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Dietary Fibers for Dogs & Cats: Overview

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With all the dietary and nutritional information out there, it can be hard to have the full confidence that you’re doing the right thing for the health of your dog or cat. The R&D Team at Nom Nom has been conducting studies and compiling an in-depth library of research on the topic. So you can find peace of mind in your meal, treat and supplement regimen for your pets.

This third-party research round-up focuses on dietary fibers, how companion animals process and use them in their gastric-system, and how much they might need in their diet.

What are dietary fibers?

Specifically, dietary fibers are plant-derived polysaccharides and oligosaccharides that are found in food and cannot be digested by mammals.1 In simpler terms, they’re edible plant-based carbohydrates that cannot be broken down by the body.2  (Which doesn’t mean they don’t bring health benefits to the table. We’ll get to that later.)

There are many different types and can be classified by their chemical structure, solubility, viscosity, and fermentability.1,3 These categories help define the unique functions of each type,4 as each class of fiber has distinguishing properties, offering distinctive health benefits in cats and dogs.

Table 1: Classifications of Fiber

Major Categories 

Properties

Solubility

Soluble

dissolves in and retains water

Insoluble

does not dissolve in water, stays intact in the GI tract

Viscosity 

Viscous

thickens in water, form gel-like solution

Non-viscous 

does not thicken in water

Fermentability 

Fermentable

metabolized by bacteria in colon to produce short-chain fatty acids (SCFA), an energy source for intestinal cells

Non-fermentable

not readily metabolized by gut microbiota, serve as bulking agent 

Table citations:3–6

Soluble and insoluble fibers are broadly considered the two major types of dietary fibers.7 However, they can take on many different properties and can have varying degrees of solubility, viscosity, and fermentability, making their impact unique.3 So, when classifying dietary fibers, it is more appropriate to state how it falls within each major category, to fully understand what it does in the body of our pets.4,8 

For example, inulin is a common dietary fiber used in pet foods and supplements,9 it can be classified as a soluble, non-viscous, fermentable fiber.4 Prebiotic fibers are also a class of fermentable fibers specifically known to benefit friendly gut bacteria.10

Why is dietary fiber important?

Despite the fact that mammals, including humans, dogs, and cats alike, cannot break down dietary fiber, it can have some important health benefits.

In humans, dietary fiber is known for a variety of health benefits including promoting regularity and gastrointestinal health, helping with weight loss, controlling blood sugar levels, and lowering blood pressure.11,12 Additionally, including fiber in the diet has shown to prevent many diseases in humans including cardiovascular disease, type 2 diabetes, and several types of cancers, notably colorectal.4 

Could the benefits humans get from fiber supplementation translate to cats and dogs?

While not a dietary requirement, there is evidence that the benefits of dietary fiber seen in humans may translate to our canine companions — including aiding in digestion and gut health, promoting weight loss, boosting immune system, and management of diabetes.3,6 

Dogs are generally considered omnivores, like humans, or facultative carnivores, either way they have the ability to process and benefit from many plant-based nutrients, including dietary fiber.13 Of course, the quality and type of fiber further impacts the benefits seen in dogs.

Cats, on the other hand, are carnivores, whose nutrient requirements come from those of animal sources.14 Compared to humans and dogs, cats have a shorter digestive tract and lack the ability to utilize fiber in the same way.15 They also have a higher demand for protein and fat than carbohydrates.14 

However, while they may not require fiber, that does not mean they can’t benefit from it (and the same is true for small amounts of phytonutrients). There is emerging evidence supporting the inclusion of moderate amounts of dietary fiber in the feline diet. 

What types of fibers are found in pet foods?

In dry kibble, beet pulp (a moderately fermentable fiber) and cellulose (an insoluble non-fermentable fiber) are some of the more common dietary fibers found.16 The reason the fiber properties of beet pulp are described as “moderate” is because it contains multiple fiber types including pectin, cellulose, and hemicellulose, giving it balanced (or moderate) solubility, viscosity, and fermentability characteristics.3 

Having a diversity of fiber types is crucial to ensuring optimal health benefits are received, as the different degrees of solubility, viscosity, and fermentability have varying health effects.17 Similarly, different foods have different blends of fibers that can offer an array of benefits to dogs and cats, as it is largely the composition of the fiber that determines its health benefits.12

Which pet food ingredients contain fiber?

