Tag: science

Co-Written by L. Amber O’Hearn and Raphael Sirtoli
Scientifically Reviewed by Sarah Neidler, PhD

The carnivore diet is really very simple. It’s simple to define although there are competing variations, see below. A carnivore diet is a plant-free diet, that typically excludes high carb dairy, so it’s a low or zero carb diet. In the most commonly practiced variation, food is eaten to hunger (ad libitum). Limiting quantity is strongly discouraged, even for fat loss.

In a sense, it’s simple to adhere to. Anecdotally, most people report that after a short adjustment phase, it’s easier to stick to than a low-carb or ketogenic diet because of how the cravings and desire for non-carnivore foods disappear.

It’s simple to do. Carnivores spend far less time thinking about food, planning menus, shopping, or cooking than people usually do on almost any other diet. The carnivore diet is still in the pioneering stages. In other words, there haven’t been any large randomised controlled trials (RCTs) “proving” that “it works” or “it’s healthy” – or that it’s unhealthy. This is true of most diets actually. And even government recommended diets that have been subject to RCTs like DASH (Dietary Approaches to Stop Hypertension) have failed to perform. The big difference here is that carnivore diets at least make sense in evolutionary terms, while the same cannot be said regarding low-fat vegetarian or the DASH diets.

People following the carnivore diet do so because they have seen the results for themselves and because they think the ideas behind it make sense, not because an authority like a doctor or a government agency approved it. It’s smart to avoid arguments by authority generally speaking. This means that carnivore dieters assume full risk and responsibility for their dietary choices, which, of course, everyone should anyway!

Keto vs Paleo vs Carnivore: just a new trend?

There are so many variations of low-carb, keto and paleo diets that it’s hard to keep track. Every time a new discussion group appears, or a new book comes out, the “rules” seem to change. Once you know the basics of these diets, it’s easy to see that most of the variations are just points on the spectrum of some variable (e.g. carb intake) within a basic dietary framework. For example, some keto groups distinguish themselves by what protein levels they think are optimal; the Ketogains coaches and Dr. Ted Naiman advise higher protein intake whilst Dr.Ron Rosedale and low-carb blogger Jimmy Moore advocate a relatively lower one.

At first, the carnivore diet seems like just a low-carb diet on the extremely low end of the carb spectrum—especially since some people call it “ZC” for Zero Carb! But this is a misunderstanding. To appreciate why, let’s look at how these diets are defined and what they are used for. Then we can see why the carnivore diet is a category of its own.

What makes a diet keto?

Keto (ketogenic) diets are very low-carb diets, but just low carb isn’t always enough to make a diet keto. The goal is to maintain a high level of ketosis.Ketosis just means that your blood (and sometimes urine) has a certain level of ketones in it. In simplified terms, it’s a “biomarker” reflecting how much your body is relying on fat for energy. Having a measurable biomarker means it’s an objective fact indicating whether your diet is ketogenic or not. This is unique to ketogenic diets.

This kind of feedback can be very useful. It puts you in control, and gives you something to monitor. It’s not surprising that many engineering and biohacking types are drawn to keto for this reason. Ketone levels are particularly handy, because they are correlated with people’s real goals like fat loss, blood sugar control, and even seizure control in epileptics—not to mention a whole slew of exciting effects that aren’t yet proven in large trials, but seem likely: commonly reported improved cognition and mood cutting-edge increases in life span.

But even the established effects of ketogenic diets don’t correlate perfectly with ketone levels, and so the obsession with ketone levels for their own sake can be a pitfall! There are good reasons to track and good reasons not to, it depends on what you’re trying to achieve.

Ketosis is affected by factors other than diet. You can enhance ketosis by doing aerobic exercise or by intermittently fasting or even by taking MCT oils or ketone supplements. These will give you more leeway, meaning that a person might stay ketogenic by eating less carbs, whereas another might eat more carbs, but make up for it with more exercise.

Like a low-carb diet, though, it doesn’t matter what kind of food you’re eating, as long as you’re in ketosis. You can be a vegetarian and be on a keto diet. You can live on Slim Jims and Diet Coke. With enough coconut oil you could even eat beans and rice and still register ketones. It is both a great strength and a great weakness that you can benefit from ketosis while eating crap.

Of course, Nutrita is all about well-formulated diets, whether that’s carnivore, keto, paleo, low-carb or lacto-ovo vegetarian. But it’s true that if you’re eating in a way that gets you pumping out ketones, you’re on a ketogenic diet.

The trouble with keto

The tragedy is that even though ketosis confers many health benefits, you can end up eating a diet that’s unhealthy in other ways. Then 1 of 2 unfortunate things may happen. They’re really 2 sides of the same coin.

First, you could make unhealthy changes to your diet in an attempt to make it ketogenic. This could cause unhealthy symptoms that lead you to conclude that ketosis is bad for you. For example, you could chronically undereat or eat only from a nutritionally incomplete food source (e.g. high fat keto bars) and suffer protein or nutrient deficiencies. Or you could accidentally start to focus on foods that can build up to intolerable levels. An easy example of this is relying heavily on brassicas (e.g. cabbage and broccoli) which could lead to digestive distress or more rarely thyroid issues.

