Fiber… Fiber… Fiber. We hear a lot about the importance of fiber in both our health and our pets’. But what is fiber? Why is it important? And most of all, why give fiber to your dog or cat?
I was listening to an interesting podcast by the Morris Animal Foundation where they talked about dietary fiber with Dr. Aarti Kathrani, Senior Lecturer in small animal internal medicine at the Royal Veterinary College. The talk was interesting enough for me to do some of my own research and find out more about the importance of fiber.
Let’s take a look at the different types of fiber, what they are, and how they can benefit our pets.
A Simple Definition of Fiber
The term “fiber” refers to certain complex carbohydrates that cannot be digested by an animal’s digestive enzymes. For example, cellulose, hemicellulose, pectin, and lignin are all fiber compounds that serve as the structural components of plants . Once we eat or feed these plants to our pets, the fiber compounds resist complete digestion until they reach our large intestine where the resident bacteria ferment these fibers and generate short-chain fatty acids (SCFAs). These SCFAs are important in human and animal health and help to maintain proper bowel function.
Different Types of Fiber
The most common classifications of fiber are soluble and insoluble types. Soluble fibers tend to gel and thicken when they come in contact with water. They also draw more fluid into the digestive tract, which helps make stools softer and bulkier. Soluble fibers are high in pectin, gum arabic, guar gum, oat hulls, nuts, some vegetables (e.g., green beans, carrots), and psyllium .
Insoluble fibers do not gel or dissolve easily. They cause the animal to have more frequent bowel movements , which leads to softer stools with a smaller diameter (i.e., less constipating ) . These types of fiber are high in cellulose, hemicellulose, lignin, and waxes .
Properties of Fiber
In addition to soluble and insoluble dietary fiber, we also have a few more properties to consider.
First is viscosity, which means how runny or thick a liquid is. Soluble dietary fiber will increase the viscosity of the contents inside our intestine and make it thicker [1,3]. This is a great property because the increased viscosity will help to slow down digestion, prolong transit time, and enhance nutrient absorption.
The second property we need to consider is fermentability which is the ease at which fiber can be fermented in our colon by bacteria to produce short-chain fatty acids (SCFAs) [1,3]. Whether the rate of fermentation is rapid or slow depends on both the type of fiber and also our colonic bacterial fermentation profile.
What are Short-Chain Fatty Acids (SCFA)?
Short chain fatty acids, or SCFAs, are produced by microbes as they ferment dietary fiber in the colon. They regulate both glucose and lipid metabolism, suppress inflammation, enhance satiety and positively impact gut motility .
SCFAs bind to the G protein-coupled receptors (GPCRs), which are a family of more than 30 proteins on the surface of colonic epithelial cells that respond to hormones and neurotransmitters. When SCFAs bind to these receptors, they can activate or inhibit signaling pathways and physiological responses in human and animal tissues .
Fiber has a prebiotic effect because it feeds and stimulates the healthy bacteria in the colon, thereby improving its function. Prebiotics are non-digestible food ingredients that beneficially affect the host by selectively stimulating the growth and/or activity of one or a limited number of bacterial species already existing in the colon (aka probiotics) .
So, How Much Fiber?
There isn’t really an upper limit for how much fiber your cat or dog should be eating. Normally, their diet will be the major source of fiber. Most dogs and cats eat a proportionally higher amount of protein in comparison to fiber, so you should feed your pet’s diet an appropriate amount of fiber – not too much, and not too little.
In terms of how much total dietary fiber is ideal per individual animal, this can range widely depending on their metabolic capacity, daily energy requirements and activity level. You can check your pet food bag and see what they have written on the nutrition guide, but this is typically written as Crude Fiber. In my opinion, knowing how much crude fiber is in your pet food is a massive underestimate because crude fiber is only measuring the amount of insoluble fiber present. If you want to accurately measure dietary fiber, then you need to consider both insoluble and soluble fiber – also known as Total Dietary Fiber. A recent study showed that when we look at crude fiber, we are only looking at ~20% of the total fiber content of the pet food .
Signs of Too Much Fiber
As with most things, too much dietary fiber could come with some disadvantages. Here are a few:
Increased Risk of Constipation – Fiber can increase the size and bulkiness of the stool which can lead to constipation .
Increased Diarrhea – As SCFAs accumulate through fiber fermentation, the buildup of negative charge inside the intestine carried by the SCFA molecules will eventually lead to water moving into the interstitial space to bring equilibrium. This means that the stools will become more loose .
