Dietary Aspects in the Treatment of Feline Diabetes Mellitus

12. Dietary Aspects in the Treatment of Feline Diabetes Mellitus

The optimal diet for feeding the diabetic cat may not yet be known. However, the concept of the most beneficial diet in feline diabetes has seen some major changes over the last few years. Certainly the major step to better glycemic control was the introduction and recommendation of diets high (≥ 45 % of calories) in protein and low (≤ 20 % of calories) in carbohydrate.

Retrospectively, it seems obvious to feed cats a high protein diet which closely resembles their natural diet. Nonetheless, recognition that this may be particularly useful for the diabetic cat has revolutionized diabetic therapy. The traditional high (≥ 30 % of calories) carbohydrate (mainly starch), high (≥ 50 g total dietary fiber (TDF)/ 1000 kcal) fiber diet, which probably was adopted indiscriminately from the recommended diet in diabetic dogs or humans, is no longer recommended for cats. This mainly refers to the carbohydrate content of diets.

One of the main goals in diabetic therapy and prevention is to maintain optimal body condition. (© Yves Lanceau/RC (Siamois)).

General Goals for Feeding the Diabetic Cat

(see also: Biourge, 2005)
Because feline DM is a lifestyle disease similar to human type 2 DM, one of the main goals in diabetic therapy and prevention is to maintain optimal body condition. As will be discussed below, high protein diets are of particular benefit in feeding diabetic cats. However, the use of these specific diets is most effective when combined with aggressive glucose lowering therapy. For this, insulin therapy is the most useful. This will help to control for glucotoxicity (see above). The best results have been obtained with twice daily insulin injections. Without insulin therapy (or other glucose lowering therapies), it is extremely unlikely that one will be able to successfully treat diabetic cats, at least in the initial phase of treatment. With the combination of insulin and diet, however, there is a good chance for diabetic remission which may allow discontinuation of insulin administration. To achieve good metabolic control and to avoid the risk of insulin-induced hypoglycemia, consistency in timing and in the diet’s caloric content is also important.

The three main goals in the nutritional management of diabetic cats are:

1. To control excess body weight.
2. To reduce postprandial hyperglycemia.
3. To stimulate endogenous insulin secretion.

Prevent or Correct Obesity

Obesity is directly linked with insulin resistance which predisposes cats to develop overt diabetes mellitus (Scarlett et al., 1994; Scarlett & Donoghue, 1998). Prevention of obesity must therefore be one of the main goals when feeding cats.

Veterinarians should clearly council cat owners to restrict feeding immediately after neutering. Diets with low energy density, i.e. with a restricted amount of fat should be used. Dry diets that are high in fat (≥40 % of calories), especially if fed free choice in neutered cats, have been linked to weight gain and the development of obesity in numerous studies (e.g., Scarlett et al., 1994; Scarlett & Donoghue, 1998). To the contrary, feeding a moderate fat (25 % of calories), moderate carbohydrate diet (35 % of calories) reduced weight gain following neutering compared to a high fat (> 40 % of calories) dry diet (Nguyen et al., 2004b).

Weight loss is encouraged if the cat is fed a high protein diet (45% protein; 25% carbohydrates on DM) rather than a diet richer in carbohydrates (28% protein, 38% carbohydrates) (Hoenig et al., 2007a). Restricting caloric intake to the actual needs is important, even if cats are fed diets that closely resemble their natural diet because, at least in the short term, high protein diets do not lead to a significant amount of weight loss if fed ad libitum. However, during restricted feeding, when cats loose body weight, high protein diets may have an additional beneficial effect of favoring the loss of body fat over lean body mass (Mazzaferro et al., 2003; Hoenig et al., 2007a).