The second is more subtle. You could be getting great benefit from the ketosis, but this masks the fact that other elements of your diet are still bad for your health. For example, you may have lost 100 lbs (45.5 kg) and no longer have diabetic glucose readings, but you don’t realize that your migraines are getting worse because they’re triggered by the tomatoes you’re having in your salads. Even though you don’t conclude that keto is making your migraines worse, you’re still oblivious to this dietary component, because you think of your diet as extraordinarily healthy. This is why keto isn’t a panacea, ketone levels are not the be-all and end-all of good nutrition.

In short, keto diets can be amazing. And because they are so effective for obesity and diabetes, you can often look the picture of health on a keto diet even while eating a lot of foods that aren’t particularly healthy. Ketosis alone is only one factor in a healthy diet.

The Paleo diet

The Paleo diet is often misrepresented as trying to replicate the paleolithic lifestyle in a clueless way. That’s a strawman and really not the point. We don’t want to throw away all the wonders of modern life!

The Paleo diet is based on a powerful principle: many of the diseases and health problems the world is now experiencing come from a mismatch between the environment we mostly evolved in and the current environment. Specifically, our bodies just aren’t made to cope with the food “environment” that we now subject ourselves to day after day.

So the idea is to eat only foods with qualities we’re adapted to handle well. What does that mean in practice? Normal insulin and blood glucose responses, no gut dysbiosis, no chronic inflammation, an acceptable level of anti-nutrients, and foods with the right ratio of bioavailable nutrients. Those foods happen to be those that were available during most of our species’ existence, much of which occurred during the ice-age. Critically, grain agriculture is only about 10,000 to 12,000 years old. From an evolutionary standpoint this is a minuscule amount of time.

The Paleo DietTM argues that we’re not fully adapted to eating grains and legumes in any significant quantities, let alone food “products” like seed (“vegetable”) oils that were introduced at scale only in the last century (e.g. soybean oil, canola oil, sunflower oil). Kurt Harris, a Paleo blogger from the 2000s, used to call these foods “Neolithic Agents of Disease”. I almost want to start a band with that name.

Besides the principle of avoiding foods that weren’t available, there are empirical benefits. Many people who try it actually feel better. There is a scientific explanation for this. Grains and legumes have high levels of plant compounds called lectins (and others) that have been implicated in some kinds of diseases, especially autoimmune ones. This may explain why so many people feel better on a Paleo diet than they did before.

The trouble with Paleo

\One problem for the Paleo Diet is deciding which foods actually qualify. Most adherents exclude dairy products, grains, legumes, and seed oils. They accept all sorts of animal foods, vegetables, fruits, nuts, and seeds, as fair game on Paleo, After all, we had access to all of those, right?

The problem comes in when you realise that the forms of many of these foods have been drastically altered by selective breeding.Fruit we see in our supermarkets today are typically much larger, sweeter, and juicier than the seedy, grainy, fibrous fruits they came from. Think crab apples! Most of the huge variety of vegetables we routinely buy also came from a much smaller selection of edible plants and have changed a great deal from their original forms. As a rule of thumb, this is why Nutrita recommends berries over bananas; berries are closer to their natural, low-sugar nutrient dense form than the high-sugar nutrient poor modern banana.

Moreover, all plants have some amount of lectins which is why humans have a remarkable ability to handle such anti-nutrients. However, many people nowadays still get into trouble with some of these plant compounds. Some versions of Paleo exclude nightshades (e.g. tomatoes, eggplant, potatoes, peppers), theoretically because they come from the “New World” (America) and therefore we wouldn’t be adapted to them specifically; practically though, it’s because they seem to negatively affect people with autoimmune diseases. But the fact is that all plants have chemical defenses that can potentially worsen disease, and so these lines begin to seem arbitrary.

As a side note, these plant compounds can also be valuable for people with diseases. In fact, most pharmaceutical drugs or supplements derive from natural plant compounds, like metformin for instance. There’s an argument to be made that plant compounds are more useful in drug form than as the basis of our diet.

A more serious problem comes from quantity, not quality. If the Paleo Diet is defined only by what you don’t eat, then many different diets qualify as Paleo, including very low and high-carb diets. As a reductio ad absurdum example, a diet of only fruit is just as “Paleo” as a diet of only meat, even though they’d have very different effects; you’d be malnourished as a fruitarian and well nourished as a carnivore.

If you’re going to argue that we shouldn’t eat grains, because we almost never ate them before agriculture, it would seem hard to justify eating fruit every day, when it would have been seasonal, or eating nuts faster than they could have been collected and shelled. There are good reasons to believe that our diets during the Paleolithic era were in fact quite limited in most plants and especially in carbs. If this is true, then to match our evolutionary environment we should follow these proportions as well. But how do we determine when a dietary practice violates the Paleolithic environment in a way that matters and not just a coincidental way?

In the extreme worst case, a Paleo diet can be mangled to look just like a Standard American Diet (SAD); take out the beans and grains, replacing the typical bread, pasta and cake with atypical bread, pasta and cake made from expensive substitute flours. While this can still be an improvement, it really doesn’t do the concept justice.

The carnivore diet

The carnivore diet is in some ways more like a Paleo diet than a keto diet. For one thing, it’s defined by what foods you don’t eat. If you’re on the carnivore diet you don’t eat plants. Since meat is on the Paleo diet, the carnivore diet could be seen as a special case of the Paleo diet. In fact, many advocates of the carnivore diet consider it to be the “true” Paleo diet, because they believe that plants were eaten infrequently as a last resort through at least some significant periods of our shared history.