When reading a pet food label, crude fiber refers mainly to cellulose and the insoluble fiber content. Total dietary fiber includes both the insoluble and soluble fiber content. But, unfortunately, the total dietary fiber is not usually available on the label, and may be difficult to obtain from the manufacturer as it is not always tested.19

Common fiber sources on the ingredient lists of pet foods:3,20 

Novel fiber sources on the ingredient lists of pet foods:3,16,21,22 

What about specifically in cat food?

While inclusion of fiber in the feline diet has shown beneficial effects, there are also associated risks such as deficiency in taurine (an essential amino acid) and gastrointestinal issues.14 Insoluble fibers can also run the risk of causing dehydration and decreased nutrient and protein digestibility at higher doses in cats.14 And the inclusion of highly fermentable and viscous fibers may reduce nutrient absorption.12 

That being said, moderately fermentable fibers — with both soluble and insoluble components — appear to have the most beneficial effects for cats in limited quantities.12,18 Beet pulp and apple pomace are moderately fermentable fiber sources that have been shown to be beneficial in cat’s diets.3,16 

Rice bran is another common fiber source included in cat foods, however, research indicates that it increases a cat’s need for taurine,3,23 So it’s better avoided for our feline friends.

Specific fiber types that may be good for cats include pectin, FOS, fructans, β-glucans, and cellulose.18,24,25 All of which can be found in whole grains, fresh fruits and vegetables — supporting the use of a fresh food diet for your cat’s health and fiber source. 

And specifically in dog food?

Most of the common and novel fiber sources, listed previously, can be found in commercial dog foods, including kibble. This accessibility of fiber sources is beneficial for dogs, as the inclusion of a variety of dietary fiber types helps to maximize health benefits.6 

It’s helpful to know the source of fiber when evaluating ingredients because some may be processed more than others. While this may not impact its function, it could cause other substances to be present as a result of processing.

Is there a better diet for fiber?

The production of kibble requires largely dry-processed ingredients and, while it is convenient and meets AAFCO standards, more and more indications point to fresh food as being more digestible and having further benefits to dogs. 

Like humans, dogs respond well to a mixture of fiber types.26 Fresh diets provide whole grains, fruits, and vegetables, which have both soluble and insoluble fiber components (Table 2), making them an excellent source of fiber for dogs.  

Table 2: Types of Fibers Found in Common Food Sources


Types of Food

Fibers Present (at varying amounts)

Soluble

Insoluble

Leafy and stem vegetables

 i.e broccoli and cauliflower

Gums* and β-glucans

Cellulose*, some hemicellulose, and lignin

Root vegetables and bulbs

i.e. carrots and onions

β-fructans*, fructooligosaccharides (FOS)*, inulin*, and β-glucans

Cellulose, hemicellulose, and lignin*

Cereals and whole grains

i.e. oats and barley

β-glucans*, β-fructans*, gums*, fructooligosaccharides (FOS)*, resistant starch* (partially insoluble), and psyllium

Cellulose*, hemicellulose, and lignin

Nuts, seeds, and husks 

i.e. flax seeds

Gums*, psyllium*, β-glucans*, and pectin (partially insoluble)

Cellulose*, hemicellulose, and lignin*

Berries 

i.e. strawberries and blackberries

β-glucans*, pectin* (partially insoluble), and gums

Cellulose and lignin

Fruits and peels

i.e. banana and citrus peel

Fructooligosaccharides (FOS)*, gums*, inulin*, pectin* (partially insoluble), resistant starch* (partially insoluble), and β-glucans

Cellulose, hemicellulose, and lignin

Beans and legumes

i.e. navy beans and lentils

Gums*, resistant starch* (partially insoluble), and β-glucans

Cellulose

* = particularly high source; table citations:4,5,17,18

What about fiber supplements?  

While food is the main way that most of our companion animals get their fiber, as most commercial brands include it, specialty diets, treats, and fiber additives and supplements are also ways to ensure your pet is getting the fiber they need.3,6

If your pet’s food is not providing them with the right amount of fiber, you have a picky eater, or another reason for not wanting to change diets, supplements offering a combination of soluble and insoluble fibers can be added to your pet’s normal diet.

