Sinking our teeth into the carnivore diet: what’s known, what’s not

T-bones for breakfast, ground round for lunch, rib eyes for dinner. Does this sound like your dream menu — or your worst nightmare? Is a diet consisting of only animal products a simple, healing way to eat or an overly-restrictive regimen that borders on an eating disorder?

A carnivore diet contains animal products only. It is plant free. In its most extreme form it includes only meat and water.

Read on to learn more about the zero-carb, carnivore way of eating. And find out the results — positive and negative — I experienced when I tried the diet for 30 days.

Disclaimer: Good research evidence is currently lacking about this way of eating. This guide summarizes what is known to date.

Why explore carnivore eating?

At Diet Doctor we do our best to provide the top scientific evidence available to support safe and sensible dietary decisions to help you improve your health.

Some burgeoning dietary regimens, however, lack high-quality evidence either for or against their use. For the carnivore diet, there are a growing number of anecdotes, a wide range of expert opinions and some interesting evolutionary theories. However, no research exists yet around carnivory that meets any of the criteria for good scientific evidence.

Should we ignore the growing popularity of carnivore eating because of these scientific limitations and pretend it doesn’t exist? Or should we acknowledge it and discuss what is known and not known about its potential benefits and harms? We have chosen the latter approach but strongly stress that much more experimental research needs to be done.


What to eat on the carnivore diet

So what do you actually eat on the diet? Also called a zero-carb diet or animal-sourced foods (ASF) diet, the carnivore diet consists of 100% animal foods — meat, fish, eggs, high-fat dairy products and animal fats. Some adherents eat only meat, salt and water.

The carnivore diet has been getting a lot of attention lately. There are Reddit forums with thousands of members, many Facebook groups, numerous articles in mainstream media, podcasts and hundreds of YouTube videos.

However, is a trial of the diet right for you?

Videos about meat

Why people turn to carnivory

At Diet Doctor we recommend above-ground vegetables in our keto guides and recipes. This suits most people very well because such vegetables are very low in carbs and contain a lot of fibre, nutrients and trace minerals. They are also filling.

One can generally eat a few servings of kale, broccoli, cauliflower, Brussels sprouts, zucchini and other veggies without exceeding 20 grams of net carbs a day. Moreover, eating a mixture of  non-starchy vegetables with animal products like meat and cheese provides good dietary variety, which can make low-carb eating more interesting and sustainable for the long term.1

Not everyone, however, achieves complete success on a low-carb ketogenic diet that is rich in vegetables. According to comments gleaned from various carnivory websites, Facebook groups and discussion forums, some people tried a keto diet first but were dissatisfied with their results, prompting the trial of carnivory.

“By and large, most people doing the carnivore diet have some persistent health issue that the keto diet did not completely fix, such as not enough weight loss, a mental health condition, an autoimmune condition, or uncontrolled cravings,” says Dr. Paul Mabry, a zero-carb US family doctor who blogs at Born to Eat Meat and manages a Facebook group, Zero Carb Doc, which now has more than 7,400 members.

Dr. Mabry says he was “a total sugar addict” who at first did well on a keto diet that included lots of vegetables. He lost 50 pounds on keto, but his weight stalled at 230 pounds — which was about 50 pounds above his ideal weight. Plus his hand eczema, cravings and tendency to overeat continued.

“Even the tiniest amount of carbs can start my cravings and binging. I can binge on vegetables,” said Dr. Mabry.

In 2015 he began a carnivore diet, eating almost 80% fat and 20% protein. His weight dropped, his hand rashes cleared and his cravings stopped. He has now maintained a weight of 180 pounds with no issues.

“I don’t think everyone needs to eat a zero-carb diet. But if you are like me, someone who is severely metabolically damaged from a lifetime of sugar addiction, I think it can help,” he says, calling it a total abstinence approach to carbs.

Australian Jane Jordan, a former nurse, did the keto diet for seven years, with good results. She lost weight, normalized her blood sugar and blood pressure, and eliminated her migraines and IBS.