Obviously, not all Paleo advocates agree with this. Some don’t even think that the Paleo diet was generally low-carb! They think we ate enough fruit and starchy tubers to stay out of ketosis. Others of us don’t find that plausible at all.

Paleo dieters often eat too many carbs to be ketogenic, sometimes purposely staying out of ketosis! People on the carnivore diet tend to be in ketosis (more below). So, the carnivore diet is more ketogenic than a typical Paleo diet is.The carnivore diet tends to avoid the above pitfalls of keto and Paleo, while capturing many of the benefits of both. Unlike keto, it is almost always composed of high quality foods, and, perhaps surprisingly, is likely to be nutritionally complete even without planning.

Like Paleo, it avoids all the plant toxins in grains, legumes, and nightshades, and even vegetable oils, and goes beyond that by cutting out all potentially noxious plant compounds, too. However, it’s not without controversy and criticism. Some of the controversy comes from within and is best represented by the two major variations.

“ZC” — “typical” carnivore

This is the version recently popularized by…

Dr. Shawn Baker
Jordan and Mikhaila Peterson
Decade-plus-long support groups led by pioneers including Charles Washington and Dana Spencer
The life and writings of Grateful Dead sound engineer, Owsley “the Bear” Stanley
Arctic explorer Vilhjalmur Stefansson and many others

The diet is more or less exactly what you would be left with if you took standard American fare and removed the plants from it: a lot of steak and burgers, some chicken and pork, bacon, eggs, fish, cheese, and cream, and not much else. Fatty cuts are recommended to avoid “rabbit starvation” — the illness that can develop if you try to subsist on only protein and insufficient calories from fat or carbs. Counting specific fat and protein targets isn’t usually part of the carnivore ethos. Spices, sauces, and sweeteners are strongly discouraged. Water is the recommended drink, although many practising carnivores drink coffee.

Coffee seems widely tolerated and is considered a drug more than a food, so it usually gets a pass, although being a plant extract, it’s not promoted. One could (and some do) make similar arguments about 100% dark chocolate or about alcohol. However, note that chocolate does contain more fibre than coffee, which may cause problems in some people. Alcohol is caloric, interferes with ketosis, and is similar to sugar in its effect on the liver. All of these are borderline cases and should be treated with care. In particular, caffeine can potentially trigger hypomania in those with a susceptibility to bipolar disorder.

Food is never limited. You eat until you are “Thanksgiving full” and then don’t eat again until you are hungry. If you think you are hungry, but wouldn’t be satisfied eating more meat, this is considered cravings or false hunger. Cravings typically subside within a few days or a week.

Ketosis is not a goal on ZC. It’s accepted that most will be in ketosis, although usually not as “deep” as sought by those on keto. Regardless, many if not most of the health benefits don’t seem to depend on ketosis at all, and are equally experienced by those who report low or no ketones.

The “PKD” (Paleolithic Ketogenic Diet) and other less typical variants

Although it’s less popular in America, some carnivores do eat organ meats. In some cases it’s because they’re culturally familiar to them; in many places those items are still typically on the menu even on standard diets. But that’s not the only reason. Some carnivores are concerned about nutrient deficiencies that should theoretically occur on a ZC diet. They notice that hunter-gatherer societies, and even western societies until very recently usually ate “nose-to-tail”. They reason that it is probably wise to continue to do so.

It is notable that no such deficiencies have been reported among ZC adherents. For instance, Dr.Tro Kalayjian never found a folate deficiency in his carnivore patients. Since our gut microbes can make folate, maybe they adapt to making more. Many believe that the absence of plant anti-nutrients (more below), and the mildly ketogenic nature of the diet reduces the need for several nutrients. This is likely to be true, but would require extensive experiments to verify. Trying to induce nutrient deficiencies might not pass ethics committees, so the answers may be a long time coming (if researchers were even interested).

Some carnivores are persuaded enough by studies on ketosis and their own experiences with the ketogenic diets that they strive for ketosis even within the carnivore diet. Indeed, this can be an extremely powerful combination! If you eat a ketogenic diet made up of only animal foods. you might say you’re following KetoAF: a KETOgenic Animal Food diet. The ketogenic approach is also taken on the PKD.

The PKD is a specific, trademarked diet used by the International Center for Medical Nutritional Intervention (formerly Paleomedicina). The strictest form it excludes all plants and is used in their clinic to treat chronic diseases. Unlike ZC, high ketosis is an integral part of their dietary intervention, and so protein and calories are limited and high fat intake is required. Organ meats must be eaten daily. Meat must be sourced to avoid additives and problematic chemicals. A typical meal might consist of brain and egg omelet, slices of cured pork fat, and a smaller portion of beef or pork meat.

Ketosis

There is a lot of confusion about the effect of protein on ketosis! Your body always needs some amount of glucose, because there are some cells that have to use it, and can’t use fat or ketones. This is not a problem on a keto diet, because the liver makes glucose out of protein in a process called gluconeogenesis. Since protein can be made into glucose, some people mistakenly believe that if you eat more protein than you absolutely need the rest will automatically be made into glucose, “kicking you out” of ketosis.

The worries over protein are overblown. Most people can eat a lot more protein than commonly assumed and stay in ketosis. But the fact is that if you eat enough protein, at some point, ketosis will drop down (not necessarily ‘kicking you out’ entirely). If you are a recovering diabetic, this threshold is likely to be lower than if you aren’t.

