A study published in 2012 found that both home-prepared and commercial diets for dogs with cancer are universally unbalanced and nutritionally unsound, reports PetMD. There is no evidence to support the idea that dogs with cancer need a diet that is any different than that needed by healthy dogs.
The 2012 study reports that most so-called cancer diets for dogs suggest a grain-free diet on the grounds that grain-free diets are low in carbohydrates, but of the 27 cancer diets evaluated, at least one-third were not low in carbohydrates, says The Skeptvet. The theory that a low-carbohydrate diet starves cancer cells was proposed decades ago, but as of 2015, there are no published studies supporting the theory that a low-carbohydrate diet is beneficial in any way to any species of animal suffering from cancer.
Modern Dog Magazine repeats this myth and suggests that dogs suffering from cancer need to eat a lot of protein and fat and avoid eating high glycemic index foods. Based on this idea, many of the cancer diets for dogs suggest feeding raw meat, but since dogs with cancer often suffer from a depressed immune system, feeding raw meat may lead to severe illness. When a dog is seriously ill, feeding a nutritionally inadequate cancer diet may lead to worsening health, says PetMD.