Often times it is recommended for cats with kidney or liver disease to start on low protein diets. However, it is important to know that the issue of protein is very complex when it comes to cats with chronic disease. Additionally, there are many other nutritional concerns when it comes to kidney or liver disease.
Excess dietary protein creates ammonia. This ammonia is converted in the liver to urea. Urea is filtered out by the kidneys. The idea behind a low protein diet is to lower the work that the kidneys or liver must do. However, when a cat is fed too little protein, muscle wasting will occur. This is especially common in kidney disease, as many kidney disease cats have a reduced appetite.
Many studies have been conducted to try to determine the minimum amount of protein that cats require, but this question has turned out to be an extremely complex one. The amount of protein a cat requires is largely dependent on what types of amino acids make up the protein. One study from UC Davis (Taylor et al.) found that kittens could be fed as low as 21% protein using a certain amino acid composition, while kittens needed 28% protein when fed a different amino acid composition. A study conducted by Purina found that adult cats needed 34% protein when fed a diet of typical commercial cat food. Legally, adult cat food must contain 26% protein, but in most cases, this is not enough.
The research on protein content of cat food shows that the types and amounts of specific amino acids are critically important. When certain amino acids are not needed, they will be converted by the body to other types of amino acids or be “burned” for energy. These processes create nitrogen waste, which the kidneys and liver must remove. Avoiding this process as much as possible is achieved by feeding a good balance of amino acids.
Choosing a Best Low Protein Cat Food for Kidney Disease
Limiting phosphorus and increasing hydration are the most important nutritional goals for cats with kidney disease. All of the kidney disease foods on our list have a low phosphorus level. We have also kept an eye out for fish oil in the ingredients, as omega-3s can delay the progression of kidney disease.
It is recommended to feed cats with kidney disease an exclusively wet low protein food diet in order to help keep them hydrated. Dry low protein food should only be fed to cats who absolutely refuse to eat a canned diet.
Considering that muscle wasting is a real concern for cats with kidney disease, it is best to choose a food with protein levels between 30% and 50% dry matter. This protein should come primarily from meat. Meat contains highly usable amino acids, which will reduce the stress on the kidneys.
The amino acid arginine specifically should be limited to the minimum level required in the diet. Arginine is especially high in nitrogen and removing excess arginine creates extra work for the kidneys. The protein in rice, peas and soy is especially high in arginine, so it is wise to avoid these ingredients when searching for a low protein kidney diet.
Best Low Protein All-Natural Brands – Dave’s Restricted Magnesium & Phosphorus
Dave is on a one-man mission to provide affordable quality pet food to the world. The protein in this food comes from pork, meaning it should be highly digestible. Despite the high meat content, this food is roughly half the price of a similar prescription diet. In line with keeping costs low, this company does not have a large sales team and the food may be difficult to find in brick-and-mortar stores outside of the New England area.
This food has extremely low phosphorus content at 0.57% on a dry matter basis. This is some of the lowest phosphorus available in non-prescription cat food. Potassium citrate and dl-methionine are included in this food to regulate urine pH and prevent crystals, which is a great added benefit. The food also contains salmon oil, so there are definitely omega-3s to help slow kidney disease.
This food is a pate texture, which can be hit or miss with some cats. Finicky cat may prefer the food mashed with a fork, with water added or warmed slightly.
Despite this pet food company being small, they have a good track record of safety and quality. They use the same manufacturing facilities as brands such as Wellness. We think this food is a great choice for cats with kidney disease.
Best Low Protein Prescription Diet – Royal Canin Renal Support D
This diet is specially formulated for cats with kidney disease and requires a prescription from a veterinarian. It is a chunks in gravy texture and even picky cats with kidney disease seem to love the flavor.
It has an extremely low phosphorus content of 0.44% on a dry matter basis. The protein in this food is primarily from chicken and pork. Wheat flour is also included, likely for the consistency of the gravy, and does not appear to be a significant contribution to the protein content.
This food is just filled with great ingredients. Fish oil will provide omega-3s to help slow kidney disease. The potassium citrate will regulate urine pH and help prevent urinary stones. Fructooligosaccharides are probiotics that will promote gut health. Marigold extract is included as an antioxidant too.
