The 'CatKins' diet
The feline diet: a historical look
When trying to develop a diet for cats, look no further than what a cat would eat in the wild: mice. Cats shouldn't be eating foods that they have difficulty processing, according to Dr. Deborah Greco, a veterinarian at the Animal Medical Center in New York City.
This internal medicine specialist, who spoke at a Sunday session, isn't arguing that pet owners should be shopping for mice to please Fluffy. Rather, they should be thinking about the nutrition in a mouse-a mouse is 3 percent carbohydrate, 40 percent protein, and 50 percent fat.
Since cats became domesticated, they have been fed various diets, and some of these diets were developed with little thought as to their natural diet in the wild. The result hasn't been good. "Many of the diseases that we treat are a result of the diets we give them," said Dr. Greco, who rattled off several examples.
Before the advent of commercial diets, owners fed cats organ meats that are low in calcium and high in phosphorus. This led to nutritional secondary hyperparathyroidism. In the 1980s, scientists linked a high incidence of struvite stones to high pH levels in food. And in the 1990s, scientists found that feeding acidifying diets to cats with struvite stones lead to an increased incidence of oxalate stones. Diets were reformulated to a more neutral pH. "The ideal pH is 6.5," says Dr Greco, which is the pH found in a mouse.
Also in the late 1980s, scientists traced a high incidence of dilated cardiomyopathy to taurine deficiency, and other researchers found that certain diets low in potassium caused hypokalemic nephropathy. Each time, nutritionists had to go back to the drawing board.
Today, cats are facing a different problem: an epidemic of obesity that comes with a price tag. "Thirty-five to 40 percent of cats are obese," said Dr. Greco, who says the peak years of obesity is between the ages of seven to 12 years.
"Obese cats are four times as likely to develop diabetes mellitus and five times as likely to develop lameness." Fat cats also have a higher incidence of non-allergic skin disease, most likely caused by the cat's inability to clean themselves as effectively, due to their size. This obesity is most likely the cause of diets with too high a carbohydrate content.
"Cats are unique in the way they handle protein, carbohydrates, and fat," Dr. Greco said. Cats are strict carnivores and, because of this, they have a tremendous ability to produce glucose from protein, but have difficulty processing carbohydrates. The feline liver has normal hexokinase activity, but no glucokinase activity. Thus, cats are limited in their ability to mop up excess glucose and store glycogen. "What happens is that glucose is going to hang around for a long period of time," she said, and it eventually becomes fat.
In addition, unlike humans, protein is the stimulus for insulin release in cats. Cats have adapted to high protein diets by being insulin resistant. This maintains blood glucose during periods of fasting, convenient for a cat in the wild, but not so good for pets eating a lot of carbohydrates.
"When you take an individual that is genetically programmed to consume high protein and low carbohydrates, and you put them on a high carbohydrate diet, what happens is their insulin resistance works against them," she said. "Their blood glucose concentrations are too high ... they can't overcome that, and they start to release more and more insulin in an attempt to reduce blood glucose levels." This doesn't work, however, and the cat eventually develops type 2 diabetes mellitus. The cat gets amyloid deposition in the pancreas, exhaustion of the pancreatic cells, and glucose toxicity from consumption of large amounts of carbohydrates.
So what's Dr. Greco's ideal cat food diet? She recommends a wet food, high in protein, high in fat, and low in carbohydrates. It's basically a "CatKins" diet, much like the Atkins diet popular today. This diet is going to keep a cat slim and help it avoid diabetes.
She recommends a wet cat food because if you are trying to mimic what a cat eats in the wild, just think of how much water a mouse contains. Wet cat food is going to give you a pH that is ideal and is, thus, the best way to prevent feline lower urinary tract inflammation. Dr. Greco said. In addition, a cat's jaws and teeth are designed for shearing and tearing meat, and cats that eat dry food grind it in a way that it ends up between their teeth. There it ferments into sugar and acid, thereby causing dental problems.
According to Dr. Greco, it all comes down to common sense. "We must use a cat's natural diet as a guideline."