Debunking the Carnivore Diet through a review of anatomy, physiology and cellular biology
As we have discussed in a previous article, Humans are Herbivores, frugivores herbivores, or fruit eaters. Despite the mountains of very clear and irrefutable evidence that leads to this conclusion, in recent years we have seen a growing number of fanatical people claiming humans are natural carnivores, or in some cases merely promoting what they call a carnivore diet. In this series of articles, we will be addressing many facets of this issue. In this part, we will address the evidence given to us by some tribal peoples as well as our human anatomy and physiology. In later parts, we will examine the history of these claims, and we will even examine some of the institutions and presenters who promote these ideas of carnivory. We will also discuss why carnivory is harmful, as well as how and why some people can get positive results from this type of program, as is commonly claimed by carnivore diet proponents.
Part 1: Tribal Peoples and Comparative Anatomy
Tribal Peoples
One common concept that has been successfully proliferated in some health-seeking circles is that in a natural setting or according to some type of ancestral tenets, humans have always hunted and eaten meat. The problem comes when we look at some tribal peoples that still live this way and we find that their lifespans are very short. The Maasai tribe, recently famous for their meat-based diet and natural lifestyle, are reported to have an average lifespan in their 40s. Another source puts their lifespan in the 50s. Autopsies on Maasai indicate they suffer from notable or extensive atherosclerosis, even in their 40s. Would such a short lifespan with notable chronic diet-induced disease conditions make sense if they lived as they were intended? No, of course not.
The Maasai have also given us another piece of interesting evidence with their customs. The Maasai men go on retreats where they indulge in large amounts of meat from cattle, sheep, and goats for up to 1 month at a time. It is common that they develop diabetes or prediabetic markers during this time. Quoting directly from the results of the observational study:
Participants more than doubled their energy intake from 2125.5 to 4690 calories. Prior to the stay, the average distribution of energy intake for carbohydrate, fat and protein was 67.1%, 23.6%, and 9.3% respectively, while this distribution during the stay was, 4.6%, 55.5% and 39.9%, respectively. Participants’ weight and cholesterol levels were significantly increased and half of participants developed disorders in their glucose metabolism. This reflects a temporary negative impact on their cardiovascular risk factors.
(https://globalhealth.ku.dk/news/2019/maasai-men-develop-lifestyle-diseases-during-calorie-saturated-health-refuge/)
Here is the study on Maasai, done specifically through autopsy, which shows that they display “extensive atherosclerosis” despite their high level of physical fitness. (https://academic.oup.com/aje/article-abstract/95/1/26/167903)
Inuits are another similar case. They’re said to be living in their natural habitat and surviving on their diet yet they have comparably very short lifespans which are considerably shorter than the rest of Canada which eats more of a western diet replete with processed junk foods. According to data from (https://www150.statcan.gc.ca/n1/pub/82-003-x/2008001/article/10463/4149059-eng.htm) the Inuit life expectancy was as low as 29 years in the 1940s, which was less than half of the average Canadian who lived to 66 at that time. This gap has narrowed over the years but Inuit do still lag behind the rest of Canada for health outcomes and life expectancy and live longer the more they seem to assimilate typical Canadian diet and customs.
So if a population is living in their natural state and eating natural food, why would their lifespan be significantly shorter than people living in a totally unnatural way? At some point we must look at the larger picture and concede that something isn’t right.
The Larger Picture: Comparative Anatomy and Physiology
Digestive Design
This will cover teeth, jaw, stomach and stomach acid, the small intestine, the cecum, and the colon from the perspective of comparative anatomy.
Stomach Acid and Digestion
First, before we take a larger survey of our digestive system, I would like to address a common claim regarding stomach acid. I am happy to concede that humans have the same stomach acid as lions. It needs to be highlighted, however, that lions have the same stomach acid as sheep and cows. In fact, all mammals as far as I’m aware (please correct me if anyone knows of an exception) produce hydrochloric acid for stomach acid. Therefore the relevant question is not, “how harsh is your stomach acid?” because lions, sheep, and humans all have the same stomach acid.
