Humans have been influencing the appearance, health, and behaviour of their canine companions ever since domesticating them. Today, dogs come in all shapes and sizes, with a range of behavioural traits. With this diversity comes differing nutritional needs due to differences in growth, disease prevalence and life expectancy between breeds. For some dogs, one dietary component that can be important to consider are purines.

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What are purines?

Purines are a group of nitrogen-containing compounds that play many crucial roles in the workings of the body. They make up part of the structure of DNA and are involved in some of the chemical processes that keep cells functioning normally. They also play a role in the nervous system.

Our cells are constantly breaking down and being replenished throughout our lifetime, releasing purines from decayed DNA and other cell structures. What is not recycled is ultimately broken down (metabolised) into by-products. In humans, this is predominantly uric acid which passes through the kidneys into urine. In people, problems with this process can lead to a condition called gout, where joints become swollen and painful due to uric acid crystals forming within them.

However in dogs, although uric acid is produced, they also metabolise purines into two other by-products: xanthine and allantoin. Dogs eliminate these through urine too, but unlike in people, if problems occur with purine breakdown, symptoms are more likely to be related to the urinary tract.

Why might I need to feed a low purine diet?

The majority of purine in our dog’s body is sourced from the breakdown and recycling of cellular purine, but a small portion of it is sourced through the diet. This allows us some ability to manipulate the concentration of purine in our pet’s body. A few health conditions have been recognised in dogs that may benefit from a low purine diet.

Several dog breeds have been found to have a genetic potential for abnormal purine metabolism; the most well-known being the dalmatian. A gene mutation carried by this breed affects the conversion of uric acid to allantoin. When high levels of uric acid arise in the urine, a condition called hyperuricosuria, urate bladder stones grow.

Bladder stones irritate the bladder lining, causing pain, bleeding, and difficulty with urination. Stones of different types grow in different urine environments, but analysis following surgical removal show that urate-based stones account for about 25% of bladder stones occurring in dogs.

Aside from dalmatians, popular breeds that may carry a gene mutation include beagles, basset hounds, cocker spaniels, bichon frise, miniature schnauzers, lhasa apsos, miniature poodles, Yorkshire terriers, dachshunds, and bulldogs. Currently, there is a genetic test available for the dalmatian and bulldog only.

Although the kidneys expel most of the by-products of purine metabolism, the liver is the site of that metabolism

As such, some forms of liver disease can also lead to hyperuricosuria. A porto-systemic shunt is a rare condition typically diagnosed in young, growing animals and is an abnormal blood circulation through the liver. If your pet is born with this condition, they may be at increased risk of forming urate bladder stones.

Other conditions that may alter purine breakdown are chronic kidney disease, a hormonal imbalance known as hyperadrenocorticism (Cushing’s disease), and some types of cancer. The concentrations of the breakdown products can be significantly impacted by these diseases but may not be observed in all affected dogs.

In continental Europe, leishmania is a common parasitic disease transmitted by biting flies. Due to international pet travel, a few cases have been diagnosed in England. A changing climate may increase occurrence of this disease in the UK and one of the main drugs used to treat the condition has been linked to the formation of urate stones.

How can I feed my dog a low purine diet?

One of the main ways to reduce purine consumption is to alter the protein content of the diet. Protein is an important dietary component and ranges in digestibility. Too much restriction can lead to loss of muscle mass. And restriction of the wrong types of protein can lead to inadequate intake of essential amino acids.

It is therefore important to only feed a low purine diet under the recommendation of your vet. In the case of dalmatians or those with genetic mutations, diet may not be the only management necessary to prevent stone formation so your vet can discuss additional treatments if your pet would benefit from these.

There are two main ways to feed a low purine diet. 

The most convenient method is to feed a commercially available prescription diet that your vet can prescribe if appropriate

These are typically kibble-based diets that are nutritionally balanced while restricting the dietary purine. They should always be offered with lots of fresh water, as a good water intake helps flush out sediment and urate crystals from the bladder.

If a prescription-grade diet is unaffordable, your dog is a fussy eater, or you just simply prefer a more natural style of feeding, then the alternative is a home-prepared diet. The biggest challenge with this is ensuring that all nutritional needs are met, not just the desired low purine. Your vet can refer you to your nearest nutritional service where a veterinary nutritionist can assist with creating recipes for your dog that meet all its needs.

Either as part of their main diet, or as treats, there are some high purine foods to avoid. Offal, game meat and many fish contain a lot of purines, as do several beans and lentils. Conversely, foods that are low in purines include peanut butter, eggs, wholegrains and many root vegetables such as carrot and potato.

An important consideration is that several low purine foods recommended for people are toxic to dogs such as grapes and macadamia nuts. Xylitol is a common sugar substitute that is also very toxic to dogs, so products like peanut butter need to be checked to ensure they don’t include this ingredient. If your dog is intolerant of grains, then wholegrains may not be an ideal low purine food for them either. As with the components of the main diet, your vet and veterinary nutritionist can recommend safe and useful low purine treats for your dog.

Conclusion

Although uncommon, medical conditions exist that may benefit from a low purine diet. As dietary purine is only a component of the body’s purine sources, any condition affecting purine metabolism should be assessed and diagnosed by a vet before deciding if a diet change is right for that animal. Nutritional needs change over your dog’s lifetime but with the help of your veterinary team, providing your dog a tasty diet that works for them can play a part in keeping your dog healthy for the future.

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