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Starving Cancer: Key Things To Know about ketogenic diet and fasting

Updated: Jun 6

A recently published case study described a pet dog whose cancerous tumor disappeared after his parent initiated a carbohydrate-free, calorie-restricted ketogenic diet.

The article by Boston University researcher Prof Tom Seyfried had the title:

Yes, you read the last word right. "Alone".

This dog became cancer-free and stayed cancer-free without any conventional cancer treatments. No chemo, no surgery, no radiation.

Is this a unique case?

What do science and data say about dietary intervention against cancer?

We spoke with experts in the field and reviewed peer-reviewed publications.

The latest research shows that dietary intervention can help fight cancers, and here are key findings based on different studies.

(Learn about other cancer-fighting strategies, including cancer immunotherapy and combination therapies.)

Cancer loves sugar

Energy is needed to fuel the growth cells. Normal cells burn glucose in the presence of oxygen to create energy. Over a hundred years ago, a scientist discovered what's now called "the Warburg effect", a deranged metabolic process in which cancer cells preferentially use glucose fermentation for energy production even without oxygen.

This highly inefficient process extracts only 1/15th of the energy compared to normal cells but still allows cancer cells to produce energy rapidly, fueling their growth and proliferation. Cancer cells need and use much more glucose than normal cells. The Warburg effect is thought to be one of the key factors in the development and progression of cancer. By depriving cancer of its nutrients, either through fasting or a ketogenic (high fat, low protein/carbohydrate) diet, one may be able to interfere with cancer growth.

Research also shows that a large amount of byproduct called lactate is created during glucose fermentation by cancer cells. Lactate acidifies the environment around tumors, weakening anti-tumor immune activity. Lactate may also inhibit anti-cancer immune cells such as dendritic cells and T-cells, while helping develop immune-suppressing cells such as MDSCs.

Excellent Results (with mice)

Many researchers have attempted to study the efficacy of dietary intervention with mouse models, and we spoke to Professor Adrienne Shenck, one of the leading researchers. In her work described in the paper titled "The Ketogenic Diet Is an Effective Adjuvant to Radiation Therapy for the Treatment of Malignant Glioma" she compared the progression of glioma (brain cancer) in mice on different diets. They measured the survival of mice on a regular Standard Diet (SD) in comparison with mice who were on ketogenic, a commercially available 4:1 (fat∶ carbohydrate+protein) formula called KetoCal (KC).

With KetoCal diet, mice survived slightly longer. (See Figure A, red curve for mice on KetoCal diet). The difference in median survival was five day.

When they compared mice who were given radiation therapy with regular diet versus KetoCal, a dramatic difference was observed. (See Figure B) The majority of mice became long-term survivors when they received radiation therapy while on ketogenic diet.

So ketogenic diet alone was making a small difference, but the beneficial effect was amplified when it was combined with radiation therapy. In this small study, almost 80% of mice were effectively cured of glioma by combining radiation therapy with a ketogenic diet.

Other mouse model studies also showed the beneficial impact of combining fasting with chemotherapy.

Fasting created a tumor environment where chemotherapy became much more effective, targeting cancer cells while leaving healthy cells protected.

The impact is summarized in this informative video interview of Professor Walter Longo, one of the leading researchers who has been studying the link between fasting, aging, and cancer,

Canine Patients and Dietary Intervention

A few years ago, there was a Facebook ad that promoted a video course on curing dog cancer using a ketogenic diet. The ad went viral and helped to promote the idea that instead of using conventional therapy, dietary intervention (and avoiding kibble) would lead to cancer cures. How many dogs have been cured with dietary intervention alone? What type of cancer? Does it work for most dogs or just a handful of lucky pups?

A Dog Becomes Cancer-Free

In a recently published paper "Case report: Resolution of malignant canine mast cell tumor using ketogenic metabolic therapy alone". Prof. Tom Seyfried of Boston University describes a dog with mast cell tumor.

