What is the evidence for a meat-based diet?
Evidence for a Meat-Based Diet: 1.0 – Evolution
Throughout human evolution, selective pressures fueled a persistent feedback loop between climate, food availability, and the advantages of a large brain.
Animal fat, with its ready-made source of long-chain fatty acids, powered the human brain to expand to 4X the size from that of our hominid ancestors.
Meat was the fork that diverged humans on our path to the top of the food chain.
But before we were using forks and knives, humans created ever-increasing sophisticated tools and weapons. And by early Homo sapiens this hunting technology included spears, daggers, and fish hooks which could be found among the bones of wildebeest, giant cape buffalo, and the large, fierce animals of the day demonstrating the skill and cooperation of a human specie that was big-game hunters. (r, r)
In fact, isotope studies of fossils reveal that the human diet 50,000 years ago was indistinguishable from a carnivore diet. (r, r) Contrary to popular beliefs about the “caveman” diet, it really was just a meat-based diet. (r)
While tools and hunting technology leave clues about the human diet over time, the evidence that is overwhelming is a look at the human body which evolved to optimize meat-eating. (r)
- Humans developed an acidic stomach to kill off pathogens in rotting animals. Our low stomach pH is a distinguishing trait among carrion feeders and carnivores. (r, r, r, r, r)
- The human gut shrank and lost most of its ability to ferment plant food into energy, turning humans into obligate meat-eaters. (r)
- Our guts mirror that of carnivores. Our cecum is a useless vestigial appendage.
And we share similar, well-developed gallbladders comparable to that of wolves and lions.
- Our small intestines absorb fat and protein from meat with extreme efficiency. (r)
A Hunter’s Body
Not only are our internal organs and tissues evidence for a meat-based diet, but so are the adaptations of our outer body.
Humans are the only living primate adapted for endurance running.
Everything from our balancing vestibular system and nuchal ligament, to our toe alignment and shock-absorbing foot structure, to our scarce body hair and cooling eccrine sweat glands, to our long lower limbs evidence a persistence hunter physique. Bodies optimized for running and hunting down prey with unparalleled stamina.
Unlike herbivores that graze and grind all day, humans eat like carnivores: prey, eat, rest and digest, repeat.
A glance at human evolution reveals a human body that morphed in accordance to obtain meat to fuel our brains.
This was the selective priority in which everything else fell in line.
Evidence for a Meat-Based Diet: 2. 0 – Energy Requirements
While our anatomy morphed us into premier hunters and meat-eaters, it also evolved our energy requirements, use, and distribution.
Our huge brains became our biggest weapon and also our most costly liability.
Fueling a big brain demands a lot of energy. Therefore humans would either need a very large gut with a large absorptive surface or a very energy dense diet (or both).
A doctor by the name of Max Kleiber discovered a law that predicts how much an animal eats based on its size. This law could also predict how big an organ should be and how much energy it should use.
Using the work from Dr. Kleiber we find that the human brain is over 7X bigger than Kleiber would predict for an animal our size. Not only that, it uses 30X more energy than would be predicted.
To accommodate the brain, Kleiber’s Law shows that the human gut shrank to just a third of the size as would be expected. Our cecum, the appendix, is practically non-existent and our colon is about half the size of what would be expected. (r)
Not only is the human gut small as predicted by Kleiber’s Law but so are our hearts, livers and muscles compared to other animals our size. (r)
Simply looking at our anatomy and the predictions from Kleiber’s equations we see humans could only maintain a brain our size by shrinking metabolically active organs, like the gut, and eating energy dense food. (r)
Evidence for a Meat-Based Diet: 3.0 – Big Brains and Big Game
Perhaps the “biggest” evidence that humans are meat-based eaters stares us right in the face every time we look in the mirror.
We have big brains. Brains unlike any other animal.
It’s our distinguishing feature. It’s the reason despite not being the biggest or strongest animals, humans climbed to the top of the food chain.
Our brain was (and is) our competitive advantage.
But the only way nature could select for our cerebral cortex was an energy dense diet. As we saw in Evidence 2.0, meat allowed us to escape the energetic constraint that limits the number of cortical neurons that can be afforded by a raw plant-based diet in the wild. (r)
Every billion neurons requires 6 calories per day.
And thanks to a combination that no other animal possesses, humans gained unparalleled cognitive abilities.