Royal Canin veterinary diets are backed by significant amounts of research and thus are more on the expensive end of cat food. Royal Canin operates as an independent company within Mars, Inc. They have their own production facilities with a good track record of safety, quality and nutritional innovation.
Best Low Protein Trusted Brand Food – Hill’s Science Diet Adult 7+ Tender Chicken
Hill’s Science Diet always seems to do a good job of controlling phosphorus levels and this food is no exception. At 0.57% dry matter phosphorus, this food is sure to help keep your cat’s kidneys healthy.
The protein in this food is primarily sourced from chicken and pork. This food also includes wheat flour and wheat gluten, which are vegetable protein sources, but it is unclear what proportion of the food wheat composes. It is possible that wheat is included in small amounts to help with the chunks and gravy texture of the food. Regardless, wheat is low in arginine content, which is good news for cats with kidney disease.
This food includes fish oil as a source of omega-3s. It also has antioxidants such as beta-carotene and vitamin C. Overall, this food would be a healthy choice for a cat with kidney disease.
Hill’s Science Diet is an interesting brand in the pet food world. They have some of the highest investment into pet nutrition research of any company. They make all of their own food and does not outsource production in order to keep an extremely close eye on quality control.
Hill’s is owned by Colgate-Palmolive which gives them access to significant production knowledge, but also heavily subjects them to corporate interests. This means that in every formula developed a balance of marketability, cost-effectiveness and health is the goal. In the case of finding a low protein food for cats with kidney disease, this food is a great example of striking this near impossible balance. Meat content and quality is high, while maintaining a reasonable price.
Best Low Protein High Calorie
Food – Nature’s Logic Duck & Salmon
Many times is can be difficult to get a cat with kidney disease to eat enough food. At a whopping 230 calories per a 5.5 oz can, you should have no trouble getting enough calories for kitty. This food is about as popular in flavor as any pate texture. If you cat isn’t a fan of the pate texture, you can try mashing with a fork, adding water and/or warming the food.
But let’s get into the great nutrition!
This food has a phosphorus content of 0.69% on a dry matter basis, very low compared to your average cat food. The protein in this food comes from duck and salmon along with some other animal protein sources. Both the salmon and the herring oil in this food are excellent sources of omega-3s for kidney health.
Nature’s Logic is a very unique pet food company. They formulate all of their foods without using any synthetic vitamins or minerals. All of the nutrition your cat needs comes from whole food ingredients. They are a small company and outsource their manufacturing, but they have never once had a recall. They also make an effort to have a representative present at each manufacturing run of their food.
Best Low Protein Dry Trusted Brand
– Hill’s Science Diet Adult 11+ Chicken
Dry food should be fed to cats with kidney disease as an absolute last effort to get them eating. The increased moisture content in wet food is essential for kidney health. However, we do know that cats, especially cats with kidney disease, can be extremely picky. If your cat will not eat wet food we recommend feeding prescription dry food for kidney disease. If you cat will also not eat prescription dry food, we recommend Science Diet Adult 11+ Chicken.
This food has a very low level of phosphorus, 0.69% on a dry matter basis. Protein is also well controlled and comes from chicken, wheat and corn. There is no pea or soy protein, indicating a limited arginine level. The food also has a very high content of omega-3s at 0.8% on a dry matter basis. The omega-6 to omega-3 ratio is an excellent 3:1, instead of the typical ratio of 5:1 seen in most quality foods. This high level of omega-3 will greatly promote kidney health and slow the progression of kidney disease.
Cats seem to like the flavor of this food too. It is very clear that Hill’s took into consideration the high rate of kidney disease in senior cats when they formulated this food.
Best Low Protein Dry All-Natural Food For Cats
– Merrick Purrfect Bistro Sensitive Stomach
Again, dry food should only be fed to cats with kidney disease as a last resort. Moisture is extremely important for the health of cats with kidney disease. We do not recommend feeding dry food to cats with kidney disease. However, as far as dry diets go, this is a good option for cats requiring a controlled protein diet for kidney disease.