It’s been demonstrated repeatedly that people can stay in ketosis even when they consume as much as 50 to 100% more protein than the calculated minimum requirements. So eating higher protein is not usually a problem for ketosis. Still, studies in other people are only able to give you a range of expectation, they can’t tell you exactly what will happen to you. The only way to know your individual protein-ketosis tolerance is to test it.

One common anecdotal finding on carnivore diets is that you can get the same level of ketosis with a higher level of protein! Like almost every aspect of this diet, this finding is too new to have been studied systematically. One theory as to why this happens is just from the carb count itself. If you are eating no carbohydrates whatsoever, that means you have to make more from protein than you would have had to if you ate even a few grams of carbohydrate. Moreover, only about half of the amino acids in meat protein can even be used to make glucose. So for example, as a rough calculation, if you used to eat 20 g carbs on keto, and then you eat none, that frees up about 40 g of extra protein you could eat just to replace that carbohydrate. The actual mechanism may have more to do with insulin (or something else) than with carbohydrates. We don’t know yet!

Are there any dangers to carnivore diets?

Due to the current lack of randomized controlled trials (RCTs) specifically looking at carnivore diets, data is lacking about their potential benefit or harm. This leaves us with lots of anecdotal evidence (i.e. N = 1’s).

Interestingly, a lot of the positive anecdotes revolve around improved mood and digestion, yet most of the negative ones involve digestive discomfort, which is somewhat contradictory.

Some people are very concerned about the prospect of not eating plants. After all, they say, “humans are omnivores”, and that means we need to eat both plants and meat in order to be healthy. Besides, “everyone knows” that we need several servings of fruits and vegetables a day for optimal health. These ideas are confused, so let’s get them straight.

Humans: carnivores or omnivores?

Depending on how you define these words, either one could be correct. But if you’re not careful about what you mean, the choice can lead to different conclusions.

If you use the word omnivore to mean an animal that eats both plants and animals, and a carnivore to mean an animal that never eats plants, you end up in a world where basically all animals are omnivores. Almost all animals consume some plants and some animals, even classical herbivores like deer, and top carnivores like cats. And if all animals are omnivores, then suddenly the word omnivore isn’t very useful anymore. What we really want to know when we use these words is not so much what an animal sometimes does or can do, but what they need and don’t need, and what they are physiologically optimised for.

Humans need meat

If you use the standard definition of carnivore meaning an animal that must eat meat to be healthy, regardless of whether they can or do also eat plants, then humans are definitely carnivores. In fact, most of the animals we think of when we think of carnivores, regularly eat some plants. There is a scale of carnivory from hypocarnivores, like bears, to hypercarnivores like felines, based on how much plant matter they eat in practice. Nevertheless, all of these animals need meat to thrive, and humans do too.

Asking people what they ate is a very unreliable way of knowing what they actually eat. A better method used by paleoanthropologists who simply can’t ask the question, involves using skeletal remains. Those bones accumulate special kinds of atoms, called ‘stable isotopes’, serving as a sort of dietary signature. How is that? Because plants contain different distributions of isotopes than animals do, and we accumulate those different isotope patterns depending on what we eat. Amazingly, we can know more than just ‘plants vs animals’, we can also distinguish between different kinds of plants, and between marine versus terrestrial animals. So what does the stable isotope evidence tell us about humans?

Humans were as carnivorous, if not more so than wolves and hyenas! We also seemed to eat more terrestrial than marine animals.

It’s mainstream knowledge amongst paleoanthropologists to classify humans as carnivores. This, however, doesn’t mean humans never consumed plants – quite the opposite actually. Studies showing humans were the main predators for large woolly mammoths and thus extensively relied on them as a food source, also provide evidence that humans likely consumed plants in sufficiently large quantities to reflect omnivory. How much of these plants were eaten rather than used medicinally is debatable, but what isn’t is that humans are obligate carnivores but facultative omnivores. This definition reflects a real, physiological need for meat (that plants alone cannot satisfy) as well as our outstanding ability to also make good use of plants whether for food or medicine.

Some people mistakenly think that because we are great apes, and our closest non-human relatives, chimps and gorillas, are essentially herbivorous, that we should be herbivorous, too. But this ignores vast changes in physiology that we underwent over the course of evolution in the homo line. Besides our bizarre looking hairlessness, there are two aspects of our anatomy that make us drastically different from other great apes: our brains and our guts.

Our guts demonstrate that we are not herbivores for the simple reason that herbivores get most of their energy indirectly from fat. For instance, Western Lowland gorillas derive 57% of their energy from fat, specifically short chain fatty acids (SCFAs)! Yes, from fat! Fat is what a vertebrate gets when it eats fiber and lets the microbes in the gut digest it. Vertebrates, including all mammals, can’t digest fiber themselves, but if they are specialised as herbivores, they have extra large guts that hold microbes to do that for them. The resulting products of microbial digestion, SCFAs, are what provide a herbivore with energy. Humans have lost all but a very small fraction of the spaces in the intestinal tract where microbes can live and perform this function. Because of this, we have very limited ability to consume fiber. If we try to eat more than our microbes have the capacity to process, at best it just comes through the other end. At worst it causes bloating, discomfort, and possibly even tears or blockages.

