Humans have evolved to be able to digest all manner of food items, from fruits and vegetables to animal products. Debate continues about what constitutes the best ratio of various types of food to support optimal human health, but a new entrant into the diet scene suggests that all plants are suspect and we should embrace a meat-only diet for improved physical well-being.
This so-called carnivore diet is a “zero-carbohydrate diet and an extreme version of the keto diet,” says Hollie Zammit, a registered dietitian with Orlando Health in Florida.
The carnivore diet “consists of consuming only animal products,” says New York City-based registered dietitian Jamie Feit of Jamie Feit Nutrition LLC. “It’s basically eating eggs and bacon for breakfast, a steak for lunch and a cheeseburger (without the bun) and bacon for dinner. There’s no gray area and no leeway for adding additional food groups.”
If you’re following the carnivore diet closely, you are only allowed to eat foods that come from an animal, which means you’ll take in zero carbohydrates, explains Dana Ellis Hunnes, a senior clinical dietitian at UCLA Medical Center, assistant professor at UCLA Fielding School of Public Health and author of “Recipe For Survival.”
Proponents of the diet say it can help you avoid or reverse common ailments such as diabetes, obesity and autoimmune diseases. But many nutritionists, including Hunnes, pan the approach. “It’s not suited for anyone except for a lion, tiger or wolf. It is dangerous for humans to eat this way and is terrible for our microbiome, heart health and the environment,” she says.
[Read: Low-Carb Diets vs. Keto Diet: What’s the Difference?]
However, there are a growing number of ardent fans of the diet. One of its primary advocates is Dr. Paul Saladino, a physician in private practice in San Diego and author of “The Carnivore Code: Unlocking the Secrets to Optimal Health by Returning to Our Ancestral Diet.” He says going carnivore is the solution to a range of health issues currently plaguing humankind. Plants, he says, simply aren’t cutting it.
“If you look at the incidence of chronic disease, no one can deny that in the last 70 years, we’ve become abysmally unhealthy,” Saladino says. “Rates of obesity and overweight are 70% of the U.S. population. Diabetes has gone from 0.9% or 1% to 13% or 14%. And that’s just diagnosed diabetes, not pre-diabetes or metabolic syndrome. Chronic disease now impacts 40% of the population. Fifty or 60 years ago, it was 10% or 15%. So, the question is, what the heck happened?”
He also notes that we’re drinking less alcohol, smoking less and exercising more, and yet we still get sicker. “Unhealthy behaviors have gone way down,” he says. “And if you look at the number of people who are eating ‘healthfully,’ that’s gone way up. But that’s just according to the U.S. dietary guidelines.”
What’s happening is a good question, and according to Saladino, the answer is that “we’re doing some things that are incompatible with our genetics and evolutionary history that are causing us to get sick.” Namely, eating plants. “Having more vegetables and eating less red meat, we’re getting sicker and sicker,” he says.
He notes that red meat bears the blame for many ailments and chronic diseases, and he thinks this is backward. Plants, he says, have varying levels of toxicity to humans, hence why so many of them are poisonous. He says it’s even why some of the ones we can eat, such as beans, must first be carefully prepared and cooked to remove toxic proteins.
“It’s not a question of if plants are toxic, it’s a question of how toxic any one plant is and how well any individual or animal can detoxify what’s in there,” he says.
By contrast, he notes that “animals don’t have toxins in their body, with a few rare exceptions of a small frog in the Amazon and puffer fish liver. But generally speaking, 99.9% of animal organs are all edible by humans. And in fact, it’s incredibly nutritious food and basically what we’ve been thriving on for 2 to 4 million years.”
[READ: How to Calculate Net Carbs in Your Diet.]
An All-Meat Diet
For meat eaters who are interested in trying the carnivore approach to eating, you’ll have to cut out all plant foods. Yes, really. The goal is to eliminate all carbohydrates, and Saladino says that, save for the odd berry or other seasonal fruit our carnivore ancestors would pick up while hunting game, plants are not on the menu.
