Dr. Mark Kinghorn – SNAP Bloor West/High Park, December 2010
Welcome back to the mid-way point in our series on pet health and nutrition. This month we're going to discuss a hot topic in today's commercial diets – the use of grain in pet foods. Many new diets have recently sprung up that are “grain-free” with the marketing message that grain, particularly corn is not a healthy pet food ingredient. Here's the problem – that's simply not true.
The first message that comes with these diets is that grain (corn in particular) will cause allergies and skin diseases. The facts are that food allergies account for 0.9% of all skin diseases in dogs, and for pets that are allergic to an ingredient in their food, studies have shown that the #1 culprit is the protein source in the diet, not the grain.
Another message I hear consistently is that corn when present in a diet is used only as filler, as it contains no nutritional value. The truth is that corn is an excellent source of carbohydrates, and essential fatty acids, and contains balanced levels of protein. Many pet food manufacturers specifically choose corn for this reason. When processed for use in diets, corn is 99% digestible in both dogs and cats.
Perhaps the greatest concern in grain-free diets is what some pet food manufacturers put into their food when they take corn out – more protein! As carbohydrates are excellent sources of energy in a diet, when removed, the energy deficit must be made up by increasing protein levels. Some diets have protein levels approaching 50% on a dry matter basis! Protein levels this high are inappropriate and unnecessary in the best of cases. And in some situations, if fed to the wrong individual, protein levels this high can even be dangerous to their health. In patients with kidney disease, studies show that high-protein diets can hasten disease progression. High protein levels may also predispose some cats to form urinary crystals that can lead to urinary obstruction, a potentially life-threatening condition.
Many of these same diets are also marketed as “ancestral” or geared towards your “modern-day wolf.” But keep this in mind: humans have more genetic similarity to chimpanzees than domestic dogs do to wolves. Domestic dogs and their digestive tracts have evolved so significantly from their ancestors in the past 1.5 million years that they are very poorly suited to digest what would have been eaten so many years ago.
I hope this will help to shed some light on the use of grain in diets. In most situations with healthy adult pets, a well-balanced, properly formulated diet will go a long way to keeping your pet happy and healthy. And as always, don't hesitate to ask your veterinarian if you have further questions. Next month we'll look at life-stage feeding as an important concept in pet nutrition.