This food has 0.9% phosphorus content on a dry matter basis. The protein is primarily sourced from chicken and turkey. Overall there appears to be a good amino acid composition of this food, but pea protein is included as an ingredient. However, pea protein is low enough on the ingredient list that it is unlikely to contribute significantly to the amino acid balance of this food.
Omega-3s are considerably high in this diet, with a 0.6% minimum content listed on the guaranteed analysis. The fact that this food is formulated for sensitive stomachs is also beneficial, as many cats with kidney disease easily feel nauseous.
Merrick is operates independently within Nestle Purina since their acquisition in 2015. They have their own production facilities and have a good record of food safety. The company strives to be transparent and readily answers consumer questions.
Merrick has been growing rapidly but maintains that they will not outsource manufacturing. This has caused some issues with consistency in some of the canned food lines. It would have been easy for Merrick to outsource manufacturing but we think that their commitment to the long-term benefits of keeping manufacturing in-house should be applauded.
Choosing a Low Protein Cat Food for Chronic Liver Disease
Lowering protein content is not the most critical aspect of choosing a food for cats with liver disease. According to articles published in the Journal of Nutrition, malnutrition can occur in cats and dogs with liver disease if protein is limited too much. The protein that is fed should be of a high quality, including arginine to help the liver convert toxic ammonia to the less toxic urea. Arginine is common in meat, pea and legume protein. Therefore, it is a good idea to keep an eye out for these ingredients when choosing a food.
Perhaps the most important aspect of a food for liver disease is a high soluble fiber content. Soluble fiber traps ammonia in the gut and can help prevent elevated levels in the body. Soluble fiber also traps the toxins that are removed through biliary excretion. The crude fiber content listed on a cat food label does not include the soluble fiber content. Unfortunately the soluble fiber content has to be estimated based on ingredients. Agar-agar and guar gum are common soluble fiber ingredients, as well as peas and oats.
A good food for liver disease must also have a low level of copper and a high level of zinc. Excess copper is stored in the liver and can become toxic. Zinc has the opposite effect and can help detoxify the liver and prevent copper absorption from food. The foods listed here have at least a 10:1 zinc to copper ratio, and controlled copper levels.
Finally, antioxidants such as vitamin E and omega-3s are critical to liver health. Although vitamin E is required in cat food, omega-3s are not required in adult cat food. We made sure that the foods on this list had fish or fish oil in the ingredients.
Best All Natural – Castor and Pollux Organix Turkey
This pate textured food is simply perfect for addressing liver disease. The protein is at a well controlled level, with organic meat as the main source. This food also has peas, a great source of soluble fiber and arginine. Salmon oil is included as an ingredient, indicating a good amount of omega-3s in this food.
This food is particularly low in copper at 11.1 mg/kg on a dry matter basis. There is also a good amount of zinc in this food, 113 mg/kg on a dry matter basis. These copper and zinc levels will do wonders to help the health of your kitty’s liver. It is also important to note that the zinc in this food is “zinc amino-acid complex.” This is a chelated form of zinc, and is much more digestible than other zinc supplements.
This food is on the higher end of the price range, but considering that the ingredients are organic, the price is more than reasonable. Cats who like pate textured foods seem to like Castor and Pollux Organix Line.
Castor and Pollux (part of Merrick) is also extremely transparent and helpful to pet owners. It only took a quick online chat with customer service for them to tell us the copper levels in all of their cat foods. Merrick was purchased by Nestle Purina in 2015, but remains independent in operation. They maintain their own production and do not outsource to Purina or to co-packers. Considering their good track record of safety, this is very good news for pet owners!
Best Trusted Brand – Royal Canin Digest Sensitive
This pieces-in-sauce textured food offers a copper content of 10.9 mg/kg on a dry matter basis and 144.0 mg/kg zinc on a dry matter basis. This 13:1 zinc to copper ratio is great for liver health. A portion of the zinc is in a chelated form as zinc proteinate. This means that the zinc should be well absorbed.
The protein in this food primarily comes from meat, meaning that it should be readily digestible and high in arginine. There is no fish oil included, but salmon is a listed ingredient, providing some omega-3s.