“It works as an elimination diet by slowly reducing intake of carbohydrates and plant-based food items and increasing intake of animal protein,” Zammit explains. “Oftentimes on an elimination diet, food items may be slowly reintroduced, but that’s not the case here. The ultimate goal is 100% intake of animal-based protein.”
Followers of the diet are instructed to eat any kind of meat and meat products from fatty cuts of beef, lamb, pork and organ meats, as well as poultry, fish, eggs and dairy products.
A typical carnivore diet meal plan
A typical menu for a day on the carnivore diet can be:
— Breakfast: 4-ounce ribeye, two eggs and bacon cooked in butter.
— Lunch: 3 ounces of salmon and 6 ounces of shrimp.
— Dinner: 2 ounces of liver and 8 ounces of filet.
“There’s no flexibility for a bun on your burger or a piece of fruit for dessert,” Zammit says.
The reason for this very restrictive emphasis on animal protein is simple, Saladino explains. “Animal meat and organs are the most nutrient-rich and bioavailable foods on the planet. They’ve been incredibly vilified for the last 60 years, but they’re an integral part of every healthy human diet.”
It’s true that organ meats are highly nutritious, being rich sources of B vitamins, several minerals, including iron, magnesium and zinc, and fat-soluble vitamins, such as vitamins A, D, E and K. Organ meat and animal meat in general contain high levels of protein. And it’s true that our hunter-gatherer ancestors ate every part of the animals they hunted, nose to tail.
The idea with this approach is to be as animal-based as possible, as opposed to plant-based. However, plant-based diets, such as the Mediterranean diet, have long been favored by many dietitians and doctors as the healthiest and most sustainable way for humans to eat for longevity and wellness. The carnivore diet turns that conventional and well-established advice on its head.
[READ: The Keto Diet and Diabetes.]
Saladino claims that the carnivore diet can be the source of healing for virtually any autoimmune or chronic disease you might be experiencing, from depression and rheumatoid arthritis to diabetes, acne and obesity. There is limited or mostly anecdotal evidence for these claims.
A few of the commonly cited improvements that proponents associate with the carnivore diet include:
— Curing SIBO, or small intestinal bacterial overgrowth.
— Rapid weight loss.
— Improved mood.
— Better glucose control.
For example, one particular aspect of health that proponents of the carnivore diet often cite is an improvement in gut health
. A common condition called SIBO, or small intestinal bacterial overgrowth, often comes up in discussions of how the carnivore diet may impact the health of the gut microbiome. Proponents suggest that SIBO, which occurs when an excessive number of bacteria take up residence in the small intestine and cause bloating, constipation, diarrhea and other GI problems, can be cured by moving to a zero-carb diet like the carnivore diet.
One very small, six-person study (that has not been peer-reviewed or validated) found that five participants who followed a zero-carb, zero-fiber carnivore diet for at least four weeks tested negative for SIBO at the end of the observation period.
SIBO is often treated using broad-spectrum antibiotics, but proponents of the carnivore diet say this is unnecessary and, in fact, while antibiotics may clear up symptoms for a time, they often return within three to nine months. Proponents say this is because the bacteria that cause SIBO needs carbohydrates to thrive, and starving them of this fuel source can wipe them out entirely from your gut.
In contrast, another small study published in the journal Nature in 2014 found that in just five days, participants who switched to a zero-carb, carnivore diet experienced significant detrimental changes to the gut microbiome, including a dramatic increase in strains of bacteria in the gut that cause inflammation and have been linked with Crohn’s disease and ulcerative colitis.
A 2017 study found that dietary changes can rapidly alter the composition of the gut microbiome for both benefit and detriment depending on the specific changes being made. In addition, a 2021 study compared changes in the microbiome over the space of four weeks on a vegan diet versus four weeks on a meat-heavy diet. This study also found that certain bacteria were augmented or suppressed in each instance but that many of the changes came down to differences in the unique biome for individual participants.