In spring 2018, when Jordan was diagnosed with early-stage glaucoma, a condition that runs in her family, she found some posts that zero-carb might help her eyesight.2 Recent research has suggested that Vitamin B3, known as nicotinamide, may potentially be an effective prevention or treatment for glaucoma.3 The foods highest in nicotinamide include meat, poultry and seafood.

“Why not try it? I had nothing to lose,” said Jordan.

After seven months of the carnivore diet, a retest of her eyes by her optometrist in October 2018 found no evidence of the disease. “I am convinced that it was the zero-carb diet that reversed it,” she says.4

While there are currently no research trials examining the diet for glaucoma, Jordan intends to stick with this way of eating for at least 12 months, and reassess after her next eye appointment.

Stories like these are anecdotes and do not equal good research evidence. We tend to hear more about the positive stories of people on carnivore. No research exists about how many achieve health improvements and how many experience negative symptoms or no improvements.

It is clear, however, that success is not guaranteed for all on the diet. Other people in Facebook groups and discussion forums have complained of rapid and alarming weight gain, bloating, digestive upset, increased body odor, increased acne, increased tartar on teeth and other unwanted or lackluster results after adopting a zero-carb diet.5


Experts weigh in: some pro, some con— some alarmed

Among low-carb experts, the carnivore diet is very controversial.

Low-carb neuroscientist Rhonda Patrick, PhD, is concerned about the potential for negative gut microbiome changes and the risk of micronutrient deficiencies. “What is attracting someone to try such a restrictive diet without any published studies or long-term evidence? Why would you do it?” she said in an October 2018 podcast with Joe Rogan, who has had many pro-carnivore guests on his show. She said the most common reason seems to be trying to influence ongoing autoimmune conditions.

Psychiatrist Dr. Georgia Ede supports a trial of the diet. In her popular Diagnosis Diet blog and in this Diet Doctor video exploring whether vegetables are truly necessary for health, she concludes “there is no clear scientific proof” that we need to eat vegetables at all. She told participants at the 2018 Low-Carb San Diego conference that she was currently trying a carnivore diet herself and, so far, was experiencing positive results, such as improved sleep, steady mood and resolution to her migraines and night-time leg cramps.

Dr. Ted Naiman says he has now had many patients who have done 30-, 60-, and 90-day trials of the carnivore diet, with generally good results and normal labs. However, he has been finding that longer term, the diet may be more concerning. “I’ve now had a small handful of patients who were doing this longer than six months who have reported vague fatigue. The lab workup in these people is usually normal except for very low folate levels, below the normal range.” (Folate, or vitamin B9, is an essential vitamin found in high amounts in green vegetables, egg yolks, organ meats, avocado and legumes. Here is a list of food folate sources.)

Dr. Steve Phinney is concerned about potential deficiencies in sodium, magnesium and potassium in those who follow the carnivore diet.

Dr. Jason Fung says, “I generally don’t recommend it to patients – there is virtually no research evidence around it. But if people are doing well on it, I don’t have a problem with it. And if micronutrients are an issue, you can always take a daily vitamin.”

Other low-carb experts who were approached for their opinion for this story decided to pass: “There are no long-term studies. I’d rather not comment,” was a common response.

Most mainstream dietary experts, who generally don’t support low-carb ketogenic eating, are alarmed. They call the carnivore diet extreme, insane, and a bad idea


Testimonials, blogs and advocates bloom

Despite the controversy, some high-profile individuals are sharing how a carnivore diet helped resolve their intractable problems, especially mental illness and serious autoimmune conditions.

One of the most prominent and dramatic stories is of Canadian Mikhaila Peterson, who had juvenile rheumatoid arthritis that was so severe she’d had three joint replacements (a hip and two ankles) before age 17. She also had extreme fatigue, anxiety and depression. In 2015 she began eliminating foods to see if a specific food was contributing to her autoimmune issues. She ended up eating just beef, salt and water — and all her symptoms disappeared.