Principles in the Formulation of Diets for Diabetic Cats

The ideal diet for the diabetic cat should be:
- Moderate in energy (< 4,000 kcal/kg DMB)
- Moderate in fat (< 30% of the calories)
- Rich in protein (> 45% of the calories)

A moderate increase in dietary fiber (25 - 30 g/1000 kcal) might be of interest to moderate the energy density of the diet and to reduce the concentration of fat and carbohydrates. The amount of food offered has to be adjusted to the body composition (Nguyen et al., 2004a, 2004b). On average, this translates into a daily energy requirement of approximately 45 - 55 kcal/kg of body weight. Because most of our pet cats are neutered and have a sedentary lifestyle, feeding highly palatable, energy rich diets should be reduced. It should be made clear to the owner that any increase in body weight above normal increases the risk of cats to develop DM and should therefore be avoided (Scarlett & Donoghue, 1998). Once established, obesity is the major risk factor for the development of feline DM because of decreased insulin sensitivity (Biourge et al., 1997; Appleton et al., 2001b). Obese cats with insulin resistance have a disturbed insulin secretory pattern even before glucose tolerance is affected (Hoenig, 2002).

Minimize Postprandial Glucose Excursions

Apart from body weight alone, however, there may also be an additional influence of diet. High carbohydrate (50 % of calories) intake will promote postprandial glycemia, especially if the carbohydrate source has a high glycemic index (Figure 26). Hyperglycemia will stimulate pancreatic betacells to secrete more insulin. This stress might become overwhelming on the pancreas of overweight cats in which insulin resistance is present. However, there are no studies to date to show that high carbohydrate diets are directly linked to the development of insulin resistance or overt DM.

Figure 26. What is the glycemic index?

Diabetic cats fed a high protein diet (protein 57%; carbohydrate 8% DMB) achieve better metabolic control than cats fed a high carbohydrate diet (protein 40%, carbohydrate 24%; Frank et al., 2001). The use of high protein diets also helps to reduce postprandial hyperglycemia (Figure 4a & Figure 4b) (63% protein DMB, 8% carbohydrate in the study by Kettelhut et al., 1980; 54% and 8% in the study by Tschuor et al., 2006).

Not only the high protein and low carbohydrate content are of importance, but also the source of carbohydrate. Carbohydrates in diets for diabetic cats were recommended to be complex with a low glycemic index (i.e., barley, corn). Rice, which has a higher glycemic index than corn, resulted in a more pronounced increase of postprandial glucose and insulin levels (Rand et al., 2004).

It is unknown at present if this aspect is still relevant considering the low amount of carbohydrates in today’s typical diabetic diets. The glycemic index in high carbohydrate diets for diabetic cats would have played a more considerable role than in diets following today’s recommendations. Neither the specific role of the glycemic index in low carbohydrate diets nor the effect of mixed carbohydrate sources have so far been investigated.

Stimulate Endogenous Insulin Secretion

The third goal can also be achieved by high protein diets because the response of pancreatic betacells to amino acids in diabetic cats is usually maintained for longer periods than their response to glucose (Kitamura et al., 1999). Arginine has a strong effect on pancreatic insulin secretion.

Use of High Protein Diets in the Treatment of Feline Diabetes Mellitus

Introduction of high protein diets to feed diabetic cats has been a major step forward in improving therapy in feline DM. Several studies have shown that high protein diets improve the metabolic situation in diabetic and obese cats.

• Hoenig (2006a, 2006b) reported that insulin sensitivity of fat metabolism was not normalized in obese cats after body weight loss when the cats were fed a high carbohydrate diet but a high protein diet (45% DMB) improves insulin sensitivity in obese cats. Diabetic cats were not tested in this study.
• The use of a high protein (57% DMB and 50% of calories) low carbohydrate (8% DMB and 13% of calories), canned diet (Frank et al., 2001) showed a clear beneficial effect over a higher carbohydrate (24% DMB and 23 % of calories), high fiber (56 g TDF/1000 kcal) diet. In diabetic cats fed the high protein diet, the insulin dose could be reduced by up to 50%, and completely withdrawn in 3 of 9 cats (Frank et al., 2001; Bennett et al., 2006).
• In our own experience (Tschuor et al., 2006), the use of a high protein (54% DMB) low carbohydrate (8%), canned diet led to a much higher rate of diabetic remission (50 - 70%) than previously observed. Interestingly, this occurred even before any marked body weight loss was apparent. Therefore, even though high protein diets have been reported to make weight loss easier in cats (Szabo et al., 2000; Michel et al., 2005), this does not seem to be required for the beneficial effects observed in diabetic individuals.