So humans can’t use that ‘large fermentation chamber’ strategy for getting energy. For the last +2 million years, starting with the homo genus. we’ve had increasingly shrunken guts and expanded brains. For the vast majority of this time, we had limited access to digestible carbohydrates, because we had neither grain agriculture nor regular use of fire with which to break down starches from tubers. Fire most likely emerged around 400,000 to 300,000 years ago. From an energy standpoint alone, we needed the protein and fat from scavenged and hunted animals.

But when you take into account the needs of a healthy brain, all doubt must be surrendered. Not only does a human brain require large amounts of energy to grow and function, but it needs very specific nutrients in quantities that could only have come by predominantly eating animal foods. These include essential fatty acids, DHA and arachidonic acid, minerals, like iron, iodine, zinc, and selenium, vitamins A, D, and various B vitamins, especially vitamin B12 which doesn’t exist in plant foods at all. Even now, with access to supplements, vegans have to be very careful if they want to provide their brains with everything that’s needed. Not only did humans hunt, as a matter of observed historical fact, but it is believed that without meat, we would never have been able to evolve with the brains we did.

Don’t humans need plants?

It’s one thing to say that humans need to include meat, but quite another to say that we don’t need to include plants. Aren’t plants where we get all of our micronutrients? As I just alluded to above, meat is actually an excellent source of macro and micronutrients. Not only can we get everything we need from animal foods, but it turns out that in almost every case, animal-sourced foods are better sources. A physiologically essential compound found only in plants has yet to be discovered.

Most of the RDAs can be easily be met on a carnivore diet (especially if you are willing to eat liver, which is perhaps the most nutrient dense food on the planet), but there are a few micronutrients that are more abundant in plant foods. It’s actually challenging to meet the RDA without them or a supplement.

This is potentially a serious issue, since nutrient deficiencies can lead to serious problems. Here again, I want to emphasize that those on this diet choose what level of risk they are comfortable with knowing that large studies have not been conducted. So they make it their responsibility to be aware of potential issues, and to make only those tradeoffs they feel good about.

Nonetheless, the theoretical deficiencies in question would take time to develop, if they developed at all. This means that you have time to try a carnivorous diet without supplements if you want so you can tell what it feels like in the short term without the potential confounding factor of taking them. Then you will be able to introduce supplements if you decide to stick with the diet for a longer term, and if that seems more sensible to you.

The interesting thing is that there are many people who have been following this diet for months, years, and in some cases over a decade without supplementation and with no signs of deficiencies. While it’s possible that these people are unusual or even dishonest, it’s very likely that nutrient needs actually change on this diet, and that the RDAs simply don’t translate. The degree to which this is true, changes the degree to which the need for plants can be argued.

Anti-nutrients and metabolic changes

Plants don’t just contribute nutrients, they contribute anti-nutrients, factors that actually make food less nutritious. Remember, the RDAs were established in the context of a high carb, grain based diet. It’s been shown that the consumption of grains, nuts, beans, and other seeds interferes with the absorption of certain minerals, particularly zinc, but also others, including calcium, magnesium, chromium, iron and manganese. This effect is largely due to phytates, anti-nutrients particularly high in the seeds of many plants. It’s thought to be a protective mechanism for the plant’s reproduction. This means that RDAs for these minerals are greatly overestimated for someone who doesn’t eat those foods.

The other reason that many RDAs are likely to be higher than what we need on the carnivore diet, comes just from it being more ketogenic. On a ketogenic diet, you get much more energy from fat and ketones than you do from glucose. It turns out that much of our requirement for micronutrients is because they are used in chemical processes for getting energy. This can have effects on many scales.

For example, levels of the thyroid hormone, T3, depend on how much glucose you use for energy. If you run on fat you make less T3. T3 is made out of iodine, and so the need for iodine strongly depends on how much glucose you use as energy, and should be expected to be lower on a carnivore diet. So it’s almost certain that people on plant-free, ketogenic diets need less of some nutrients than the RDA insists. The trouble is we don’t know how much less, because the relevant experiments haven’t been done.

Let’s consider as examples 3 micronutrients that people sometimes worry about when considering a plant-free diet: the electrolytes potassium and magnesium, and vitamin C.

The process of adapting to a ketogenic diet, carnivorous or not, involves an initial stage of water losses, that sometimes lead to temporary losses in potassium, sodium, and magnesium. For this reason, many clinicians recommend replacing these during this adaptation phase. What about after that?

Potassium

Potassium is a mineral that is abundant in the body. It’s necessary for life, so of course, meat contains it, but not in the quantities found in fruits and vegetables. Do we really need the RDA of 4.7 g a day?

The Institute of Medicine (IOM) determines RDAs, and publishes documents explaining how they came up with them. In their potassium chapter (as in several others) they tell us the RDA was hard to determine. In fact they explicitly say that there is insufficient data to make an RDA for potassium, because they couldn’t find enough experiments to prove a particular amount would reduce the effects they were concerned about: high blood pressure, kidney stones and possibly bone loss. Instead they determined adequate intake based in large part on epidemiological studies that correlated potassium intakes with these issues in a high-carb, plant-based population. By the way, the mobile app Nutrita is the only one that takes this into account when displaying RDAs or detailing the nutrient density of foods.

One factor they did cite as affecting potassium balance was fibre intake, with more fibre resulting in more potassium passing through undigested. Another factor they cited was sodium intake. Basically, the more salt you consume, the more potassium you need to balance it, so if you add salt to your carnivore diet, you may be more likely to have inadequate potassium than someone who doesn’t.

