Can Meat Really Heal?

In this episode of the Plant Free MD, Dr. Anthony Chaffee answers listener questions about the carnivore diet and keto. Among the views he shares:

• A ketogenic diet helps fight cancer by “starving” cancer cells and helping the body fight the disease.
• Pure grass-fed beef and water is the best diet, especially for serious illness, and grain-finished beef is almost as good.
• Studies show no link between red meat and colorectal cancer, or any cancer.
• The keto community is moving toward a carnivore approach as people recognize that some foods cause harm.
• The old advice to avoid dietary cholesterol was wrong, and carbohydrates and sugar are the real problem.
• Professor Thomas Seyfried, whom Dr. Chaffee interviewed in an earlier episode, is right that cancer is a metabolic disease of the mitochondria.
• By lowering blood sugar and improving mitochondrial function, a ketogenic diet may help prevent cancer.
• Cancer rates have roughly tripled over the last 40 years as people ate more plant foods, carbohydrates and sugar.
• Cancer cells also feed on glutamine, and a glutamine-blocking drug called DON could help alongside the diet. He criticizes regulators for not approving it for human use.

These are Dr. Chaffee’s views, offered in a live Q&A rather than as a review of the evidence. Several of them go well beyond what has been tested in people, and a few are contradicted by the data. The sections below set out what the research actually shows, so you can weigh the episode’s claims for yourself.

What the evidence shows

Ketogenic diets and cancer: promising in animals, unproven in people

The idea behind using a ketogenic diet against cancer is that many tumor cells depend heavily on glucose. If carbohydrate intake drops and the body runs on ketones, the theory goes, cancer cells lose their main fuel while normal cells adapt. Cancer Research UK notes that this rests on early studies, mostly in animals, and that better research in humans is needed before anyone can know whether the diet can prevent or cure any type of cancer (Cancer Research UK).

The human evidence so far is thin. A 2021 systematic review of 39 studies with 770 patients found that most studies were low quality and at high risk of bias, with no conclusive evidence of anti-tumor effects or improved survival. Most patients lost a significant amount of weight, side effects were mild to moderate, and many people did not stick with the diet (Römer et al., 2021). A separate review of 13 clinical studies in which the diet was added to standard treatment found only two randomized trials. Four studies reported better survival or longer time to progression, and the authors concluded that more high-quality studies are needed (Klement et al., 2020). A 2021 critical assessment summed it up: animal studies suggest anti-tumor and preventive effects, human trials are equivocal, and the effects in people are “essentially unknown” (Lane et al., 2021).

The most recent and most positive review, published in 2026, focused on glioblastoma, an aggressive brain cancer. It pooled 41 human studies, ranging from randomized trials to case series and conference abstracts. More than 75 percent of patients maintained ketosis, side effects were limited to mild digestive symptoms and fatigue, and patients who stuck with the diet had a median survival of 29.4 months, compared with 14.6 months in historical controls (Firdous et al., 2026). That comparison needs a plain caveat. Historical controls are patients treated in the past, not a group randomly assigned to standard care at the same time. People who choose a demanding diet and stick with it may differ from typical patients in ways that affect survival on their own, and care has changed over the years, so the gap cannot simply be credited to the diet. The authors themselves call for phase III trials to establish whether the diet works.

The same is true of prevention. The claim that a ketogenic diet protects against cancer by improving mitochondrial function comes from animal and laboratory work, not from studies that followed people over time. We did not find any published trials of a carnivore diet for cancer, and Dr. Chaffee himself says in the episode that there are none.

The metabolic theory of cancer is a hypothesis

Professor Thomas Seyfried argues that cancer is primarily a metabolic disease. In his view, the genetic instability seen in tumors is a downstream effect of disturbed energy metabolism linked to faulty mitochondria, and tumor growth could be managed by shifting the body from glucose and glutamine to ketones (Seyfried et al., 2014). It is a serious research program, but it remains a hypothesis, and the diet-based therapy it points to has not been proven in controlled human trials (see above). Even on its own terms, Seyfried’s framework is about managing tumor growth alongside other treatment, not about a diet that heals cancer.