Zammit, however, notes that for some people with irritable bowel syndrome or inflammatory bowel disease, symptoms such as bloating and flatulence may decline after adopting the carnivore diet because you’ll be consuming far fewer FODMAPs, a type of carbohydrate that can cause gastrointestinal distress in some people.
Rapid weight loss
The all-meat diet may result in weight loss because it’s high in fat. High-fat foods “promote meal satiety,” meaning that “you’ll feel fuller longer,” Zammit says. “Feeling satiated from consuming these food items can help reduce your caloric intake, as you won’t feel as hungry, likely leading to weight loss.”
Sara Riehm, a registered dietitian and certified specialist in obesity and weight management with Orlando Health in Florida, adds that the carnivore diet encourages followers to minimize their intake of high-calorie, processed foods.
“This can help create a calorie deficit, meaning we are consuming less energy than our body uses throughout the day. Creating this sort of deficit can lead to weight loss,” she explains. “However, severe calorie deficits can compromise our muscle stores and put us at risk for malnutrition.” She adds that “daily calorie needs vary for everyone” and it’s best to consult with a dietitian if you’re interested in losing weight.
There’s some evidence that suggests excessive sugar intake can affect the brain, which could contribute to the development of depression. Cutting back on sugar and processed carbs may improve mood, as has been observed with the keto diet in some studies, such as this 2018 one. As an extreme form of keto, the carnivore diet, it can be argued, might also confer some mood-boosting benefits.
Better glucose control
Reducing your intake of carbohydrates may also help with blood glucose control, which may be helpful for people with diabetes. “When you eat a food containing carbohydrates, such as grains, fruit, starchy vegetables or dairy, the carbs are broken down in simple sugar molecules, which enter the blood as glucose,” explains Riehm. “Our cells need this sugar, called glucose, for energy. It is the type of energy our bodies have evolved to utilize most effectively.”
However, too much glucose can impact blood sugar levels. Over time, this can lead to the development of Type 2 diabetes. Reducing the amount of simple sugars in the diet or adding fiber can help stabilize blood sugar levels. Riehm recommends looking for foods that contain fiber.
“Fiber can slow down the digestion of carbohydrates and lead to a slow, steady rise in blood sugar that our bodies are better equipped to handle,” she says.
Proponents of the carnivore diet go a step further and remove virtually all carbohydrates from their diet to achieve better glucose control. Results from a social media-based survey of people who had followed the carnivore diet for at least six months were published in the December 2021 issue of Current Developments in Nutrition.
The survey found that participants with diabetes reported benefits related to diabetes and insulin resistance, with 74% saying the condition had “resolved” and 24% saying it was “improved.” The survey authors noted that “all respondents with diabetes discontinued noninsulin injection agents, 84% discontinued oral medications and 92% of participants with Type 2 diabetes mellitus discontinued insulin.”
While such results may seem overwhelmingly positive, it’s worth keeping in mind that surveys such as this rely on self-reporting and are not considered the gold standard for scientific studies. Zammit cautions against confusing anecdotal support with scientific understanding.
“This diet demonizes plant-based foods, such as fruits, vegetables, whole grains, beans, lentils, nuts and seeds, while promoting claims of improving fatigue, digestion and autoimmune diseases,” says Zammit “These claims are not based on sound science, but rather anecdotal reports.”
As Riehm notes, while this way of eating might work for some people, “decisions about your health should always be based on evidence-based information backed by science.”
Shaky health claims are one thing, but risks to health stemming from this way of eating are another. Most registered dietitians strongly discourage the adoption of the carnivore diet.
“Frankly, this is not a healthy diet,” says Antonette Hardie, a registered dietitian with the Ohio State University Wexner Medical Center in Columbus. She cites several health risks associated with this diet, including:
— Elevated cholesterol levels.