Added fiber can also supplement a pet’s health — treating or preventing a medical condition, or promoting weight loss. In this case look for specific types of fiber to help particular needs. For example, inulin is one of the more common fiber supplements provided to dogs,9 and psyllium powder is commonly used in both dogs and cats for gastrointestinal health and regularity.27 

Fiber supplements are usually in powder form, made to be added directly to your pet’s food.  Unflavored powders are easier to mix into your pet’s food undetected,28 while treats come in a wide variety of flavors for picky eaters. Avoid supplements with unnecessary additives such as sugar or try more natural sources,28 like a fruit or vegetable snack. 

What about the dose (cats)?

For healthy cats, having small amounts of fiber (<10 g/Mcal — or grams per every 1000 kilocalories) may help to get gut bacteria normalized,18 unless a cat has a history of constipation or megacolon (abnormal dilation of colon) in which higher amounts are often used. 

For cats, more often than not, a powdered supplement mixed into wet food is an easy way to add fiber to their diet. Vets usually recommend adding about 1 teaspoon once- to twice- daily for common medical conditions, but you can start with less and slowly increase to see how your cat responds.28

What about the dose (dogs)?

For healthy dogs, a safe moderate fiber content that allows for optimum health benefits is higher, at 5-10 g/Mcal.29 Some foods are higher in soluble fiber that’s not reflected in the crude fiber measurement on the label, and this soluble fiber can have benefits of improving stool quality and providing for a healthy and adaptable microbiome.  

Increasing your dog’s fiber content above 10% of their diet may be necessary for treatment of certain health conditions, but should be discussed with your veterinarian, as negative side effects notably on nutrient digestion and stool quality could occur at this dose.29  

The correct dose to provide your dog or cat is going to depend on their unique situation, condition, size, current diet, fiber type(s), and fiber supplement form. Veterinarians frequently observe that some dogs do better on a lower fiber diet and others on a higher fiber diet.  

Most products will provide an outline of dosing guidelines to follow, but it is best to consult your veterinarian about the proper dosage for your pet. If your pet has very specific nutritional needs or sensitivities you can also consult with a veterinary nutritionist.

Bottom Line -  should you give your pet fiber?

Even if your pet doesn’t have a specific condition that fiber may help, including it in their diet can still benefit certain conditions — like digestive health and the microbiome -- and help prevent harmful ones. Additionally for dogs, fiber can help with immune maintenance, cardiovascular health and weight management.

Consider testing your pet’s gut health as you may also be able to see shifts in the microbiome before and after starting fiber. (To us, that sounds like a lot of fun!)

Overall, fiber can be beneficial to your pet’s health. But make sure you don’t give them too much of a good thing.