Peterson’s father is the highly controversial University of Toronto psychologist Jordan Peterson, PhD, the bestselling author of 12 Rules For Life. Peterson witnessed his daughter’s improvements, adopted the same diet, and has said it caused his long-term depression to lift. Since Peterson is a divisive intellectual, a current cultural lightening rod dubbed a “custodian of the patriarchy” by The New York Times, his adoption of the diet has added to the diet’s growing notoriety and detractors as well as to its growing adherents. Both Mikhaila and Jordan’s stories have been featured on Diet Doctor.

Other high-profile advocates include orthopedic surgeon Dr. Shawn Baker, Kelly Hogan who blogs at My Zero Carb Life and Esmée La Fleur who runs the ZeroCarbZen website, where she interviews other carnivores about how the diet has impacted their health.

Meat Rx, Dr. Baker’s website, collects hundreds of testimonials of personal health transformations. Just Meat, curated by bitcoin entrepreneur Michael Goldstein, has a large collection of articles, historic documents, archeological studies and other carnivory links.

Included at Just Meat are all the archives of the late Owsley Stanley, a.k.a “The Bear”, the former sound engineer (and LSD supplier) to the Grateful Dead. Stanley was a carnivore for some 50 years, and while the rock band happily took his drugs, they would not take his dietary advice. His story is fascinating reading.

Some of the most scientific and nuanced writing on the carnivore diet is being done by Amber O’Hearn, who has two blogs, Empirica and The Ketogenic Diet for Health. A computational mathematician, O’Hearn has been a carnivore for more than a decade and says she will stay on it for life, because it is the only way of eating she has found that controls her bipolar disorder. She speaks at many low-carb conferences, and her full-length podcast is available on the member side of Diet Doctor.

“I don’t advocate eating a carnivore diet for no reason at all,” O’Hearn says. “If you can eat a more varied low-carb diet with good results, why wouldn’t you?” But she also rejects the dominant, unchallenged view that humans simply must eat vegetables for health and that pure carnivory is physiologically implausible.

Vector of human evolution concept

Threads of evidence from our ancient past

So, do we need to eat plenty of plants for good health? What evidence exists that our human ancestors survived, and maybe even thrived, on a largely meat-based diet?

Many of the people listed above draw upon some common archeological, anthropological and physiological sources to argue that humans evolved to be carnivores, and that fatty meat and organ meats are humans’ optimal diet. As hunter-gatherers, they say, people may have eaten plants, tubers, nuts and seeds when meat was scarce — and gorged on summer fruit and berries to fatten up for winter — but such foods weren’t necessary to maintain health. Meat was.6

Here are some of the key points commonly used to argue that homo sapiens evolved to eat a diet mainly of meat and fat.