— Non-alcoholic fatty liver disease.
— Chronic kidney disease.
— Constipation and other gastric problems.
— Malnourishment and nutrient deficiencies.
— Psychological impacts.
— Weight regain.
— Environmental Concerns.
Zammit agrees that eliminating all food groups from your diet except one is not a risk-free endeavor. “There’s a lot to unfold here. But since I’m an oncology dietitian, let’s start with cancer risk.”
It’s long been established that plant-based diets may help ward off cancer.
“We have strong evidence from several meta-analytical studies that demonstrate a plant-based diet can greatly reduce your risk of several cancer types, as well as other disease states, including cardiovascular disease and diabetes,” Zammit says.
Similarly, “it’s well known that a diet heavy in red and processed meats can increase risk of stomach and colorectal cancer. We also know that a diet rich in saturated fat can increase risk of liver cancer,” she adds.
Elevated cholesterol levels
One major drawback of the carnivore diet is that many of the foods that are encouraged are high in saturated fat and cholesterol.
“Numerous studies have shown that consuming excessive amounts of saturated fat and dietary cholesterol can increase cholesterol, clog arteries and increase our risk for heart disease,” Riehm says. “While these foods can be included in a balanced diet, it’s important to consume them in small portions to avoid compromising our health.”
For these reasons, Feit says the carnivore diet “is definitely a fad diet. Although it may have proposed benefits, it’s important to realize that this can never be considered a healthy diet. As stated by the American Heart Association, saturated fats need to be replaced by unsaturated fats in order to decrease heart disease, which is a leading cause of death. A diet consisting of all food groups is always a better way to go.”
Elevated cholesterol levels can lead to atherosclerosis, heart attack and stroke. “If you have a personal or family history of cardiovascular disease and hyperlipidemia, the carnivore diet is not for you,” Zammit says.
Non-alcoholic fatty liver disease
Another potential concern with the carnivore diet is the risk of developing non-alcoholic fatty liver disease, or NAFLD.
“(This disease) is caused by the accumulation of saturated fat. This isn’t always reversible by changing your diet,” Zammit says. “When we have this buildup of saturated fat, it can cause inflammation of the liver, increasing the risk of liver cancer.”
A 2022 study published in BMC Gastroenterology found that diets heavy in red meat, sweets, fast foods and refined grains increase risk for NAFLD.
Chronic kidney disease
The diet is also a poor choice for people with chronic kidney disease, or CKD, even if they aren’t on dialysis. “With chronic kidney disease, you’re instructed to actually limit your protein intake,” Zammit explains.
She adds that “the average protein needs of a healthy individual are 40 to 65 grams per day. When you have CKD, your kidneys no longer have the ability to remove protein wastes, which will then build up in the blood and can cause a whole host of unpleasant symptoms, including nausea and vomiting, decreased appetite and weakness.”
Constipation and other gastric problems
Because the carnivore diet is bereft of all plant matter, it contains virtually no fiber. “Due to the lack of fiber, most people will end up with constipation,” Zammit says.
Hunnes adds that subsisting solely on animal products “will increase IGF-1 in the body.” That hormone, called insulin-like growth factor, can lead to increased inflammation throughout the body that can in turn cause a number of additional problems. “It will destroy the (gut) microbiome because it is highly acidic and produces a lot of TMAO, an inflammatory compound that is extremely detrimental to the microbiome,” she says. Studies into exactly how the gut microbiome influences health are ongoing, but scientists are unraveling the myriad ways a healthy balance of bacteria in the gut may influence good health throughout the body.
For his part, Saladino says humans don’t need fiber, and he calls it “one of the greatest cons ever foisted upon humans.” He says we don’t need fiber to digest animal products and it causes more GI distress than it alleviates.
Malnourishment and nutrient deficiencies
“There’s also an increased risk of malnourishment, since you would no longer be consuming a balanced diet,” Zammit says. In particular, she explains, “vitamin C would be lacking, increasing risk of scurvy.”
