Pet Food Nutrition: the Truth About Corn

 

There has been an increasing trend in the movement of pet food companies to exclude ingredients like corn based on the perception that it is an undesirable ingredient. It has been described as an indigestible "filler" ingredient (ingredients that do not contribute to any nutritional or beneficial properties to a food) that leads to food allergies. The reality is that most concerns regarding corn are invalid.

Remember: true food allergies are uncommon in dogs and cats. It has been estimated that only 1% of all skin diseases can be attributed food allergies; more often flea-allergy dermatitis and atophy are responsible. Most gastro-intestinal conditions that respond well to diet changes are actually more food-sensitivities or intolerances to properties of the diet such as fat or fibre content.

Further more, corn is a rare cause of food allergies. More often, allergies occur to other ingredients including beef, dairy and chicken. In general, animal-based protein is more commonly a cause of allergies rather than plant-based ingredients.

So while there is little evidence to support the exclusion of corn, corn is also a source of essential nutrients. It contributes fibre, protein, vitamins, minerals and high-digestible carbohydrate to a diet. It is also one of the riches sources of linoleic acid, an essential fatty acid, and as such is not a "filler" ingredient.

When it is properly processed (ie: rolled, ground, flaked, cooked), corn's digestibility greatly increases. Whole ground corn cooked via extrusion (the way that most dry pet food is made) has been shown to have a digestibility of greater than 97% in dogs and cats!

Corn, like many other ingredients, has managed to develop a bad reputation based little on fact and more on myth. As always it is important to educate yourself on interpreting pet-food ingredients and marketing strategies, differentiating real information from hype. As always, your veterinarian can help you sort out fact from fiction when choosing an ideal diet for your pet.

Vanessa Tonn, DVM
Bowmanville Veterinary Clinic

Pet Food Nutrition: Grain-Free Diets

Dogs and cats are both classified in the order Carnivora. Does that mean that they should receive a strict meat-only diet? Are certain carbohydrate-sources better or worse than others? Do grain-free diets provide health benefits over those that contain grains?

Contrary to popular belief, grain-free diets do not offer health benefits over diets than contain grains. Dogs are actually considered omnivores (and thus more similar to bears, skunks and racoons), and both dogs and cats have the ability to digest, utilize and benefit from a nutritionally balanced diet containing carbohydrates, including grains. In fact, animals do not treat grains differently from other sources of carbohydrates like potato and apple – the body recognizes the food by the nutrients it provides, not by its source. The starch (the main carbohydrate) in grains is actually highly digestible for both dogs and cats – 95% or higher.

Many manufacturers, in an attempt to make their diet stand out in a competitive market, advertise grain-free diets as being healthier, when in reality they are readily comparable to their grain-containing counterparts. Many grain-free diets are not actually lower in carbohydrates, but rather use alternative sources of carbohydrates, such as potatoes and tapioca, which are actually lower in protein and higher in sugars than grains.

So what other benefits do grain-free diets claim? Some claim that the risk of food allergies, obesity or diabetes is higher in diets that contain grains as the source of carbohydrates. True food allergies (reaction of the immune system to certain food proteins) are actually quite rare but can be caused by any ingredient that has protein. Food intolerances (which don’t involve the immune system) are usually in response to certain nutrient profiles, such as high-fat diets, and are rarely related to grains specifically. The most common allergies in dogs are beef, dairy, wheat, chicken and egg; in cats beef, dairy and fish are most common. Usually animal proteins are more common causes of allergies than grains or other carbohydrate sources. However, if an animal is truly allergic to a single type of grain (for example, wheat), feeding other types of grains (like oats and rice) should not be a problem.

Obesity is a serious disease that affects a large number of our animal friends. However, the main cause in both dogs and cats is excessive calories – regardless of the source. Many grain-free diets are actually higher in calories and fat; they can be easy to over-feed and the fat makes them very palatable. Regardless of the type of diet fed, owners should monitor their pet’s body condition and weight carefully and feed accordingly.

Diabetes in dogs is related to the destruction of specific cells in the pancreas, and cannot be induced with diet. However, it has been shown that achieving and maintaining optimal weight and providing a consistent diet and meal times can help in managing the disease in dogs. Cats, on the other hand, are prone to developing diabetes if their weight is not-well managed. As mentioned above, diets containing grains do not promote obesity. While some research has shown that diets with lower carbohydrate content can be useful in managing diabetes in cats, most of these diets contain grains.

