Diet and diabetes mellitus
From Felipedia
As a prefix to a consideration of what to feed diabetic cats, it must be pointed out that the majority of commercially-fed dry cat food has approximately 30-40% carbohydrate content, well above the natural carbohydrate content (approx 10%) of wild foods that a cat would eat. Hence, it is not surprising that the introduction of low carbohydrate (i.e. high protein) diets to feed diabetic cats has been a major step forward in improving therapy in feline diabetes.
Several studies have shown that high protein diets improve the metabolic situation in diabetic and obese cats[1]. Restriction of carbohydrates to less than 15% of the diet is critical for management of diabetes in cats. Research data on cats suggests that cats have a long postprandial period, and mean glucose concentrations are not different between cats that are meal-fed every 24 hours versus ad libitum fed cats[2].
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 In diabetic cats fed the high protein diet, the insulin dose could be reduced by up to 50%, and completely withdrawn in 3 of 9 cats (Frank et al., 2001; Bennett et al., 2006).
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.
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High Protein Diets in Prevention of 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-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.
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.
Potential Problems of High Protein, Low Carbohydrate Diets
The question about the long-term effect of high protein diets on renal function has been raised. However, it should be stressed that there is no indication that the long term feeding of diets high in protein causes a deterioration of kidney function in normal cats or in cats with early kidney disease (Finco et al., 1998). Obviously, high protein diets are contraindicated for cats with uremia, and nephropathy is a relatively common finding in diabetic cats (Nelson, 2005). To the author’s knowledge, however, no study has investigated this question in detail.
In cases where impaired renal function and azotemia occur concurrently in diabetic cats, the use of diets with reduced amounts of protein may be warranted to minimize the risk of a uremic crisis. In these cases, one may envisage the combination of such a diet with drugs like acarbose, which limits gastrointestinal carbohydrate absorption. However, hard data to support this idea are lacking.
Despite a clear improvement in the management of diabetic cats since the introduction of diets high in protein and low in carbohydrate, many questions remain to be answered.
- Is protein or carbohydrate the key factor, i.e., is it the high protein or the low carbohydrate content that is most important?
- Do some particular amino acids such as arginine, have beneficial effects? Hence, would different sources of protein play a role (Leray et al., 2006)?
- What are the long term consequences of feeding these diets for the risk of diabetic ketosis or diabetic nephropathy? At present, there is no indication that the long term feeding of diets high in protein leads to a deterioration of kidney function in normal cats or in cats with early kidney disease (Finco et al., 1998).
- What are the long term consequences of feeding high protein diets on body weight and body composition?
References
- ↑ Rand, JS (2010) Use of long-acting insulin in the treatment of diabetes mellitus. In August, JR (Ed): Consultations in feline internal medicine. Vol 6. Elsevier Saunders, Philadelphia. pp:286
- ↑ Farrow, HA, Rand, JS & Sunvold, G (2008) Diets high in protein are associated with lower postprandial glucose and insulin concentrations than diets high in either fat or carbohydrates in normal cats. J Vet Intern Med 16:360
(See diabetes mellitus)