Use of High Protein Diets in the Prevention of Feline Diabetes Mellitus

It has been hypothesized that feline pancreatic beta-cells may not be well adapted to high dietary carbohydrate loads and that high carbohydrate diets may be detrimental in cats. Nonetheless, the long-term consequences of overfeeding healthy cats with carbohydrates in respect to their contribution to the development of feline diabetes is currently unknown. One report mentions that insulin sensitivity is decreased and that hyperinsulinemia prevails in cats fed a high carbohydrate diet compared to cats fed a high protein diet (Hoenig, 2002). On the other hand, another study did not reveal any effect of a high protein (approx. 57% DMB protein 22% DMB carbohydrate) versus a medium protein (32% DMB protein, 49 % DMB carbohydrate) diet on insulin concentration and insulin sensitivity during an IVGTT or an arginine stimulation test in normal weight cats (Leray et al., 2006). More detailed experiments on a possible direct influence of high protein versus high carbohydrate diets to the development of insulin resistance, beta-cell failure and eventually DM in cats are clearly warranted.

The underlying mechanisms that could explain the positive effects of high protein, low carbohydrate diets are not clear. It has been suggested that the positive effect of these diets may be linked to a decrease in IGF-1 levels (Leray et al., 2006; but see Alt et al., 2007 reporting low IGF-1 levels in diabetic cats that normalize upon insulin treatment). Interestingly, in the study by Leray and colleagues no effect of a high protein (50 % protein calories) dry diet on insulin sensitivity was observed in normal weight cats (Leray et al., 2006). This was different from findings in other species. Therefore, it is unknown whether feeding cats with high protein diets is an effective means to prevent the development of diabetes mellitus. Clearly, this question remains unanswered at present.

Dietary Carbohydrate and Fiber Content in the Diet of the Diabetic Cat

The traditional diet for the diabetic cat contained relatively high (≥30 % of calories) amounts of carbohydrate and of dietary fiber (≥50 g TDF /1000 kcal). Dietary fiber is considered beneficial because it slows gastric emptying, gastrointestinal glucose absorption, increases insulin sensitivity and improves the control of nutrient metabolism by releasing gut hormones (Nelson et al., 2000). Viscous soluble fibers were considered of most value because they slow the transport of glucose to the surface of the gastrointestinal mucosa (Nelson, 2005).

A study compared the outcome on the diabetic management of two canned diets with a protein content of approximately 40% of energy, one containing low amounts of carbohydrate (12% of energy) and dietary fiber (0.1 g/100kcal), and one containing moderate amounts of carbohydrate (26% of energy) and high amounts of fiber (approximately 5 g/100 kcal) (Bennett et al., 2006). The rate of diabetic remission was higher in the former diet (>60% versus approx. 40%). Hence, a low content of carbohydrate clearly seems to be beneficial, and seems to outweigh the relatively low fiber content in this diet.

Psyllium seeds have been traditionally used in weight loss diets. Mucilage is able to absorb a great deal of water in the stomach, forming a voluminous gel.This slows down gastric emptying.

A study by Nelson et al (2000) compared two diets with similar amounts of protein (44% of dry matter), one containing a high amount (13% DMB), and one containing a low amount of fiber (2% DMB). The high fiber diet was beneficial. However, it also contained markedly less carbohydrate (27 versus 38% DMB) and slightly more protein. All factors combined might therefore have been responsible for the beneficial effect.

Overall, there is good evidence that the optimal diet for a diabetic cat should have a high protein and low carbohydrate content. Under these conditions, a high fiber content may be of slightly less importance than previously thought. However, by slowing gastrointestinal transit, dietary fiber still has its place in diets for diabetic cats. Further, a high fiber content leads to overall caloric dilution of the diet which clearly may help to control body weight in cats.