Scurvy, a disease that was common among sailors in the 18th century, causes swollen and bleeding gums, anemia, loss of teeth, weakness and poor healing of wounds, and it can be deadly.
“In addition to all the medical and nutritional issues one may encounter on a carnivore diet, there’s also the psychological aspect of following a restrictive diet” that you need to consider before you adopt this approach to nutrition, Zammit says.
She explains that “following any restrictive diet can often lead to loneliness and social isolation. It can build distrust with yourself, disconnecting the relationship you have with your body and food. All this can affect your quality of life in a negative way, especially if following long term.”
As such, if you have a history of eating disorders, you’d be well advised to avoid this diet.
Lastly, if you’re undertaking the carnivore diet in an effort to lose weight, be aware that rebound weight gain can be an issue when you inevitably tire of this limited diet and begin adding back other foods. “With such a restrictive diet, you are prone to gain weight back and then some,” Hardie says.
Hunnes points out that risks to human health are not the only drawback to the carnivore diet. “It’s also terrible for the environment. Animal foods are one of the most environmentally destructive things on the planet. If humans reduced our meat consumption, we could save huge amounts of land, water and emissions every year.”
She notes that meat production consumes 10 times as much water as plant-based forms of protein. Farming meat also uses 10 times as much land as an equal amount of plant protein requires.
Meat production “is responsible for something like 80% to 90% of all deforestation in the Amazon,” and it releases 100 times as much carbon dioxide into the environment as plant-based proteins, she says. “It is truly one of the most destructive things we can eat for the environment, but also for our health.”
How Much Does a Meat-Based Diet Cost?
Typically, meat products cost more than plant-based foods, and as such, “you may have to shell out more money than you realize to follow this diet,” Zammit says. “Although you won’t be spending money on the food items you used to include, you’ll make up for it and then some by having to purchase animal protein for all your meals.”
This cost is compounded by the fact that the diet encourages only using “grass-fed and ethically sourced protein, which is very expensive, and not everyone has the privilege to obtain, depending on their neighborhood and socioeconomic status,” she says.
Carnivore Diet: Bottom Line
“Keep in mind that when it comes to your overall health, diet is just one piece of the puzzle,” Zammit says. “Genetics, age and gender play a huge role in how your body reacts to certain food items or diets, and this isn’t something we can change.”
She also warns about being careful when comparing yourself to other people. “The human body is incredibly complex. There are no ‘bad’ foods, just bad overall diets. Behavior and lifestyle modification are still the best predictors of your health and happiness. At the end of the day, nourish your body based on your individual needs and preferences.”
She also recommends that if you’re thinking of beginning a particular diet, “please contact your local registered dietitian to help educate and guide you.”
If you’re looking for a healthy way of eating, Hardie notes that “there is so much more research out there that promotes a plant-based diet or Mediterranean diet versus any other fad diet. The carnivore diet is just another fad diet that isn’t sustainable over time and can lead to several chronic illnesses such as high cholesterol and heart disease.”
Hunnes agrees that the carnivore diet is “not a healthy diet and our bodies did not evolve to life off meat. We are not carnivores.”
Saladino, however, says he’s never felt better since adopting this lifestyle, and he encourages those who feel the need to make some changes to check it out.
“If you’re kicking ass in every way, shape and form, then don’t change a thing. But if you’re looking to improve body composition, libido, emotional stability, mental clarity, autoimmunity, inflammation, chronic disease, I’m so excited to offer these ideas as a tool for people who might not have considered them because we’re so stuck in this rigid paradigm around plants versus animals. It’s a diet for every homo sapiens person that isn’t thriving.”
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Carnivore Diet Review: Benefits, Risks, What to Expect originally appeared on usnews.com
Update 03/22/23: This story was previously published at an earlier date and has been updated with new information.