A more relevant question is, what is the environment of the stomach like? What is the concentration of that stomach acid in your stomach while digesting food? Lions have an average stomach pH so low they can digest whole bones. They can bite the hand right off your arm and swallow it and it will liquefy completely. Omnivores like wolves or bears can do this as well.
Of course, humans cannot digest bones. All obligate carnivores and all omnivores can digest bone in this manner, but humans cannot. Sure, we produce the same type of stomach acid that obligate carnivores do, but the overall pH of our stomachs does not allow us to digest bone the way that carnivores and omnivores can.
Teeth and Jaw
When we look at an animal’s teeth to try and discern their optimal diet, we are looking at their incisors, canines, and molars.
For herbivores,the front teeth, called incisors, should be prominent as they are generally used to sever plants with a bite. Carnivores and omnivores have much less prevalent incisors, and their incisors tend to come to a fine point rather than an edge. As humans, we of course have prominent and edged incisors just like herbivores.
If you look at carnivore or omnivore incisors, they are typically very small, being less than a quarter of the size of the adjacent canine. While the function of incisors is largely the same across herbivores, omnivores and carnivores, the shape is different and they do function slightly differently. Carnivores and omnivores have incisors that come to a point, whereas herbivores have incisors that form into a flat edge. This seems to be designed for biting fruit and greens cleanly which are typically much softer than flesh. Carnivore and omnivore incisors are sharper and the point allows them to nibble away at flesh or skin more easily.
Canines are a more ambiguous tooth as they serve a more diverse purpose. Canines can be for tearing flesh, tearing the skin of fruit, and for social displays or combat. There are many examples of herbivores which have large or prominent canines.
Perhaps the greatest example of an herbivore with prominent canines is the hippopotamus. Despite eating only plants, hippos have massive canines they use to battle crocodiles, lions, leopards and hyenas.
There is also a species of deer called the Sabre-Tooth Deer which despite being obligate herbivores has massive canines that look like fangs. With the Sabre-Tooth Deer, it is only the males which have the large canines, and they seem to be used mostly for courting, territorial and mating disputes.
Gelada Baboons are yet another example. They are the only primate which eats primarily grass, which makes up 90% of their diet, however, they have large canine fangs which they use for protection.
Camels also have prominent canines, despite an entirely herbivorous diet. Camels use their canines to crush woody desert plants for food.
Molars can also be very diverse across different types of animals. Carnivore and omnivore molars are meant to be able to cause significant shearing and snap bones, so they form points that are very hard and useful for cracking bones to get to the marrow. Rather than meeting directly, they tend to pass and overlap so they are able to work almost like a pair of scissors. Herbivores, on the other hand, exhibit varying degrees of flatness in their molars, and their molars meet so they can crush plant matter repeatedly. Ruminants like cows can have very flat molars, while frugivore species have molars that form interlocking surface areas with peaks and valleys.
While not necessarily completely flat, they tend to be designed to chew the same type of plant matter over and over again, whereas carnivores and omnivores are designed to just tear pieces away so they can swallow them whole without much chewing. Carnivore and omnivore stomach acid is much stronger, so there is less of a need for them to chew up their food thoroughly. Herbivores get a lot of water from the plant matter they are designed to eat, and are designed to chew the same foods over and over again in order to pulverize the food in order to extract the water, and in the absence of an incredibly harsh environment within the stomach, this extra pulverizing in the mouth also makes food easier to digest and break down.
An additional piece of anatomy that seems to confirm this view is the jaw. Carnivore and omnivore jaws work on a single powerful hinging joint which is on the same plane as the teeth. This seems to be designed to inflict maximum bite power and shearing force, whereas herbivore jaws are more complex, with the jaw joint that hinges above the plane of the teeth. They also possess less capacity for a powerful bite and the added complexity of the jaw joint also allows for side-to-side movement of the chin. This side-to-side movement enables herbivores to reposition them with each chewing movement, chewing the same material over and over.
Carnivores and omnivores cannot wag their chins back and forth the way humans can. This is a property that is unique to herbivores because our jaws are designed to chew the same fibrous plant materials over and over in order to pulverize them so that we can extract the maximum water content and make them easier to digest and breakdown over the course of our longer digestive tracts. For herbivores, digestion starts in the mouth; carnivores and omnivores seem to only be using their teeth and jaws to break up the material enough to swallow it.
