Against The Grain: The Rise Of Grain-Free Diets
Written by Board of Advisor member Dr. Justin Shmalberg, DVM on August 11, 2017
Posted in General
A quick trip to any pet supply store will reveal a plethora of diets marketed to be free of grains, especially in the fast-growing market of natural pet foods. Grain-free diets are often viewed interchangeably as low carbohydrate, high protein, or highly digestible. But ingredients don’t always tell the full nutritional story, which is why it’s important that grain-free diets be viewed in the context of both ingredients and nutrients. Surprisingly, we know very little about direct comparisons between grain-rich and grain-free diets when fed over a long period of time. Exploring the reasons for the rise in grain-free diets, the types of carbohydrate and protein replacements for grains, and the nutritional content of such foods allows pet owners to be better prepared to make an informed decision.
How They Got There In The First Place
Grains have been a mainstay of pet diets since the beginning of prepared commercialized pet foods. From a business standpoint, grains and grain-products were in ready supply due to excess agricultural production and processing of human foods. It’s no surprise that many pet food companies were born from human food companies as this minimized waste and lowered costs of pet foods. Grain protein and energy were a source of essential nutrients in pet foods, and could be included at a lower cost than animal proteins made from the labor-intensive process of raising animals for food. If necessary, grains could be split into various parts to build a pet food that met the calculated nutritional requirements of a dog or cat. For example, corn could be divided into corn oil, corn starch (or syrup), and corn gluten. The gluten is the protein part of a grain, made up of individual building blocks, or amino acids, of proteins which help build transporters, muscle tissues, and other substances necessary in the body. It is different from the specific ‘gluten’ proteins (gliadins) found in wheat and related grains to which some humans and some Irish Setters may be sensitive.
Dogs and cats need certain amino acids in their diet, and corn gluten was used less than corn oil and corn starches or syrups in human food products. As a result, testing revealed that corn gluten and other grain proteins could provide these building blocks at a lower cost and be mixed with other vegetable or animal proteins to provide the required nutrients for pets. Grains could also contribute carbohydrate calories, fiber, and essential fats to the diet. Corn was not the only common grain; wheat, oats, and rice were other products frequently found in the majority of pet foods in the United States.
Not The Intended Outcome
Unfortunately, contaminated grain products were associated with pet illness and death during the pet food recalls of 2006, with the primary culprit being wheat gluten from China that was used in the diets of many major manufacturers. The wheat gluten (or protein) itself was not to blame, but rather an intentional addition of an undetectable substance known as melamine, which made wheat gluten seem to have more protein than it actually did. There was already an undercurrent of sentiment that animal proteins might be better for dogs, but this recall resulted in a dramatic increase in diets without grains, which has continued to grow in market share.
Why Go Grain-Free?
Pet owners choose grain-free diets for a number of reasons. The primary reasons are that grains are regarded as ‘fillers’ with poor digestibility, a source of allergies, or an inferior ingredient selected to reduce cost. After switching to a grain-free diet, owners most commonly report a reduction in the frequency and size of the stool, an improvement in coat, or a reduction in allergies. People want to know if there is any truth to these claims. It is true that some grains are less digestible than animal products for protein and less digestible than some root vegetables for carbohydrates, but some grains would still be considered easily digestible. Whole grains often contain fiber, either soluble or insoluble, which can impact how much of the food is absorbed. Insoluble fiber adds bulk to the stool whereas soluble fiber is used by bacteria; both can have health benefits in certain doses.
Food allergies are usually attributed to protein content of the food, with animal proteins being the most commonly reported allergens. However, animals could theoretically be allergic to a grain protein, such as the gluten extracted from a particular cereal. Grains are a less expensive source of protein and generally more than just a “filler” because in some cases, they may be more digestible than certain meats. There are some types of corn which is more digestible than some types of lamb, for example. The digestibility of any food is determined by the body’s ability to break the food down. When cooked appropriately, most grains can be used (at least in part) to provide energy and essential nutrients.
Benefits Versus Downsides
If some grains can be digested and absorbed, is there a way to explain the perceived health benefits of grain free diets? Many of the carbohydrates used in grain-free diets are highly digestible because they are mainly starches or sugars, which are very low in fiber. Common grain-replacement ingredients include potato, sweet potato, and tapioca, which are all root vegetables. The low fiber content of these foods explains why the stool is smaller on some of these diets. This outcome is typically welcomed by owners of dogs with normal digestive systems. It is important to remember that grain-free is not the same as carbohydrate-free, and most kibble diets require carbs to help the kibble keep its signature shape and texture. Grain-free diets contain less fiber than some grain-containing diets, which means the pet should be fed less, making the bag last longer. If fed in these appropriate amounts, grain-free diets can be the same cost as grain-rich diets.
The reduction in allergic symptoms reported by some feeders of grain-free diets is harder to explain. A few grain-free diets have unique animal proteins, such as kangaroo, which could reduce allergic symptoms because they do not contain chicken, beef, lamb, or other allergens. Some dogs may have true grain allergies, though this is very rare. The majority of dogs with allergies are actually allergic to something in the environment, such as pollen, and it’s possible that something in their diet may help reduce inflammation. We know that high levels of omega 3 and some other fats can affect allergic symptoms and inflammation. Many grain-free diets are formulated to be high in these fats. As a result, this change in the nutrient profile compared to a ‘typical’ food may be the most plausible cause for improvement. However, the high fat content of most grain-free diets makes them a potential problem in overweight animals or dogs with certain conditions like pancreatitis.
A pet’s coat may benefit from grain-free diets as well. Higher fat diets, especially those with increased linoleic acid, an essential Omega 6 fatty acid, are known to improve the quality of the coat. This is not unique to only grain-free diets, but the tendency for such diets to be higher in total fat is likely to blame. Dogs also tend to enjoy foods that are high in fat, which explains many pets’ enthusiasm for such diets. If owners are not aware of the increase in calories compared to alternative options, dogs may become obese.
Making Your Decision
Dogs are fairly flexible in the types of diets they can consume to get their essential nutrients, and many dogs do well on grain-free foods. It is still important to compare the protein, fat, and caloric density of diets being considered because they impact digestibility along with skin and coat health. Grain intolerance or aversion is rare in dogs but some grain-free diets on the market do not have health benefits for individual dogs due to the presence of different ingredients and nutrients. Not all grain free diets are the same, however. There are high carb, lower fat grain free diets as well as high fat, lower carb options. It’s always best to look at a combination of nutritional and ingredient information when evaluating food options. This way, you can ensure your pet has the best diet for his or her life stage, activity and medical condition.
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Janice Huntingford, DVM, has been in veterinary practice for over 30 years and has founded two veterinary clinics since receiving her Doctor of Veterinary Medicine at the Ontario Veterinary College, University of Guelph. She has studied extensively in both conventional and holistic modalities. Ask Dr. Jan