- Primate Brain = Ability to pack more neurons into smaller spaces
- Meat = Allows the escape from the energetic constraint of a raw plant-based diet in the wild (that limits all other primates to the smaller number of cortical neurons)
- Cerebral Cortex = Selective advantage to obtaining meat and thus survival
Humans surpass all other animals in the number of neurons in the cerebral cortex. Only made possible by a meat-based diet. (r)
From this large cerebral cortex we gained the ability to cooperate in flexible ways in large numbers. We formed collaborative social units with divisions of labor that made hunting megaherbivores (that were so big they were considered immune to carnivores) possible. (r, r)
Perhaps damning evidence for humans being predominant meat-eaters can be seen in the extinction of these megafaunal herbivores.
The fossil record shows that when humans entered a new location, the rate of extinction of big mammals rose. (r)
Homo erectus is thought to be responsible for the decimation of elephant populations. (r) Recent research looking at stable isotope data show that both Neanderthal and early modern humans ate a carnivorous diet of mammoth deer and rhinos. (r, r, r)
However, with a preference for eating big, fat game, these animals started to disappear.
Before agriculture the average mass of a non-human mammal in North America was 200 lbs. Today it’s 15 lbs. (r)
If we put the pieces together, we can see that the transition to an energy dense brain fuel, meat, allowed humans to amass a remarkable number of neurons. And nature preferentially selected prefrontal cortex growth for coordination, cooperation and communication.
Complex language and social coordination enabled humans to feast on the biggest, baddest animals in the world.
The human brain was the force behind our ability to hunt mammoths 2X the size of an elephant. It’s how we climbed to the top of the food chain.
This climbing wasn’t a result of muscle, rather brain power that led to robust social structures, nuanced and detailed coordinating and communicating where we relied on each other and helped each other for the greater good of all.
No other animal does this like humans. And no other animal has a brain like the human brain.
It’s this meat:brain self-reinforcing feedback loop that led Sapiens to rule the world.
NOTE: this brings up valid questions and concerns regarding environmental impact and sustainability issues of humans eating a meat-based diet. This is discussed in Meat Health Academy.
Evidence for a Meat-Based Diet: 4.0 –
From the evidence thus far, we can see that humans evolved to eat meat, it reshaped our bodies and built our brains. To meet our energy requirements in the wild, we became obligate meat-eaters. But not only obligate meat-eaters, we can see from the fossil record and extinction of megafauna animals that humans became predominant meat-eaters.
This was the state of the human diet up until the Agricultural Revolution about 12,000 years ago.
But if we zoom in the lens of the human ancestral diet a bit further to more modern times, we find that some societies were able to fend off the degrading health impacts of agriculture. These modern day predominant meat-eating societies display dramatic evidence for a meat-based diet.
Arctic and sub-arctic hunter-gatherer cultures that include the Cree of subarctic Canada, the Nenets of northwestern Siberia and Chukotka natives of northern Russia, the Nordic Sami of Scandinavia, and Eskimos of the arctic regions of North America, Northeastern Asia, and Greenland were free from the impact of agriculture, and followed a diet that was exclusively (or close to it) meat.
Tundra predominates in these areas. Seasons cycle from -60 below to highs of 50 degrees in the summer. Topsoil is frozen for most of the year. Plants are limited to lichens, mosses, and sparse grasses and shrubs. (r)
These people ate, often exclusively, animal-based diets. They hunted reindeer and fished for trout and caribou.
And for centuries they were renowned for their good health, longevity, and vitality.
Reports from explorer-scientists in the seventeenth and eighteenth centuries indicate an absence of disease and the presence of vitality and agility into old age.
North vs South Sweden
One such report came from the renowned scientist Carl Linnaeus in the 1700s. For 6 months he studied the people in northern Sweden where they lived on meat and fish. He compared these people with those of south Sweden who ate peas, buckwheat porridge, bread and vegetables. (r)
His conclusions: In the north they are fit and healthy. In the south they are fat, deficient in iron, and have rotting teeth.
The Inuit of Greenland
The Inuit of Greenland ate a diet polar opposite of that recommended by doctors today. They ate meat without restraint. Every meal was loaded with saturated fat and cholesterol. They ate little to no fruits or vegetables. Their diet was absent of fiber. Yet, they lived free of heart disease, cancer, and most modern chronic diseases.
Contrary to popular belief eating arctic birds, caribou, seals, walrus, polar bears, and fish provide complete nutrition – all the macro and micronutrients necessary – in their natural and most bioavailable forms.