  • Evolution of human brain size: Over the span of human evolution, the size of the hominin brain has dramatically increased. Brain size likely grew every time a more nutrient-dense, energy-rich animal food source was eaten, especially animal fat.7 In short, some declare that animal meat and fat gave us our brains and made us human.
  • Evolution of the human gut size: As our brains were growing, the length of our digestive tract was shrinking.8 Herbivores like cows, rabbits, and horses have long, complicated digestive tracts to break down plant cellulose while carnivores like lions, wolves, and dogs have short, simple digestive tracts. In ominvores like humans, the GI tract is slightly longer than that of carnivores but much shorter and less complex than that of herbivores.
  • Ancient human and animal remains: Anthropologic studies have found evidence of meat-eating among our distant ancestors going back more than 2 million years. Caches of both human and animal bones in ancient caves and burial sites yield important clues. Cut marks and smashed ancient animal bones show probable evidence of butchery and marrow extraction.9
    Analysis of the ratio of nitrogen and carbon laid down in ancient human and Neanderthal bones can give potential information about the protein source of their diets.10Studies have found that Neanderthals likely had an almost exclusive diet of large fatty mammals like woolly mammoth but that early modern humans may have survived because of their ability to eat from more varied sources like freshwater fish and smaller mammals — while still predominantly carnivorous.11
  • Cave art: Bones found in caves are one clue, but what did early modern humans draw in ancient caves such as Spain’s Altamira cave and France’s Chauvet cave? Berry bushes and leafy greens? Nuts and tubers? Nope. Animals! Lots and lots of animals: bison, horse, doe, auroch, wild boar and even (in some cave systems) rhino, mammoths and lions. It is believed these drawings, which are often more than 30,000 years old, were symbolic shamanistic rituals created to increase the success of the hunt, the tribe’s primary and most important food source.
  • Agricultural revolution brings a decline in health: Best-selling author and academic Jared Diamond penned a famous 1987 essay, The Worst Mistake in the History of the Human Race, in which he amasses multiple lines of evidence to conclude that the invention of agriculture “was a catastrophe from which we have never recovered.”12
  • Meat-only study: Jump ahead to the early 20th century when arctic explorer Vilhjalmur Stefansson (1879-1962) did three expeditions in the Canadian arctic, living with the Inuit. For at least seven years he lived on meat alone. Others did not believe such a diet could be healthy, so in 1928 he and an expedition teammate were admitted to a ward of New York’s Bellevue Hospital to be fed a meat-only diet (with plenty of organ meat) for a year and “to be intensively studied on every clinical angle.”13
    At first the meat served was too lean, making Stefansson sick, but as soon as the fat was upped the pair thrived. A second 1930 paper, based on that year-long study, found no vitamin deficiencies, normal bowel function, improved dental health and that “the subjects were mentally alert, physically active and showed no specific physical changes in any system of the body.”14 In the late 1950s, a few years before his death, Stefansson was interviewed on television about his experiences, which makes fascinating viewing.
  • The teeth of the Inuit: In 1929, around the same time as the Stefansson study, a Harvard dentist studied the teeth of the Inuit. He concluded that “eating a strictly meat diet is the ideal way in which to keep the human mouth in a healthy condition.”15
  • The essential role of Vitamin B3: Found naturally in meat, fish, eggs, cheese and milk — as well as some plant foods — vitamin B3 is an essential nutrient for the functioning of all our cells and nervous system. Also called nicotinamide or nicotinic acid, its presence in the human diet, some theorize, has played a key role in human evolution, especially in brain and central nervous system development.16
    A vitamin B3 deficiency, called for centuries by the name pellagra, was a horrible condition known by the four Ds —dermatitis (scaly skin sores), diarrhea, dementia and death. In 1915 US epidemiologist Joseph Goldberger  found that it was caused by a diet “poor in animal protein.”17
While none of these factors prove that in our modern age we would be better off limiting ourselves to a carnivore diet, they are key arguments used by carnivore diet proponents that humans evolved to rely heavily on animal-sourced foods.


Paleomedicina in Hungary: treating dire conditions with a zero-carb diet

While an increasing number of doctors are recommending the low-carb ketogenic diet to treat a variety of medical conditions, currently we are aware of only one medical clinic that is using the zero-carb, all animal-sourced diet as a therapy for a wide variety of serious conditions. That clinic is Paleomedicina in Zalaszentgrót, Hungary.

The team, headed by research neuroscientist Dr. Zsófia Clemens and physician Dr. Csaba Tóth, uses its paleo-ketogenic diet therapeutic protocol to treat a wide array of autoimmune conditions, type 1 and type 2 diabetes, mental health conditions and even cancer.

Developed in 2010-2011, their protocol follows what the clinic believes early modern humans evolved to eat. The diet has a ratio of two parts animal fat to one part animal protein. Acceptable protein sources are fatty red meats and organ meats, preferably from pasture-raised animals. No nitrates, nitrites or additives to meat are allowed. A very small amount of vegetables — mostly leafy greens — are allowed as long as they do not take people out of ketosis, but they are not deemed to be necessary.

On the diet, eggs are at first eliminated but re-introduced after about six weeks to see whether they trigger any negative symptoms (for some, they do.) The diet does not allow any dairy products, fruit, sugar, grains, starchy vegetables or processed carbohydrates.