The Role of Specific Fatty Acids

The role of different types of fatty acids in obese cats has also been evaluated. One diet was enriched in omega-3 polyunsaturated fatty acids (n-3 PUFA; total fat content 20.1% on DMB; 9.6% of fat consisting of n-3 PUFA), the control diet contained reduced amounts of n-3 PUFA (total fat content 19.8%; 1.5% of n-3 PUFA). The diet high in n-3 PUFA was shown to improve the long-term control of glycemia and lower plasma insulin levels (Wilkins et al., 2004). In contrast, saturated fatty acids were considered to have detrimental effects on glucose control. The proposed underlying mechanism of omega 3-PUFA’s role in metabolism may include an activation or increased expression of PPAR-gamma, and thus an increase in insulin sensitivity.

Trans- and cisconfiguration of fatty acids.

Trans-fatty Acids

Patricia A. Schenck, DVM, PhD
Trans-fatty acids (TFA) are a specific type of unsaturated fat. Naturally occurring unsaturated fatty acids are mostly in the cis-configuration. In TFA, the spatial configuration is different because the hydrogen atoms are on the opposite sides of the double bond. TFA are found naturally in ruminant meats and dairy products. They are created by microbial transformation of cis-unsaturated fatty acids in the forestomachs. High levels of TFA, however, are also created during industrial hydrogenation or deodorization mainly of plant oils. The concentration of TFA in ruminant fats is approximately 5 to 8 g/100g fat, whereas the TFA of partially hydrogenated vegetable oils averages 45 g TFA/100g oil.

TFA and Human Nutrition
Recently, public interest has focused on the potential health risks associated with TFA intake in humans. Dietary TFA have been suggested to increase insulin resistance in humans, increasing the risk for the development of type 2 diabetes mellitus. Therefore, the replacement of TFA with polyunsaturated fat was postulated to markedly reduce the risk for the development of diabetes. Because of these potential health risks, some government agencies require the clear labeling of TFA contents in human foods, and some countries such as Denmark restrict the sale of processed oils containing high levels of TFA (e.g., more than 2% TFA in Denmark). In the United States, TFA have to be itemized separately in the Nutrition Facts label of food products.

Not All TFA Are Equal
It is very important to stress that not all TFA are equal. The negative effects of some TFA that are mainly created during industrial processing of vegetable fat have to be clearly separated from effects of other TFA that are created by microbial fermentation in the ruminants’ forestomachs. At least some of the latter TFA, e.g. the C-18 trans-vaccen acid, may rather have beneficial health effects. Trans-vaccen acid can be metabolized to conjugated linoleic acid which has been shown to have antidiabetic effects and anti-cancerogenic effects in animal experiments.

TFA in Cat and Dog Food 
Currently, there is no reason to believe that pet food containing TFA derived from ruminant sources has any deleterious effects on animal health. To my knowledge, no studies evaluating the effects of TFA in pets have been reported at this time nor have the different effects of TFA derived from ruminant sources versus industrially processed vegetable oils been looked at in cats or dogs.

Trace Elements and Antioxidants

The trace element chromium has been considered an essential cofactor for insulin action. The exact mechanism of chromium action to increase insulin sensitivity is unknown. However, the data are conflicting and far from conclusive. At present, there is no clear evidence to recommend the use of chromium. To the author’s knowledge, the effect of chromium in diabetic cats has not been tested. Compared to other treatment options, chromium’s beneficial effect appears negligible.

Vanadium, another trace element, seems to have comparable effects to chromium yet may act through different mechanisms. Only preliminary results are available which suggest that vanadium may have some beneficial effects in diabetic cats. The recommended dose was 0.2 mg/kg per day, administered via food or water (Nelson, 2005).

Glucotoxicity induced by chronic hyperglycemia contributes to progressive beta-cell damage and insulin resistance. In part, this is due to increased intracellular oxidative stress. Whether widespread use of antioxidants may help to reduce these effects, has, to the authors’ knowledge, not been investigated in well-controlled studies in cats. However, these compounds are considered safe based on the current scientific data. One may therefore consider fortifying diets with antioxidants.