And while not necessarily a 100% correlation, most herbivores also have an enzyme in their saliva called salivary amylase which helps to begin to digest and break down starches and sugars. This is generally not present in omnivores and carnivores, but is generally present in herbivores. Salivary amylase is present in humans.
Fiber
It is also frequently cited that insoluble fiber has no nutritional components and is not able to be digested. This is mostly true, however it still serves a purpose. Not only does it sweep through our digestive tract which keeps it relatively clean, it also helps to house and proliferate digestive bacteria which are very important for our overall health. Gut bacteria not only help digest our food, they also provide us with nutrition that can be difficult to get elsewhere. They also help regulate our neurotransmitters. And of course extra fiber also helps keep us having regular eliminations which is our largest avenue of detox and critical to good overall health.
Sometimes carnivore diet promoters will claim they utilize nearly 100% of the meat they eat and that they don’t need to have daily or any type of regular digestive elimination. In a larger context, this makes no sense at all, because even though lions are designed to eat flesh and can digest bone, they still poop. All carnivore and omnivore mammalian species have regular and consistent bowel elimination. It makes absolutely no sense that humans eating meat will not need to poop. Will they poop less? Of course, because they’re not eating fiber. Fiber is an essential part of a healthy diet not because we get any value from it directly, but because it helps keep things moving throughout the gastrointestinal tract and it helps promote a healthy gut biome.
I am also willing to concede that because of the absence of fiber, flesh is able to liquefy or dissolve more than the average plant food. However, not all of the constituents of flesh are useful or even healthy for us. Though present in all types of meat, red meats and seafood are particularly high in purines, which break down into uric acid which can contribute to many health issues, such as gout, kidney stones and other kidney issues, arthritis, heart disease and heart failure.
Failure to eliminate waste is not a benefit. It’s a myth that humans are able to utilize all the meat they eat. While after a series of chemical reactions we may be able to utilize some of the components of flesh, it still contains harmful compounds and still requires our liver and kidneys to deal with a greater burden than ideal plant-based options. It is also a more laborious process to utilize the nutrition that is locked away within flesh. We will look at part of this process in more detail in an upcoming section called, “Chemistry of Glucose, Protein and Fats.”
Digestive Tract
Next, in perhaps the most well known area of comparative anatomy, we will look at the length of the digestive tract. The way this was initially conceived is to measure the length of the digestive tract not on its own, but to compare it to the length of the body cavity in which it rests.
Carnivores and omnivores also tend to have much shorter digestive tracts than herbivores. Not only is their stomach acid much more harsh, but they also have harsher byproducts from the flesh they consume to contend with, so they possess a shorter digestive tract to eject waste more quickly. Herbivores however require long digestive tracts to fully break down as much fibrous plant matter as possible and to separate water from food as much as possible. Herbivores also absorb nutrition through the entirety of their digestive tracts, including their colons, whereas the colon of the omnivore and carnivore is very short and meant only to eject waste.
This design is also illustrated specifically in the cecum, which is a section of the digestive tract between the small and large intestines. Species that eat grass tend to have the most well- developed cecum, whereas species that thrive on meat have a very small cecum. Just prior to the cecum, there is an ileocecal valve, which prevents food from going backwardbackwards up the digestive tract. The cecum is also where further digestion and fermentation happens. So there is a valve that protects the earlier part of the gastrointestinal tract from pressures that may accumulate due to fermentation, and then there is what appears to be a specialized fermentation chamber. This may be why it seems to be more developed in herbivores which depend more on these processes to get the most out of their plant foods, whereas carnivores and omnivores do not require this process to extract all of their nutrition from their food. Humans have a relatively large and well-developed cecum.
The entire process of digesting meat is faster and more harsh, whereas plant matter is a slower and more gradual process with less harmful byproducts, and so the entire design of the digestive tract appears to reflect this. Carnivores and omnivores seem designed to be expecting to take in more toxins through their ideal food source, so their waste removal organs are more robust, their digestive tract is shorter, and they can easily accommodate this greater burden with regularity. Humans have a relatively long digestive tract and relatively small waste removal organs, as well as a colon which is able to absorb nutrition; These are all characteristics of herbivores.