Since 2013, the clinic has used their paleo-ketogenic diet to treat more than 10,000 patients, according to Dr. Tóth. They’ve published case studies of the reversal of Crohn’s disease, halting of the progression of type 1 diabetes, reversing a precancerous condition, and halting the growth of malignant cancer of the soft palate and of the rectum.18 Their groundbreaking but controversial work has been featured in a number of podcasts, articles and presentations. Their findings have not yet been reproduced by others research sites or studied in experimental trials.

In an interview with Diet Doctor, Dr. Tóth described how he searched for years to find a way to cure his own health problems: type 2 diabetes, high blood pressure, severe eczema and severe Crohn’s disease. He first found the paleo diet, which helped his conditions but did not cure them.

It was only when he combined the paleo diet with the ketogenic diet that his health problems resolved.19“Moreover, every clinician in the clinic now eats this way, too,” he says. “We are convinced that this is the healthy way of eating and feeding oneself.”


The role of intestinal permeability

Drs. Tóth and Clemens say their experience suggests that a key mechanism of the diet may be its positive impact on the function of the intestine, healing and reversing intestinal permeability, also sometimes called “leaky gut.”

While in the past mainstream medicine largely dismissed the theory of illnesses being linked to a leaky gut as being pseudo-science, recent research is confirming that a breakdown of the gut barrier can occur.20 Over the last decade research from a number of academic institutions around the world has been showing that an increase in intestinal permeability is a common feature of a number of autoimmune and chronic disease conditions.21

A “healthy” intestine absorbs nutrients and energy for use by the body but is more likely to keep out microbes, antigens and other potentially disease-causing agents. The theory is that increased permeability allows unwanted substances to cross the intestinal barrier, triggering inflammation and a dysfunctional immune response.22 “If you have high intestinal permeability, then it is a high probability that all biological membranes are malfunctioning, such as the blood-brain barrier,” said Dr. Tóth.23

All of Paleomedicina patients undergo a test, called PEG400, to measure their level of intestinal permeability before and after starting the diet. Patients ingest a solution. If they have intestinal permeability, compounds in the solution cross the intestinal barrier and then are measured six hours later in the patient’s urine. The higher the level in the urine, the greater the intestinal permeability. Dr. Tóth said at Paleomedicina they have shown by repeating the test that their paleo-ketogenic diet can restore the gut wall to normal permeability within a few months.24


What about colon cancer?

Don’t we need to eat vegetables and fibre to prevent colon cancer? Leading health institutions like the World Health Organization and the World Cancer Research Fund declare that red meat causes colorectal cancer and constantly urge us to eat less of it. Wouldn’t a meat-only diet up the risk of cancerous cell changes?

Nina Teicholz, in her book The Big Fat Surprise and in this Diet Doctor video, dissects the poor epidemiological and weak science behind the claim that red meat causes cancer and concludes there is no evidence of a link at all. Diet Doctor has an in-depth guide to red meat and another one on diet and cancer that discuss the weak evidence on red meat and cancer as well as exploring whether vegetables are protective.

None of the people eating the carnivore diet interviewed for this article, or the many people writing and posting about it, are concerned about their own personal risk for colon cancer from the diet. Most said they are more concerned about how vegetables and grains may irritate their colons and that, personally, their intestinal function had seemingly improved on the diet.

In fact, some point to the 2009 epidemiological study suggesting that vegetarians in the UK had higher rates of colon cancer than meat eaters.25 In this study, there should have been a “healthy user bias,” meaning vegetarians would usually be more physically active, have lower BMIs, have higher levels of education and be more economically secure. Therefore, it would be assumed that these tendencies would skew the results even more in their favor, giving them lower rates of colon cancer. Yet that didn’t occur in this study.

Colon cancer rates in the last decade have been increasing among people age 19 to 39 in many parts of the world, including the US, Australia and Canada.26 The reason is not known, but authors of the studies noting this increase say it may be associated with the obesity epidemic, sugar consumption, an unidentified environmental factor, or another as-yet-unknown risk factor.


N=1: My one-month trial

When Dr. Andreas Eenfeldt asked me to research and write this guide to carnivore eating, it became clear I should give the diet a try myself.

