highly adapted for a herbivorous diet. Our posture is in common with neither carnivores nor omnivores, but well aligned to herbivores. Our intestinal tract is well adapted to a herbivorous diet not an omnivorous one, and certainly not a carnivorous one. Surely, the disproportionate instances of heart disease and cancer in meat eaters is strong evidence that we simply cannot process animal products and it is killing us and our environment.

    To those that think these articles are about preserving ‘a way of life’, remember, the vegetarian/vegan way of life will ALWAYS exist, regardless of whether or not the meat industry is changed or ideally, eradicated altogether. At the very least, the meat production industry needs to change, if not for animal welfare, then for human existence and continuation. We cannot continue to have an industry that is more toxic to the environment than all transport industries put together, to satisfy the greed of the minority, for a product that is not only a non-necessity, but is hazardous to health, more so than tobacco, aids and any drug you care to mention put together! Only through education, things WILL change. Lets face it, only 60-70 years ago, Heroin was thought to be so safe, it was readily available at stores, including Harrods in London! Meat is the carcinogenic Heroin of today, there are more victims and addicts of meat to support, and the worlds health infrastructure cannot cope.
    I would urge you, with the plethora of information available so easily today, research this with an open mind. Don’t jump to ridicule and try and see pass the activism. Don’t research in ‘defensive mode’ where you are looking for a way to reject any piece of information presented, rather look at it holistically and you will find the truth. Ghandi said of Truth, that it comes in stages: first they ignore you, then they ridicule you, then they fight you, then you win!