Keto diets as pet food: dangerous or beneficial?

Two basic types of ketogenic diets exist: a ketogenic diet based on long-chain triglycerides (LCT) and a ketogenic diet based on medium-chain triglycerides (MCT). Currently, the MCT diet is the only one implemented in veterinary medicine while the use of the LCT diet is described anecdotally and is currently not backed up by an extensive body of evidence.

Tumor research

The use of the LCT ketogenic diet in humans has been extensively studied in tumor research. Studies indicate that tumor cells have increased glucose consumption, most likely due to mitochondrial dysfunction. Therefore, dietary changes, such as the ketogenic high-fat LCT diet, which induces oxidative metabolism, and limits glucose consumption, represent a possible nutritional approach for inhibition of tumor growth.

Like master, not like pet

The metabolic pathway of ketone bodies is well known: free fatty acids are metabolized in the liver to ketone bodies acetoacetate, -hydroxybutyrate and acetone. Ketone bodies are further transported to various tissues and used as energy sources. Although metabolic pathways are similar, we must be aware that humans and pets are quite different when it comes to energy utilization, as there are marked metabolic differences between these species.

In dogs, in contrast to humans, a significant increase of ketone bodies in the blood does not lead to marked ketosis even after long-term fasting. Moreover, the concentration of ketone bodies is at least 10 times higher in humans than in dogs after fasting. These data suggests that dogs utilize ketone bodies far more efficiently than humans.

Cats, as obligate carnivorous species, are known to have high protein requirements and are sensitive to hepatic lipidosis development during marked increase in fatty acids oxidation. They are, therefore, a species where a high-fat LCT diet could lead to significant health risks when amino acid and gluconeogenetic capacity is not met. Additionally, cats, like dogs, are thought to possess effective mechanisms for ketone bodies utilization, and a state of ketosis is not easily achieved.

Not without risk

The use of a ketogenic diet in dogs and cats, as nutritional management during treatment or recovery in tumor patients, has not been described in existing veterinary scientific literature. Therefore, it is presumptive to claim that the use of an LCT ketogenic diet is without risk.

According to existing guidelines, a dietary plan for small animal oncology patients should include an individually adapted nutrition plan, with the consideration of clinical symptoms, prognosis and concurrent pathologies. Tumors in dogs and cats often lead to changes in food intake and nutritional status, so oncology patients should receive individually tailored nutritional support to minimize chemotherapy side effects.

Potential uses

Contrary to the use of the LCT ketogenic diet in oncology patients, the use of the MCT diet in epileptic dogs provided promising results. Ketosis has neuroprotective and anticonvulsant activity, and the research has shown that alterations in neuronal metabolism and neurotransmitter function in ketosis could be beneficial.

Namely, it was found that the frequency of seizures is significantly lower in dogs fed the MCT diet. The ketogenic MCT diet is designed to improve the shortcomings of the classic LCT diet. The fatty acids used in MCT are caprylic and capric acid, and to a lesser extent caproic and lauric acid.

The MCT diet, unlike the LCT diet, is not based on macronutrient ratios but on the concentration of medium-chain fatty acids that are able to derive ketone bodies. The main advantage of the MCT diet is better absorption and faster transport of fatty acids to the liver, avoiding the thoracic duct and chylomicrons formation, resulting in faster β-oxidation and the formation of ketone bodies.

The MCT ketogenic diet requires less fat to achieve a beneficial concentration of ketone bodies: just 10% of energy must be supplied through MCT. A lower proportion of fat and thus a higher proportion of protein and carbohydrates in the diet contributes to better palatability and minimizes the risk of pancreatitis or hepatic lipidosis contrary to a high-fat LCT ketogenic diet.