Diabetes and Obesity: Preventable Epidemics
|Written by Elizabeth Hodgkins, DVM|
|Wednesday, May 13, 2009 11:41 AM|
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Unfortunately, these early attempts to produce dog foods were driven entirely by a desire to find profitable uses for excess commodities, specifically corn and other grains as well as meat unfit for or unused for human consumption, rather than a desire to provide genuinely health-promoting foods for pet dogs. Because Alpo's canned meat was completely un-supplemented for vitamin/mineral balance, it caused serious deficiency diseases in dogs that consumed it as most or all of their diet. As a result of the resulting scandal, the company decided to add a general vitamin/mineral supplement to its canned meat, and all other processors followed suit. Purina and other companies making kibbled dog food also began adding vitamins and minerals to their kibble, which was marketed as an adjunct to fresh meat or canned meat foods for completeness.
As decades passed, many dog owners began to favor kibbled dog food because of its economy, convenience and keeping qualities. Pet food-producing companies responded to this market demand by adding protein ingredients to their kibble in an attempt to produce a more complete dry food. Finally, the American Association of Feed Control Officials, a regulatory body that then supervised the quality and safety of livestock feeds, agreed to accept responsibility for supervising pet foods as well. For the first several years of this oversight responsibility, AAFCO reviewed available literature and compiled a list of minimum and maximum levels of key nutrients that must be present in a dog food labeled as complete and balanced. No actual feeding studies were required, but random samples of a company's foods (this requirement applied to canned as well as dry foods) were expected to meet the established minimums and maximums. Even though this was an important improvement in the assurance of the quality of these foods, their ingredient content continued, and continues to this day, to be ingredient-cost and ingredient-availability driven. Meeting nutrient requirements is achieved by adding supplements when the ingredient mix that is most cost effective does not provide the right balance alone.
Into this environment enters the cat as an increasingly "kept" pet for which owners began to clamor for complete and balanced commercial foods as well. While it was understood by manufacturers that the cat had some unique nutritional requirements as a result of its status as an obligatory carnivore (e.g. the need for preformed vitamin A because the cat cannot synthesize this vitamin from dietary beta-carotene as humans and dogs can, the need for high levels of arginine and taurine because of high use and limited internal synthetic capabilities for these amino acids, the need for dietary arachidonic acid because of an inability to produce this fatty acid internally, etc.), these requirements were somewhat cavalierly addressed by the pet food companies, as we will explore shortly in the matter of the devastating taurine-deficiency problem with most canned cat foods that arose in the late 1980s.
Certainly, the cat's completely unique metabolic machinery designed for high production of energy from protein and near exclusion of carbohydrate as an energy substrate was entirely ignored. Essentially, as dry cat foods began to emerge in response to cat-owner demand, they were little more than dry dog foods, processed into smaller, cat-sized kibble, with a slightly different vitamin/mineral mix added.
In fact, both canned and dry cat foods are the product of marketing and food technology considerations, not the science of feline nutrition. Witness the fact that canned and dry forms of the exact same formula of any brand with corresponding forms, have entirely different macronutrient profiles. Canned product has relatively high protein (usually about 40-55% on a dry matter basis, moderate fat (usually 25-35% DMB) and low carbohydrate (usually about 2-8% DMB). Dry foods bear absolutely no nutritional resemblance to their corresponding canned version. A dry food will typically have about 20-33% protein, 10-25% fat, and 20-50% carbohydrate! In addition, dry foods often have relatively high fiber content (5-8%) while canned foods, unless they have fiber deliberately added as a separate ingredient, have negligible fiber. Why would different physical forms of the exact same formula, for the exact same "life stage," have such very different macronutrient contents? Do kittens and cats have different needs depending on whether they are eating canned or dry? The short answer is no, of course not. The cat has the exact same needs whatever form of food it consumes, so why the great difference in these formulas?
The demands of food technology in the production a dry kibble using the process of extrusion, (same as breakfast cereal for humans) dictate the macronutrient profile of dry pet foods. Extrusion is the expansion and "popping" of kibbles through a high heat, high pressure process that will not occur without substantial starch content in the slurry that is fed into the extruder. A canned food formula, sent through an extruder, will end up a damp puddle the end of the machine, rather than fluffy, air filled kibbles ready for drying. So, tons of corn, rice, wheat, oats, barley and other grains (the less expensive the better, of course) are added to the meat meal and low volume ingredients that comprise dry pet foods because the product form will not materialize otherwise.
Further, dried kibble is almost completely unpalatable for the typical cat. This is not surprising; one would expect that this species would recognize high cereal foods as "not food." In response, an entire industry has grown up, right alongside the expansion of the dry dog and cat food industry, to produce and provide potent palatability enhancers for coating pet food, especially cat food. These palatability enhancers may be acidified yeast (cats like the taste and/or mouth feel of acid substances), but more commonly are meat "digests." Digests are produced when food animal entrails are fermented into a sprayable liquid mixture with acid added and then sprayed onto the outside of the dry cat food kibble. Few pet owners, including those adamantly opposed to the feeding of raw foods to their pets, would be so complacent about commercial dry pet foods if they witnessed the production and application of this ingredient. Thus, cats are essentially "tricked" into the consumption of a food they would not ordinarily consume, through the application of tasty outer coatings. One is reminded of the application of candy coatings on the outside of children's breakfast cereal to enhance the consumption of relatively low nutritional-value breakfast foods.