I wasn’t so sure I wanted to. I love vegetables and salad. I have a big vegetable garden; tending it and eating its bounty is a source of joy. Plus, I’ve had no outstanding health complaints since adopting the ketogenic diet in 2015. I’m now happy with my weight; I’ve no auto-immune conditions nor mental health concerns; I’ve no trouble controlling carb cravings.

In short, unlike many who try the carnivore diet, I didn’t have an overwhelming motivation — except this guide — to try this way of eating.

In addition, I was reluctant to tell my family and friends I was eating only meat. It felt extreme. It did not lend itself to dinner parties, lunch dates with girlfriends and other forms of socializing. I didn’t want to get lectures about the evils of meat, or have friends think I’d developed an eating disorder.

So, I embarked on a quiet trial, not telling anyone I was doing it. At first I thought I would just do a week, but I learned that would be too short to demonstrate anything.

“It takes about 30 days to see appreciable differences from this diet and often longer, compared to a merely ketogenic one,” advises O’Hearn.

Calmer gut, lower body fat, more hot flashes

First, here is how I ate:
  • I either had eggs and bacon for breakfast or skipped breakfast completely. I did have a cup of coffee with full-fat cream every morning.
  • For lunch I would often cook ground beef with butter and salt, sprinkled with a bit of grated cheddar cheese. If I hadn’t had breakfast, I might instead have two eggs for lunch, or an omelette with cheddar cheese. Sparkling water was my go-to drink all day.
  • For dinner, it would usually be a piece of meat — steak, rib eye, pork chop, sausage, lamb chop, liver — with a tiny bit of fresh kale or lettuce from my garden (such as is allowed on the Paleomedicina protocol). It was not enough greens to call it a salad —and it had no dressing — but was just a bit of color so my plate did not look so bare. I honestly found it hard to see a plate with just meat on it. Seeing the green and chewing a few sprigs of kale or parsley with the meat felt refreshing. I called it my palate cleanser.
  • I did not snack at other times of the day. Already being keto-adapted helped with this. I could not have eaten this way if I had not already been three years on a low-carb, keto diet.
The results:
  • GI tract: The first four days I had significant digestive upset —mostly diarrhea hitting in the middle of the night. Not nice. But then my gut settled down and was remarkably calm for the next 30 days.
  • Weight: I lost 5 pounds within two weeks and kept it off for the 30 days. In three years of ketogenic eating my weight had become very stable. I thought it was as low as I could realistically go as a 60-year-old woman. It was not. Within a month of stopping eating carnivore, however, I had gained 4 pounds back.
  • Body fat: My body fat percentage, which had come down from 36% to 29% on the keto diet, came down even more to 26.5%. My exercise routine stayed the same.
  • Fasting blood glucose: My fasting blood glucose was 85-86 mg/dl (4.7 or 4.8 mmol/L) every morning — optimal.
  • Ketones: My daily ketone levels were not as high — usually about 0.3 to 0.7 mmol/L. When I ate a low-carb ketogenic diet my ketones would typically be 1.5 to 2.0 mmol/L, optimal nutritional ketosis.
  • Hot flashes: I would get extremely hot, especially after my evening meal and in the middle of the night. At first I thought it was a return of menopausal hot flashes, but then in a Facebook discussion among others with the same reaction, it dawned that it might be protein thermogenesis — the meat sweats — from the digestion of protein. At times I was uncomfortably hot. It made me think maybe this internal, meat-driven furnace was how our paleolithic ancestors survived in winter climes wearing just animal hides and tree bark.
  • Better skin: Some long-standing sun damage (keratoses) on my legs and shoulders simply disappeared. Weird.
  • Brain: I did not notice any difference in mood, mental acuity or mental energy between keto and carnivore. If anything, I think I feel mentally happier eating vegetables. It may have been because I was not outside tending and using the produce from my garden during the month and not socializing with others over meals.
  • Cravings increased: On the low-carb keto diet I’ve generally had no cravings. On carnivore my cravings actually increased — substantially. I especially longed for fresh salad, raw and steamed broccoli, fresh fruit and berries —and even bread and popcorn. I craved sweets, too. At a party during the month, I could not resist the dessert table, which hadn’t occurred in the past on the keto diet. I think I wanted a different mouthfeel, a different taste, even for just a moment. Greater cravings may have also been caused, in part, by higher protein intake. Dr. Paul Mabry notes that those of us with long-standing insulin resistance who do the carnivore diet have to be very careful of protein/fat ratios.27 The goal is not to spur excess insulin release with too much protein and not enough fat. I am not sure what was happening with me but I found the cravings tough.
  • Monotony: I definitely felt deprived of flavours and textures, and as time went on I was just less interested in eating meat. It was very easy to skip a meal because at times I simply didn’t hanker for any more flesh. But, on the other hand, shopping was simple and meal prep and clean up was super fast.