While grain-free diets can provide excellent nutrition, they do not offer health benefits over diets than contain grains. It is important to assess your pet’s diet based on overall nutrient profile rather than individual ingredients, and to not be swayed by marketing tactics.

Vanessa Tonn, DVM

Bowmanville Veterinary Clinic

Pet Food Nutrition: Food Allergies & Food Intolerances

Itch, itch, scratch, scratch. Does your dog lick at his paws, rub his belly on the floor or have chronic

ear infections? Many people assume that dogs and cats with itchy skin have an allergy to ingredients in their food – but actually food allergies in pets are less common than environmental allergies to pollens, molds or dust mites. It can be tricky to differentiate environmental allergies (termed atopic dermatitis) from food allergies, but sometimes atopic dermatitis can present as skin conditions that occur seasonally, while food-allergies are more typically year-round (although not all animals follow these patterns).

Some cats and dogs present with diarrhea that resolves with a change in diet. In these cases, it is more likely that the animal is responding to differences in fat, fibre and digestibility of the food, rather than to a specific ingredient. In fact, “adverse food reactions” can be divided into two categories: food allergies and food intolerance.

• Food allergy involves an immune-response to specific proteins in the food. Signs can include gastrointestinal signs (vomiting, diarrhea) or – more commonly – skin problems (itching, redness, infections). 
• Food intolerances do not involve the immune system, and can contribute to gastrointestinal symptoms or – less commonly – skin issues. An example of food-intolerance includes lactose-intolerances, which rarely occurs in dogs and cats, but is common in humans.

How can we diagnose food allergies? 

A strict elimination diet is a good way to reliably diagnose a food allergy or intolerance. The new diet needs to be fed exclusively for 6-10 weeks (with no additional treats, table scraps, rawhides or dental chews), then the animal can be re-challenged with the original diet.

Choosing an elimination diet can be difficult. Exotic ingredients such as lamb, duck and venison are not always good, especially if a dog has been exposed to these ingredients in the past. Unfortunately many pet foods are introducing new and exciting ingredients that sound healthy, which actually complicate matters when trying to rule-out food allergies. 

Finding novel ingredients requires a thorough diet history – including all pet foods, treats, table-scraps, etc. It is important to find novel meat and carbohydrate sources, as carbohydrates can contain allergens as well. A proper elimination diet should contain one protein and one carbohydrate source, plus all the vitamins and minerals required to make the diet complete and balanced.

An alternative option to novel ingredient diets is a hydrolized diet. These diets contain proteins that have been chemically or enzymatically hydrolyzed to reduce them to a smaller size that is less likely to trigger an allergic reaction.

Many over-the-counter pet foods boast the benefits of their novel protein diets meant for food allergies. However, in many cases these diets still contain more than one protein and carbohydrate source, either intentionally or through unintentional contamination from other food lines made in the same manufacturing plant. A true hypoallergenic diet should be created in a facility with strict cleaning protocols, and should always be the first diet manufactured to decrease the risk of contamination. Furthermore, hydrolized diets are not available in over-the-counter recipes. It is possible to use over-the-counter diets as a management diet once a food-allergy is diagnosed, but should not be used during the strict elimination diet period to diagnose a food allergy.

What about grain-free or gluten-free diets?

While there has been a lot of marketing talk lately regarding a movement to grain-free options for dogs and cats, in reality grains are less common causes of allergies than animal products. The most commonly reported food allergies in dogs are beef, dairy, wheat, chicken and egg; in cats beef, dairy and fish are more common culprits. See our next blog in the nutrition series for more about grain-free diets.

In humans there are medical conditions (e.g. celiac disease) that cause people to be sensitive to gluten, a protein portion of some plants. It is currently a popular trend towards pet-foods labelled as gluten-free. However, gluten-sensitivity has only been reported in a small, related family of Irish Setters, and never in cats. There is no evidence to support that gluten-free diets have any health benefit in the majority of dogs and cats.

While food allergies do occur in dogs and cats, environmental allergies and food intolerances are more commonly the causes of skin and gastrointestinal problems. If you are concerned about the possibility of food allergies for your pet, you need to consider a proper food-allergy diet trial done under the supervision of your veterinarian.

Vanessa Tonn, DVM

Bowmanville Veterinary Clinic