Grain Free Cat Foods

Is this a trend that is based on real science, or a fad that has caught on?

First, we must understand that a cat is an obligate carnivore.  That means the cat, be it a tiger or an ordinary house cat, must eat other animals to fulfill their needs for certain types of nutrients. In their natural habitat, cats are hunters that consume prey high in protein with moderate amounts of fat and minimal amounts of carbohydrates. Cats also require more than one dozen “essential elements”, including vitamins, minerals, fatty acids, and amino acids. “Essential” means the nutrients must be supplied by the diet because the cat cannot create it. Several of these “essential” elements include the amino acids taurine and arginine, certain fatty acids such as arachidonic acid and vitamins niacin, A, D and B-12.  What is the primary or only source of these needed nutrients? Animal tissue. Once again, the carnivorous cat utilizes animal sources of nutrients more readily than plant sources. For example, cats cannot convert beta-carotene from plants to vitamin A (as some animals do), so they need preformed vitamin A from an animal source. Preformed vitamin A needs no conversion.

Why not a dog food for a cat?  Because dog foods have lower protein, taurine, niacin, vitamin B6, methionine and choline than what cats need.  Also, dog foods will not typically address the urinary acidification and magnesium content appropriate for reducing the risk for struvite crystal formation. A key point to remember is that cats are neither small dogs nor humans.
Every protein source contains different levels of amino acids and each protein is different in its ability to be broken down into amino acids. The ability of a protein to be used by the body and its amount of usable amino acids is termed “biological value”. Egg has the highest biological value and sets the standard by which other proteins are judged. Egg has a biological value of 100. Fish meal and milk are close behind with a value of 92. Beef is around 78 and soybean meal is 67. Meat, bone meal and wheat are around 50, and corn is 45. Things like hair and feathers would be very high in protein, but would be down at the bottom of the list for biological value.
Does a high protein percentage (as shown on the package) mean that a pet food is automatically better than others with lower percentages?

No, a higher percentage of protein doesn’t mean that a pet food is always better than another food with a lower percentage. A lower protein percentage isn’t automatically bad, either, provided that the protein included in the food comes from a good source such as fish, chicken or lamb. Don’t rely solely on the percentage of crude protein shown in the guaranteed analysis on the package when choosing a food. While it seems safe to assume that a high percentage of protein means that a food contains a lot of useable protein (and is therefore better than another food), this is not always the case. Always evaluate the source of the protein – not just the amount – when considering and comparing pet foods.
In summary, a cat’s natural diet is low in carbohydrates and they are not designed to digest carbohydrates. Regardless of whether grain or non grain carbohydrates are used, they are added to dry cat food because it is mechanically necessary to produce the kibble and carbs are less expensive than meat; not because carbohydrates are healthy or necessary for your cat. The same can also be said of the protein source in cat foods; plant proteins are easier to bind and thus easier to hold a kibble together, but not necessarily the best proteins to use for a cat’s diet.  Where is the line for too much plant protein versus animal protein in a feline diet? It wasn’t but 30 years ago or so that a large company tried to market an all soy- based cat food, only to discover the taurine deficiencies cats ran into with this approach; but on a positive note, this is how feline taurine requirements were identified!

Grain free cat foods are all hype.  What is important are low carbohydrate cat foods, as that is where the science of common sense really lies.