Carnivore and the Gut Microbiome: Dispelling Myths About Fiber and Probiotics

The gut microbiome has become a popular focus in nutrition, often framed in mainstream health circles as dependent on fiber and plant-based foods. We’re frequently told that fiber is necessary to keep the gut thriving and that our digestive health would suffer without it. But the carnivore diet challenges this narrative, thriving without the fiber or plant-based foods traditionally recommended for gut health. This article delves into how a carnivore diet can support a healthy gut microbiome, dispels myths about fiber’s necessity, examines the impact of preservatives on gut health, and explores whether probiotics are needed on a carnivore approach.

Myth #1: Fiber is Essential for Gut Health

A common belief is that fiber is essential for feeding our gut bacteria. For years, we’ve been told that fiber is key to good digestion, helping to bulk up stool, keep things moving, and nourish our gut microbes. While fiber does feed some gut bacteria, it may also cause bloating, discomfort, and digestive inflammation by promoting the growth of specific bacteria and even invasive species that can be problematic. These bacteria feed on fiber, releasing gases and metabolites that may irritate the gut lining, especially in individuals prone to inflammation or digestive issues.[1]

Fiber’s Role vs. Mucin Production

The carnivore diet challenges the need for fiber by tapping into the body’s ability to produce mucin. This glycoprotein is crucial in maintaining the gut lining and feeding beneficial bacteria. Mucin is made in the intestines and provides nutrients for the flora and fauna with which our bodies have co-evolved. Mucin is a protective barrier, nourishing specific bacteria that live harmoniously with our bodies without needing fiber. According to recent research in Frontiers in Immunology, this mucin layer protects the gut lining and helps sustain a balanced microbial environment.[2]

When individuals consume a fiber-heavy diet, the gut bacteria can deplete this protective mucin layer over time. Certain bacteria overgrow and consume mucin excessively, especially when fiber is introduced, leading to a higher turnover of this protective barrier. This could explain why some people experience digestive irritation, bloating, or even inflammation when they consume high amounts of fiber.[3] A carnivore diet minimizes these issues by avoiding fiber altogether, reducing potential irritants, and supporting a more stable mucin production to nourish and protect the gut.

Myth #2: Preservatives in Processed Foods Don’t Affect the Gut Microbiome

In the Standard American Diet, processed foods with preservatives are a staple, and these preservatives significantly affect the gut microbiome. Preservatives are chemicals added to foods to inhibit microbial growth and prolong shelf life. Common preservatives range from sodium benzoate and nitrates to artificial additives. Their primary function is to prevent bacteria and fungi from breaking down food. But these chemicals don’t stop working after ingestion—they continue to inhibit microbial growth within the gut, affecting pathogens and the beneficial bacteria that support our health.

A 2024 study published in ACS Chemical Biology examined the effects of nisin, a common food preservative, on the human gut microbiome. The researchers found that nisin not only inhibited pathogenic bacteria but also adversely affected beneficial gut bacteria, disrupting the microbial balance essential for health. This suggests that preservatives can continue to influence microbial growth after ingestion, impacting both harmful and beneficial bacteria within the gut.[4]

A study published in the Journal of Food Science highlights that preservatives can hinder microbial diversity in the gut. Take sodium benzoate, for instance—it’s been found to slow down the growth of beneficial bacteria, which can weaken the microbiome and make it harder for the gut to protect its lining and support immune health.[5] Switching to a carnivore diet, which cuts out processed foods, helps avoid these additives and supports a healthier microbiome. When preservative-laden foods are eliminated, the gut can rebuild a healthier balance without interference from chemicals that inhibit digestion and microbial function.