The fact that this food is specially formulated for sensitive stomachs is important too. Gut health and the amount of work the liver has to do are closely tied. Promoting a healthy gut reduces the workload on the liver. Controlled soluble and insoluble fiber levels are part of what makes this food good for sensitive stomachs. Carob bean gum is the ingredient that provides soluble fiber.
Finding a legacy brand of cat food who would readily reveal the copper content of their cat foods proved difficult. Purina promised the information, but after several attempts never followed up. Hill’s would only provide the information through their veterinarian-only nutrition consult service. It is great that they have this service, but it makes comparing between foods or brands nearly impossible, even for veterinarians and animal nutritionists. Many times it also forces pet owners to buy expensive prescription food when a regular over the counter food would work just as well. Royal Canin was by far the most transparent big brand. Although we had to ask the customer service chat to look up each food individually, they were happy to assist with finding a low copper cat food.
Royal Canin is independent within Mars, Inc. and has a good safety and quality tack record. Each of their foods undergoes significant testing and research, not just their prescription veterinary diets. Although they do use feed grade ingredients, Royal Canin maintains their own production facilities and keeps a close eye on safety.
Best For Picky Eaters – Wellness Morsels
If your cat quickly gets tires of flavors of food, Wellness Morsels are the best option for you. These pouches come in a handful of flavors and are a “pieces in sauce” texture. Reviews show that most cats love the flavor. The price is similar to other foods we have chosen for this list.
Wellness Morsels have well controlled copper levels at 12 mg/kg on a dry matter basis or even lower. Zinc is always around a 10:1 ratio with copper, which is the ideal. The protein in this food is at a reasonable level and comes from high-quality animal sources. There is also soluble fiber included in this food, as guar gum is an ingredient.
Ideally, we would like to see fish oil included in these foods. Some flavors have salmon as a main ingredient, but others do not have a good source of omega-3s. However, if you have a picky eater, the benefits of this food far outweigh the cons.
If you are purchasing this food in the store, be extremely careful. There are many similar cat foods made by Wellness that do not have the same nutrition. They may be much higher in protein or copper content. Luckily, Wellness makes all of their nutritional data readily available online. You can always double check the nutrition of the type of Wellness food you have purchased.
Wellness (aka Wellpet) is owned by an investment group, but the company appears to have maintained their overall philosophy on pet food. They have used the increased access to capital to diversity products and make foods in many textures and styles.
Unfortunately, Wellness outsources their production of their foods to co-packers. However, Wellness has a long track record of good safety and quality. They seem to keep a close eye on their manufacturers. This particular food is made in Thailand. Unlike China, this should not be cause for concern for pet owners. Canned and pouched pet food manufacturing in Thailand grew from the human-grade tuna industry. Thailand has excellent health and safety standards in pet food.
Best For Fatty Liver Disease (Hepatic Lipidosis) – Hound and Gatos Chicken, Lamb and Salmon
The most common liver problem in cats is fatty liver disease. Although this disease does not require limiting protein, we wanted to mention which food would be recommended. In cats, fatty liver most often occurs when a cat has stopped eating. In this case, eating any food is better than continuing to starve. Ideally, cats diagnosed with hepatic lipidosis should eat a low carbohydrate, high carnitine food. This helps the liver metabolize the unhealthy fat buildup. Like other types of liver disease, food should still limit copper and have good levels of zinc and soluble fiber.
This food is a high-meat canned cat food in the pate texture. The main ingredient in this food is lamb, which is naturally high in carnitine. The carbohydrate content of this food is at an extremely low 2.3% on a dry matter basis. Copper is at 8.5 mg/kg on a dry matter basis. Zinc is in a chelated form, meaning it is readily digestible and is in an 11:1 ratio with copper.
There is soluble fiber in this food in the form of agar-agar. There is also salmon oil listed in the ingredients along with salmon, so omega-3 levels should be significant. Although the formula is simple, this food is really great stuff. Hound and Gatos saw no need to over complicate a good food!
Hound and Gatos is a small company so they outsource their manufacturing to a facility in South Dakota. Even though they don’t have the resources to make the food in-house, they invest significantly into safety testing, including DNA testing their protein sources. Independent pet food safety groups have awarded Hound and Gatos for their safety and transparency standards.