What is a Purine?
A Purine is a part of the bases adenine and guanine which are constituents of nucleic acids (DNA/RNA) which, when fully broken down in the body form uric acid and xanthine, theobromine (stimulant in chocolate) and caffeine. Purines provide part of the chemical structure of virtually all genetics and are, therefore, naturally found in almost all cells and foods. Certain foods (primarily high protein) contain concentrated levels of purines. This is why high protein foods increase uric acid/ammonia production, sometimes leading to gout in humans. New purines are synthesized in the body’s own genetic matrix and they may also be consumed in high levels in the form of high protein foods or in low levels in the form of certain vegetables (which do not affect the uric acid production in the body). Purines are then broken down and excreted, through a longer process than this chart shows, via the Uric Acid cycle, which is different in dogs and cats than it is in humans.
Foods with very high purine levels(up to 1,000 mg per 3.5 ounce serving):
Anchovies, Grains, Gravies, Kidneys, Liver, Sardines, Sweetbreads
Foods with high and moderately high purine levels (5-100 mg per 3.5 ounce serving):
Asparagus, Bacon, Beef, Bluefish, Bouillon, Calf tongue, Carp, Cauliflower, Chicken, Chicken soup, Codfish, Crab, Duck, Goose, Halibut, Ham, Kidney beans, Lamb, Lentils, Lima beans, Lobster, Mushrooms, Mutton, Navy beans, Oatmeal, Oysters, Peas, Perch, Pork, Rabbit, Salmon, Sheep, Shellfish, Snapper, Spinach, Tripe, Trout, Tuna, Turkey, Veal, Venison
What’s good and bad about Purines and the Uric Acid Cycle?
Again, Purines break down into Uric Acid which, as a matter of fact, is an antioxidant that assists in preventing damage to our blood vessel linings and is a powerful scavenger of singlet oxygen, and free radicals, making it one of the major antioxidants of plasma that protects cells from oxidative damage, thereby contributing to an increase in life span of our species and decreasing the risk for cancer. However, when humans consume excessive levels of purines (proteins) or xanthines (caffeine) excess uric acid is produced and at least among modern Homo sapiens, a high level of uric acid is strongly associated and in many cases predicts development of cardiovascular disease, hypertension, and metabolic syndrome, visceral obesity, insulin resistance, dyslipidemia, diabetes type II, kidney disease and cerebrovascular events. In general, we want purines in our diet.
Uroliths in dogs and cats
Clinic Review Articles, Veterinary Clinics of North America Small Animal Practice “Urology” by Joseph W. Bartges, July 2015, pg 27, states under the section for Purines and Urates that, “most information concerning urate uroliths is derived from dogs, with little information available for cats.” While, “Urate is the third most common mineral found in uroliths in dogs and cats, … and the second most common urolith, occurring in dogs and cats less than 1 year of age (infection-induced struvite is the most common urolith ….” “Urate uroliths form when urine is oversaturated with urate and usually ammonium. These uroliths form because of liver disease (usually a portosystemic vascular shunt) or because of an inborn error of metabolism resulting in hyperuricosuria... more common in dogs and cats less than 7 years of age.” This document goes on to show that when affected pets are switched from dry kibble foods to low purine canned diets, about a 30% resolution rate is seen WHEN COMBINED with allopurinol medication every 12 hours. Liver surgery is the treatment of choice for liver shunts. No mention is made of the fact that the pets were switched from dry kibble to canned diets and the increase in moisture in the food could be a contributing factor in the resolution of the issue. A protein-restricted alkalinizing diet has been shown to have greater than 90% reduction in uroliths, though the moisture content of diet is not mentioned and no supplementation was attempted. (1)
Purines and HUMANS
A U.S. National Library of Medicine scientific article states that, “Uric acid is a final enzymatic product in the degradation of purine nucleosides and free bases in humans and Great Apes. The pathway of purine catabolism in humans is shortest among vertebrates because about 8–20 million years ago during primate evolution the activity of urate oxidase (uricase, is an enzyme catalyzing conversion of uric acid to allantoin) was lost in a two-step mutation process. In other mammals, the last enzymatic product of purine degradation chain is allantoin, which is excreted in the urine. As a consequence, humans have to cope with relatively higher levels of uric acid in the blood (200–400 μM) and are prone to hyperuricemia (formation of urinary stones) and gout.” It can be assumed that the reason for this evolutionary alteration is because Humans and Apes are evolved to eat primarily fruits, not meats (2) and therefore should have no need for an additional step to assist uric acid elimination. Uric acid levels in the blood can be increased by the breakdown of purines in conditions such as excessive protein consumption, muscle wasting, necrosis, anemia, epilepsy, recurrent infection and other conditions, all of which the body may not be able to keep up with uric acid elimination needs. When uric acid accumulates monosodium urate crystals can deposit in tendons, joints, kidneys, and other organs. This accumulation of uric acid crystals is called gouty arthritis, or simply "gout.”
Purines and DOGS
Hyperuricosurie is a disease characterized by the formation of uric acid stones in the urinary tract.
