How does a “kidney diet” help my pet ?
By Dr. Dan Su, MS, DVM, DACVIM (Nutrition)
Chronic kidney disease, or CKD, is a common issue that can afflict our pets, especially cats. When it comes to CKD in pets, nutrition modification is the mainstay treatment, as we typically do not pursue dialysis or kidney transplants like we would for humans. This is why your veterinarian prescribes kidney diets when your pet is diagnosed with CKD. The good news is that these dietary modifications can help our pets live longer and slow down CKD progression. Let’s take a deep dive into what these modifications entail.
First up, phosphorus control is the most important when it comes to slowing down kidney disease progression. Healthy kidneys normally filter out excessive phosphorus. However, when they get sick, they don’t filter as well, leading to elevated phosphorus levels in the bloodstream. These elevated levels kickstart a chain reaction, ultimately culminating in CKD mineral and bone disorder, which mineralizes organs (including the kidneys) and furthers the disease. Reducing dietary phosphorus is the primary strategy to combat this. Later on, your veterinarian may recommend adding phosphate binders into your pet's food to prevent phosphorus absorption. Recently, research has also shown that not it’s not just the amount of phosphorus, but also the form it takes, that can affect kidney health (especially in cats).
Next, we've got protein, a nutrient that often springs to mind when discussing CKD nutrition. However, it is actually quite controversial where protein stands. Protein metabolism contributes to the buildup of uremic toxins, making CKD pets feel unwell. So, it seems logical to feed lower protein diets to CKD patients. However, it's equally crucial to provide an adequate protein supply to prevent muscle loss and protein malnutrition, both of which can spell trouble for survival. Depending on the severity of CKD, there might be room for slightly higher protein diets compared to the conventional kidney diets. Yet, there's an exception to the rule: when proteinuria (protein in the urine) is detected. Under normal circumstances, protein shouldn't make an appearance in urine, and when it does in CKD cases, it signifies damage to the kidney's protein-filtering mechanisms. In these scenarios, additional dietary protein could further stress the already struggling kidneys. A lower protein diet without causing protein malnutrition is necessary in these cases.
Sodium is another element that's often on pet parents' radar for CKD management. But, just like with protein, things aren't as clear-cut as they might seem. High blood pressure is frequently linked to CKD in pets, so it's easy to assume that restricting dietary salt is the way to go, given what we think about for humans with high blood pressure. Surprisingly, there's no solid evidence proving that dietary salt intake worsens blood pressure in pets, while excessive restriction might even cause harm.
Potassium is another electrolyte that may get affected by CKD due to the kidney’s role in regulating electrolytes and acid-base balance. It is more common for cats to be low in blood potassium levels, while dogs can develop either hyperkalemia (high blood potassium level) or hypokalemia (low potassium level). In these cases, dietary modifications can be made to either increase or decrease potassium levels, while also keeping in mind medications that can affect these levels.
Apart from these dietary puzzle pieces, there are other players on the field. Omega-3 fatty acids, particularly EPA and DHA (commonly found in fish oils), are known for their anti-inflammatory properties, which may be helpful with CKD, given the ongoing kidney inflammation. Antioxidants, like vitamins E and C, also have a role to play, combating oxidative damage contributing to kidney issues in chronic conditions. Recent research has even delved into prebiotic fibers that may help reduce the absorption of metabolic products that worsen clinical signs and CKD progression.
Now you know why your vet has recommended a kidney diet. If you want additional help for your pet with CKD, it may be helpful to reach out to a board certified veterinary nutritionist. A veterinary nutritionist can help you navigate the most important part of CKD management, while taking into account your pet’s overall condition (weight, muscle mass, energy level, clinical signs, etc.) to ensure they have the best quality of life possible. If commercial diets don't cut it for your four-legged friend, don't fret – we are here to help!
