Mixed Feeding & Gastric Acidity

WHY IS AN ACIDIC STOMACH IMPORTANT FOR DIGESTION?

Meat protein stimulates strong stomach acidity (by triggering the production of hydrochloric acid in acid-secreting cells within the stomach). Carbohydrates do not stimulate strong stomach acidity. A complex cascade takes place when a dog or cat ingests food, put simply: 80% of the gastric juices secreted are a direct result of chemoreceptors in the stomach detecting the presence of meat-based proteins. This keeps the stomach at a very low pH of around 1-2 (a low pH means high acidity). This low stomach pH is important because:

• Digestive enzymes work best in an acidic environment.
• The acidity in the stomach will sterilise ingested pathogens (bacterial or fungal).

When a dog or cat swallows a commercial pet food (high carbohydrate, high plant protein, low meat protein diet), acid-secreting cells in the stomach are not stimulated to produce as much hydrochloric acid, thus the pH does not drop as low. The acidic chyme (food mixed with gastric juices) leaving the stomach is the trigger for the next stage of digestion in the small intestine. The acidity encourages the flow of bile and the flow of pancreatic enzymes necessary to continue the digestive process. If the stomach contents are not sitting at a pH of around 1-2, then digestion is impaired throughout the rest of the digestive tract as well.

WHAT DOES THIS MEAN FOR DOG & CATS?

A diet high in carbohydrates is not optimal for promoting adequate stomach acidity. A raw meaty bones diet requires a highly acidic stomach for digestion. Dogs and cats should not be fed a combination of processed and raw diets. If they are fed a combination, they can experience a range of problems:

• They may struggle to properly digest their foods.
• They may become constipated with undigested bone spicules impacted in the rectum (a very painful situation).
• Raw meaty bones can sit for long periods in the stomach, which may lead to vomiting bone, or worse still, an obstruction.
• They may experience a gastro-intestinal upset when the bacterial load of the ingested food runs riot in the alkaline stomach environment. Gastric acidity is needed to sterilise ingested pathogens. Processed pet foods are often contaminated with salmonella and mycotoxins - the gastric acidity is a first line of defence, so dogs and cats with reduced acidity are vulnerable.

PROCESSED PET FOODS

Meat protein is the most expensive component in pet food. As a result there is a lot of commercial pressure to keep meat proteins levels to a minimum in processed pet food: keeping production costs low, while maximising profit.

How do processors minimise meat protein?

• They incorporate high levels of carbohydrate (corn, wheat, rice, potato etc) in their pet foods.
• They boost protein content with plant-based proteins (soy, pea protein etc), which are much cheaper than meat sources.

Dogs and cats eating these processed foods struggle to properly digest it. There is a very simple reason for this: Dogs and cats need a highly acidic stomach in order to properly digest their food BUT... the carbohydrates in processed foods make the stomach less acidic.

WHAT SHOULD WE FEED CATS & DOGS TO OPTIMISE DIGESTION & GOOD HEALTH?

Dogs and cats are carnivores; their digestive tract is geared to respond to meat based proteins. A species-appropriate diet is the first step in optimising digestion, and ensuring the availability and absorption of essential nutrients. A well-nourished pet is a healthy pet! Because at Raw Essentials we obtain our meat-based diets directly from our hunters, farmers and processors; and because we are sourcing NZ product and not paying huge global shipping fees; and because we donʼt have secret recipes or the need for expensive marketing campaigns – we can bring you the highest quality meat-based protein diets for your cats and dogs.

ACIDITY & BUFFERING

Carnivores ingesting their evolutionary diet of prey have naturally high gastric acidity.(1,2) High dietary protein is the most significant stimulatory factor of acid within the stomach.(3,4,5,6,7) Additionally, protein provides the best buffering capacity as food enters the small intestine.(4) Diets with high carbohydrate content do not stimulate adequate gastric acidity.(7) This is unsurprising given Raubenheimer’s(12) work on the established macronutrient preferences for cats and dogs.(12,13) He states that commercially available cat foods will put cats into a “chronic state of nutritional imbalance” which “raises welfare concerns, and will also in the long term likely affect cat metabolism and health.”