But like the people in south Sweden who had incorporated modern foods from agriculture, beginning in the late 1800s grains and processed foods started to creep into the Inuit diet. The modernizing of their traditional diet led to obesity, diabetes, and cancers that were largely nonexistent prior to contact with these modern “foods.” (r,r, r, r ,r)
It isn’t just the people stuck in the cold climate, forced to eat animals due to the lack of fruits and vegetables, that chose a meat-based diet though. People in temperate climates who had access to plant-based food (before agricultural invasion) eschewed it in favor of meat as well.
The North American Plains Indians ate buffalo and pemmican, the Masai, Samburu, and Rendille warriors of East Africa subsisted on meat and milk, the Nagas – pigs, the Brazilian Gauchos – cattle, and the Marsh, Arabs, and Berbers of the tropics – camels.
American Plain Indians
Known as some of the tallest people in the world with fine physiques, the Native American Indians hunted large game like deer, buffalo, wild sheep and goats, antelope, moose, elk, caribou, and bears. And not only did they look good but they had a remarkable record of health and success.
Before the Colonial Period when Indians were decimated and pushed off on to reservations, there were ~25 million Indians demonstrating remarkable health. They could run down buffalo on foot. Their muscles were strong and so were their bones evidenced by their absence of arthritis, bone deformities, and dental decay.
The North American Plain Indians are a prime, yet tragic, example of what happens when a traditional meat-based diet gets westernized.
Isolated to reservations and fed processed foods and refined carbohydrates, Indians were forced to abandon their natural meat-based diets. In short order Native American Indians started suffering from modern diseases: obesity, diabetes, and heart disease.
The history of the Pima is a tragic story that has been repeated all over the world. Europeans bring in agriculture and white flour, sugar and other processed food become dietary staples. Their traditional meat-based diet is abandoned.
The result: The health of native populations gets destroyed.
Studying the intersection of meat-based traditional diets and the introduction of western foods to these indigenous people demonstrate a natural experiment which is nothing short of tragic.
When we study traditional meat-based diets we see excellent health with low rates of chronic diseases and health problems. But when we look at what happens when western food creeps in – grains, sugar, processed foods – we see the problems that plague modern industrialized societies skyrocket. Obesity, diabetes, heart disease, and cancer become commonplace. (r, r, r)
Plant – Meat – Paradox
We’re told meat gives you cancer. Saturated fat clogs arteries. Plant-based foods are required for fiber, antioxidants, and health.
Yet this is not what researchers found in these meat-based societies.
In fact, they found the exact opposite.
While eating little to no plant-based foods – no fruits, no vegetables, no fiber – but instead subsisting on a high-fat, high-cholesterol diets of seal fat, walrus, and fish, Eskimos not only survived, but early physician explorers discovered they were virtually free of cancer.
By today’s understanding of nutrition, these Arctic and Temperate meat-eating societies should all have died from cancer and heart disease. They should all have been wildly deficient in vitamins and minerals and suffered from scurvy and carbohydrate deficiency.
Why did these people eat a meat-based diet when plants were widely available?
Even when plant-based foods were available to indigenous people they often eschewed it in favor of meat. At most, plant-based foods were just a supplement to their meat-based diet.
The reason is obvious if you look at an area before agriculture and industrialization. People followed the “optimal foraging theory” which means they didn’t bother to dig a meter deep for a yam that provided 100 calories but took 300 calories of work to get to.
Indigenous people ate food that yielded the most bang for their buck. They ate meat because that is what they had evolved to capture, eat, and digest. (r)
Researching the Meat-Plant-Paradox
Thanks to a number of unfortunate “studies” and subsequent spreading of false information, it became “common knowledge” that grains were healthy and vegetable oils were the “healthy” fats. Meat was dangerous. It caused heart disease and cancer.
Because of this, these meat-eating societies represented a “paradox.”
How could they abstain from these “healthy” plant-based foods yet not suffer the chronic diseases of the day? How could they survive without fruits and vegetables?
So in 1972 researchers turned to Point Hope, Alaska to see if they could answer this paradox. Here, people still maintained a mostly meat-based diet.
What they found was that besides eating 50% of their diet from animal fat their rate of heart disease was 10X lower than the white population in the United States. (r)
Surely this was impossible, so in the 1980s researchers looked back to Greenland to find that Eskimos eating a diet most similar to their traditional diet had heart disease at the miniscule rate of just 3.5%. But this was not the case with those who had greater contact with a modern diet. (r, r)
Similar findings were made among the Masai.
A study estimated that they ate 66% of their daily calories from animal fat, averaging over 600 milligrams of cholesterol per day and heart attacks were essentially unknown among the Masai.
