The carnivore diet, an extreme eating pattern consisting entirely of animal products, has gained popularity with bold promises about weight loss and health improvements. However, it raises serious red flags when it comes to cancer prevention, particularly colorectal cancer. This article explores the potential risks and benefits of the carnivore diet in relation to colon cancer, examining the scientific evidence and offering balanced perspectives.
What is the Carnivore Diet?
The carnivore diet is a restrictive eating pattern that consists entirely of animal products. It completely excludes all plant-based foods and focuses exclusively on meat, fish, eggs, and select dairy products. On the carnivore diet, you eat beef, pork, chicken, fish, eggs, and limited dairy products like butter and hard cheeses.
When you stop eating carbohydrates, your body can’t use glucose for energy anymore. Instead, it switches to burning fat and producing ketones, a process called ketosis. Your body becomes a fat-burning machine, which sounds great on paper. Proponents claim this metabolic shift leads to rapid weight loss, steady blood sugar, and reduced inflammation.
The Link Between Red and Processed Meats and Colorectal Cancer
Decades of research link red and processed meats to increased cancer risk, particularly colorectal cancer. A study supported by the National Institutes of Health and led by the USC Norris Comprehensive Cancer Center analyzed data on red and processed meat intake from 29,842 people with colorectal cancer and 39,635 people without cancer. It found that those who consumed more red or processed meat faced, respectively, a 30 or 40% increased risk for colorectal cancer.
The researchers also identified two genes, HAS2 and SMAD7, that altered cancer risk levels based on red or processed meat consumption levels. People with a common variant of the HAS2 gene found in 66% of the population faced a 38% higher risk of colorectal cancer if they consumed the highest level of meat. People with two copies of the most common variant of the SMAD7 gene present in about 74% of the population faced an 18% greater risk of colorectal cancer if they ate high levels of red meat.
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These findings suggest that there’s a subset of the population that faces an even higher risk of colorectal cancer if they eat red or processed meat.
Potential Mechanisms Linking Meat Consumption to Cancer
Several possible mechanisms may underlie the epidemiological associations between meat consumption and cancer. These include the formation of heterocyclic amines in meat when it is cooked. These heterocyclic amines require acetylation by P450 enzymes, and individuals with the fast-acetylating genotype who eat high amounts of meat may be at increased risk of large-bowel cancer.
NH3 and N-nitroso compounds (NOC) formed from residues by bacteria in the large bowel and probably also important. NH3 is a promotor of large-bowel tumours chemically induced by NOC, and some of the chromosomal mutations found in human colo-rectal cancer are consistent with effects of NOC and heterocyclic amines.
Additionally, a new Cleveland Clinic study has identified diet-derived molecules called metabolites as main drivers of young-onset colorectal cancer risk, especially those associated with red and processed meat. Younger colon cancer patients had higher levels of metabolites associated with the production and metabolism of an amino acid called arginine, and with the urea cycle compared to their older peers. These differences may be tied to long-term consumption of red meat and processed meat.
The Role of Gut Microbiome and Inflammation
A disrupted gut microbiome increases inflammation throughout your body, and chronic inflammation is a known cancer risk factor. Red meat actually promotes inflammation in the body.
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Red meat is a little bit more difficult to digest, so they stay in your system a lot longer. So not only does it stay in your stomach a lot longer to digest, but once it passes through the stomach, small bowel and in the colon, it stays in the colon a little bit longer. So it's important that you marry that with high fiber diet, exercise, and hydration so that you can get the waste eliminated.
The Carnivore Diet: Claims vs. Evidence
While some people share anecdotal stories online about the carnivore diet, these personal experiences don’t replace proven cancer treatments. Following an extreme restrictive diet instead of evidence-based medical care can delay proper treatment and worsen outcomes.
By eliminating all plant foods, you remove fiber, antioxidants, and phytonutrients that protect against cancer. Meanwhile, the diet emphasizes red and processed meats that research links to increased cancer risk, particularly colorectal cancer.
While some followers report reduced inflammation, red meat actually promotes inflammation in the body. Any temporary improvement probably comes from eliminating processed foods and removing over consumption in calories overall, not from eating only meat.
The Importance of Plant-Based Foods
The best diet for cancer prevention includes plenty of plant foods. This doesn’t mean you can’t eat meat. It means making meat a supporting player rather than the star of every meal. Choose lean proteins like fish and poultry more often than red meat, and when you do eat red meat, keep portions moderate and pair them with colorful vegetables and whole grains.
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Ketogenic Diets and Colorectal Cancer: A Different Perspective
While the carnivore diet may pose risks, some research suggests that ketogenic diets, which are low in carbohydrates, may have a role in slowing the growth of colorectal cancer. When mice in the lab are on low-carb diets, like the "keto" diet many people follow, the liver makes a ketone that slows the growth of colorectal cancer.
To find out how different diets affect the progression of colorectal cancer in mice, Levy’s lab team collaborated with the lab of Christoph Thaiss, PhD. Then they used a standard chemical technique that causes colorectal tumors to develop. They observed that the mice who were fed 1 of the 2 most ketogenic diets had a decrease in the number and size of tumors. Mice on all the other diets developed colorectal tumors. And when the lab teams put those mice on a ketogenic diet, the growth of their colorectal tumors drastically slowed.
The scientists traced the effect to the ketone molecule called beta-hydroxybutyrate (BHB). Her studies found a new and unexpected role of ketones in the body and added a new type of diet to help prevent colorectal cancer. What’s more is that Levy’s work demonstrated that the tumor-slowing effect of a ketogenic diet can be reproduced with a dietary supplement. BHB is widely available as a dietary supplement marketed for weight loss. Clinical trials are being set up to test ketone supplementation in people with colorectal cancer.
It's important to note that ketogenic diets are not the same as the carnivore diet, as they can include plant-based foods.
Red Meat PROTECTS Against Colon Cancer: A Contrarian View
Some sources argue that there is no strong evidence to support the claim that red meat causes colorectal cancer. They point to the EPIC (Oxford) study, where the actual amount of 'benefit' of reducing red meat consumption observed was just four fewer deaths out of a thousand people over eleven years. They argue that's not statistically meaningful and the cause of death could be a whole host of other things, there is no way to prove that those 4 extra deaths in the 1,000 people was due to the fact they ate red meat.
They also criticize the lumping together of processed meat with red meat in studies, as well as the potential for 'healthy user bias,' where people who eat grass-fed beef are more likely to be health-conscious in other areas of their life.
The Nutri(RECS) Study 2019 concluded that there is no strong evidence that red meat causes heart disease, colorectal cancer or anything else.
The Importance of Screening and Early Detection
Increased monitoring and screening for colorectal cancer is an extremely helpful tool. What is much more feasible is to give everyone in the system a simple test to measure a biomarker that determines their colorectal cancer risk.