Diabetes mellitus (DM) is a common disease and its prevalence is increasing (Box 1). The mainstay of treatment for DM is exogenous insulin injections alongside dietary modification (Behrend et al., 2018). This article will focus on the role of nutritional support in the management of DM in dogs. A second article in a future issue will look at how this differs in cats.
Where concurrent conditions, such as pancreatitis or obesity, coexist and may have contributed to the development of DM or ongoing instability of DM, nutritional management of these is crucial to consider, and is also briefly covered in this article.
The key goals of DM treatment include minimising clinical signs or associated complications, which requires control of blood glucose to below the renal threshold for as much of a 24-hour period as possible, avoiding clinically significant hypoglycaemia, and, in cats, remission (Behrend et al., 2018). However, over 20 percent of dogs and cats diagnosed with DM are euthanised within 12 months of diagnosis, most commonly due to negative impacts on the quality of life of the owner (Neissen et al., 2017). Thus, it is also crucial to ensure that the level of diabetic control aimed for is within the constraints of the owner’s capability. Strategies with a low hypoglycaemia risk and decreased impact on owner lifestyle are desirable (Neissen et al., 2017), and diet can be a key element within this. Maximising owner adherence and ensuring the treatment and management approach is tailored to the individual pet and owner is key, and this includes any dietary plan.
Nutritional management of canine diabetes
Type 1 diabetes mellitus is most common in dogs with beta cell loss primarily due to immune-mediated destruction or pancreatitis (Rand et al., 2004). Optimal management of canine diabetes mellitus involves a consistent schedule of insulin injections, meals and exercise, aiming to maintain blood glucose concentrations as close to normal as possible to help minimise clinical signs whilst avoiding hypoglycaemia.
The two most important principles of feeding diabetic dogs are to support good glycaemic control and to provide sufficient calories to achieve and maintain optimal body condition (Fleeman and Rand, 2001). Additional goals include managing complications of diabetes such as hypercholesterolaemia and other lipid changes, and oxidative stress. Owners should be aware that a consistent insulin-dosing and feeding routine will maximise the likelihood of success, although, for practical reasons, a certain amount of compromise may be necessary and, in most dogs, is well tolerated.
Consistency of intake, as well as the timing and size of meals, is of greater importance to help maximise diabetic control in dogs compared to cats. For canine diabetics, feeding a complete and balanced diet at consistent times in consistent quantities is crucial to maximise glycaemic control (Behrend et al., 2018) (for example, 50 percent of the main meal ration fed in two equally sized meals at the same times each day). Ensuring the diet is highly palatable is key to ensuring predictable intake and should be a priority for appropriate diet selection (Fleeman and Rand, 2001).
Consideration of the nutritional profile of the food fed is also important. Many dogs will do well on a complete and balanced diet with a range of nutritional profiles (Behrend et al., 2018). However, multiple studies have demonstrated that diets that contain increased quantities of soluble and insoluble fibre within the diet can help to reduce post-prandial hyperglycaemia and fructosamine levels (Nelson et al., 1998; Kimmel et al., 2000; Behrend et al., 2018). Mixed fibres (for example, maize, barley, soya, pea fibre) may be better at controlling post-prandial hyperglycaemia in dogs than insoluble fibre (cellulose) alone (Graham et al., 1994). Complex carbohydrates such as barley and soya lead to a flatter post-prandial blood glucose curve compared to carbohydrates such as rice with a higher glycaemic index, and the diet fed should be low in simple carbohydrates and sugars (Graham et al., 1994). Addition of the alpha amylase inhibitor, phaseolamin, has the ability to reduce the post-prandial spike in blood glucose levels in humans (Barrett and Udani, 2011). This may also help to reduce post-prandial glycaemic rises in dogs and has now been incorporated into a commercial diet designed to support canine diabetes mellitus.
Consideration of comorbidities
Achieving and/or maintaining an optimal body condition score is a key aim of appropriate management in diabetic dogs. Consideration needs to be given to obesity, where present, and the presence of any concurrent conditions such as pancreatitis. Where two or more conditions coexist, precedence should be given to providing nutritional support tailored towards the condition most impacting on the dog’s quality of life.
Where obesity is present, it should be managed with appropriate caloric restriction since obesity contributes to insulin resistance. Diets with complex carbohydrates and higher fibre levels may both assist with minimising post-prandial hyperglycaemia and help with weight loss.
On the other hand, some diabetic dogs may be underweight. In these dogs, it is important that any diet fed is of high quality, palatable and not designed for weight loss. In such dogs, higher fibre levels may inhibit weight gain and may potentially reduce palatability. For this reason, some underweight diabetic dogs may do better on a highly digestible diet not specifically designed for diabetic dogs (Fleeman and Rand, 2001).
Extensive pancreatic damage, which likely results from chronic pancreatitis, is responsible for the development of diabetes in 28 percent of diabetic dogs (Rand et al., 2004). High-fat diets and hypertriglyceridaemia have been proposed as possible inciting causes of canine pancreatitis and low-fat diets should be recommended for dogs with concurrent chronic pancreatitis and DM. These may have a reduced fibre level, but glycaemic control can still usually be maintained with exogenous insulin (Fleeman and Rand, 2001). It is important that recurrent episodes of pancreatitis are minimised as this can negatively impact on glycaemic control: higher doses of insulin may be temporarily required, and conversely, hypoglycaemia may occur if a dog is inappetant and vomiting but receives their usual dose of insulin (Fleeman and Rand, 2001). Appropriate nutrition with a low-fat diet is a key component to long-term pancreatitis management.
Any dietary transition in a diabetic dog should be done gradually to minimise negative impacts on glycaemic control. Providing a written dietary plan for the owner, including the type of food that should be fed, amount to feed at each meal and timing of meals, alongside an area for notes to be made by clients with respect to the amount eaten at each meal, clinical signs (for example, water intake) and insulin dose required may help support adherence to any diet plan and allow evaluation of the success of any nutritional management recommended.
Dietary modification plays an important role in the management of DM to help maximise glycaemic control, minimise clinical signs and maximise quality of life in diabetic dogs. It can also have a key role in supporting any coexisting conditions that may complicate diabetic control in dogs. Whilst the nutritional profile can have a significant role, it is perhaps of slightly less importance in dogs compared to cats, whereas aiming for a consistent schedule of insulin injections and food intake, alongside managing comorbidities such as pancreatitis, is key.
A free example of an owner food “diary” to assist in the nutritional management of diabetic dogs can be found online.