Gastric pH in dogs fed raw and pelleted diets

There are many differences in the digestion of fresh, raw food versus dry, extruded food. Many of these differences are some of the main reasons why raw diets can be superior to kibble. Minimally processed animal proteins are easily digestible and provide optimal amounts of a wide variety of amino acids, which are then used for almost every metabolic function in the body. Antinutrients, which can interfere with the absorption of vitamins and minerals, are not a concern with low- or no-carb diets. Raw diets have been shown to promote healthier gut flora than dry foods, improving digestion and overall health.

There are two main reasons why owners are discouraged from adding raw foods to the diet: digestion rate and stomach pH.

In this article, I will examine the issue of stomach pH, ​​how it relates to healthy digestive function, and whether the claims are true or not...

The stomach pH values ​​of kibble-fed dogs are significantly less acidic than raw-fed dogs, and does this mean that dogs cannot safely consume both raw and dry foods?

What is gastric pH and why does it matter?

Stomach pH refers to the acidity scale in the stomach. The pH scale ranges from 0 to 14, with the lowest numbers being the most acidic, the highest numbers being the most basic or alkaline, and 7 being neutral.

Stomach pH is a very important component of digestion. The environment in the stomach needs to be welcoming to the beneficial bacteria that help the body break down food, but it also prevents pathogenic bacteria from surviving and causing infections.

The stomach also needs to be a favorable environment for enzymes. There are a handful of different enzymes and hormones that aid in digestion, and many of them are either produced in the stomach or their production is influenced by the stomach environment. pH is a major factor affecting the production and activity of these hormones and enzymes.

Digestion lesson

We'll be starting our digestion lesson soon, but first, a quick psychology lesson! Have you ever heard of Pavlov's dogs? Pavlov noticed that his dogs would salivate when his lab assistant entered the room, even if he didn't bring food with him, and he hypothesized that the dogs were associating the lab assistant with food. He discovered that he could associate the sound of a bell with food, thus causing his dogs to salivate only at the sound of the bell. This is what led to his discovery of what we call classical conditioning: a conditioned but unlearned response to a stimulus.

In this case, the stimuli are the anticipation of food. It turns out that salivation is not the only thing that happens when dogs anticipate food. In fact, just thinking about food can start the first phase of digestion.

Before your dog even takes a bite of food, the sight, smell, and even the thought of food triggers the cephalic phase of digestion. Signals from the brain tell cells in the stomach wall to begin secreting gastric juice. Tasting, chewing, and swallowing further intensify this process. Approximately one-third of all gastric acid and pancreatic secretion occurs during this main phase, which can last for more than 4 hours in dogs.

Once food has been swallowed and reached the stomach, the presence of food particles stimulates the secretion of a hormone called gastrin. Gastrin's job is to trigger the production of even more stomach acid, further acidifying the stomach. The amount of stomach acid produced will depend on the contents of the meal; hormones regulating stomach acid production respond as needed. If the meal requires more acidity, more stomach acid will be produced, and vice versa.

During protein digestion, a substance called pepsinogen is secreted from the stomach lining. Below a pH of 4, pepsinogen is converted to pepsin, an enzyme that helps break down proteins into smaller polypeptide chains and individual amino acids. Pepsin functions effectively between a pH of approximately 1.5 to 4.5, but is most active around a pH of 2 to 3.5. Because stomach acid has already been secreted before, during, and after food is swallowed, the stomach is acidic enough for pepsin to be maximally active.

Lipase, the enzyme that helps digest fats, is most active at pH 4 and is irreversibly inactivated at or below pH 1.5. Because the acidic environment of the stomach is not optimal for lipase, most of the digestion of food in dogs takes place in the small intestine. Amylase in dogs is not present in saliva, as it is in humans, and is also not active in an acidic environment, so most of the digestion of carbohydrates also takes place in the small intestine.

