Diabetes and Obesity: Preventable Epidemics
|Written by Elizabeth Hodgkins, DVM|
|Wednesday, May 13, 2009 11:41 AM|
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Today, the cat is the favorite house pet in the United States, at least if your definition of "favorite" is "most numerous." The cat has outnumbered the dog, the previously "most numerous" pet species, for a decade or more and this trend shows no signs of reversing itself anytime soon. Those of us involved in any of the pet care industries or professions know very well that we are seeing more and more well-cared-for felines, belonging to people and families that are intensely bonded to their kitty family members.
Men, as well as women, in all socioeconomic strata, are attached to their pet cats in a way that I could never have anticipated in 1977 when I graduated from veterinary school. In short, the cat has become not only legitimate as a pet underfoot, but also a focus of attachment and affection for humans who are often willing to do anything and everything necessary to provide their felines long, healthy, and happy lives.
This desire and willingness to care for a pet cat's every need has resulted in some significant improvements in health and longevity for felines today. For example, the increasingly common indoor existence enjoyed by cats has greatly reduced the incidence of most infectious diseases within cat populations and has markedly curtailed death and injury to cats from automobile accidents, attacks from dogs or wildlife, or other sources of trauma. More routine spaying and neutering of household pet cats has positively affected the number of abandoned and neglected cats put to sleep in shelters. Unfortunately, while so much is better for cats today, this species has nonetheless paid a price for the heightened level of care it receives from the millions of devoted cat owners in the country. That price is loss of health associated with poor nutrition in the form of commercial dry cat food diets.
First, some background on the evolution of the cat for context. Today's domestic cat evolved from one or more small wild cat species in Africa and southern Europe. The environment in which these progenitor cats developed was vegetation sparse and small-animal-prey rich, causing this top-predator mammal to become dependent on meat, and meat's primary energy nutrients, protein and fat, for sustenance. Over time, some of the pathways for carbohydrate metabolism that were developing to a high degree in herbivorous and omnivorous species in more carbohydrate-rich environments were discarded by the primitive cat. In fact, eventually this species so drastically rearranged its processes for dietary energy extraction that its metabolic systems began to use protein for energy at a constant, almost invariable rate, without the switches for up and down regulation of that protein "burn" ( gluconeogenesis from amino acids) that is active in omnivores and herbivores. That is, the cat will use dietary protein for routine energy production at a high level EVEN in situations where dietary protein is very limited. Because of these evolutionary "choices" made long ago, the cat rapidly begins to consume its structural proteins for energy during starvation or protein deprivation of any other kind (e.g., protein-restricted diets). In short, the cat is a "carbohydrate cripple" with a huge protein dependency!
Given the forgoing, it is not at all surprising that we now find many of our feline patients fat, sluggish, and eventually, diabetic. For all of our good intentions in bringing the cat into our homes as a pampered pet, we have done the species a tremendous disservice in providing its members a diet far more appropriate for a cow in a feedlot than an obligatory carnivore. Because of the food technology of dry food production, dry cat foods are loaded with carbohydrate from cereal. This carbohydrate is absolutely required in the extrusion process; dry pet foods are essentially breakfast cereal for pets with a little added meat meal for palatability. Further, because this cereal undergoes processing at high heat and pressure during extrusion, it becomes pre-digested and enters the pet's bloodstream essentially as "sugar." Nothing in the cat's evolutionary development could possibly have prepared it for a steady diet of this sugar laden "junk food."
Not all cereals are created equal, of course. Some have much higher glycemic indices than others, meaning they cause a greater rise in blood glucose when consumed and digested. Perhaps the most offensive of all cereals used in pet foods is corn, (from which corn syrup is derived, giving a good idea of how much sugar corn actually contains). Because it is plentiful and cheap in this country, corn is one of the favorite dry pet food cereals used by the industry. Sadly, even the most expensive, so-called premium dry pet foods contain high amounts of this ingredient.
An additional consideration is the cat's unique system of satiety signals from food. Logically, because the cat evolved in an environment rich in protein and fat, but deficient in carbohydrate, consumption of fat and protein evolved as the signal to the cat that it could cease intake. Consumption of carbohydrate, however, has a minimal effect on intake in the cat even as energy requirements are met and exceeded with this nutrient. Thus, not only is the cat relatively incapable of handling repetitive substantial carbohydrate loads of the kind represented by dry cat food, it is also unable to respond appropriately to that consumption with appetite satisfaction. The end result is cats that overeat, constantly flood their systems with glucose overloads, spiking repeated surges of insulin from their limited carnivore's pancreatic reserve, and become obese. For a large number of cats, their metabolic systems eventually become overwhelmed by this chain of events and its unremitting stress on the pancreas, resulting in diabetes.
Assuming the preceding description of the present state of nutrition for pet cats is correct, how could this possibly be? How and why would a multi-billion dollar US pet food industry "conspire" to foist essentially "poisonous" food off on cat owners, often at very high prices and at exclusive, inconvenient outlets such as veterinary facilities and pet stores? To begin to answer that question, we must go back, once again, into history. At the middle of the last century, there were no commercial pet food products to speak of. Pet animals were fed from the table or the local butcher's discards. However, during the 50's and 60's, the market for convenient dog foods began to grow. Companies like Purina Mills, a cereal grain processing company, recognized this emerging market and began to make baked biscuits for dogs. Over time, Purina and other cereal-processing companies began producing kibbled dog food with the same technology used in making breakfast cereal for humans. At the same time, Alpo began to can discarded meat scraps and/or condemned meat for dogs. Because of their convenience and affordability, both types of food had appeal for dog owners and growing sales of these products encouraged additional output by these and a few smaller processors.