Hi everyone! I am back to chat about another health/wellness/diet trend. One of my favorite things to do on this blog is to examine scientific evidence to see what true risks and benefits different wellness trends carry. I’ve covered topics like celery juice, the keto diet, plant-based meat substitutes, supplements for immunity, etc,. And today, I’m going to be discussing the carnivore diet.
Now, as a general disclaimer, yes, I am vegan. That said, I do my best to remain objective when writing and creating content, to separate my own feelings and opinions from scientific evidence. In fact, I’ve pointed out some of the nutritional concerns of the vegan diet (including adequate B-12, DHA, zinc, iron, calorie, and protein consumption) in this post. So, all that’s to say, I will do my best to stick to the facts about this diet, regardless of my own dietary preferences.
*Disclaimer: As always, this is general information intended for healthy adults. Your needs may vary based on medical status, lifestyle, or life-stage. Please never replace generalized health information you’ve read online with individualized clinical care.
Furthermore, as I’ve mentioned repeatedly, there are many ways to have a healthy diet, and the best diet is the one you can maintain long-term that allows you to meet your nutrient requirements. And hypothetically, for most healthy people, all foods can fit into a healthy diet.
With all those disclaimers done, let’s dive into the science of the carnivore diet.
First of all, what is the carnivore diet?
The carnivore diet is a diet that consists entirely of animal products; namely, meat, eggs, fish, and other animal products. Different interpretations of the diet also allow cheese and things like butter.
What are some claims made about the carnivore diet?
Proponents claim that the carnivore diet leads to weight loss, general ‘healing,’ blood sugar regulation, reverses rheumatoid arthritis, improved cognitive function, digestion, and athletic performance, etc. Proponents also like to mention that it is free of ‘anti-nutrients’ including lectins and plant fibers, that may inhibit the absorption of certain nutrients.
It’s also touted as a supreme form of an elimination diet, and many claim it will ‘heal’ the gut, and lead to a longer more prosperous life.
What does the science say about the carnivore diet?
Well, the science is supremely lacking. I couldn’t find any scientific evidence that has tested a carnivore diet in humans and measured its ability to ‘heal,’ stabilize blood sugar, improve cognitive function, etc.
Because I could find no scientific studies on the carnivore diet, I read up on similar (but more inclusive) diets, including the Paleo diet and the ketogenic diet.
When it comes to anti-inflammatory claims made by the carnivore diet, a 2017 study on a small sample of mice suggested that a ketogenic diet may suppress inflammation.
However, these results should be interpreted with caution as ketogenic diets include a wider variety of foods than does the carnivore diet, and this study was done on animals, not humans.
When it comes to psychological illness, although there are no studies to support the use of meat-only diets, a 2017 review found that the use of ketogenic supplements may suppress anxiety and depression-related behaviors in rats and mice.
However, many of these studies had small sample sizes, and were short in durations. Furthermore, these animal studies are conducted in controlled environments, and extrapolating these results to humans should be done with caution.
Regarding improved digestion, there is no evidence to support that consuming a carnivore diet will prevent or decrease digestive ailments or symptoms. However, it could be argued that the elimination of fiber may ease IBS symptoms in some people.
One study that many advocates of the carnivore diet like to cite does support the idea of decreasing fiber intake for improved digestive symptoms; however, the study showed improved digestion upon lowering or stopping fiber intake in a sample of 63 people with idiopathic constipation.
This group of individuals was already experiencing severe constipation, therefore it is unclear if these findings are generalizable to the general population.
That said, a diet that only allows three meats is devoid of most fermented oli-, di- and monosaccharides, alcohols and polys (FODMAPs), which may cause or exacerbate IBS symptoms in some people; therefore, elimination of these foods may lead to improvement in functional gastrointestinal symptoms. That said, avoiding fiber may not be best for everyone.
Adequate fiber intake is also associated with lower body weights. Furthermore, increasing fiber intake has been shown to benefit some gastrointestinal disorders, including gastroesophageal reflux disease, constipation, and hemorrhoids. Thus, advocating for a diet devoid of fiber may therefore be harmful to some.
What about improved cognition that the carnivore diet promises? While again no studies have tested all-meat diets and cognitive function, a 2010 study in aged rats suggested that diet-induced ketosis may improve cognitive performance. However, as mentioned above, a ketogenic diet is much more inclusive to a wider-variety foods than is the carnivore, and the study was done on older rats, not humans, so extrapolating these results should be done carefully.
Regarding the concerns about diets that include plants having anti-nutrients, it is true that certain things like phytic acids, lectins, and tannins may inhibit the absorption of certain nutrients. However, many of the studies done on these anti-nutrients have not been done on humans and have overstated claims. Furthermore, cooking, fermenting, and soaking foods with these components may increase absorption.
And importantly, eating a varied, robust diet is likely to balance out or make up for any nutrients that may have been inhibited due to anti-nutrient presence in the first place.
Nutritionally speaking, such a restrictive diet eliminates many beneficial health foods, such as fruits, vegetables, whole grains, legumes, nuts, seeds and pulses, which are beneficial to long-term health. Advocating for a diet devoid of these antioxidant and phytochemical-rich plant-foods may be harmful to some.
Additionally, the diet is composed of only meat, and some individuals may consume high levels of red and processed meats.
High levels of red meat consumption are associated with increased risks of colorectal cancer, and limited evidence suggests a possible association between red meat consumption and increased risks of cardiometabolic outcomes.
And while it is true that meat, eggs, and fish can be rich sources of certain nutrients like iron, zinc, protein, and omega-3 fatty acids, there are some nutrients that may be hard to get on a carnivore diet.
For example, most meat and animal products have little to no vitamin C, which may increase risks of scurvy. Furthermore, many meats and other animal products may be high in saturated fats, which when used to replace monounsaturated and polyunsaturated fats, has been shown to increase LDL cholesterol and total cholesterol levels.
Additionally, it’s important to consider the impact of the restrictive nature of such a diet on someone’s psychological function. A 1996 review on the physiological consequences of food restriction found that restrictive diets lead to binging once food is available, and psychological preoccupations with food and eating, increased emotional responsiveness and distractibility.
It’s well documented that livestock foods carry a higher carbon and water footprint than most other foods. And unfortunately, grass-fed cattle have even higher carbon and water footprints compared to factory or commercial farmed animals.
So, because this diet is comprised of only animal products, it carries a significantly higher carbon and water footprint compared to many other dietary patterns that include plants.
Take home: The Carnivore Diet: what does the science say?
All foods can be part of a healthy diet, and there are many different ways to consume an overall healthy diet. While there have been many grandiose health claims made about the carnivore diet, there is little to no scientific evidence to support these promises. Vitamin C, fiber, and other micronutrients may be low on a carnivore diet, and should be monitored in those who follow this dietary pattern. Additionally, the carnivore diet carries a high carbon and water footprint.
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