Why I tried carnivore again

• The carnivore diet rose rapidly as advocates promoted it for athletic performance, body composition, obesity, autoimmune disease, mood disorders, fatigue, skin problems, and other chronic illnesses; more recently, major advocates such as Paul Saladino moved away from strict carnivore and reintroduced fruit and other plant foods.
• Carnivore did not simply fail as a fad: beneath the internet debates and social-media hot takes is a more nuanced story, which motivated another trial.
• An earlier fairly liberal five-month carnivore diet included dairy, eggs, and coffee and was a surprisingly positive experience; the later 30-day trial used the lion diet, the strictest and most extreme version, with no dairy, eggs, seafood, coffee, or organ meats—just meat, salt, and water.
• The experience is one data point and a springboard into the bigger story of carnivore's popularity, controversies, what the science shows, and what remains to be learned.

Gut health

• Zero fiber did not cause constipation: bowel movements occurred every day, and by day 30 they were about as close to perfect as they had ever been.
• A 2012 World Journal of Gastroenterology study found that eliminating dietary fiber in people with irritable bowel syndrome with constipation improved bowel frequency from one movement every 3.75 days to one per day, eliminated bloating and straining, and produced worse symptoms as fiber intake increased. [1]
• Ulcerative colitis took several years of life away, showing how severe inflammatory bowel disease can be.
• A case series of 10 medically confirmed Crohn's disease or ulcerative colitis patients included severe cases requiring biologic drugs or intestinal surgery; most had already tried vegan, vegetarian, low-FODMAP, paleo, and other elimination diets, and every patient experienced substantial, life-changing improvement on a fiber-free carnivore diet. [2]
• One patient said a keto-carnivore diet let him forget he had Crohn's disease without drugs or surgery, and another said this lifestyle had allowed six years without having to worry about colitis. [2]
• Removing carbohydrates produces ketone bodies, including in the gut, where they act as signaling molecules that can reprogram immune cells to make them less inflammatory. [3]
• Ketone signaling may also help intestinal stem cells renew and better heal the gut lining. [4]
• Cell Host & Microbe research found that a fiber-free diet altered the metabolism and location of the pathobiont Mucispirillum and ameliorated colitis in an animal model; at a high level, removing fiber can starve problematic gut organisms, although the actual mechanism involves intraluminal migration. [5]
• Fiber-free diets are already used for refractory inflammatory bowel disease and can produce response rates around 60-85%; conventional medicine generally administers them as unpalatable fiber-free liquid formulas, while eating meat could achieve the same endpoint of fiber elimination.
• A study compared 10 healthy people eating carnivore for an average of about three years with 874 matched controls eating a mixed diet with more fiber and found no significant difference in microbiome diversity metrics, challenging the assumption that dietary fiber is essential for maintaining microbiota diversity. [6]
• Carnivore does not stop bowel movements, does not necessarily destroy microbiome diversity, and has therapeutic potential for certain people with compromised gut health, including the kind involved here; this does not make carnivore a panacea, but it makes it interesting and somewhere to start.

Nutrient deficiencies

• Some concerns about nutrient deficiencies are legitimate and warrant serious attention, beginning with calcium: standard carnivore with dairy is not a calcium problem, but dairy-free lion diets deserve attention and concern.
• Muscle meat provides only about 10-20 mg of calcium per 100 g versus a general target of 1,000-1,200 mg per day, requiring roughly 11 lb of beef; for years of carnivore, especially a lion diet, a calcium source such as an actual supplement, 100 g of Parmesan per day, or eggshell-derived calcium would be something to seriously consider.
• Omega-3 is another real concern and was already a priority: a prior month of 1,000 sardines produced an omega-3 index around 16%.
• After 30 days on nothing but ruminant meat, with no fish, sardines, or omega-3 supplements, the omega-3 index fell from 15.68% to 10.51%; 10.51% remained within the optimal range, but the decline was rapid and was expected to continue.
• With two copies of APOE4 and vulnerability to Alzheimer's disease, maintaining high omega-3 intake is non-negotiable; a serving of grass-fed beef may provide about 50 mg of omega-3 versus roughly 1,500 mg in a can of sardines, a 30-fold difference, so in this domain sardines beat steak.
• A subtle omega-3 deficiency is difficult to detect and could matter over decades for brain health, so any future carnivore diet would include a healthy amount of seafood or added omega-3.
• Meat is relatively low in vitamin C, particularly after cooking, yet historical all-meat diets did not inevitably cause scurvy; in 1928 Vilhjalmur Stefansson ate nothing but meat for an entire year under continuous medical supervision at Bellevue Hospital without developing scurvy, and his physicians published the results. [7]
• Stefansson learned this dietary pattern from Inuit populations consuming diets almost entirely composed of animal foods such as seal, whale, and caribou with minimal plant matter, without developing scurvy.
• Vitamin C and glucose are structurally similar molecules and compete for some of the same cellular transporters; when carbohydrate and sugar intake are high, glucose floods those transporters and outcompetes vitamin C for entry into cells. [8]
• Without sugar in the diet, vitamin C dietary needs drop because vitamin C is absorbed more efficiently.
• Vitamin C can also be regenerated after oxidation through an NADPH-dependent antioxidant system, and a zero-carbohydrate diet that produces ketones might support that NADPH system and help regenerate vitamin C.
• After more than 100 lb of meat in 30 days, the result was remarkably unremarkable: bowel function continued, scurvy did not occur, cheese and coffee were greatly missed, physical well-being was good, nutrient blood tests were normal, thyroid and cortisol were normal, and cholesterol was essentially unchanged; a roughly 20 mg/dL cholesterol drop was within normal noise.

