Evolutionary events shaped the cat’s core metabolism such that their systems are uniquely set up to metabolize a diet which is high in moisture, high in protein, and very low in carbohydrates. Because this is the diet they have relied upon for tens of thousands of years, they do not have the ability to process carbohydrates very efficiently (1-4). This becomes extremely important when selecting a diet for cats with diabetes, as I’ll discuss below.
Normal Glucose Metabolism and Postprandial Glycemia in Cats
So what are these specific feline adaptive mechanisms that have developed to meet the requirements of a carnivorous diet?
- First, cat’s gluconeogenic pathway provides an almost continuous source of carbon skeletons for glucose or energy production.
- Secondly, glucokinase concentrations are markedly reduced or absent, whereas hexokinase activity is increased. This is in marked contrast to the liver of omnivores (dogs, man), which contains both glycolytic enzymes that act to catalyze the phosphorylation of glucose during glycolysis.
- Finally, cats have reduced amylase and disaccarharide activity in the small intestine, reduced and delayed insulin secretion, and delayed gastric emptying (1-4).
In healthy humans and dogs, postprandial hyperglycemia normally persists for 2 to 5 hours (5-6). In contrast, a recent study of healthy cats found that both serum glucose and insulin concentrations remained significantly increased for a median time of 12 hours following ingestion of a moderate carbohydrate meal (25% ME), and that both glucose and insulin concentrations remained above baseline values for 24 hours in approximately 20% of the cats (7). Most feline diets (especially dry foods) contain ever higher amounts of carbohydrate and therefore would be expected to result in more severe postprandial hyperglycemia and a longer time to return to baseline.
Dietary Management of Cats with Diabetes Mellitus: Key Part of Treatment!
In cats with diabetes, a primary goal of therapy is to minimize the degree of hyperglycemia that develops after feeding in order to lessen the subsequent demand on beta-cells to secrete insulin. By doing this, we decrease the effect of “glucose toxicity” and allow the pancreatic islet cell to hopefully recover (8,9).
But how do we do this? It has long been known and is a well accepted “dogma” by most practicing veterinarians who specialize in feline medicine that feeding a low-carbohydrate diet is the mainstay in the treatment of diabetes mellitus, especially if remission of the diabetic state is the goal. Feeding a low carbohydrate diet will improve insulin sensitivity, reduce or eliminate the need for exogenous insulin, and help stabilize glucose metabolism in these cats (9-12). Again, one major way a low-carb diet improves the diabetic state is by helping to prevent severe and prolonged postprandial hyperglycemia.
The sooner one starts the diabetic cat on a low-carbohydrate diet, the better. By “low-carb,” I mean a diet that provides less than 10% of the calories as carbohydrate. Some cats will do fine on a slightly higher-carb diet (12-14%) whereas others do best on a diet containing less than 7% carbohydrate.
To achieve these low carbohydrate levels, we must formulate a homemade diet or feed a canned food. I'd recommend that one go to Dr. Lisa Pierson's website at www.catinfo.org. Once there, you should review the “Protein/Fat/Carbs Chart” on the sidebar of the homepage to select an appropriate low-carb diet.
None of the available dry cat foods are very low in carbohydrates and most are too low in protein. It’s best to limit the amount of dry food that is fed to diabetic cats, or even better, not feed dry food at all.
When we reduce the content of carb in a cat food, we must raise the content of either protein or fat, or both. I like to do both, feeding my diabetic cats a diet that mimics the composition of their prey in the wild: about 40-60% of protein with the remaining amount in fat. This higher than average protein level also helps restore and maintain lost muscle mass, since many diabetic cats will develop muscle wasting or “sarcopenia” as they age (13-17).
Dietary Management of Diabetic Cats and Remission
Another plus for feeding low-carb, hi-protein diets in cats with relatively early diabetes is that this diet composition (together with insulin treatment) greatly improves the diabetic remission rate (18-20). If the diabetic cat goes into remission (no more insulin needed to maintain euglycemia), we recommend maintaining a restricted carbohydrate diet for life to help prevent relapse of the diabetic state.
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- American Diabetes Association. Postprandial blood glucose. Diabetes Care 2001;24:775-778.
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