Researcher Stephen Phinney has pointed out that preserving lean mass requires adequate potassium. In his review Ketogenic Diets and Physical Performance, he reported on male cyclists in a metabolic ward on a Ketogenic diet. Through a combination of meat and supplements, the subjects were taking 2 to 3g of potassium a day. Although there were some initial losses during adaptation, after 4 weeks, potassium levels stabilised. This is less than the RDA by almost half.

Beef and pork contain about 300 to 400 mg of potassium per 100 g. So as a rough estimate, you’d need about 1.5 to 2 pounds (0.7 to 1 kg) of meat a day to reach the level of potassium in that experiment. Most carnivores do eat this much in practice. Moreover, most carnivores are not losing lean mass, which would be an expected result of potassium deficiency.

Unlike some minerals, like magnesium, which can be depleted in tissues, but still look normal from blood levels, potassium deficiency tends to be reflected more quickly in blood levels. So this can also be tested for.

Magnesium

Once again, as with other minerals, magnesium absorption is affected by fibre and by phytates. The first two sections in the IOM’s chapter on magnesium requirements talk about how magnesium absorption is very negatively affected by fibre, phytates, and inadequate levels of protein. Since none of these are a concern on a carnivore diet, we should expect that our need for magnesium intake is considerably less than average.

And again, there was not a lot of data available to examine what the real need is. Most of the experiments used to determine adequate levels were simply the levels found in self-selected control diets in experiments designed to deliberately cause magnesium depletion. That is, they took people on their own regular diets and verified that they weren’t excreting more magnesium than they were taking in, and then experimentally induced magnesium deficiencies—but not by decreasing magnesium intake!

How did they induce magnesium deficiencies? By adding extra fiber or oxalates. Oxalates are another form of anti-nutrient that’s high in many plants, including many leafy greens. The IOM also listed some experiments where subjects were in positive magnesium balance even with only about two thirds of the current RDA for magnesium. This only happened with higher protein intakes, but these higher intakes were still less than 75 g/day. In other words, the current recommendation for magnesium is largely based on the amount you would need to make up for a typical western diet if it had a lot of fiber or high oxalate plants in it, or not enough protein.

If that weren’t enough to cast doubt, magnesium is also highly involved in carbohydrate metabolism. Diabetes depletes magnesium stores, as does glucose itself. Having lower insulin and glucose may reduce the need for magnesium, but it’s an empirical question. So once again, carnivores are pioneers, and we can’t know all the answers, but we can be quite confident they won’t be the same answers as high carb dieters are going to get.

How would you know you if you had a magnesium deficiency? Since magnesium deficiency isn’t normally reflected in blood levels, it’s harder to tell if you have it than just taking a blood test. Because of that some people fear that a carnivore diet could be silently inducing a subclinical magnesium deficiency.

On the other hand, it turns out that many people in the general population test low for magnesium blood levels [37]. Not only that, but some researchers have called for raising the reference range, largely because more people at the bottom half of the range have been found to have symptoms of metabolic syndrome. This spawns 2 questions.

First, do people on carnivore diets tend to have magnesium levels below normal or in the lower half of normal? The answer to that seems to be no. In a study of 50 patients following a plant-free diet, only one of them was below reference range, and even then just barely. Given the previous findings, this means they had less occurrence of low magnesium than the general population, which should be surprising, since the majority of them were being treated for diseases that typically are associated with low blood magnesium. Although “before” values were not published, it seems reasonable to guess that in many cases magnesium levels were actually restored by the diet.

Second, even if people on carnivorous diets did in fact have lower blood levels of magnesium, would that put them at risk for metabolic syndrome? The answer to that might also be no, given that low carb diets reliably reduce markers of metabolic syndrome. However, it seems more likely that carnivorous dieters would have normal levels of magnesium, despite lower intake.

In fact, you could turn the reasoning on its head. Since magnesium deficiency is associated with metabolic syndrome and inflammation, and since carnivorous diets tend to reverse symptoms of metabolic syndrome, then carnivorous diets are likely to result in adequate magnesium levels. This is speculative, but it’s not more speculative than the worry about subclinical deficiencies.

So if you are worried about magnesium levels, you could check your blood levels and see where you are in the range. Another way to tell is by calcium and potassium levels. It turns out that at moderate levels of deficiency, both calcium and potassium will often be low in the blood. Early signs of a serious deficiency would result in serious symptoms, like “loss of appetite, nausea, vomiting, fatigue, and weakness […] As magnesium deficiency worsens, numbness, tingling, muscle contractions and cramps, seizures, personality changes, abnormal heart beat, and coronary spasms can occur”.

Vitamin C

Vitamin C is another nutrient that some people worry about on carnivore diets. I’ve written about the science of vitamin C needs in depth before. The worry arises because it’s one of the few nutrients that are actually much more abundant in plants foods than in meat. And the RDA is hard to meet on meat alone. Despite that, meat has been known since the times of early Arctic explorers specifically for its ability to cure scurvy, the disease that results from lack of vitamin C.

Adding to the confusion, the USDA database lists beef, pork and bone marrow as having no vitamin C, even though that isn’t technically true. The amount of vitamin C in those meats is, in fact, probably enough to combat scurvy if it’s eaten in the high amounts most carnivores do, and if it’s not overcooked (cooking destroys vitamin C). Anecdotally, many long term carnivores have gone for years without supplemental vitamin C and show no signs of scurvy, which should take only a couple of months to appear.

