By Dr. Becker
Today we’re going to take a closer look at dietary fiber.
Dietary fiber can be generally defined as complex carbohydrates that are resistant to the digestive enzymes produced by an animal’s GI tract.
A primary source of fiber is plants. However, the fur, bone, cartilage, tendons, and ligaments of prey animals also function as fiber in the intestine, as does the hair that cats swallow during grooming.
New Research on Animal Fiber Sources
As it turns out, animal fiber may be extremely important in the nutrition of strict carnivores like cats. In a recent study with captive cheetahs1, 14 cats were divided into one of two dietary categories – they were fed either raw, boneless beef supplemented with appropriate vitamins and minerals, or whole raw rabbits with fur.
The cheetahs were fed one of these two diets for a month. The study showed that when the cheetahs were eating the raw whole rabbit diet, there were positive changes in their fatty acid profiles and feces, and a significant decrease in production of toxic metabolic chemicals.
This is the first study of its kind to point to animal fiber as beneficial to the digestive tracts of large cats, with potentially similar functions as soluble or insoluble plant fibers.
The study also raises the question of whether plant fibers in the diets of cats are an adequate substitute for animal fiber, and, of course, it should prompt all cat owners – whether they’re feeding raw, canned, or dry food to their pets – to reevaluate whether their kitties are getting appropriate sources and amounts of dietary fiber.
Plant Fiber: Soluble, Insoluble, Fermentable, non-Fermentable
Though fiber is indigestible and most types have no nutrient value, it does play an important role in the digestive process. The presence and type of fiber in the digestive tract determines how fast food passes through. Depending on the type of fiber, it can either speed up the process or slow it down.
Fiber increases bulk and water in the intestinal contents. It can slow down the rate at which food passes through the digestive tract in animals with too-fast transit times, and it can speed up the process in animals with slow transit times. That’s why fiber benefits both diarrhea and constipation.
Some fibers are also broken down in the intestine into fatty acids, which help prevent overgrowth of unfriendly bacteria. Fiber allows time for nutrients and water to pass from the large intestine into the bloodstream, and fiber also binds certain toxins in the gut and removes them from the body in feces.
Soluble fiber dissolves in water and is more digestible than insoluble fiber. Soluble fiber promotes smooth passage of food to the GI tract, while insoluble fiber speeds up the rate at which food passes through.
Soluble fiber sources include certain types of legumes, oats, rye, barley, some fruits and vegetables, root tubers, root vegetables, psyllium husk, flaxseeds, and nuts. Insoluble fiber is also found in whole grain foods, wheat and corn bran, beans, peas, some nuts and seeds, as well as the skin of potatoes, lignans, green beans, cauliflower, zucchini, and some fruits, including avocado, as well as the skin of some fruits, including kiwifruit and tomatoes.
Fibers are also fermentable and non-fermentable. A fiber is fermentable if the bacteria in the GI tract can break it down. Fermentable fibers contain nutrients that can be turned into energy for use by an animal’s body. Soluble fibers are generally more fermentable than insoluble fibers.
Most fibers are a mix of both soluble and insoluble. There are single fiber sources that can perform the work of both types by providing bulk as an insoluble fiber, and providing food for gut bacteria as a soluble and fermentable fiber. The whole thing can be somewhat confusing.
The types of fiber used most often in dry and canned pet foods include beet pulp, buckwheat and other grain hulls, flaxseed, fruit pectin, guar gum, oat and other brans, peanut shells, powdered cellulose (powdered cellulose is a fancy word for wood pulp), psyllium, and tomato pomace.
Fiber Requirements of Pets
Wild canines and felines have no physiologic requirement for these types of plant fibers. The only fiber wild dogs and cats ingest is whatever is found in the already-digested stomach contents of their prey, and, of course, the fur, tendons, and ligaments they ingest from eating whole prey.
Although the amount of fiber found in the diet of wild dogs and cats is small, it serves a very important role, as the cheetah study pointed out. Likewise, dogs and cats fed processed commercial diets benefit from the addition of a small amount of the right kind of fiber as well. Our goal when feeding raw food diets to pets is, of course, to mimic the GI contents that would naturally be found in their prey.
A fiber-deficient diet will cause diarrhea or constipation in dogs and cats. Many pet food companies market an ultra-high fiber diet. After all, they’re incredibly cheap to produce and they keep bowel movements very consistent. These really high fiber diets create very large stools that actually many pet owners have come to view as somewhat normal.
I have clients in my practice who believe it’s totally normal for their dog to poop a huge amount, six to eight times a day. When they start their dogs on raw food, a lot of my clients’ number one question is, “Where did all the poo go? The poo’s so small and they’re only pooping once or twice a day.”
When pets consume unnecessary fillers, like wads of fiber, it inhibits digestion and absorption of many vital nutrients. A small amount of fiber is very important, but a diet loaded with fiber is very detrimental, unless, of course, you’re feeding a horse or cow.
If you’re feeding your dog or cat a balanced, species-appropriate diet with appropriate supplementation, including pet probiotics and digestive enzymes, and your pet is easily producing small, firm stools, she’s getting the exact amount of fiber she needs.
When Your Pet’s Diet Doesn’t Provide Enough Fiber
I have found several brands of commercially available raw food diets to be overall quite constipating for many animals. I believe this is due to the lack of fiber in the food.
Of course, opening a bag of raw food to find hair, skin, or guts would be totally disgusting, not to mention no one would buy it. So I understand why raw pet food companies are opting not to be completely biologically appropriate when it comes to fiber content. However, many pets consuming commercially available raw food diets do need a source of roughage added to their food.
In the wild, dogs and cats get to choose how much skin, hair, and GI contents they consume with each prey animal they catch, but this isn’t true of pets living in family homes. This means sometimes pets may need a little additional fiber for effective elimination.
If this is the case with your dog or cat, I recommend adding ground leafy veggies, like maybe a teaspoon for every 10 pounds of body weight, one or two times a day. If that isn’t effective, you can certainly try adding some psyllium husk powder (half a teaspoon for 10 pounds of body weight), or coconut fiber, a teaspoon for 10 pounds of body weight, once or twice a day.
If your pet is consistently producing narrow, loose stools – I call them pencil stools – that curl into a pile of poo that’s pretty much impossible to pick up, then he may benefit from the addition of a soluble fiber called slippery elm bark to his food. When slippery elm combines with digestive juices, it produces a gel-like material called mucilage, which coats and soothes the GI tract and helps to firm the stool. About a half a teaspoon for every 10 pounds of body weight per meal should do the trick.
Additionally, canned or freshly steamed 100 percent pumpkin can also be very beneficial for these pets. About a teaspoon of pumpkin for every 10 pounds of body weight, one to two times a day, on the food can very effectively firm a loose bowel, and keep stools very regular.