DON is an experimental drug, not a treatment you can get

The glutamine drug in the episode is DON (6-diazo-5-oxo-L-norleucine). It has been studied for about 60 years. Low daily doses in the 1950s suggested some anti-tumor activity, but later trials at higher doses were limited by severe nausea and vomiting, and clinical development was abandoned (Lemberg et al., 2018). Researchers are now developing prodrugs, modified versions designed to deliver DON to tumors while sparing the gut (Novotná et al., 2024). None is an approved cancer treatment.

The diet-plus-DON results that the episode refers to come from mice. In two mouse models of glioblastoma, DON combined with a calorie-restricted ketogenic diet improved survival, and the diet allowed a lower drug dose (Mukherjee et al., 2019). That is a reason to run human trials, not a basis for patients to seek out the drug.

Meat, cancer and the carnivore diet

The episode’s claim that red meat has no link to cancer runs against the main international assessment. The International Agency for Research on Cancer classifies processed meat as carcinogenic to humans (Group 1) and red meat as probably carcinogenic to humans (Group 2A), largely on the evidence for colorectal cancer (Bouvard et al., 2015). As the World Health Organization explains, these groups describe how strong the evidence is that something can cause cancer, not how likely cancer is at a particular level of intake (WHO). So the finding is not that a steak is as dangerous as a cigarette. But it is also not “no link.”

The largest data set on people who eat a carnivore diet is a 2021 social media survey of 2,029 adults who had followed it for at least six months. Respondents reported high satisfaction, few side effects and improvements in a range of conditions. Among those who shared lab results, LDL cholesterol was markedly elevated, at a median of 172 mg/dL. The authors note that the findings may not generalize and that the long-term effects need study (Lennerz et al., 2021). Self-selected, self-reported survey data cannot show that the diet heals anything. Meat does supply nutrients that are harder to get elsewhere, such as the well-absorbed heme iron covered in our article on iron-rich foods and absorption, and our guide to how much protein you actually need covers protein targets.

Cholesterol and carbohydrates: more nuanced than either side

On dietary cholesterol, Dr. Chaffee has a partial point. A 2020 American Heart Association advisory found that observational studies generally do not show a significant link between dietary cholesterol and heart disease. Most intervention studies, however, link intakes above current averages to higher LDL cholesterol, and the advisory still recommends eating patterns that are relatively low in cholesterol (Carson et al., 2020). Blood LDL itself is a different matter. Genetic studies, cohort studies and randomized trials consistently show that LDL causes atherosclerotic heart disease (Ference et al., 2017). That matters for a diet that raises LDL in many people. Our article on saturated fat and heart health goes into more detail.

On carbohydrates, the picture is not “low is always better.” In a US cohort of 15,428 adults followed for a median of 25 years, the lowest mortality was seen at about 50 to 55 percent of energy from carbohydrate. In a meta-analysis of cohorts with 432,179 participants, both low (under 40 percent) and high (over 70 percent) intakes were linked to higher mortality than moderate intake. The source mattered: replacing carbohydrates with animal fat and protein was linked to higher mortality, and replacing them with plant sources to lower mortality. These are observational findings, so they show association rather than cause (Seidelmann et al., 2018). The episode’s broader worry about heavily refined, sugary food is better supported, and our look at ultra-processed foods and our review of seed oils cover related ground.

Are cancer rates really rising?

It depends on what you measure. The number of new cancer cases each year rises as the population grows and ages, but the US cancer death rate has kept falling through 2023, averting an estimated 4.8 million deaths since 1991. The American Cancer Society credits reductions in smoking, earlier detection and better treatment. Five-year relative survival has reached 70 percent overall, up from 63 percent in the mid-1990s (Siegel et al., 2026). Those trends do not fit the idea that modern treatment has failed, or that rising plant and carbohydrate intake explains cancer.

If you have cancer, talk to your oncology team first

Do not replace or delay cancer treatment with a diet or an unapproved drug. If you are interested in a ketogenic or other restrictive diet, discuss it with your oncologist and a registered dietitian before you start. Cancer Research UK notes that ketogenic diets lack fiber, fruit and vegetables, can lead to low calcium, vitamin D and electrolyte levels, can cause kidney stones in people with a family history of them, and that people often stop the diet because of tiredness, diarrhea, constipation, vomiting or stomach pain (Cancer Research UK). Unplanned weight loss during treatment is a particular concern, and it was common in the trials (Römer et al., 2021). If you want to try a diet approach, ask your care team whether there is a clinical trial you could join.