But the RDA for vitamin C is way higher than the small amount needed to prevent scurvy. Should we be concerned? One reason many carnivores aren’t concerned is because the remainder of the RDA is based on speculative reasoning about antioxidants. Oxidation is a natural process that’s happening continuously in the body. Like everything else, though, it’s a matter of balance. When oxidation is perfectly offset by anti-oxidation, life proceeds normally. But when oxidation gets out of proportion, disease happens.

Vitamin C is an antioxidant, but it’s not the only antioxidant, and it’s not even one of the most important ones. The most important ones are those we make ourselves, including uric acid, and glutathione. There have been experiments showing that, in other animals, sufficient glutathione prevents vitamin C deficiency by sparing its use. Glutathione may be higher on Ketogenic diets and its precursors – the building blocks used to build it – are abundant in meat.

Moreover, the speculation behind the need for extra vitamin C is based largely on the hope that its antioxidant properties might help with heart disease and diabetes—in other words metabolic syndrome diseases. I say hope, because study results are mixed and inconclusive. The therapeutic effect of a low carb diet on markers of metabolic syndrome greatly outweighs any observed effect of vitamin C on them.

Also, ironically, one of the greatest drivers of oxidative stress is glucose. Further, glucose actually competes with vitamin C for uptake in cells, meaning that lower blood sugar increases the availability of whatever vitamin C is there. These reasons might explain why we don’t so far see any negative health consequences of lower vitamin C intake in carnivores.

Vitamin C helps us form collagen, a crucial component of functional arteries and youthful skin. It also helps synthesize L-carnitine, a compound that helps us burn fat by transporting fats into our mitochondria. By eating a carnitine rich diet we’ll have less of a need for vitamin C to synthesize it, thus freeing more of it for collagen synthesis and other crucial processes. What foods are highest in carnitine? Animal foods of course! This may be one way carnivore diets are vitamin C sparing. I wrote about these vitamin C needs in the context of a carnivore diet in more depth here.

Finally, I’ll just mention liver again. Liver, especially chicken liver, is by far the best animal source of vitamin C. Eating just a couple ounces a day would more than double a typical non-liver eating carnivore’s vitamin C intake.

Meat is very high in most nutrients, and those that are harder to get with meat are likely to be needed in lower quantities than generally believed. Given this fact, many carnivores skip the supplements. Others continue to take ones that they are worried about. It’s very much a personal choice. Note that taking supplements is not without risks, as some supplements have been shown in trials to actually worsen health outcomes.

Won’t the carnivore diet leave me fiber deficient?

Fiber has never been shown to be an essential component of the human diet. Indeed there have been societies such as the Inuit and Mongolians that ate only small infrequent amounts of plants, and they were not unhealthy.

It’s interesting that over the century various reasons have been proposed for why fibre is crucial and yet none of them has ever been proven. Most of the time, they simply aren’t relevant. For example, people defending fibre will often bring up studies comparing high carb diets, with more or less of the starch and sugar being replaced with fibre. Inevitably, the higher fiber diets are better for glucose control or other health outcomes. It’s not hard to see that these studies say nothing about diets that didn’t have high levels of starch or sugar in the first place.

People tend to think fiber is the crucial element in plants responsible for reducing blood glucose and insulin excursions, but this is wrong! It’s been known that fiber is not responsible since the 1980s when research giant Gerald Reaven conducted controlled studies demonstrating this. What actually seems to matter is the state or quality of the starch networks, meaning if the starch network is refined (i.e. made into flour) then this worsens metabolic responses compared to if the starch networks are intact (e.g. potato vs potato flour). It just so happens that fiber is also present when the potato isn’t made into potato flour.

More generally, since fiber tends to be present only when the starch network is unrefined, dietary epidemiological studies will detect fiber as a signal of reduced refined carbs. So if you ever see an epidemiological study claiming that fiber is correlated to better health outcomes, this is a likely explanation for the finding.

But what about gut health? Shouldn’t fiber help with idiopathic constipation (i.e. constipation with no known cause)? Apparently not. Singaporean researchers found that “patients who stopped or reduced dietary fiber had significant improvement in their symptoms while those who continued on a high fiber diet had no change”. They conclude that “ Idiopathic constipation and its associated symptoms can be effectively reduced by stopping or even lowering the intake of dietary fiber”. It seems like the carnivore diet’s lack of plant fiber isn’t obviously harmful – although this doesn’t entail that any amount of fiber more than zero is bad.

In recent years, claims have shifted toward ideas about colon health. The idea is that because fiber is fermented into short chain fatty acids (SCFAs), and because SCFAs are readily used for energy by the colon, and because one SCFA, butyrate, has positive effects on colon health when it’s metabolised, that therefore we need fiber to keep our colons healthy. There are many issues with this chain of reasoning.

One is that fiber isn’t the only source of SCFAs. We can, and do, make them out of proteins as well. Second, just because a cell uses something for energy doesn’t mean it’s necessarily the best source of energy. Alcohol is readily used in the bloodstream, above other sources. That doesn’t make it good. Third, the most important metabolite of butyrate is a ketone body, D- beta-hydroxybutyrate, and it’s not clear how much of the positive effects of butyrate would be met just as well by a Ketogenic diet (see my in-depth blog post on this).

