Diabetic Diets for Dogs and Cats: Assessing the Evidence

Nutritional management can be an important adjunct to medical management of canine and feline diabetes. Once a pet has been stabilized on an insulin regimen, a change in diet may provide benefits to disease management. Consideration of essential nutrients of concern can help to optimize diabetic control and obtain ideal body condition.

There is no “one-diet-fits-all” approach to diabetes. Species, body condition, pet preferences, and comorbid diseases guide the optimal diet choice. Although controversy exists and approaches for optimal nutrition in pets differ, this article reviews the evidence behind various approaches to diabetic diets.

The American College of Veterinary Nutrition (acvn.org) and Today’s Veterinary Practice are delighted to bring you the Nutrition Notes column, which provides the highest-quality, cutting-edge information on companion animal nutrition, written by the ACVN’s foremost nutrition specialists.

The primary objectives of the ACVN are to:

• Advance the specialty area of veterinary nutrition
• Increase the competence of those practicing in this field
• Establish requirements for certification in veterinary nutrition
• Encourage continuing education for both specialists and general practitioners
• Promote evidence-based research
• Enhance dissemination of the latest veterinary nutrition knowledge

The ACVN achieves these objectives in many ways, including designating specialists in animal nutrition, providing continuing education through several media, supporting veterinary nutrition residency programs, and offering a wide array of resources related to veterinary nutrition, such as this column.

Nutrients of Concern

Before selecting a “diabetic diet,” consider the nutrients of concern that will guide the optimal nutrient profile. Common nutrients of concern in dogs and cats are shown in Box 1.

Many pets with diabetes have increased thirst or may experience polydipsia/polyuria, so fresh, clean water should be available at all times. Energy (calorie density) depends on body condition and whether the pet needs to gain or lose weight to obtain ideal body condition. Although not yet directly linked to outcomes in diabetes, protein and fat should be considered in pets with some comorbid conditions. For example, dogs with concurrent pancreatitis or hyperlipidemia may need dietary fat restriction, while overweight cats and dogs may need increased protein to ensure that their essential needs are met while they undergo calorie restriction. Chromium, a trace mineral, has been evaluated as a potential nutrient of concern because of its involvement in glucose regulation, but studies have not shown clinical benefit to supplementation.¹ Optimal levels of fiber and carbohydrates differ between species and are discussed in detail below.

Understanding Fiber

Different types of fiber can have different properties and benefits (or adverse effects). Fiber types can be defined in a few ways. In a clinical setting, however, describing fibers by their solubility in water is the most relevant.

Soluble fibers, such as pectins and gums, are best at absorbing water. Adding soluble fiber can promote healthy colonic mucosa and immune function in the colon, but this type of fiber is not as active in glucose control. Insoluble fibers, such as cellulose, have less water-holding capacity, but by adding bulk, they can slow absorption of dietary carbohydrate, which can be a benefit to glucose regulation in diabetic dogs. Some ingredients, such as beet pulp, are mixed-fiber sources and may have some of the benefits of both soluble and insoluble fibers.

Although the term “high-fiber diet” can be confusing, a rough estimate of the amount of insoluble fiber in a food is the crude fiber content. Of note, percentages on pet food labels are “guaranteed analyses” and thus indicate only a maximum or minimum; they cannot be compared between diets of different moisture or calorie content.^a

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^aFor more information on fiber and comparing fiber contents of diets, see “Featuring Fiber: Understanding Types of Fiber and Clinical Uses” in the 2017 January/February issue of Today’s Veterinary Practice.

Canine Diabetes

Although terminology varies, this article uses the clinically applicable terms insulin-dependent diabetes mellitus (IDDM) and non–insulin-dependent diabetes mellitus (NIDDM). Dogs are more commonly diagnosed with IDDM; thus, while diet can play an integral role in management, it should be used in conjunction with medical management.

The first aspect of dietary management to consider should be calorie density. Dogs with diabetes can present underweight, overweight, or even at ideal weight, so focusing on achieving or maintaining ideal body weight can guide diet choice based on calorie density. Calorie density is also intricately associated with another important nutrient of concern for diabetic dogs, fiber, which is commonly used to dilute calorie density. Diet selection based on individual pet needs can therefore be critical. For example, a food high in fiber and low in calorie density would be contraindicated for an underweight dog that cannot eat enough of the food to meet its energy needs.

The Case for Fiber

Although it would seem logical to reduce dietary carbohydrates in both dogs and cats for better glucose control, research has shown that for dogs, carbohydrate content in diets is not as clinically beneficial as fiber content. In fact, a study showed no difference in diabetic control in dogs fed canned diets that differed in carbohydrates by a factor of 9 (ie, 2% carbohydrate metabolizable energy [ME] vs 26% ME).² Research shows that the effect of insoluble fiber on diabetic control in dogs is more promising. Researchers found that dogs with naturally occurring IDDM had better fasting blood glucose and urinary glucose excretion while on a high-fiber diet (6.0 g/100 kcal) compared with a lower-fiber diet (2.6 g/100 kcal).³ Another clinical trial comparing diets with differing soluble and insoluble fiber concentrations showed that dogs with naturally occurring IDDM had better glycemic control while on the diet with high insoluble fiber.⁴

A challenging confounder in these studies is the correlating caloric dilution that results from the addition of fiber. It is not known whether the mechanism of action providing benefit is the addition of insoluble fiber itself, the subsequent lower calorie density, or the combination of the two. For dogs in which higher fiber is not contraindicated, the evidence suggests that diets with higher insoluble fiber may help with diabetic control after dogs are stabilized with medical management.

