by Armaiti May, D.V.M, C.V.A. • Dr. May’s Veterinary House Calls

In general, dogs are much easier to maintain on a vegan diet than are cats. Although cats are biologically carnivores, in many cases they can be successfully maintained on a vegan diet as long as it meets all of the nutritional requirements specific to cats and their overall health is adequately monitored, with particular attention to urinary tract health. Cats require the same nine essential amino acids that are needed in the diet of all mammals. However, in addition, cats also require arginine and taurine. Taurine is found naturally in meat but can be supplied in synthetic form. Without adequate taurine, cats may go blind and may develop dilated cardiomyopathy (a type of heart disease).

One problem which can afflict cats even if they are on a nutritionally balanced and complete vegan diet is FLUTD (feline lower urinary tract disease), which is a syndrome that is more likely to occur if urinary struvite crystals or stones form secondary to urinary alkalinization and a diet too high in magnesium. Male cats are much more likely to get FLUTD and urinary obstruction, but female cats can (rarely) be affected as well. Ensuring adequate water intake is important for preventing excessive urine crystals, which can be accomplished by feeding a canned diet, adding water to dry food, or adding a pinch of salt to food to stimulate thirst.

Cats on a vegan diet can develop abnormally alkaline (high pH) urine due to the more alkaline pH of plant based proteins in comparison to the acidic pH of meat-based foods which cats have evolved to eat. When the urine pH becomes too alkaline, there is an increased risk of formation of struvite (also known as magnesium ammonium phosphate) bladder crystals and/or stones. Calcium oxalate stones can also occur, but these do not occur if the urine is too alkaline, but rather if it is too acidic. Such stones can create irritation and infection of the urinary tract and require veterinary treatment. In male cats who form such crystals or stones, they can suffer more severe consequences than simply irritation or infection of the urinary tract because the stones can actually cause an obstruction of the urethra so the cat cannot urinate. This is a life-threatening emergency requiring immediate veterinary care; this involves passing a urinary catheter to relieve the obstruction, placing an indwelling urinary catheter, and starting supportive intravenous fluid therapy, along with appropriate pain management and antibiotics if indicated. These “blocked” cats frequently need to be hospitalized and monitored closely for several days before they can go home and the associated veterinary fees can easily be between $1000-$1200. The sooner a problem is identified and the cat is treated, the better the prognosis for recovery. Some cats who get blocked repeatedly require a highly specialized (and expensive, ~$2000) surgery called a perineal urethrostomy (PU).

Cat guardians who put their cat on a vegan diet should have their veterinarian check the cat’s urine pH 1-2 weeks after switching them to a vegan diet and then once a month for the first several months to ensure the pH remains stable. If the pH is too high, urinary acidifiers may help the urine pH to become more acidic. Urinary acidifiers that may be used include methionine, vitamin C, and sodium bisulfate. James Peden, author of Vegetarian Cats and Dogs states there are natural urinary acidifiers, including asparagus, peas, brown rice, oats, lentils, garbanzos, corn, Brussels sprouts, lamb’s quarters (the herb Chenopodium album, also known as pigweed), most nuts (except almonds and coconut), grains (not millet), and wheat gluten (used in kibble recipes). Once the pH is regulated, the urine pH should be checked at least twice a year. If a cat shows signs of pain or straining while using the litter box, immediate veterinary attention should be sought. It is important to not supplement the cat’s diet with urinary acidifiers unless it is actually needed because a too acidic pH can cause a different kind of stone to form (calcium oxalate stones). While many cats appear to thrive on a vegan diet, there are also anecdotal reports of cats with recurring urinary tract problems, including infections associated with previous urethral obstructions caused by urinary crystals.

For cat guardians who find it too tedious to monitor their cat’s urine pH, they should perhaps consider feeding a non-vegetarian cat food or not keeping a cat as a companion. Another option is a special pH-adjusted vegan formula available through Harbingers of a New Age (www.vegepet.com/) which requires the caretaker to make home-baked kibble using the supplement mix and the vegan recipe provided by HOANA. Most of the available veterinary prescription diets (such as those manufactured by Hill’s and Purina) which are designed to aid in treatment of a variety of illnesses, including diabetes, kidney failure, liver disease, inflammatory bowel disease, and urinary stones do contain animal products. Hill’s c/d is a prescription diet low in dietary magnesium formulated to prevent recurrence of struvite urinary stones by maintaining a normal acid urine pH (between 6.2-6.4). Many cats are very picky eaters. Although adding vegan mock meats and nutritional yeast to flavor vegan cat food will encourage many cats to eat it, there may be many cats who still refuse to eat, especially if they are sick. Cats who are anorectic for a prolonged period are at high risk for developing hepatic lipidosis (fatty liver syndrome), a serious condition that requires extensive veterinary care. Some cats may require more patience and a gradual transition from a meat-based diet to a vegan diet if they are accustomed to eating a meat-based diet. Most commercial pet foods contain “digest” which consists of partially digested chicken entrails, that makes the food more palatable. On the positive side, many cat and dog guardians have reported improved overall health, vitality, coat quality, and fewer problems with skin allergies, food allergies, and various degenerative diseases.

A recent study published in JAVMA (Journal of American Veterinary Medical Association) by Gray, Christina M.; Sellon, Rance K.; Freeman, Lisa M. Nutritional Adequacy of Two Vegan Diets for Cats. J Amer Vet Med Assoc 2004, 225(11):1670-1675 showed two commercially available vegetarian cat foods (Vegecat KibbleMix and Evolution canned diet for adult cats) to be deficient in several key nutrients. The two vegan diets were subjected to nutritional analysis and compared to Association of American Feed Control Officials (AAFCO) nutrient profiles for the maintenance of adult cats. The Evolution food was determined to be deficient in protein, methionine, taurine, arachidonic acid, vitamin A, pyroxidine, and niacin. Vegecat KibbleMix was found to be deficient in methionine, taurine, arachidonic acid, and pyroxidine. According to both of these vegan cat food companies, thousands of the cats on their diets are healthy, which raises the question of how this could be if the diets are truly inadequate. Only one sample of each diet was used in this study, so it is entirely possible that the sample represented a rare occurrence of a mixing error at the factory, but this still raises legitimate concerns about the quality control measures (or lack of appropriate quality control measures) at these companies. The maufacturer of Harbingers of a New Age (producer of Vegecat KibbleMix) expressed shock at the results of the study and showed an intent to find and correct the source of the problems in the production of his cat food supplements. In response to the results of the study, Eric Weisman, Evolution Diet CEO (2004) stated, “We have ten to twenty thousand healthy and long living dogs, cats and ferrets living on the Evolution Diet. Major animal sanctuaries use our products and stand behind them. These sanctuaries use our products because they have lower rates of illness and mortality when their animals are placed on our foods.”

It is unclear whether any reliable quality control measures have been instituted since the publishing of these results. A survey of the health of cats on various vegan diets was performed by a veterinary student at University of Pennsylvania and published in the Journal of the American Veterinary Medical Association in July 2006. It showed that most of the cats surveyed on a vegan diet did not suffer from subnormal taurine blood levels and were for the most part in good general health.

In summary, more studies are needed to document the health of cats on a vegan diet in the scientific literature. More rigorous quality control measures need to be implemented at the factories of vegan pet foods to prevent future mistakes in mixing and consequent inadequate diets. Guardians need to be educated about the potential health benefits and risks associated with meat-based and vegetarian diets, and should demand appropriate quality control assurance from any pet food manufacturer they do business with. It is also crucial that future studies involving nutritional adequacy of a particular diet test many samples of the diet in question rather than just one.

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