The Kidney Diet

Suggested diet for rats with kidney disease

Kidney disease is not uncommon in older rats especially males and is thought to be the third most common cause of death after respiratory illness and tumours. It accounts for many deaths where the rats just gradually decline and die for no apparent reason. Treatment in humans is dialysis and transplantation, which are obviously unavailable to our small pets, but diet also plays a large role in maintaining balanced blood chemistry and delaying the need to start dialysis. The following treatments should be considered palliative; they should improve quality of life and possibly slow down the progression of the disease process. But there is no cure.

Much of the malaise that accompanies kidney failure is due to high levels of toxins circulating in the blood. This is called uraemia. Protein is broken down in the liver and this process produces waste products (particularly urea) which are then excreted by the kidneys. When the kidneys are failing the urea is able to build up in the blood.

Symptoms of uraemia are:

• tiredness
• itching
• loss of appetite
• nausea
• breathlessness
• fluid retention
• weakness
• encephalopathy (toxicity of the brain causing confusion/clumsiness and eventually coma leading to death)

It has been found that controlling protein intake does not slow down the progression of kidney disease, but it does significantly improve comfort and well-being. Interestingly it is not simply a matter of feeding a low protein diet, but it is important to consider the quality of the protein and how easily it is broken down, as some protein sources yield larger amounts of toxins.

With this in mind the best sources of protein are egg and fish, then chicken and finally the red meats. Of the vegetable protein sources, soya is the most useful.

It has traditionally been the case that when a rat is elderly and 'failing' we increase the protein load he has to deal with by feeding foods such as EMP, porridge, scrambled egg etc. I would suggest that we might consider an alternative approach. In the absence of other obvious symptoms it is wise to assume that all elderly rats in decline have a degree of kidney damage. For many this will be serious enough to be the cause of their decline. For the rest, feeding a 'kidney-friendly' diet will only serve to protect their kidneys from further damage.

As well as considering the amount and quality of the protein given, the other main factor affecting the progression of the disease is phosphorus intake. When the kidneys begin to fail phosphorus (which is a component of all foods) isn't excreted as efficiently and blood levels begin to rise. Calcium and phosphorus are closely linked, and as the phosphorus level rises calcium is pulled out of the bones. This not only weakens the bones, but increases the levels circulating in the blood. These minerals can then be deposited in soft tissue around the body. They then cause inflammation and discomfort. Where they are deposited in the kidneys they will serve to increase the rate at which the kidneys fail.

Reducing dietary intake of phosphorus is critical to slowing the progression of the disease process. This can be done in two ways: avoiding high phosphorus foods in the diet and giving phosphate binders along with food. The medications (calcium carbonate) that we take as antacids, are good phosphate binders and are very safe.

The kidney friendly diet
The following diet is one that I have devised and am now feeding to all my elderly rats. Whole grains (especially wheat) are high in phosphorus as is un-processed corn. For this reason I decided to keep the Alpha Herbal (AH) in this mix to a minimum. There is a risk that a healthy renal diet is going to be very low in copper, and it was for this reason that I decided to include any Alpha Herbal at all. You may wish to supplement copper. The easiest way to do this is to crush a copper tablet and mix inot their dry food. Holland and Barrett sell copper as an individual supplement.

Dry mix:

• Alpha Herbal rabbit food (approx 20% by volume).
• Hills Prescription Diet k/d Canine (approx 20% by volume). This is a dog kibble designed to support chronic renal failure in dogs. It is low phosphorus and restricted protein (primarily egg based). It is a useful source of copper in this diet too (14mg/kg). It has a high fat content, but I feel the other benefits outweigh this at this time in a rat's life. Much of the rest of the dry mix is very low fat. A 2kg bag cost about £10 but will last you a good while. If you have ethical problems feeding a product from this manufacturer you can substitute with a daily mix of cooked rice/seaweed powder/raw beaten egg/garlic/crushed copper tablet - all cooked for a minute until solid in the microwave.
• Pasta spirals - uncooked/Egg noodles - uncooked (together approx 15% by volume). Noodles are a lower phosphorus alternative to pasta, but I include them in roughly equal amounts. Do not substitute with all pasta.
• Broken low salt unflavoured rice cakes (approx 15% by volume).
• Bite-sized shredded wheat/corn flakes/puffed rice/Special-K or similar (30% by volume). Do not substitute other cereals unless you check phosphorus levels first. Shredded wheat seems to be one of the few low-ish phosphorus whole grain wheat based cereals. Oats are high in phosphorus, as is bran.

As well as this I feed half a pack of the Lite Nature Diet between the 12 rats I have on this diet. To this wet food I add the following:

• 1 teaspoon of flax oil (shown to slow progression of disease)
• 2 crushed Rennie tablets (binds phosphate in the diet)*
• 1 crushed vitamin B complex tablet (improves associated anaemia and may help slow spinal degeneration)
• 1 crushed Glucosamine and Chondroitin tablet (may slow spinal degeneration)

*You do not need to feed the Rennies to older rats that do not have obvious signs of kidney problems. However, all rats over the age of 18 months will probably benefit from the diet without this supplement.

I tend not to give these rats other 'treats', though they do get a little fresh veg at times. Most mineral rich veg (such as kale, broccoli, pak choi) is rich in phosphorus, but the benefits of a small amount in the diet probably outweigh this. If fed at the same time as the wet food above some of the phosphorus would be 'removed' by the phosphate binders. Of these, kale performs best for highest copper (advantageous) and lowest phosphorus.

Foods that are particularly high in phosphorus that should be avoided are whole-wheat, bran, oats, unrefined corn, dairy (soya products are better) and nuts.

In closing I need to point out that this is very much work in progress. I have had a number of very positive reports about elderly rats becoming more energised after changing onto this diet.

Adequate quantities of fresh water should be available at all times.