Another relevant observation is that one specific type of bacteria, Akkermansia Muciniphila, is increased on Ketogenic diets and when fasting (suggesting it isn’t from any plant foods consumed on Ketogenic diets). This bacteria is widely held to be beneficial, because it correlates inversely with metabolic syndrome. Giving it to mice even delays the development of obesity and insulin resistance. These bacteria live right in the mucosal layer of the colon feeding on the mucous and in turn producing butyrate. So it’s quite plausible that a ketogenic diet increases the availability of butyrate to the colon due to bacteria, but not the ones that make it out of plant fiber.

It makes very little sense to develop a theory of what a healthy gut biome looks like by suggesting it should match the biome of healthy people, and then to turn around and reject a diet that improves someone’s health because the biome doesn’t match your previous data. Until we know a lot more, a healthy gut biome should be defined as the gut biome of a healthy person.

While none of these points prove that we wouldn’t benefit from more fibre, they point out weaknesses in the pro-fiber arguments. The fibre-for-the-colon arguments are largely speculative. This is another area where some basic research on outcomes in carnivorous diets would be very helpful. Certainly many of the people currently enjoying a carnivore diet are doing it specifically because the lack of fibre reduces inflammation in the colon.

And this brings us to the crux of the carnivore experience. Why on earth would you do it, anyway?

Can a carnivore diet be healthy?

The main benefits that draw people to carnivorous diets and keep them there are not benefits that are currently supported by studies. That is, they are evident in anecdotal reports. But the reports share similarities and are growing by the day.

The most commonly reported effects of this diet are improvements in the following:

Digestion, including from those who were suffering from IBS, IBD or Crohn’s Autoimmune conditions, including asthma, arthritis and psoriasis Skin conditions, including rosacea, eczema and keratosis, Mood disorders, including depression, anxiety, schizophrenia and bipolar disorder, Diabetes, obesity and pathological insulin resistance more generally What’s the current science on the carnivore diet?

Very few studies have been conducted specifically with plant free diets. The International Center for Medical Nutritional Intervention has published several case studies for Crohn’s, Type 1 and Type 2 diabetes, and cancer.

Are carnivores just as crazy as vegans?

Some people see this diet and immediately think that it is rooted in the same kind of extremism as veganism, but the two are quite different. It should be noted that veganism has its roots in religion, unlike carnivory, and this matters. The most prominent and vocal vegans are vegans for reasons other than health. They are striving for an ideal that has no empirical basis, only a value judgment. To this kind of vegan, eating animals is morally wrong and therefore any exception to it is a moral transgression. This means that the more you approach the ideal the better person you are. Just like other morally based systems of thought, it often leads to outrage about the behaviour of others, and political action to try to control this, sometimes including violence and vandalism.

The carnivore diet has a sound evolutionary basis. It’s based in empiricism and practical concerns. The “purest” version of a carnivore diet is adopted for a trial as a baseline, to determine whether and to what degree plants are causing negative reactions in someone’s health. Purity here refers to a well- controlled scientific experiment, unlike purity in the vegan context which is a moral judgment. Foods are avoided based on a cost-benefit analysis informed by personal experiment. If someone decides to eat something they desire that causes them pain or disease symptoms, this is not considered an immoral act, nor anyone else’s business.

There are certainly vegans who are motivated by health rather than ethics. This kind of vegan is much more similar to a carnivore, because his or her beliefs are rooted in a combination of their interpretation of the science and personal experience. And they are similar, too, in that they are willing to take lengths for their health that cause them social inconvenience.

We both stand out socially as extreme, in the sense that many common foods are completely avoided. However, the vegan has much more social support today than ever before. Many restaurants offer vegan options, and everyone is familiar with the diet. Veganism may be viewed as extreme, but it is generally held only to be an extreme version of an accepted point of view. Plant-based diets are in vogue, even among those who recognize that humans need some animal foods for health.

Ironically, a vegan diet is much more extreme from an anthropological standpoint than a carnivore diet. There has never been a multi-generational society that is even close to vegan, whereas there have been multiple societies that ate plants only infrequently. This is, of course, for physiological reasons, as discussed above. Animal sourced food is an evolved need for humans.

This guide is focused on the human health aspects of the diet, but it’s worth mentioning concerns about the effects of such a diet on the environment. We must prioritise human health. Allowing humans to be sick for the sake of other animals strikes us as ethically questionable. That said, we would still like to treat other animals and the environment with as much care as possible. There is no way for humans to live without making some impact on their environment. Vegetarian food crops like soy, wheat, and corn are not sustainable alternatives to meat. They devastate ecosystems and animals living in them. Fortunately, despite popular opinion, livestock production can be compatible with a healthy planet. Interested readers should delve into holistic management initiatives and regenerative agriculture for more information. It is in everyone’s best interest to find ways to make the healthiest food as sustainable as possible, and we would always advocate for the respect and best treatment of all living things.

Conclusion

The carnivore diet is both new and old. It’s new in the sense that it has gained attention on social media these last 10 years, with a steep uptick in the last 5. In another sense, it’s truly old because low-carb diets have been the default diet for humans throughout their evolutionary history. What it certainly is not, is ‘just a fad’.

Much remains to be discovered about how this way of eating impacts our health, but it’s certainly worth a try if you’re struggling with autoimmune diseases, obesity, diabetes or psychiatric issues. Going on a carnivore diet as a short-term experiment is reasonable and safe, albeit socially challenging.

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