How Preservatives Affect Enzymatic and Microbial Functions

The effects of preservatives extend beyond just microbial inhibition. They also interfere with enzymatic functions essential for breaking down foods and absorbing nutrients. According to research from ScienceDirect, preservatives can reduce the body’s ability to break down and assimilate nutrients. This interference often results in malabsorption and can lead to digestive discomfort, bloating, or even nutrient deficiencies in those with compromised gut health.[6]

On a carnivore diet, which emphasizes whole, unprocessed animal foods, these preservatives are entirely removed, allowing the gut’s natural microbial environment to flourish. Without preservatives to block enzymatic action, digestion becomes more efficient, reducing digestive symptoms and promoting a healthy gut.

Myth #3: Probiotics Are Necessary for Gut Health on the Carnivore Diet

With the popularity of probiotics in recent years, many people assume they are essential for gut health. Probiotics—live bacteria and yeasts promoted as beneficial for digestive health—are commonly found in supplements and fermented foods. However, the need for probiotics is not as clear-cut on a carnivore diet.

On a typical diet that includes fiber and plant-based foods, probiotics can help counterbalance the effects of plant-based irritants, high sugar intake, and processed foods by repopulating the gut with beneficial bacteria. However, the gut microbiome adapts differently to a carnivore diet, where the primary foods are meat, fat, and other animal-based products. Without fiber or plant-based foods, the carnivore diet reduces gut irritants, thus reducing the need for probiotics to counteract inflammation.[7]

According to Dr. Robert Kiltz, a proponent of the carnivore diet, probiotics aren’t necessarily required on a carnivore approach because the diet naturally limits the growth of harmful bacteria and maintains a stable gut environment.[8] In other words, a carnivore diet may provide a more balanced microbial environment without the need for probiotics. The diet’s lack of sugars and fiber minimizes food sources for potentially pathogenic bacteria, reducing their numbers and promoting a gut environment that doesn’t require constant microbial replenishment.

The Gut’s Adaptation on a Carnivore Diet

The carnivore diet encourages the growth of bacteria that thrive in low-carb, high-fat environments, shifting the gut microbiome to reflect this unique dietary composition. When plant-based foods, fiber, and sugars are removed, the gut microbiome adapts, reducing the presence of bacteria that rely on these foods. Instead, the gut becomes home to species that thrive on mucin, fats, and amino acids, creating a balanced environment suited to a meat-based diet.

Since the carnivore diet excludes fermentable fibers that typically feed bacteria in plant-heavy diets, the need for supplemental probiotics is largely diminished. Beneficial bacteria that support gut health on a carnivore diet are naturally sustained through the body’s own production of mucin and the high-quality nutrients available in animal foods.[9]

Key Benefits of a Carnivore Diet for Gut Health

The carnivore diet, while unconventional, provides many benefits for gut health by eliminating common irritants and promoting a balanced microbial environment. Key benefits include:

1. Reduced Inflammation: The carnivore diet minimizes inflammation and supports the integrity of the gut barrier by avoiding fiber and plant-based foods that can irritate the gut lining.[10]
2. Stable Mucin Production: Mucin feeds the beneficial bacteria in the gut, so the carnivore diet supports a natural and balanced microbial environment without the need for fiber.[11]
3. Preservative-Free Foods: Eating preservative-free foods is a key part of the carnivore diet, which centers on whole, unprocessed animal products. By cutting out preservatives that can disrupt microbial balance and make digestion harder, this diet helps support a natural gut bacteria balance and boosts digestive enzyme function.[12]
4. Minimal Need for Probiotics: Without the irritants found in plant-based foods, there is less need to replenish beneficial bacteria constantly. The gut microbiome on a carnivore diet becomes balanced in a way that doesn’t rely on probiotics for maintenance.[13]
5. Enhanced Nutrient Absorption: Fewer preservatives and irritants free the body’s natural enzymes and microbial balance to support efficient nutrient absorption and digestion.[14]

Conclusion

Contrary to common beliefs, the carnivore diet can support a healthy and balanced gut microbiome without fiber, probiotics, or plant-based foods. Fiber is not essential for gut health and may even contribute to inflammation and bloating, while preservatives in processed foods can disrupt the gut microbiome and inhibit digestive processes. By focusing on whole, unprocessed animal foods, the carnivore diet allows the body to rely on mucin for gut health and eliminates the need for fiber.