The biggest surprises to me were how it nudged my stalled weight a few pounds, the calm gut and the improved skin. The most difficult was the tedium, the surges of body heat, the cravings and my self-imposed feeling of social isolation from the diet.

I thought often of Amber O’Hearn’s comment, “If you can eat a more varied low-carb diet with good results, why wouldn’t you?”

That described me to a T (make that a T-bone!). I didn’t really need to do the diet, so the trade-offs were high. I had no concerning health reason to motivate me; it felt restrictive and limiting. I did not eat out with friends for a whole month. I was glad when my trial was over.

I’m now back eating a low-carb ketogenic diet with plenty of above-ground vegetables. I am happier making many of the delicious Diet Doctor recipes. That way of eating feels more enjoyable, balanced and sustainable to me.

That said, however, I understand better why those with severe or incurable conditions with poor therapeutic options might try carnivore eating. In the absence of any good scientific evidence pro or con, doing their own n=1 trial over a few months might determine if they are likely to experience any benefit.

Short term, it is unlikely that it would do any harm. But as Dr. Naiman notes above, longer periods of zero-carb eating might cause health issues for some people. So it is important that anyone considering a trial should pay close attention to their individual responses. If there’s no improvement over weeks or a few months, it’s likely not helping, and people can feel satisfied returning to a more varied and less restricted low-carb ketogenic diet.

/ Anne Mullens

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  1. This has been shown in both observational studies and trials lasting up to two years:

    Diabetes, Metabolic Syndrome and Obesity 2019: Diet, diabetes status, and personal experiences of individuals with type 2 diabetes who self-selected and followed a low carbohydrate high fat diet [descriptive observational study; weak evidence]

    Frontiers in Endocrinology 2019: Long-term effects of a novel continuous remote care intervention including nutritional ketosis for the management of type 2 diabetes: a 2-year non-randomized clinical trial [non-randomized study; weak evidence]

    Annals of Internal Medicine 2010: Weight and metabolic outcomes after 2 years on a low-carbohydrate versus low-fat diet: a randomized trial [randomized trial; moderate evidence]

    Diabetes, Obesity and Metabolism 2018: Effects of an energy-restricted low-carbohydrate, high unsaturated fat/low saturated fat diet versus a high-carbohydrate, low-fat diet in type 2 diabetes: A 2-year randomized clinical trial [randomized trial; moderate evidence]

  2. [hypothesis and anecdotal report; very weak evidence]

  3. Journal of Glaucoma 2018 Glaucoma as a metabolic optic neuropathy: making the case for nicotinamide treatment in glaucoma [overview article; ungraded]

    Science 2017: Vitamin B3 modulates mitochondrial vulnerability and prevents glaucoma in aged mice   [mouse study; very weak evidence]

  4. [hypothesis and anecdotal report; very weak evidence]

  5. [anecdotal report; very weak evidence]

  6. Journal of Nutrition 2003: The critical role played by animal source foods in human (homo) evolution [overview article; ungraded]

  7. PLoS One 2011: Man the Fat Hunter: The Demise of Homo erectus and the Emergence of a New Hominin Lineage in the Middle Pleistocene (ca. 400 kyr) Levant [evolutionary study; ungraded]

  8. International Journal of Molecular Sciences 2018: The expensive-tissue hypothesis in vertebrates: gut microbiota effect, a review [review article; ungraded]