Palatability has also been shown to promote the production of acid within the stomach.(6) Foods which require a high level of mastication (and thus production of saliva), such as raw meaty bones, have higher buffering capacity.(4)

The stimulation of high levels of gastric acidity is important for digestion and absorption of nutrients, as well as protection from potentially pathogenic organisms.

Gastric acid (HCL) enhances the absorption of nutrients (such as calcium and iron).(8) It promotes protein digestion by activating pepsin.(8)

Gastric acid is a very important line of defence against food/water-borne pathogens.(8,1,9,2,10,11) Potentially pathogenic bacteria are regularly found on many popular brands of processed pet foods, pet treats. These processed foods have a well established link to illness in humans. Although the link between contaminated raw food and human illness is currently tenuous at best(14), common sense dictates that contaminated raw food be considered as a potential source of food-borne illness – raw food should be carefully sourced and stored, and appropriate hygiene measures implemented in the home.

REFERENCES

1. Callaway, E. (2014). Microbes help vultures eat rotting meat. Nature, 26 November 2014).
2. Beasley DE, Koltz AM, Lambert JE, Fierer N, Dunn RR. (2015) The Evolution of Stomach Acidity and Its Relevance to the Human Microbiome. PLoS ONE 10(7): e0134116. doi:10.1371/journal.pone.0134116
3. Saint-Hilaire, S.,Lavers, M.K., Kennedy, J. & Code, C.F. (1960). Gastric acid secretory value of different foods. Gastroenterology, 39(1).
4. Lennard-Jones, J.E., Fletcher, J. & Shaw, D.G. (1968). Effect of different foods on the acidity of the gastric contents in patients with duodenal ulcer. Gut (BMJ), 9, 177-182.
5. Lichtenberger, L.M. (1982). Importance of food in the regulation of gastrin release and formation. American Journal of Physiology 243, G429-441.
6. Brooks, F.P. (1985). Effect of diet on gastric secretion. American Journal of Clinical Nutrition, 42, 1006-1019.
7. DelValle, J. & Yamada, T. (1990). Amino acids and amines stimulate gastrin release from canine antral G-cells via different pathways. Journal of Clinical Investigation, 85, 139-143
8. Smith, J.L. (2003). The role of gastric acid in preventing foodborne disease and how bacteria oversome acid conditions. Journal of Food Protection, 66(7):1292-1303
9. Hunt, R.H. (1988). The protective role of gastric acid. Scandinavian Journal of Gastroenterology, 23(supp146):34-39
10. Cook, G.C.(1985). Infective gastroenteritis and its relationship to reduced gastric acidity. Scandinavian Journal of Gastroenterology, 111:17-23
11. Martinsen, T.C., Bergh, K. & Waldum, H.L.(2005). Gastric juice: a barrier against infectious diseases. Basic and Clinical Pharmacology and Toxicology, 96(2):94-102
12. Simpson, S.J., & Raubenheimer, D. (2012). The Nature of Nutrition: A Unifying Framework from Animal Adaptation to Human Obesity. Princeton University Press.
13. Hewson-Hughes, A.K., Hewson-Hughes, V.L., Colyer, A. Miller, A.T. McGrane, S.J. Hall, S.R. Butterwick, R.F. Simpson, S.J. & Raubenheimer, D.(2012, 23 October). Geometric analysis of macronutrient selection in breeds of the domestic dog, Canis lupus familiaris. Behavioral Ecology, doi:10.1093/beheco/ars168
14. Thomson, L., & Mair, A. (2013). Analysis of the 2012 American Veterinary Medical Association Position statement on Raw-Feeding. http://www.rawessentials.co.nz/media/documents/AVMA%20statement%20rebuttal.pdf