These meat-based societies didn’t suffer from the epidemics of modern diseases. Cancers were virtually absent. The world’s #1 killer, heart disease, was nowhere to be found. Diabetes, obesity, high blood pressure were all absent as long as modern agricultural foods were absent. (r)
From the Sami of northern Scandinavia to the Inuit of Greenland to the American Plain Indians – all were healthier than we are today – all evidence for a meat-based diet.
Stone Age Bodies in a Fast Food World
As we saw with the North vs South Swedes, the American Plain Indians before and after the Colonial Period, and the modernization of the Inuit diet – when the plant-based western food arrives, so does disease. (r, r)
Diabetes was virtually unknown among the Maya of Central America until the 1950s when they switched to a Western diet and diabetes skyrocketed.
Siberian nomads like the Evenk who were reindeer herders and the Yakut who ate a diet heavy in meat had almost no heart disease until the fall of the soviet union when many settled in towns and began eating market foods. Today about half the Yakut are overweight and a third have hypertension. (r)
The “discordance theory” is that we’re trapped in Stone Age bodies in a fast-food world. Stone age bodies that are designed to eat meat. A fast-food world that is dominated by cheap, processed plant-based foods like grains, sugar, and vegetable oils.
Evidence for a Meat-Based Diet: 5. 0 – Longevity and Health
A devastating example that highlights this is pellagra, a disease caused by a lack of meat in the diet, resulting in brain atrophy (dementia) and subsequent low IQ and poor social behavior (also resulting in gut dysbiosis and numerous physical impairments). (r, r, r, r)
Health and Longevity
The evidence for a meat-based diet can be witnessed at all ages.
In the Womb
DHA is an omega 3 fatty acid, a primary structural component of the human brain, and for the most part only found in animal-based foods (and algae). In a recent randomized controlled trial pregnant women given DHA supplementation had children with larger total brain volumes, more gray matter, as well as a larger corpus callosum and cortical volumes compared to the placebo group. (r)
Another study compared meat vs iron-fortified cereal as an infant’s first complementary food. The researchers found that infants weaned onto meat had larger head circumferences and higher behavior index than the cereal group. The infants weaned onto cereal not only had smaller head circumference but also low levels of zinc and iron. (r)
As a Kid
The brain is doing its most rapid growth and wiring in utero and in the subsequent early years after birth. Research shows that children that eat meat have better adult cognition than those who don’t. (r) This is further highlighted in this study which shows that kids eating a plant-based diet in early childhood is predictive of cognitive difficulties in adolescence. (r)
As an Adult
Poor diet in adolescents can have dire consequences as an adult.
- 20% of Americans suffer from a mental disorder in a given year
- 4 of the 10 leading causes of disability are mental illnesses
- ~20% of doctor’s appointments are related to anxiety disorders
- 1 in 5 young people suffer from a mental health problem
- Suicide is the 2nd leading cause of death for 10-34 year olds
The causes of mental health problems are thought to be multifactorial with biologic and physiologic changes like low levels of certain neurotransmitters (serotonin, dopamine, and norepinephrine). There are genetic associations. There are environmental and societal impacts and influences.
But what often gets left out is diets’ potential impact on mental health issues.
Meat provides complete nutrition. Plants do not. This is critical when it comes to fueling the brain.
Fat:The brain is 60% fat. And animal fat is different than plant-based fats.
Cholesterol: The brain contains 25% of all our bodily cholesterol. Plants don’t provide cholesterol. Research shows that dietary cholesterol promotes repair of demyelinated lesions in the brain. So it’s not surprising to see that high cholesterol helps prevent dementia. (r, r, r, r)
Popular media would have you believe that cholesterol is bad. But cholesterol not only helps prevent dementia, but it protects against infectious disease, has no bearing on heart disease, and even reduces the chance of death from all causes by 30%. (r, r, r, r)
Besides fat and cholesterol the brain also needs fuel from compounds found mostly or exclusively in meat.
Vitamin B12 is vital to making our DNA, RNA, and blood cells. And it can only be obtained via animal-based foods. A deficiency from lack of meat can lead to tiredness and weakness, megaloblastic anemia and can devastate the nervous system – implicit in depression, confusion and dementia. (r, r, r)
Acetyl-L-carnitine is only in animal-based food, particularly red meat and contributes to the production of the neurotransmitter acetylcholine, which is required for mental function. Depression is linked with low levels of acetyl-L-carnitine. (r)
Carnosine, like carnitine, it has the root “carn” which means “flesh,” as it’s found mainly in animal-based food. This neurological peptide has been shown to suppress stress, improve behavior, cognition, and well-being in humans. Research suggest a biochemical link between inadequate carnosine and depression-associated phenomena (as well as aging – as it is one of the most powerful antiglycating agents known). (r, r)
Taurine is only found in animal products, and it’s known that low levels of taurine lead to decreased cognitive development in young children. (r)
Doesn’t the brain need carbs/glucose?
