Prebiotics

Prebiotics are defined as a “substrate that is selectively utilized by host microorganisms, conferring a health benefit.” These differ from probiotics in that probiotics are the actual microorganisms that serve to improve the microbial ecosystem via their presence, whereas prebiotics provide the substrate for favorable microbial growth, which then alters the microbial ecosystem(Xia et al., 2024). Thus, prebiotics and probiotics have different mechanisms, though the end result is similar: a shift in the microbial populations such that it favors the animal or person (host).

Prebiotics can be derived from a variety of natural sources and include fructooligosaccharides (scFOS), isomalto-oligosaccharides, galacto-oligoscharides, inulin, and even novel sources like red ginseng fiber(Song et al., 2023). Collectively, these are non-fermentable, non-digestible fibers that stimulate the growth of beneficial bacteria in the intestines.

Intestinal microbes metabolize the prebiotics and produce various substances, and it is the resulting products of this metabolism that can confer beneficial effects. Such substances include organic acids such as short-chain fatty acids (SCFAs)—acetate, propionate, and butyrate—and lactic acid, which can have direct beneficial effects on the local immune system within the intestinal tract(McGrath et al., 2024).

Prebiotics have also been demonstrated to result in the increase of “good” bacteria within the intestines, including Bifidobacterium and Lactobacillus, while reducing the number of Clostridium perfringens (considered a “bad” bacteria) and other proteolytic pathogens(Duysburgh et al., 2025). This shift in microbial composition can therefore improve dysbiosis, which has been linked to inflammation and development of various disease states(Xia et al., 2024). Recent research particularly highlights the benefit of combined prebiotic and probiotic supplementation—often termed synbiotics—in promoting microbial diversity and saccharolytic fermentation in both healthy dogs and those with soft stools(Gramenzi et al., 2024).

While the molecular mechanisms are fascinating and provide the building blocks of clinical medicine, consistent demonstrated evidence of a clinical benefit in health and disease remains to be well documented. However, emerging data suggests prebiotics may support immune parameters in elderly dogs and facilitate favorable growth and GI health markers in puppies(Rodiles et al., 2025);(McGrath et al., 2024).