Mast cell tumors are common malignancies that are often treated with surgery alone or with a combination of surgery and chemotherapy, depending on the grade of tumor. A 7-year-old pitbull was diagnosed with a cutaneous mast cell tumor. The pet parent did not pursue standard-of-care treatments (surgery, chemotherapy, radiation therapy) because of potential side effects.

They switched the dog's diet to raw vegetables with cooked fish and lentils. The tumor continued to grow, "invading local tissues and reaching a size of about 4cm." The patient's diet was switched to a calorie-restricted raw ketogenic diet. They used a calorie counter.

According to the report, "the patient’s parent estimated that a 60 lb (27.3 kg), light-duty working dog should consume about 1,500 kilocalories (Kcal)/day. Consequently, a 40% restriction of this value was used to estimate a daily caloric intake for this patient of about 900 Kcal/day. The new diet was formulated to contain the following ingredients: 1. One organic raw chicken leg with bone (150 Kcal); 26 g fat: 36 g protein. 2. One organic raw chicken egg (54 Kcal); 1.5 g fat: 6.0 g protein. 3. One tablespoon (14.3 g) of pure coconut oil (120 calories); 14.3 g fat: 0 g protein. 4. Three teaspoons (12.6 g) of grizzly pollock oil for dogs (120 calories); 12.6 g fat: 0 g protein. This carbohydrate-free dietary formulation produced about 444 Kcal/meal with a fat: protein ketogenic ratio of about 1.3:1 and was fed to the patient twice/day in the morning and in the evening at 12 h intervals."

"The patient lost 2.5 kg during the course of the calorie restriction and maintained an attentive and active behavior. The patient passed away eight years later on June 4, 2019 (age 15 years) from failure to thrive due to an enlarged heart with no evidence of mast cell tumor recurrence"

A 7 year old canine patient whose tumor disappeared after being placed on a ketogenic diet, and without the use of any conventional cancer treatments.

This is an interesting case and may give hope to many pet parents.

Are there any other reports of dogs who experienced unexpected cancer regression or extended survival with the help of dietary intervention?

KetoPet Sanctuary Program

KetoPet Sanctuary, a group that created a 53-acre sanctuary in Texas and adopted and cared for dogs with cancer, reported several case studies to advance understanding of dietary intervention.

They investigated if a ketogenic diet combined with hyperbaric oxygen therapy and standard of care (e.g. surgery, chemotherapy) would reduce cancer burden and increase survival.

They selected canine patients who had confirmed neoplasia by histological evaluation or cytology, had measurable malignancy of at least 1 cm in diameter, PET scan positive tumor, and excluded patients who had malnutrition, life expectancy of less than 12 weeks, and significant comorbidities.

The ketogenic diet consisted of raw meat, fat, and vegetables (See here for more information). The dogs also received daily walks.

Dogs were given standard cancer treatments, including surgery, chemotherapy, and or radiation therapy, and also provided with hyperbaric oxygen therapy

Source: Epigenix Poster"KetoPet Sanctuary: An Update of the Combination of Standard Care, Ketogenic Diet, and Hyperbaric Oxygen Therapy on Tumor Progression and Survival in Dogs with Cancer"

They observed the beneficial impact of their approach with several pups. For example, according to their publication, an 8-year-old Mixed breed/Rottweiler with hemangiosarcoma, who was given a prognosis of 66 days, survived for 132 days.

A 6-year-old German Shepherd patient with high-grade lymphoma received a combination chemotherapy with hyperbaric oxygen therapy and the ketogenic diet. He was in remission for over 27 months, compared to the expected survival of 12 months with CHOP alone.

KetoPet Sanctuary team summarized their findings in a series of articles published in the IVC (Innovative Veterinary Care) Journal.

The survival outcomes were summarized in a table in their publication for 22 dogs with different cancer types ranging from mast cell tumors to hemangiosarcoma.

By combining conventional therapies, a ketogenic diet, and hyperbaric oxygen therapy, they concluded that a subset of dogs were able to enjoy prolonged survival times.