The honest takeaway

Dr. Chaffee is a passionate advocate for a meat-based diet, and some of his points, such as the shift away from strict limits on dietary cholesterol and concern about heavily refined food, have support. But the episode’s cancer claims run far ahead of the evidence. Ketogenic diets for cancer are a legitimate research question, with promising animal data, encouraging glioblastoma results that rest on comparisons with historical controls, and no conclusive evidence from human trials. DON is an experimental drug with a history of serious side effects. The carnivore diet has no trial evidence for treating any disease. Treat this episode as one doctor’s perspective, not as medical advice, and bring any diet questions to your care team.

References

• Cancer Research UK. Alternative cancer diets: ketogenic diet. Cancer Research UK
• Römer, M., Dörfler, J., & Huebner, J. (2021). The use of ketogenic diets in cancer patients: a systematic review. Clinical and Experimental Medicine, 21(4), 501–536. PubMed
• Klement, R. J., Brehm, N., & Sweeney, R. A. (2020). Ketogenic diets in medical oncology: a systematic review with focus on clinical outcomes. Medical Oncology, 37(2), 14. PubMed
• Lane, J., Brown, N. I., Williams, S., Plaisance, E. P., & Fontaine, K. R. (2021). Ketogenic diet for cancer: critical assessment and research recommendations. Nutrients, 13(10), 3562. PubMed
• Firdous, J., Asif, A. E., Haris, H. M., et al. (2026). Efficacy and safety of ketogenic diet in glioblastoma: an updated systematic review and meta-analysis. Neurological Sciences, 47(5), 461. PubMed
• Seyfried, T. N., Flores, R. E., Poff, A. M., & D’Agostino, D. P. (2014). Cancer as a metabolic disease: implications for novel therapeutics. Carcinogenesis, 35(3), 515–527. PubMed
• Lemberg, K. M., Vornov, J. J., Rais, R., & Slusher, B. S. (2018). We’re not “DON” yet: optimal dosing and prodrug delivery of 6-diazo-5-oxo-L-norleucine. Molecular Cancer Therapeutics, 17(9), 1824–1832. PubMed
• Novotná, K., Tenora, L., Slusher, B. S., & Rais, R. (2024). Therapeutic resurgence of 6-diazo-5-oxo-L-norleucine (DON) through tissue-targeted prodrugs. Advances in Pharmacology, 100, 157–180. PubMed
• Mukherjee, P., et al. (2019). Therapeutic benefit of combining calorie-restricted ketogenic diet and glutamine targeting in late-stage experimental glioblastoma. Communications Biology, 2, 200. PubMed
• Bouvard, V., Loomis, D., Guyton, K. Z., et al. (2015). Carcinogenicity of consumption of red and processed meat. The Lancet Oncology, 16(16), 1599–1600. PubMed
• World Health Organization. Cancer: carcinogenicity of the consumption of red meat and processed meat (Q&A). WHO
• Lennerz, B. S., Mey, J. T., Henn, O. H., & Ludwig, D. S. (2021). Behavioral characteristics and self-reported health status among 2029 adults consuming a “carnivore diet”. Current Developments in Nutrition, 5(12), nzab133. PubMed
• Carson, J. A. S., et al. (2020). Dietary cholesterol and cardiovascular risk: a science advisory from the American Heart Association. Circulation, 141(3), e39–e53. PubMed
• Ference, B. A., et al. (2017). Low-density lipoproteins cause atherosclerotic cardiovascular disease. 1. Evidence from genetic, epidemiologic, and clinical studies. A consensus statement from the European Atherosclerosis Society Consensus Panel. European Heart Journal, 38(32), 2459–2472. PubMed
• Seidelmann, S. B., et al. (2018). Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis. The Lancet Public Health, 3(9), e419–e428. PubMed
• Siegel, R. L., Kratzer, T. B., Wagle, N. S., Sung, H., & Jemal, A. (2026). Cancer statistics, 2026. CA: A Cancer Journal for Clinicians, 76(1), e70043. PubMed

Related reading

• Saturated Fat and Heart Health: Revisiting an Old Debate With New Evidence
• Seed Oils: What the Concerns Are and What the Evidence Shows
• How Much Protein Do You Actually Need? A Look Past the Bro-Science

This article is for general educational purposes and is not a substitute for personalized medical advice. Anyone with cancer, or concerned about their cancer risk, should speak with their doctor before making major changes to their diet or treatment.