Decreased Nutrient Density – The more fiber present in your dog’s or cat’s meal, the lower other nutrients (protein, vitamins, minerals, etc.) are going to be in comparison to less fibrous foods .
Decreased Palatability (flavour) – Let’s face it, adding fiber isn’t always full of flavour. Adding fiber can sometimes make your pet food taste more like sawdust than anything else.
Decreased Appetite – Fibrous meals have been shown to decrease feeding times and overall appetite. This can prolong the feeling of fullness and satiety  .
Increased Flatulence – When food moves through your dog or cat’s intestines, bacteria and microbes will use this as an opportunity to ferment that which cannot be digested. This process creates byproducts (namely SCFAs and gases) which will eventually be expelled. Adding fiber to your pet food can result in increased flatulence  .
Advantages of Fiber
Now that we’ve learned about what fiber is and how it works, let’s cover some of the advantages fiber can have on your pet’s health:
Obesity – Obesity is a huge problem for both dogs and cats. Some studies have shown that adding fiber to the diet of your pet can help with weight loss, as it can increase satiety [9,10] .
Diarrhea – We touched on this before, but the addition of soluble fiber absorbs water from the intestines and forms a viscous gel . This helps normalize the consistency of the stool and prolong its transit time through the gut.
Constipation – In high amounts, fiber and SCFAs can attract water into the intestines, helping to normalize bowel movements [4,10].
Nutrient Absorption – Dietary fiber can increase nutrient absorption because it slows the emptying rate of the stomach. This results in a higher concentration of nutrients being present in your pet’s intestinal tract at any given time .
Conclusion– The Importance of Fiber
Including fiber in your pet’s diet is loaded with benefits. Now, this doesn’t mean to go ahead and add spoonful’s of fiber to each meal – that can be bad.
We have to understand which types of fiber our pets can benefit from and supplement this in moderation. We can see that adding fiber to your pet’s diet is a double-edged sword. Veterinarians see many cases of pets with diarrhea, and often adjusting the fiber content is adequate to make the stool healthy again. Approaching gastrointestinal problems from the perspective of your pet’s diet can address the root of the problem instead of using a blanket antimicrobial therapy and hoping that the soft stool goes away.
The bottom line is that when done right, there are some great health benefits to adding fiber to your dog or cat’s diet. However, if you are going to add fiber, consult your vet first. Your pet’s current health is a big contributing factor in whether they should even have dietary fiber included in their meal plan and how much. Also remember that this information is general; some animals may be sensitive to dietary fiber and not show any of the issues discussed in this article.
Share this article with your friends and family to spread the word about fiber for pets! Fiber is ignored by many manufacturers, but it has the potential to make a big difference in your pet’s health.
- Williams BA, Mikkelsen D, Flanagan BM, Gidley MJ. “Dietary fibre”: moving beyond the “soluble/insoluble” classification for monogastric nutrition, with an emphasis on humans and pigs. J Anim Sci Biotechnol. 2019;10:45. Published 2019 May 24. doi:10.1186/s40104-019-0350-9
- Schroeder N, Marquart LF, Gallaher DD. The role of viscosity and fermentability of dietary fibers on satiety- and adiposity-related hormones in rats. Nutrients. 2013;5(6):2093-2113. Published 2013 Jun 7. doi:10.3390/nu5062093
- den Besten G, van Eunen K, Groen AK, Venema K, Reijngoud DJ, Bakker BM. The role of short-chain fatty acids in the interplay between diet, gut microbiota, and host energy metabolism. J Lipid Res. 2013;54(9):2325-2340. doi:10.1194/jlr.R036012
- Sun M, Wu W, Liu Z, Cong Y. Microbiota metabolite short chain fatty acids, GPCR, and inflammatory bowel diseases. J Gastroenterol. 2017 Jan;52(1):1-8. doi: 10.1007/s00535-016-1242-9. Epub 2016 Jul 23. PMID: 27448578; PMCID: PMC5215992.
- Wernimont SM, Radosevich J, Jackson MI, et al. The Effects of Nutrition on the Gastrointestinal Microbiome of Cats and Dogs: Impact on Health and Disease. Front Microbiol. 2020;11:1266. Published 2020 Jun 25. doi:10.3389/fmicb.2020.01266
- Donadelli RA, Dogan H, Aldrich CG. The effects of fiber source on extrusion processing parameters and kibble characteristics of dry cat foods. Transl Anim Sci. 2020;4(4):txaa185. Published 2020 Oct 8. doi:10.1093/tas/txaa185
- Backus R. Management of Satiety. WALTHAM Focus 2006:16(1):27-32.