  9. Nature 2010: Evidence for stone-tool-assisted consumption of animal tissues before 3.39 million years ago at Dikika, Ethiopia [evolutionary study; ungraded] Journal of Human Evolution 2018: The manual pressures of stone tool behaviors and their implications for the evolution of the human hand [evolutionary study; ungraded]

  10. BioOne Complete 2014: An introduction to the isotopic studies of ancient human remains [evolutionary study; ungraded] Journal of Human Evolution 2005: Isotopic evidence for diet and subsistence pattern of the Saint-Césaire I Neanderthal: review and use of a multi-source mixing model [evolutionary study; ungraded]

     

    American Journal of Physical Anthropology: Contributions of biogeochemistry to understanding hominin dietary ecology [evolutionary study; ungraded]

  11. Proceedings of the National Academy of Science (USA) 2009: Isotopic evidence for the diets of European Neanderthals and early modern humans [evolutionary study; ungraded]

  12. [hypotesis not based on clinical evidence article; ungraded]

  13. Journal of the American Medical Association 1929: The effect on human beings of a twelve months’ exclusive meat diet [case study; very weak evidence]

  14. Journal of Biological Chemistry 1930: Clinical Calorimetry: Prolonged meat diets with a study of kidney function and ketosis [case study; very weak evidence]

  15. [very weak evidence]

  16. International Journal of Tryptophan Research 2017: Meat intake and the dose of vitamin B3 – nicotinamide: cause of the causes of disease transitions, health divides, and health futures? [overview article; ungraded]

    International Journal of Tryptophan Research 2017: Meat and nicotinamide: a causal role in human evolution, history, and demographics [overview article; ungraded]

  17. [very weak evidence]

  18. Crohn’s disease:

    International Journal of Case Reports and Images 2016: Crohn’s disease successfully treated with the paleolithic ketogenic diet [case study; very weak evidence]

    Type 1 diabetes:

    International Journal of Case Reports and Images 2014: Type 1 diabetes mellitus successfully managed with the paleolithic ketogenic diet [case study; very weak evidence]

    Reversing pre-cancer:

    Journal of Cancer Research and Treatment 2018: Complete cessation of recurrent cervical intraepithelial neoplasia (CIN) by the paleolithic ketogenic diet: A case report [case study; very weak evidence]

    Malignant cancer:

    J American Journal of Medical Case Reports 2016: Halted progression of soft palate cancer in a patient treated with the paleolithic ketogenic diet alone: A 20-months follow-up [case study; very weak evidence]

    American Journal of Medical Case Reports 2017: Treatment of rectal cancer with the paleolithic ketogenic diet: A 24-months Follow-up [case study; very weak evidence]

  19. [anecdotal experience; very weak evidence]

  20. Clinical Review of Allergy and Immunology 2012: Leaky gut and autoimmune disease [overview article; ungraded]

  21. Clinical and Translational Gastroenterology 2016: Human intestinal barrier function in health and disease  [overview article; ungraded]

    BioMed Central Gastroenterology 2014: Intestinal permeability – a new target for disease prevention and therapy [overview article; ungraded]

  22. Frontiers in Immunology 2017: Leaky gut as a danger signal for autoimmune diseases [overview article; ungraded]

  23. [hypothesis; very weak evidence]

  24. [case study and clinical experience; very weak evidence]

  25. American Journal of Clinical Nutrition 2009: Cancer incidence in vegetarians: results from the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford) [cohort study with HR <2; very weak evidence]

  26. Cancer Causes & Control 2014: Changes in colorectal cancer incidence rates in young and older adults in the United States: what does it tell us about screening [descriptive study; ungraded]

     

    Journal of Gastroenterology & Hepatology 2015: Rising incidence of early-onset colorectal cancer in Australia over two decades: report and review [descriptive study; ungraded]

     

    Preventive Medicine 2017: Increasing colorectal cancer incidence trends among younger adults in Canada [descriptive study; ungraded]

  27. [clinical experience; very weak evidence]