The Right Diet for Cats with Kidney Disease - The Conscious Cat
In one older study, (2000) Elliott J, Rawlings JM, Markwell PJ, Barber PJ 41 pp235-42, 29 cats were fed a reduced protein, low phosphorus therapeutic kidney diet, while a further 21 cats did not eat this diet. Some of the cats (presumably in both groups) were also given phosphorus binders. The cats fed the therapeutic kidney diet survived longer than the other cats, but it is not clear whether this was due to the reduction in phosphorus intake rather than the reduction in protein intake. The study concluded "Feeding a veterinary clinical diet (with intestinal phosphate binders where necessary) specifically formulated for feline renal failure was associated with a highly significant beneficial effect on survival of cats presenting with naturally occurring stable CKD. This is the first prospective dietary study involving naturally occurring feline CKD cases where survival from first diagnosis has been assessed."
(1999) Polzin DJ, Osbourne CA, James K, , adapted from articles presented at the 1998 Purina Nutrition Forum, sees things differently. It states: "In cats, dietary supplementation with n-3 PUFA had no apparent deleterious effect on lipid metabolism, immune function, blood pressure, or renal function. At higher levels of supplementation, renal function was actually increased in normal cats. These data support the assertion that this dietary maneuver is safe for normal cats and provides some encouragement for further consideration for dietary n-3 PUFA supplementation in cats with renal disease, systemic hypertension, or hypersensitivity reactions."
Feline "renal diets" are specifically formulated for the purpose of clinical management of cats with chronic kidney disease (CKD). These diets include commercial products and diets specifically designed for cats with CKD formulated by boarded veterinary nutritionists. "Renal diets" have been considered the "gold standard" therapy for managing cats with CKD for many decades. Based on evidence from clinical studies, the IRIS Board suggests renal diets be considered for cats with IRIS CKD Stage 2 and recommend feeding renal diets to cats with IRIS CKD Stages 3 and 4.Recently, use of "renal diets" in treating cats with CKD has become controversial, weighing the potential benefits of these diets mitigating the clinical consequences of CKD versus the purported potential risk of protein malnutrition consequent to the high protein requirements of cats. As a result, some veterinarians have recommended feeding diets containing high levels of dietary protein instead of "renal diets". This divergence in therapeutic opinion has evolved from recent studies suggesting that senior cats may require more protein than younger cats and the observation that at least in some cats with CKD, body weight, body condition score and/or muscle mass may decline over time. Further, substantial loss of lean mass has been shown to be associated with increased mortality in cats with CKD. The specific point of disagreement between these two schools of thought is focused on how much protein should be fed to cats with CKD. More specifically, those advocating feeding higher protein diets to cats with CKD have generally recommended feeding commercial or non-renal therapeutic diets containing more protein instead of feeding the currently available "renal diets" specifically designed for cats with CKD. These high protein diets do not include the other dietary modifications found in "renal diets".Veterinarians typically use therapeutic diets in much the same way as they use pharmaceuticals to manage medical conditions. When they prescribe feeding a "renal diet" for cats with CKD, they expect the diet to achieve four specific goals: 1) to ameliorate or prevent clinical consequences of CKD including signs of uremia; 2) to slow progression of CKD and prolong survival; 3) to minimize derangements of electrolyte, calcium and phosphorus, and acid-base balance; and 4) to maintain adequate nutrition. To achieve these multifaceted goals, modifications beyond just reduced protein content are incorporated when formulating renal diets, including: reduced content of phosphate and sodium; increased content of omega-3-polyunsaturated fatty acids, antioxidants, fiber, vitamin D and potassium; and a neutralizing effect on systemic pH. Clinical trials have supported clinical benefits of "renal diets" formulated similar to these dietary modifications.The third study was a retrospective study performed in 31 first-opinion veterinary practices in The Netherlands and compared survival times for cats fed one or more of 7 commercial feline "renal diets" to those not fed a "renal diet". (Plantinga, 2005) Median survival time for cats fed a "renal diet" was 16 months compared to 7 months for cats fed their usual (non-renal) diet.