The team did not publish any Kaplan Meier survival curves or capture detailed immune response data from their pups. Without a more controlled study, it is difficult to conclude the efficacy of this strategy but they contributed an important finding that a safe ketogenic diet for dogs could be designed.

The Ketopet Sanctuary facility is now closed, but the group is still helping educate the public about ketogenic diet and much information is available on their website.

You can also read more about their study in a three-part publication in IVC Journal. ("KetoPet Sanctuary: ketosis, cancer and canines", Part 1, Part 2, Part 3)

Human trials

While many human dietary intervention trials have been launched in the past decade, most studies have not reported outcomes due to difficulty enrolling cancer patients or adhering to the protocol. However, in 2022, several study results were published, including details on the impact of fasting on the immune response.

Fasting-Mimicking Diet is Safe and Enhances Anti-Tumor Immunity

Safety and immune response were studied in a trial involving 101 human cancer patients.

In this study, 101 cancer patients were enrolled to undergo a cyclic fasting-mimicking diet (FMD) consisting of periodic 5-day long FMD followed by approximately 16-23 days of normal eating. Patients completed a median number of 4 FMD cycles. Multiple cancer types were included in the study. Many of the patients had advanced-stage cancer, and each patient also received concurrent cancer treatments, including chemotherapy, radiation therapy, and immunotherapy treatments.

The study determined that adding dietary intervention was safe, with little adverse side effects.

The cyclic FMD also helped create an anti-cancer tumor environment, including an anti-cancer immune response.

For example, immunosuppressive regulatory T cells and MDSC cells were downregulated, while cytotoxic T-cell became more active and infiltrated tumors more successfully.

5 (out of 101) patients experienced extraordinary tumor response

The response and survival of the participating patients were reported in a related paper with the title "Exceptional tumour responses to fasting-mimicking diet combined with standard anticancer therapies".

Five patients with advanced solid tumors and very poor prognoses experienced exceptional responses.

According to the publication, they "identified five patients with advanced, poor prognosis solid neoplasms (n = 1: extensive stage small cell lung cancer; n = 1: metastatic pancreatic adenocarcinoma; n = 1: metastatic colorectal cancer; n = 2: metastatic triple-negative breast cancer), who achieved complete and long-lasting tumor responses when treated with a combination of cyclic FMD and standard systemic treatments "

The researchers conclude that "FMD may have significantly contributed to enhancing the anti-tumor efficacy of standard cancer treatments that rarely result in complete and long-term tumor remission when used alone"

Please email if you'd like to read the paper or see the supplementary data documenting the response of the patients.

More studies are needed to determine how to combine dietary intervention with cancer treatments best to help dogs and people, but it is becoming evident that fasting or a ketogenic diet could play an important role in the battle against cancer.


Here is a quick summary of what the research on the ketogenic diet/fasting is revealing

  • Mouse studies have shown dramatic benefits when dietary intervention is combined with cancer therapies such as radiation therapy and chemotherapy.

  • It's possible to design safe dietary interventions for human and canine studies (based on ~100 patients, not yet thousands of patients)

  • Dietary intervention works better when combined with other treatments such as chemotherapy, radiation, immunotherapy

  • There are some isolated case reports of dogs whose tumors shrank or disappeared with dietary intervention alone

  • About 5% of human patients with advanced cancer enjoyed long-term survival when cyclic fasting-mimicking diet was added to standard cancer therapy.

Though we didn't go into the details here, there are other studies (human and some canine) that show that

  • There is strong evidence that fasting reduces the toxic side effects of chemotherapy in human patients. (A canine patient studies have also been carried out)

  • The gut microbiome is intimately linked to the successful response to immunotherapy

  • Avoiding antibiotics prior to immunotherapy leads to better outcomes (with human cancer studies)

CCA is launching several related studies. We'll share more details in future articles.

Questions? Email us at info@ccralliance, and we'll get back to you as soon as we can!

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All information the Canine Cancer Alliance website provides is for informational purposes only. It is not intended to be a substitute for professional veterinary advice.

Always seek guidance from your veterinarian with any questions you may have regarding your pet’s health and medical condition.

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