Myth or Fact: You Can’t Mix Kibble and Raw Food?

MYTH!

This is one that I see everywhere and it’s really quite frustrating. It makes people think that they need to have an all or nothing mentality when in reality, it’s often difficult for people to be able to commit to a fully raw diet. Multiple dogs, large dogs, high energy dogs, limited income and limited ingredient accessibility are all situations that may make it impossible for individuals to feed a fully raw diet.

There are 2 main reasons why you may hear that mixing the 2 is dangerous. Let’s explore them.

Myth #1: Kibble fed dogs have a higher stomach pH while raw fed dogs have a lower stomach pH which enables them to digest raw meat and bones

Truth: The digestion process results in constantly changing pH levels for proper digestion no matter what the diet is

Let’s start with a review of digestion. Digestion starts in the mouth with chewing which is called mechanical digestion. Food is then moved down the esophagus to the stomach. The stomach distends which stimulates the secretion of gastrin and neurological stimuli stimulates the secretion of hydrochloric acid- the result is the production of gastric juices. The food that enters the stomach is mixed with the gastric juices to produce a semi-liquid mass called chyme which is then moved to the small intestine. Bicarbonate is released by the pancreas to neutralize the chyme to allow for proper enzyme activity.

What does this mean in the context of differing stomach pH? Well, as you can see, the pH is always changing depending on the stage of digestion. Additionally, in order for proper nutrient absorption, a neutral pH is needed, not an acidic pH.

As far as I am aware, there are no studies comparing the stomach pH of raw fed dogs vs. kibble fed dogs or even studies examining the pH of raw fed dogs. However, there are many studies looking at the stomach pH of kibble fed dogs. These studies show that the basal (resting) pH is around 4 or 5 and once the gastric juices are produced, the acidity drops down to around 2. I’m not sure we would really want a normal stomach pH lower than that or we would be risking ulcers.

Myth: Raw diets digest faster than kibble thus creating a “traffic jam” in the stomach and inhibiting the digestion of bones

Truth: Everything digests at different rates

To start, have you ever heard someone say you shouldn’t eat sushi because cooked rice and raw fish digest at different rates? Probably not. So why would that matter in dogs?

There are few studies on the rate of stomach emptying for dogs fed a raw diet but there are many in kibble fed dogs. What researchers have determined is that there are many factors that impact stomach emptying including the size of the food particles, the size of the meal, fat and fiber content, moisture content. Some studies even suggest that the size of the dog impacts the rate of digestion. While the difference in moisture content of raw vs. kibble diets may cause them to digest at different rates, that doesn’t mean that one will be blocked by the other. That’s simply just not how digestion works.

There has been one experiment done that used x-rays and barium to show the digestion process of both kibble and raw using the same dog. Unfortunately, the page that did the experiment is no longer available so I can’t link it. What was interesting about the experiment was that it showed that raw actually took longer to digest than kibble- which is exactly the opposite that most people like to think.

Sources:

Akimoto, M. “Gastric Ph Profiles of Beagle Dogs and Their Use as an Alternative to Human Testing.” European Journal of Pharmaceutics and Biopharmaceutics, vol. 49, no. 2, 2000, pp. 99–102, https://doi.org/10.1016/s0939-6411(99)00070-3.

Boillat, Carol S., et al. “Assessment of the Relationship between Body Weight and Gastrointestinal Transit Times Measured by Use of a Wireless Motility Capsule System in Dogs.” American Journal of Veterinary Research, vol. 71, no. 8, 2010, pp. 898–902, https://doi.org/10.2460/ajvr.71.8.898.

Case, Linda P., and Daniel P. Carey. “7 Digestion and Absorption.” Canine and Feline Nutrition, 3rd ed., Mosby, St. Louis, MO, 2011.

Keinke, Oliver, et al. “Mechanical Factors Regulating Gastric Emptying of Viscous Nutrient Meals in Dogs.” Quarterly Journal of Experimental Physiology, vol. 69, no. 4, 1984, pp. 781–795, https://doi.org/10.1113/expphysiol.1984.sp002868.

Mahar, Kelly M., et al. “Gastric Ph and Gastric Residence Time in Fasted and Fed Conscious Beagle Dogs Using the Bravo® Ph System.” Journal of Pharmaceutical Sciences, vol. 101, no. 7, 24 Apr. 2012, pp. 2439–2448, https://doi.org/10.1002/jps.23159.

Miyabayashi, Takayoshi, and Joe P. Morgan. “Gastric Emptying in the Normal Dog a Contrast Radiographic Technique.” Veterinary Radiology, vol. 25, no. 4, 1984, pp. 187–191, https://doi.org/10.1111/j.1740-8261.1984.tb02143.x.

Nelson, OL, et al. “Gastric Emptying as Assessed by Barium-Impregnated Polyethylene Spheres in Healthy Dogs Consuming a Commercial Kibble Ration.” Journal of the American Animal Hospital Association, vol. 37, no. 5, 2001, pp. 444–452, https://doi.org/10.5326/15473317-37-5-444.

Sagawa, Kazuko, et al. “Fed and Fasted Gastric Ph and Gastric Residence Time in Conscious Beagle Dogs.” Journal of Pharmaceutical Sciences, vol. 98, no. 7, 2009, pp. 2494–2500, https://doi.org/10.1002/jps.21602.