The pH of the stomach also affects what happens outside the stomach. As chyme (the mixture of partially digested food and gastric juices) begins to leave the stomach, the acidic pH stimulates the hormones secretin and cholecystokinin to be produced in the duodenum (the first part of the small intestine). Their job is to trigger the release of bicarbonate (which works to neutralize the acidic chyme so it doesn’t damage the small intestine), trigger the release of pancreatic enzymes (proteases to further digest proteins, lipases to digest fats, and amylases to digest starches), trigger the liver to produce bile (which further aids in the absorption of fats in the small intestine), and begin to inhibit the production of stomach acid.

As the rest of the chyme leaves the stomach, hormones such as somatostatin further inhibit stomach acid production by preventing the release of more hormones such as gastrin or secretin.

Digestion continues in the jejunum (Empty intestine — makes up 2/3 of the small intestine, located between the duodenum and the ileum (lumen intestine). and the ileum of the small intestine.

... But since this article is primarily about stomach pH, ​​not intestinal pH, our adventure through the digestive system need not go any further.

Once the food is digested, the stomach pH will become less acidic, as there is no need to maintain a highly acidic environment in the stomach unless gastric juices are needed for digestion; and if the stomach remains too acidic, ulcers can develop. So the stomach pH rises slightly until the next time your dog anticipates taking another bite of food... and then it all repeats itself again!

So, as you can see, stomach pH is definitely not constant. It is normal for stomach pH to fluctuate depending on what was eaten, how much was eaten, or how long it has been since something was eaten. Regulating stomach pH is a normal part of healthy digestion.

What is the difference in stomach pH in dogs fed a raw diet versus dogs fed pellets?

Unfortunately, due to the invasive nature of measuring gastric pH in animals, there are limited studies measuring gastric pH in dogs. The majority of current studies do not necessarily focus on optimal canine digestion, but rather use the dog as a model to study pharmacokinetics and how gastric pH may affect the metabolism of certain drugs.

There have been no studies comparing the stomach pH of dogs fed a raw diet to dogs fed a kibble that I am currently aware of (as of January 2018). Most of the recent studies have involved dogs fed a dry diet, as this is the standard diet for dogs (much to the dismay of raw food eaters). However, what limited research we do have shows that dogs fed a dry diet still have a highly acidic stomach pH: around an average of 2.

It is very likely that the average gastric pH will differ slightly between raw-fed dogs. It may even differ slightly between kibble-fed dogs, depending on the protein, fat and carbohydrate content of the mix, or between dogs on different home-cooked diets.

The bottom line is this: at this point in time, there have been no studies comparing the stomach pH of dogs fed a raw diet to dogs fed a kibble. There have been no studies that have specifically examined how mixing raw and kibble affects a dog’s stomach pH. Therefore, no one can really say how much of a difference in pH there really is between raw and kibble-fed dogs. What we can do is make observations about a dog’s digestive system and look at the evidence.

What does this mean in terms of raw and pellet feeding?

Any time a dog's diet changes, there will be an adjustment period. Stomach pH is one factor in this adjustment. This is why a gradual transition is recommended when switching from one diet to another. A gradual transition can be done when switching from kibble to raw as well (which is my preferred method for most dogs).

However, the claim that dogs fed kibble actually have neutral or alkaline stomach pH is completely unfounded and verifiably false. An alkaline or neutral stomach pH would not be able to digest raw or kibble and would lead to severe malnutrition.

This means that the significance of this difference in gastric pH between raw and pellet-fed dogs is greatly exaggerated.

What we do know from current research is that dogs fed dry food have highly acidic stomach pH values ​​and that the dog’s digestive system is well-equipped with a complex network of hormones and enzymes that regulate stomach acid production. We know that owners have been successfully feeding raw and kibble together for decades. And we know that fresh food is very beneficial for our dogs’ health. All of this being said, if you ask me, it’s safe to say that we should be encouraging owners to add fresh foods to their dog’s diet in whatever capacity.

But as many people witness the benefits of raw diets and learn more about the pitfalls of dry food, their passion for optimal nutrition can encourage a more extremist “all or nothing” mindset. I strongly believe that this mindset is detrimental to dogs whose owners do not have the means/opportunity (freezer/refrigerator) to feed raw: instead of being encouraged to improve their dogs’ diets in any way, they are being told that it is actually dangerous to introduce raw foods into their dog’s diet.

And that's a shame.