Clinical Consideration in Dogs

• At each visit, obtain a full dietary history that includes treats, chews, table scraps, and food used for medication administration to help ensure consistency and improve diabetic control. Sample diet history forms, as well as other helpful nutrition resources for veterinarians and clients, can be found online at the World Small Animal Veterinary Association Nutrition Toolkit site (org/nutrition-toolkit).⁵
• When higher-fiber diets are considered, let clients know in advance that the increased fecal bulk will result in more frequent need to eliminate. For dogs, this may mean that clients need to schedule more walks during the day to avoid accidents.
• Commercial diets are a better source of fiber supplementation because they can be formulated to still provide the appropriate essential nutrients to pets (added fiber can decrease absorption of nutrients from the diet). Canned pumpkin is popular with clients as a fiber supplement, but the amount needed to see an effect may unbalance the total diet (ie, the pumpkin would provide substantially more than 10% of the pet’s total calories).

Avoid fiber supplements containing added flavors or sweeteners, such as xylitol, which can be harmful to pets.

Feline Diabetes

Unlike dogs, cats can be diagnosed with IDDM or NIDDM, although the typical presentation is overweight cats with NIDDM. Also contrary to dogs, some cats with NIDDM can achieve remission. Obesity has been associated with NIDDM in cats and should be an initial consideration in selecting diets (ie, diets with lower calorie density that are appropriate for weight loss if necessary in obese cats). Any dietary change, especially one incorporating weight loss, should be introduced only after the cat has been stabilized on an insulin regimen.

Regardless of overweight status, adequate protein should remain a priority throughout diabetic management. Protein needs may change during weight loss (because of caloric restriction and relative nutrient density) or as a result of the catabolism that can accompany uncontrolled diabetes. The exact needs of each cat will differ and should be monitored by assessing muscle condition and altering protein content of the diet as needed.

Fiber Versus Carbohydrates: What’s the Evidence?

Only a handful of published studies address optimal diet composition (particularly fiber and carbohydrates) for cats with naturally occurring diabetes. Most have evaluated the effect of lower-carbohydrate diets. However, a study in cats with NIDDM fed a diet high in insoluble fiber (5.8 g/100 kcal) showed improved glycemic control compared with a diet low in insoluble fiber (1.1 g/100 kcal).⁶ Other studies have shown a positive effect of low-carbohydrate diets (<5 g/100 kcal), including improved glycemic control and diabetic remission, in cats with naturally occurring NIDDM.^7–10

Although it may seem that a low-carbohydrate diet has solid evidence to support its use, almost all of these studies have noteworthy limitations, such as not controlling for caloric intake or weight loss, small sample size, or comparison of diets that differed in more than just carbohydrate content. With at least some evidence to support both low-carbohydrate and high–insoluble-fiber approaches, the bottom line from the available studies is that both approaches may have some benefit in the regulation of feline diabetes, although low-carbohydrate diets look more promising.

Low-carbohydrate diets may not be appropriate for every cat. For example, many low-carbohydrate dry diets tend to be higher in calories because of the need for fat and protein to replace the carbohydrates. High-calorie foods, even if low carbohydrate, would be contraindicated in an obese cat with NIDDM because diabetes is so closely associated with obesity. Each cat should be evaluated individually, with considerations made for overall health.

Clinical Considerations in Cats

• Although it is not as common for cats to be given a variety of treats, clients often switch out flavors or textures, assuming that diets within the same line or product name are similar. These can have drastically different nutrient profiles, and clients should be instructed to carefully read labels and not switch foods without consulting with the veterinarian first.
• Similarly, dry and canned diets, even of the same product (veterinary therapeutic diets included), may not have the same nutrient profile and should not be used interchangeably without ensuring the nutrient profile meets the needs of the pet.
• One approach owners may find on the internet is to use “any kitten diet,” which wrongly assumes that all canned diets made for growing kittens are low in carbohydrates. This is not always the case, and, again, flavors and consistency can be concerns in over-the-counter diets that are not formulated and produced to be exactly the same from batch to batch.

Prevention

Although multiple studies show obesity is strongly associated with diabetes, the other risk factors for diabetes (and, thus, possible strategies for prevention) are less clear and have been considered controversial. Of the epidemiologic studies available, it appears risk factors for diabetes include obesity, male sex, physical inactivity, and indoor confinement, but not dry-food feeding or carbohydrate content.^11–13

Veterinary Therapeutic Versus Over-the-Counter Diets

Some veterinary therapeutic diets require a prescription because they are outside the Association of American Feed Control Officials guidelines for a healthy pet, but high–insoluble-fiber or low–carbohydrate-diet nutrient profiles can also be found in over-the-counter foods. Of consideration, however, is the consistency and strict processing protocols in veterinary diets that may not be found in over-the-counter diets, which may have more batch-to-batch variability. This variability may be fine for a healthy pet, but the consistency a veterinary therapeutic diet has for diabetic regulation may be beneficial. More peer-reviewed studies are warranted to further support this notion.

Regardless of prescription diet status, all clients should be warned about the risks of substituting flavors, textures, or even dry and canned versions of the same food (Box 2). Each product may have a drastically different nutrient profile and should be evaluated before switching. Additionally, a study has shown that semi-moist foods, especially those with sucrose, fructose, or other simple carbohydrates, resulted in higher postprandial blood glucose and insulin responses and should be avoided in pets with diabetes.¹⁴

More Tips for Clinical Management of Diabetes

• For clients who really want to provide treats, encourage the same treat at the same time each day or use a portion of the daily kibble as treats.
• Setting expectations is crucial, and it is helpful to discuss with clients that dietary management alone may not be successful.

Clients sometimes seek home-cooked diets. Consistency can vary because diets are made daily or weekly by owners and will have mild variability with each batch. As a result, such diets may not be ideal. Recommend a consultation with a board-certified veterinary nutritionist (acvn.org) to ensure the diet is formulated properly without any deficiencies.¹⁵