Chemistry of Glucose, Protein, and Fat
It is also important to note that all animals, be they carnivores, omnivores, or herbivores, utilize glucose within their bodies as their primary fuel source. Carnivores and omnivores depend on gluconeogenesis and glycerols to get most of their glucose, whereas herbivores consume more glucose and depend less on these measures.
Gluconeogenesis takes place primarily in the liver, kidneys, and digestive tract, and is the process of refining protein or fat sources into usable glucose, amino acids, fatty acids and glycerol. This process takes some energy and yields some byproducts, and can be considered less efficient than consuming glucose directly. It is also worth noting that even when humans are operating in ketosis, studies show it takes 15 to 20 percent more calories to accomplish the same baseline tasks than if they were operating on glucose. This seems to show that not only is glucose the true baseline fuel source for all animals, but it is also more efficient than fats or proteins for humans which is a strong indicator that fruit is our optimal food.
Protein Purpose and Utilization
On the topic of protein, T.C. Fry, a notable Natural Hygiene author, has offered another fascinating piece of the puzzle. He compares the amount of protein present in the mother’s milk of different species. I have copied his information into a table below:
The first number is the average number of days a newborn takes to double its weight. The second number is the average percentage of protein present in the mother’s milk of that species.
| Species | Days to Double Weight | Average % of Protein in Milk |
| Man | 180 | 1.6% |
| Horse | 60 | 2% |
| Cow | 47 | 3.5% |
| Goat | 19 | 4.3% |
| Pig | 18 | 5.9% |
| Sheep | 10 | 6.5% |
| Dog | 8 | 7.1% |
| Cat | 7 | 9.5% |
To quote T.C. Fry on protein:
The highest need for protein in the diet occurs for most animals during the above periods when the newborn is doubling its birth weight. It is important that we realize the protein content in mother’s milk, the optimum food nature has provided for rapid growth of the young, is far below the usual foods that are recommended because of their protein content (such as meat, nuts, legumes, grains, etc.). Protein is indeed important for growth, but we might well question the alleged necessity for concentrated, high-protein foods.
The second role of protein is in the repair of tissues or replacement of worn-out cells. After an organism reaches its full growth (usually between 18 and 22 years for humans), protein is needed only to supply the loss incidental to tissue waste. Cell degeneration and waste occur primarily because of toxicity in the body. If we adopt a lifestyle and diet that introduces a minimal amount of toxins into the body, then tissue waste will decrease significantly. As a result, actual protein needs will also diminish. After an individual reaches adulthood, the only protein needs are for the repair and replacement of tissues that have deteriorated, due largely to body toxicity.
Protein is not used directly as fuel for the body or for muscular activity. In muscular work, excretion of nitrogen as a result of protein usage increases only very slightly. Instead, it is the excretion of carbonic acid and absorption of oxygen that increase. These changes indicate that an expenditure of energy is derived mainly from non-nitrogenous foods (such as carbohydrates and fats) and not from protein. It is true that the body can use protein to generate fuel for physical activity, but it does so by breaking the protein down into a carbohydrate form. Protein is used as fuel only when there is either an excess of proteins or a lack of carbohydrates. When this occurs, the body splits off the nitrogenous matter from the protein molecule and uses the remaining carbon contents to produce fuel. This process not only involves a net loss of energy, but it also places an unnecessary strain on the liver, kidneys and other organs to eliminate the unusable nitrogenous wastes.
It is for this reason that the popular high-protein, low-carbohydrate diets in weight loss and also why they are dangerous. Since the body has to expend so much energy in converting the excess protein into the needed carbohydrates for fuel, a net loss occurs in the body and the dieter loses weight. At the same time, he also places a heavy burden on his kidneys to eliminate all the uric acid generated by this protein breakdown and simultaneously overworks an already exhausted liver.
If more physical activity is anticipated, it is only necessary to increase the carbohydrate intake of the diet. Proteins are very poor in fuel-efficiency and do not aid directly or efficiently in muscular activity.
Check back soon for part 2 and more of this series! Or for further reading check out What is the Natural Human Diet? or The Nature and Purpose of Disease series!
