How Prebiotics Improve Your Dog’s Digestion

Special ingredients support the friendly bacteria that aid digestive health.


[Updated August 22, 2018]

Prebiotics (no, it’s not a typo) nourish probiotics, the beneficial bacteria discussed last month that support digestive health, the immune system, and more. A prebiotic is defined as “a nondigestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon and thus improves host health.”

Pet Dolphilus prebiotic for dogs

Prebiotics are soluble, fermentable fiber, a type of nondigestible carbohydrate, also called resistant starch. Fructooligosaccharides (FOS) are the most common, but other oligosaccharides, arabinogalactans, and lactulose are also considered prebiotics. Sources include inulin (a form of FOS extracted from chicory), larch (a source of arabinogalactins), pectins, beet pulp, gums (e.g., guar gum), and wheat dextrin (Benefiber).

Prebiotics are included in many probiotic supplements (the combination is called “synbiotic,” referring to the synergy between the two). Food sources of soluble fiber include legumes (beans, lentils, peas), whole grains, fruits, vegetables, and Jerusalem artichokes (sunchokes). Some commercial dog foods have added sources of soluble fiber, such as chicory. Soluble fiber supplements are also available.

Why Should Dogs Use Prebiotics?

Prebiotics support the growth of probiotics, which help keep bad bacteria under control in the dog’s gut. By supporting the good bacteria, prebiotics help to prevent disease, improve digestion and nutrient absorption (especially minerals), and enhance the immune system. Dogs fed prebiotics are less likely to get diarrhea caused by the overgrowth of bad bacteria, and soluble fiber also helps to prevent or treat diarrhea by absorbing water and slowing intestinal transit. Fed to females during pregnancy and lactation, prebiotics provide enhanced immune protection to the puppies through colostrum and milk, and the puppies have an enhanced response to vaccines.

Soluble fiber is fermented by bacteria in the colon to short-chain fatty acids (SCFAs), the primary fuel for the cells of the colon. Increased concentration of SCFAs and numbers of beneficial bacteria support gastrointestinal health and the immune system.

Prebiotics may be especially beneficial for dogs with immunosuppression or digestive disorders, and for all dogs following antibiotic therapy. Studies done on rats show that prebiotics may help correct hyperlipidemia (high blood triglycerides or cholesterol) brought about by diabetes and other conditions. Human studies have shown that prebiotics may reduce the risk of colon cancer and irritable bowel disorders.

Use Care When You Give Your Dog Fiber Supplements

Prebiotics included in probiotic supplements are unlikely to cause any problems. Fiber supplements, however, should be used with caution. Too much soluble fiber can lead to gas and loose stools. Insoluble fiber (roughage), such as cellulose, speeds intestinal transit time (laxative effect) and reduces mineral absorption. Both types of fiber bulk up stools.

It’s important that dogs drink enough water when taking fiber supplements (especially insoluble fiber); add water to food if needed.

Dosing Prebiotics

Probiotics and prebiotics are best given together. Follow label instructions when using products made for dogs. When using products made for humans, adjust the dosage based on the size of your dog compared to an adult human (e.g., give about half the human dose to a dog weighing 50 to 60 pounds, or one-quarter the human dose to a dog weighing 25 to 30 pounds). If using a fiber-only supplement, start with low doses and increase gradually. Decrease the amount or switch to a different product if you see signs of gas or diarrhea.

Recommended Prebiotic Sources:

1. Thorne Veterinary’s ArabinexVET, an arabinogalactan product

2. Metamucil Clear & Natural, an inulin product

3. Jarrow’s Pet Dophilus contains inulin

4. Vetri-Science’s Vetri-Probiotic contains FOS and arabinogalactan powder

5. Nusentia’s Probiotic Miracle contains inulin

6. Garden of Life’s Primal Defense contains cereal grasses that act as prebiotics

Mary Straus is the owner of Straus and her Norwich Terrier, Ella, live in the San Francisco Bay Area.

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Mary Straus has been a regular contributor to Whole Dog Journal since 2006. Mary first became interested in dog training and behavior in the 1980s. In 1997, Mary attended a seminar on wolf behavior at Wolf Park in Indiana. There, she was introduced to clicker training for the first time, and began to consider the question of how we feed our dogs after watching the wolves eat whole deer carcasses. Mary maintains and operates her own site,, which offers information and research on canine nutrition and health. has been created to help make people more "aware" of how to make the best decisions for their dogs. It's designed for people who like to ask questions and understand the reasoning behind decisions, rather than just being told what to do.  Mary has spent years doing research for people whose dogs have health problems, or who just want to learn how to feed them a better diet. Over this time, she has learned a great deal about dog nutrition and health, including the role of diet, supplements and nutraceuticals.  In 2007, she was asked by The Ivy Group to contribute to The Healthy Dog Cookbook. She previously also wrote a column for Dog World.


  1. We’re using Fortiflora probiotics for my dog following surgical removal of abscessed lipoma behind his intestines. Also using a prebiotic and pumpkin to correct severe diarrhea that lasted for two months. Am I over treating him based on your recommendation above?
    My supplements worked until about a week ago, and now his stools have gotten less solid, some very loose, and A LOT of gas through the day and evening. Is it time to stop the pumpkin, and what’s the best prebiotic to use with FortiFlora?