The brain can use a variety of fuels like glucose and ketones. But it doesn’t require you to eat any carbohydrate. The body can make all the glucose it needs from fat and protein. There is no such thing as an essential carbohydrate.
In fact, our brain evolved and expanded in a low glycemic environment. The brain needs stable blood sugar and insulin levels. It needs meat. Refined carbs disturb this natural balance which interferes with the proper functioning of neurotransmitters like dopamine and serotonin that influence mood and cognition.
As discussed in Health Dangers of Plant-based Foods (which is also going to be further explored in Part II in this series – Your Brain on Plants), since the advent of agriculture and the gradual transition from a meat-based diet to a plant-based diet, human health has deteriorated.
Today we have adjusted to this “new normal.“
Asthma and allergies are almost expected with kids. IBS, indigestion, acid reflux is considered normal digestion. Depression, diabetes, dementia, and dental abnormalities. All normal. We fight fatigue and brain fog daily. It’s normal. Acne, autism, and autoimmune disorders went from non-existent to commonplace. Osteoporosis and obesity.
A meat-based diet was replaced with – what is now normal – a plant-based diet.
It became normal to call meat unhealthy and unsafe.
When in fact no one is congenitally allergic to red meat and animal fat. It is the safest food there is. Any allergies that have been recorded are due to a tick or mite bite (that transfers a cross-reactive sugar molecule called alpha-gal into the body).
Perhaps we need to redefine normal to rediscover health.
Like mental and physical health, there are numerous factors that go into living a long life. One of those factors is undoubtedly diet. And the evidence suggests, the more meat you eat, the younger you look and the longer you live.
When studying longevity an interesting place to start is looking at telomere length. Telomeres affect cell lifespan. The longer the telomere the longer they live.
There was a study on red meat that found an “unexpected relationship” between the frequency of red meat consumption and telomere length. (r) More so than exercise or any other factor, red meat consumption correlated with longer telomeres.
But do longer telomeres result in longer life?
Trying to isolate for “pure meat-eaters” today is nearly impossible but Hong Kong is about as close as we can come. They eat about 1lb of meat per person/day. The most in the world. Turns out they have the longest life expectancy in the world. (r)
Japan also recently hit an all time high in life expectancy in tandem with their meat-eating. (r)
People in India eat about the least amount of meat in the world. They also have one of the shortest life expectancies.
This is consistent with the data from FAO that shows as meat-eating increases so does life expectancy.
Yes this is epidemiology which comes laced with flaws and limitations, but these findings can’t be ignored. Especially (contrary to popular claims) numerous studies show that plant-based diets show no longevity benefits. (r, r) And in fact, research is showing red meat intake to be inversely associated with cardiovascular disease and with cancer – two of the leading causes of death. (r)
The short life spans found in India are consistent with the findings in vegans.
There was a massive study conducted at Oxford that compared all cause mortality among regular meat-eaters and vegans.
Although these were not pure meat-eaters (they ate other junk too) they still had a 14% decrease in relative risk of death compared to vegans. (r)
Evidence for a Meat-Based Diet: 6.0 – The Problems with Plants
Evidence 6.0 is going to take a look from the other side – “the negative evidence.” This is the evidence against a plant-based diet, and thus evidence in favor of a meat-based diet.
Recap: of Evidence for a Meat-Based Diet:
In Evidence 1.0 through 3.0 we saw that humans evolved and are designed to eat meat.
We saw in Evidence 4.0 that the advent of Agriculture brought about a natural experiment that has had tragic results when indigenous populations switch from their native meat-based diet to a plant-based diet.
In Evidence 5.0 we saw how the brain and the body have essential nutrition that must be supplied from animal-based foods. And when this nutrition is neglected there are deleterious health consequences.
Evidence 6.0 is the “Health Dangers of a Plant-based Diet” which puts the full picture together.
If you scrolled to the bottom here just looking for an overview, here is a TL;DR 15-min synopsis on the Scientific Reality of Meat and Human Health. It’s an excellent overview.