Potential medical uses

• Nothing horrific or miraculous occurred because a ketogenic diet already worked for ulcerative colitis; carnivore may be not merely a diet but a potential medical intervention for people in need.
• Carnivore functions at its core as one of the most extreme elimination diets possible, removing almost every potential dietary trigger at once, and this can be transformative for people whose immune systems react to specific plant compounds.
• Strong human evidence for autoimmune and inflammatory diseases beyond inflammatory bowel disease is desperately limited, but this is a deficiency in the scientific literature that needs investigation, not something to hide from or brush under the rug.
• Unless hordes of people are simultaneously fabricating improvements in lupus, rheumatoid arthritis, multiple sclerosis, psoriasis, and other autoimmune conditions, carnivore is helping at least some people; whether it is called a fad, fringe, or salvation, the questions are why it is helping and how to avoid throwing that signal away.
• The combination of mechanistic ketone data, microbiome research, and clinical evidence on fiber-free diets in inflammatory bowel disease is enough of a signal to warrant serious investigation.
• Carnivore-style animal-based ketogenic diets have emerging interest for anorexia because mental health disorders are not purely abstract psychological phenomena but arise from altered neurochemistry and changes in brain metabolism; fundamentally altering brain metabolism with ketones could also improve mental health across depression, anxiety, binge eating disorder, addiction, bipolar disorder, and anorexia.
• Patients with anorexia have said that a carnivore diet quite literally saved their lives. [9]
• A paper on animal-based ketogenic diets in severe anorexia includes an illustrative patient, Katherine, who was 39 when interviewed, had struggled with body image since age seven, and at age 34 maintained a BMI of 10.7—on death's doorstep—and on some days subsisted on little more than lettuce with zero-calorie stevia sweetener. [9]
• After adopting carnivore in desperation, Katherine said, "This solved all of my issues. All of them." For the first time in decades she experienced mental clarity and calm, her weight recovered to a healthy level, as did her relationships, and she remained healthy for years. [9]
• People with mental health disorders or eating disorders should not self-manage with carnivore; eating disorders are serious, complex conditions that require professional support.
• This belongs on clinicians' radar as a potential tool in their toolkit.
• For anorexia, where outcomes are horrible, mortality is high, and current care is pitifully unsuccessful, curiosity about outside-the-box tools that are helping people and saving lives is necessary; this is the most reasonable thing in the world. [9]

Who should try it?

• This is guidance rather than a prescription: carnivore makes the most sense as a therapeutic intervention for people with refractory gastrointestinal conditions, autoimmune conditions, or metabolic health conditions, and less sense for healthy people already thriving on their current diet or anyone unwilling to monitor key biomarkers.
• Stopping carnivore reflects lack of need, not failure; different bodies need different things, and that should not be stigmatized.
• Someone can regain health through a 30-day carnivore elimination reset or a five-year extreme lion diet and later gradually broaden the diet a little without that meaning the diet failed; the person has evolved.
• Carnivore is not a religion or simply a movement to join or reject, but a fascinating, powerful tool that will not be right for everybody and may be exactly what someone needs at a particular moment to save their life; that deserves curiosity, not ridicule.

References

1. [03:44] Stopping or reducing dietary fiber intake reduces constipation and its associated symptoms — https://doi.org/10.3748/wjg.v18.i33.4593
2. [04:41] Case report: Carnivore–ketogenic diet for the treatment of inflammatory bowel disease: a case series of 10 patients — https://doi.org/10.3389/fnut.2024.1467475
3. [06:10] Ketone body β-hydroxybutyrate ameliorates colitis by promoting M2 macrophage polarization through the STAT6-dependent signaling pathway — https://doi.org/10.1186/s12916-022-02352-x
4. [06:17] Ketone Body Signaling Mediates Intestinal Stem Cell Homeostasis and Adaptation to Diet — https://doi.org/10.1016/j.cell.2019.07.048
5. [06:24] Fiber-deficient diet inhibits colitis through the regulation of the niche and metabolism of a gut pathobiont — https://doi.org/10.1016/j.chom.2023.10.016
6. [08:23] Long-term adherence to the carnivore diet and its impact on the gut microbiota: a cross-sectional study — https://doi.org/10.1530/MAH-25-0015
7. [12:25] Clinical Calorimetry: XLV. Prolonged Meat Diets with a Study of Kidney Function and Ketosis — https://doi.org/10.1016/S0021-9258(18)76842-7
8. [13:01] Human erythrocytes transport dehydroascorbic acid and sugars using the same transporter complex — https://doi.org/10.1152/ajpcell.00044.2014
9. [16:58] Animal-based ketogenic diet puts severe anorexia nervosa into multi-year remission: A case series — https://doi.org/10.4102/jir.v6i1.84