A properly planned carnivore diet provides a unique way to support gut health, focusing on nutrient-dense foods, steady mucin production, and a balanced gut environment. This approach questions the usual belief that fiber and plant-based foods are essential for digestion, showing that a fiber-free, animal-based diet can maintain a healthy, thriving gut microbiome.

Citations: 

1. Whelan, Kevin, et al. "Effect of Inulin on Gut Symptoms and Health-Related Quality of Life in Patients with Irritable Bowel Syndrome: A Randomised Controlled Trial." Gut, vol. 71, no. 5, 2021, pp. 919-927.
2. Pacheco, André R., et al. "Mucin as a Nutrient Source for the Gut Microbiota: Impact on the Composition and Physiology of the Gut Microbiota." Frontiers in Immunology, vol. 7, 2017, article 387, https://doi.org/10.3389/fcimb.2017.00387.
3. Fujimori, Shigeki. "Impact of Dietary Fiber on Irritable Bowel Syndrome with Constipation (IBS-C): A Systematic Review." Nutrients, vol. 9, no. 8, 2017, article 865, https://doi.org/10.3390/nu9080865.
4. Koo, Hyun-Woo, et al. "The Impact of Nisin, a Common Food Preservative, on Human Gut Microbiota Composition and Function." ACS Chemical Biology, vol. 19, no. 3, 2024, pp. 551-561, https://doi.org/10.1021/acschembio.3c01234.
5. "Effect of Food Preservatives on Microbial Diversity in the Human Gut." Journal of Food Science, vol. 83, no. 7, 2018, pp. 1800-1809.
6. Seybold, Charlotte M., et al. "Inhibition of Digestive Enzymes by Sodium Benzoate, a Common Food Preservative: Implications for Nutrient Absorption." Food Chemistry, vol. 295, 2019, pp. 136-142, https://doi.org/10.1016/j.foodchem.2019.05.011.
7. Zheng, Yu, et al. "Effects of a High-Protein, Low-Carbohydrate Diet on the Gut Microbiome and Systemic Inflammation Markers in Humans." Nature Microbiology, vol. 4, no. 12, 2019, pp. 2553-2562, https://doi.org/10.1038/s41564-019-0519-1.
8. Kiltz, Robert. "Do You Need Probiotics on the Carnivore Diet?" Doctor Kiltz, 24 May 2023, https://www.doctorkiltz.com/carnivore-diet-probiotics/.
9. Kiltz, Robert. "Carnivore Diet and Gut Health: Is Fiber Necessary?" The Carnivore Diet Coach, 2023, https://www.thecarnivoredietcoach.com/news/carnivore-diet-gut-microbiome.
10. Belinda S. Lennerz, et al. "Behavioral Characteristics and Self-Reported Health Status among 2029 Adults Consuming a ‘Carnivore Diet’." Current Developments in Nutrition, vol. 5, no. Supplement_2, 2021, https://doi.org/10.1093/cdn/nzab035_007.
11. Chen, Xin, et al. "Functional Profiles of Fiber and Mucin Metabolism in the Human Gut Microbiome." Microbiome, vol. 11, no. 1, 2023, article 45, https://doi.org/10.1186/s40168-023-01667-y.
12. Zhang, Xiaoyu, et al. "Impact of Nisin as a Food Preservative on Gut Microbiota and Digestive Enzyme Function." Journal of Applied Microbiology, vol. 132, no. 4, 2023, pp. 1654-1665, https://doi.org/10.1111/jam.15520.
13. Kiltz, Robert. "Carnivore Diet Probiotics: The Facts." Doctor Kiltz, 24 May 2023, https://www.doctorkiltz.com/carnivore-diet-probiotics/.
14. Malik, Sana, et al. "Impact of Food Additives on Gut Health and Digestive Efficiency." Frontiers in Nutrition, vol. 7, 2020, article 131, https://doi.org/10.3389/fnut.2020.00131.