References

  1. Cho, S., DeVries, J. W. & Prosky, L. Dietary fiber analysis and applications. (1997).
  2. Fiber. The Nutrition Source https://www.hsph.harvard.edu/nutritionsource/carbohydrates/fiber/ (2012).
  3. de Godoy, M. R. C., Kerr, K. R. & Fahey, G. C., Jr. Alternative dietary fiber sources in companion animal nutrition. Nutrients 5, 3099–3117 (2013).
  4. Fiber. Linus Pauling Institute https://lpi.oregonstate.edu/mic/other-nutrients/fiber (2014).
  5. Center, S. A. Nutritional support for dogs and cats with hepatobiliary disease. J. Nutr. 128, 2733S–2746S (1998).
  6. Finlay, K. Benefits of High-Fiber Dog Foods. American Kennel Club https://www.akc.org/expert-advice/nutrition/benefits-high-fiber-dog-foods/ (2018).
  7. Kris Gunnars, B. Why Is Fiber Good for You? The Crunchy Truth. Healthline https://www.healthline.com/nutrition/why-is-fiber-good-for-you.
  8. Joe Leech, M. S. Legumes: Good or Bad? Healthline https://www.healthline.com/nutrition/legumes-good-or-bad (2019).
  9. Flickinger, E. A. & Fahey, G. C., Jr. Pet food and feed applications of inulin, oligofructose and other oligosaccharides. Br. J. Nutr. 87 Suppl 2, S297–300 (2002).
  10. Beloshapka, A. N. et al. Fecal microbial communities of healthy adult dogs fed raw meat-based diets with or without inulin or yeast cell wall extracts as assessed by 454 pyrosequencing. FEMS Microbiol. Ecol. 84, 532–541 (2013).
  11. Burkhalter, T. M. et al. The ratio of insoluble to soluble fiber components in soybean hulls affects ileal and total-tract nutrient digestibilities and fecal characteristics of dogs. J. Nutr. 131, 1978–1985 (2001).
  12. Sunvold, G. D. et al. Dietary fiber for cats: in vitro fermentation of selected fiber sources by cat fecal inoculum and in vivo utilization of diets containing selected fiber sources and their blends. J. Anim. Sci. 73, 2329–2339 (1995).
  13. Axelsson, E. et al. The genomic signature of dog domestication reveals adaptation to a starch-rich diet. Nature 495, 360–364 (2013).
  14. Zoran, D. L. The carnivore connection to nutrition in cats. J. Am. Vet. Med. Assoc. 221, 1559–1567 (2002).
  15. Verbrugghe, A. & Hesta, M. Cats and Carbohydrates: The Carnivore Fantasy? Vet. Sci. China 4, (2017).
  16. Koppel, K. et al. The Effects of Fiber Inclusion on Pet Food Sensory Characteristics and Palatability. Animals (Basel) 5, 110–125 (2015).
  17. Types of Fiber and Their Health Benefits. WebMD https://www.webmd.com/diet/compare-dietary-fibers (2010).
  18. Barry, K. A. et al. Dietary cellulose, fructooligosaccharides, and pectin modify fecal protein catabolites and microbial populations in adult cats. J. Anim. Sci. 88, 2978–2987 (2010).
  19. Justin Shmalberg, D. V. M. Treatment of Obesity in Cats and Dogs | Today’s Veterinary Practice. Today’s Veterinary Practice https://todaysveterinarypractice.com/nutrition-notes-treatment-of-obesity/ (2013).
  20. Baert, J. R. A. & Van Bockstaele, E. J. Cultivation and breeding of root chicory for inulin production. Ind. Crops Prod. 1, 229–234 (1992).
  21. Swanson, K. S. et al. Fruit and vegetable fiber fermentation by gut microflora from canines. J. Anim. Sci. 79, 919–926 (2001).
  22. Panasevich, M. R. et al. Modulation of the faecal microbiome of healthy adult dogs by inclusion of potato fibre in the diet. Br. J. Nutr. 113, 125–133 (2015).
  23. Stratton-Phelps, M., Backus, R. C., Rogers, Q. R. & Fascetti, A. J. Dietary rice bran decreases plasma and whole-blood taurine in cats. J. Nutr. 132, 1745S–7S (2002).
  24. Barry, K. A., Hernot, D. C., Van Loo, J., Fahey, G. C., Jr & de Godoy, M. R. C. Fructan supplementation of senior cats affects stool metabolite concentrations and fecal microbiota concentrations, but not nitrogen partitioning in excreta. J. Anim. Sci. 92, 4964–4971 (2014).
  25. Nelson, R. W. et al. Effect of dietary insoluble fiber on control of glycemia in cats with naturally acquired diabetes mellitus. J. Am. Vet. Med. Assoc. 216, 1082–1088 (2000).
  26. Respondek, F. et al. Short-chain fructooligosaccharides influence insulin sensitivity and gene expression of fat tissue in obese dogs. J. Nutr. 138, 1712–1718 (2008).
  27. Dodman, N. Psyllium (Metamucil®) for Dogs and Cats. PetPlace https://www.petplace.com/article/drug-library/drug-library/library/psyllium-metamucil-for-dogs-and-cats/ (2016).
  28. How to Add Extra Fiber to Cat Food | Cuteness. Cuteness.com https://www.cuteness.com/article/add-extra-fiber-cat-food (2009).
  29. The Facts You Need Before Feeding Your Dog a Fiber Regiment - Whole Dog Journal. Whole Dog Journal https://www.whole-dog-journal.com/food/the-facts-you-need-before-feeding-your-dog-a-fiber-regiment/ (2001).

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