The end product of purine catabolism is Allantoin except in Humans, Apes and ALL Dalmatian breed dogs.
The Dalmatian breed, like humans, has lost the ability to resorb uric acid due to a mutation in urate transport protein, yet other breeds have not. This makes Dalmatians more prone to uric acid stone formation if they are eating a high protein/purine diet or suffer metabolic cannibalism diseases. It is believed that this genetic mutation was the result of intentional breeding patterns for more distinctive spotting patterns on the Dalmatian. It is possible for other breeds (Bulldog, Black Russian Terrier, American Staffordshire Terrier, Retriever, Parson Russell Terrier, South African Boerboel, Weimaraner, Big Munsterland Pointer, German Shepherd) to have this same genetic mutation, but it is not common. Dalmatian mixed breeds and other breeds appear to tolerate purines and uric acid levels appropriately. (3) Hyperuricosuria is an autosomal recessive inherited disease caused by single nucleotide exchange of c.G563T in SLC2A9 gene (gene for urate transport) that will develop only in dogs that inherited the mutation from both parents. (4) Therefore, unless the dog is a Dalmatian or has a rare genetic mutation they can tolerate high levels of Purines from food and/or illness. For Dalmatians and dogs with the SLC2A9 mutation see below for supplemental options.
Purines and CATS
The differences between the physiology of the Feline compared to that of a dog or human are numerous. Among other differences, cats have an essential requirement for high levels of dietary protein and amino acids. Cats need significantly higher levels of dietary nitrogen because they don’t conserve nitrogen as well as other species. Cats have no ability to utilize unsaturated fats without supplemental arachidonic acid. They require dietary Vitamin D (pork, free run poultry, fish) as they can’t get it from the sun. Since Taurine is an amino acid that is primarily free floating in tissues, cats fed cooked proteins (where the taurine has leached out in the process of cooking) tend to be deficient in Taurine. Plant proteins such as soy or cheese do not contain taurine. Cats also have virtually no ability to tolerate glutamic acid found in vegetable proteins. High levels of glutamic acid (vegetable protein) in a cats body often results in sporadic vomiting and thiamin deficiency.
Feeding a low protein diet to a feline does not decrease their enzyme activities for metabolizing amino acids. Rather a low protein diet causes the Feline body to digest its own proteins for survival, a conditional called muscle wasting, where amino acid destruction continues despite dietary restrictions. As a result of being an obligate carnivore (meaning their bodies will not adjust to digesting plant proteins even if that is all that is fed) their metabolic pathways to breakdown by-products of protein are far different than those of herbivores and omnivores.
Cats require high levels of the amino acids arginine (found in meats, fish stock, diary or spirulina), ornithine (found in meats, cheeses, eggs and spirulina), and citrulline (melons) for appropriate uric acid cycle functioning and elimination of uric acid buildup in the body. Cats can convert arginine to citrulline utilizing high levels of ornithine transcarbamylase, they do not get citrulline from their diet. Therefore, if their diet does not contain sufficient levels of arginine and ornithine, citrulline levels will be inadequate and uroliths (crystals/stones) and/or hyper-ammonemia (buildup of ammonia) will develop. (5) For a deeper understanding of the obligatory high protein/purine needs of felines and their relationships with arginine, ornithine and citrulline see “Nitrogen Metabolism and Excretion,” published 1995, pg 154, by Patrick J. Walsh and Patricia Wright. (6) In summary, the only reason that a cat wouldn’t be able to tolerate high levels of purines is if the diet is inappropriate. Even in the case of muscle wasting changing the diet should resolve the problem.
What do I do about Purines in my pet on a high protein diet or with a medication condition?
Plaintain herb contains allantoin which may be useful in supplementing insufficient production of allantoin in the excretion of uric acid and ammonia. (9) This could be useful for Dalmatians, dogs with genetic mutations, pets with metabolic cannibalistic conditions such as excessive exercise, anemia, necrosis, muscle wasting, recurrent infection, and epilepsy. Elemental Provisions can provide this in powder for or you can find it in Honest Kitchen Perfect Form in lower levels.
Raw Goat Milk and Cow Milk Kefir - Dairy foods contain purines and actually appear to lower our risk of uric acid buildup caused by meat protein consumption. (7)
In the rare event that a dog is incapable of tolerating purines boiling high-purine foods in water can cause break-down of the purine-containing components and eventual freeing up of the purines for absorption. For example, in some animal studies, where rats were fed cooked versus non-cooked foods, the animals eating the cooked version experienced greater absorption and excretion of purine-related compounds. On the other hand, when foods were boiled, some of the purines were freed up into the cooking water and became lost from the food (because the water in which the food was boiled got discarded after cooking). From this evidence, the exact opposite conclusion would make sense: cooking of high-purines reduces the purine risk. When it comes to the moderately high-purine vegetables like asparagus or peas or spinach, there is no reason for you to avoid them in raw form, provided you keep your portion sizes down and your total portions within your practitioner's guidelines. (8)