The Link Between Diet and Domestication, or Is My Dog Designed to Eat Grains?
Evolution of the Domestic Dog
Remains similar to domestic dogs have been found in burial sites in Siberia dating back as far as 33000 years ago. Similar remains have been found at archeological sites throughout the Middle East whose origins go back 10000 years ago.
Many changes have occurred in dogs as a result of their domestication and their relationship with people. These changes include both morphological changes (i.e. changes in form and structure) and behavioral changes.
Some of the morphological changes associated with domestication in dogs include:
• Skull shape and size – the domestic dogs that we know today have a variety of different skull shapes and sizes depending on their breed
• Size of the teeth, especially the canine teeth
• Brain size – wolves have larger brains than our domesticated dogs
Associated behavioral changes include:
• Decrease in aggression
• Altered social behavior – despite many claims to the contrary, our domestic dogs do not behave the same as their wolf cousins, even in a group situation
• Cognitive capacity
Is There a Link Between Diet and Domestication?
Though we don’t know exactly where or when the process of domestication began, we do know (or at least theorize) that, early on, wolves followed humans and scavenged on their kill sites. As human behavior changed and humans began to settle in specific areas to farm as well as hunt and fish, wolves began to scavenge from garbage dump sites utilized by these communities. This scavenging eventually lead to an improved ability to digest carbohydrates in some of these animals. This dietary adaptation in turn lead to an increased chance of survival for these same animals.
Exactly what type of adaptations occurred to make this change in carbohydrate digestion possible? This is a question that is answered by the results of a scientific study published in the journal Nature entitled “The genomic signature of dog domestication reveals adaptation to a starch-rick diet“.
Let’s talk about the key findings of this study. There are several genes associated with digestion and absorption: three genes that affect fat metabolism, three that affect starch metabolism, two that affect digestion of nutrients, and one that affects absorption of nutrients.
Starch digestion is accomplished in three steps. Each step involves a different gene that encodes for a specific protein or enzyme responsible for the completion of each step. Three of these genes look very different in the dog than in the wolf.
In the presence of amylase, starch is converted to maltose. This reaction is governed, at least in part, by the gene known as AMY2B and its corresponding protein, the AMY2B protein (or amylase 2B). The study revealed that dogs have 4-30 copies of this gene, depending on the breed of the dog, while wolves have only 2 copies of the gene. We know, from previous studies, that when additional copies of a gene are present, the expression of that gene increases. In this case, dogs produce a much higher concentration of the AMY2B protein. According to the study results, dogs exhibit a 28-fold increase in expression of the gene in the pancreas than do wolves (i.e. dogs produce more of the enzyme than wolves). In the serum (or blood), levels are five times higher in dogs. These changes are responsible for a greater capacity to digest starch in dogs, many times higher than that of wolves.
The second gene the study identified and examined is the MGAM gene. This gene codes for the production of maltase, another enzyme important in the digestion of starches. In the dog, two different forms of the enzyme were found; only one in the wolf. The structure of the second was noted to be similar to an enzyme found in omnivores and/or herbivores. A 12-fold greater expression of the gene was also found in dogs.
A third gene looked at in the study is the SGLT-1 gene. Responsible for the transport of glucose across the membrane of the intestinal tract, this gene plays a key role in the absorption of carbohydrates. In dogs, this gene codes for a completely different protein than in the wolf and allows for improved transport of glucose and, therefore, improved absorption of carbohydrates in dogs.
Yes, there’s a lot of science here and this is just a brief synopsis. However, what is important to understand is that, based on this study, dogs are well adapted to digesting and absorbing starches, much moreso than their wolf ancestors.
Is Starch Derived from Grains Bad for Your Dog?
If the grains are processed properly, dogs can digest and absorb them very well. They are well adapted to be able to do so.
Are there some dogs that are sensitive to or allergic to grains? Yes, probably. But it’s not nearly as common as many people seem to believe.
In people, celiac disease is common. It is an immune reaction to glutens, the protein portion of grains. This disease is rare in dogs. A similar disease has been documented in Irish Setters and certain lines in this breed seem to be predisposed. However, the disease has not recognized in other breeds at the current time.
Is feeding a grain-free or gluten-free diet a bad thing for a dog? No, it’s a perfectly acceptable feeding choice. Is it necessary? Not in the majority of cases. Pet owners feeding grain-free foods should also realize that a grain-free diet does not necessarily equate to a low-carbohydrate diet.
We believe that food allergies account for approximately 10% of all allergies in dogs. (Flea allergy and atopy are also common but not food-related.) These are the most common food-related allergens diagnosed in dogs:
As you can see, corn and wheat are low on the list of suspects. It’s not impossible to develop an allergy to these foods but other foods should be considered as well when exploring the possibility of food allergies in a specific dog.
Courtesy of Ken Davies, https://petloverguy.com