Carbohydrate Metabolism
Perhaps the most dramatic alterations in metabolism of animals with a wide variety of cancers occur in carbohydrate metabolism. For example, when dogs with a wide variety of malignancies without clinical evidence of cachexia were evaluated with an intravenous glucose tolerance test, lactate and insulin concentrations were significantly higher when compared to controls.19 The hyperlactatemia and hyperinsulinemia did not improve when these dogs were rendered free of all clinical evidence of cancer with either chemotherapy or surgery.15 Metabolic alterations result in part because tumors preferentially metabolize glucose for energy by anaerobic glycolysis forming lactate as an end product.2,16 The animal must then expend necessary energy via "futile cycling" to convert lactate to glucose by the Cori cycle resulting in a net energy gain by the tumor and a net energy loss by the host.14,16-19
The inability of some tumor bearing animals to tolerate glucose parenterally may have some bearing on the dietary management of the cancer patient. Logically, it can be concluded that diets high in simple carbohydrates may increase the total amount of lactate produced and the need for the host to utilize energy unwisely for conversion of lactate. This may have long-term detrimental effects on animals with cancer.
To test this hypothesis in the dog, a group of dogs with lymphoma were evaluated to determine if a diet high in simple carbohydrates is detrimental compared to a diet low in simple carbohydrates.20 In this study, dogs were randomized and fed isocaloric amounts of either a high fat diet, or a high carbohydrate diet before and after remission was attained with up to 5 dosages of doxorubicin chemotherapy. As hypothesized, the mean lactate and insulin levels from the dogs fed the high carbohydrate diet was significantly higher than the level from the dogs fed the fat diet after the dogs were fed the diets and put into remission with chemotherapy. Interestingly, dogs fed the high fat diet were more likely to go into remission. This study showed, therefore, that diet was effective for influencing response to therapy and select aspects of carbohydrate metabolism.
The bottom line is that simple carbohydrates may not be ideal for the cancer patient. Therefore, when considering a diet for a pet with cancer, a diet that has minimal amounts of simple carbohydrates may be ideal.