Probiotics are trendy, but is there science behind the trend? According to some recent scientific evidence funded by the Winn Feline Foundation, the answer is yes, at least for cats.
- Offering supplemental probiotics proactively, even if the cat doesn’t appear to have an immediate medical need, appears to have no deleterious impact, and likely offers benefits (which additional new research, aside from what is noted here, also supports).
- Not all probiotics supplements are the same, and some have minimal science to back up their effectiveness. Ask your veterinarian about Purina FortiFlora.
- Interestingly, just because testing demonstrates that a nasty pathogenic organism is present in the gut, this does not mean the organism is causing clinical disease.
- At worst, cats and kittens with diarrhea are assisted by supplemental use of a probiotic. At best, the diarrhea goes away and stool returns to normal with probiotic use.
Currently, one of the hot topics in medicine is information about the microbiome of particular organ systems, particularly the gastrointestinal tract (GIT). The microbiome of the gastrointestinal tract is considered to be diverse, consisting primarily of anaerobes. Along the way, commensal and pathogenic microorganisms, plus their interactions, will impact the state of the microenvironment. This microenvironment and their byproducts (e.g., pH or fatty acid production) interact through the local immune system and enterendocrine signaling ultimately affecting the health status of the GIT.
The normal microbiome in adult dogs and cats is composed mostly of organisms from the phyla Actinobacteria, Bacteroides, Bifidobacteria, Firmicutes, Fusobacteria, and Proteobacteria. It is believed that alterations in normal microbiome composition contribute to acute and chronic enteropathies. There may also be an effect, both locally and outside the GIT, partly as a result of alterations in microbial byproduct formation (e.g., increased serum D-lactate concentrations in cats with GIT disease).
Probiotics are comprised of live microorganisms that, when consumed in large enough quantities, can lead to a beneficial health effect. How probiotics confer this effect include displacement of pathogenic organisms, production of antimicrobial byproducts, improvement in GIT epithelial barrier function, improvement in micronutrient absorption, and modulation of the enteric and innate immune responses. The authors note that even minor alterations to the microbiome can affect whether those benefits are realized.
The actual live microorganism concentration can vary greatly (0.008 percent to 215 percent of the labeled concentration) due to stability of the manufacturing process, contamination, long term storage, or just the fastidious nature of some microorganisms. Two products containing the same microorganism strain and concentration could have different effects on the FIT because the manufacturing process differed. Interactions among microorganism species are very important when considering the use of combination probiotic organisms with multiple microorganisms or when assessing synbiotics (a product that combines a prebiotic and probiotic). Prebiotics are defined as substrates for microorganism fermentation that can be tailored to a specific microorganism’s growth needs.
When studying probiotics, one must be aware that the in-vitro studies have limited clinical applicability because of the inability to evaluate their impact on microbial byproduct formation, microorganism interaction, and other influences. It is noted that studies on the use of probiotics should define the study population clearly (diet, diet history, and microbiome before probiotic administration) and fully describe the probiotic (exact strain, dose, and dosage regimen). Part One. (VT)
Jugan MC, Rudinsky AJ, et al. Use of probiotics in small animal veterinary medicine. J Am Vet Med Assoc. 2017 Mar 1;250(5):519-528.
Part one of this paper about probiotic use in small animals discussed general considerations regarding the nature of probiotics and similar products such as prebiotics and synbiotics. The following is Part Two which discusses the evidence for use of probiotics in different health situations.
Evidence for use of probiotics in healthy cats: In vivo studies have been conducted on the use in healthy small animals. While these studies of healthy animals often provide apparently positive effects of probiotics, their implication for disease states is unknown. One significant point noted is that no study has found major negative effects of probiotics administered to healthy animals which suggests probiotics are relatively safe to use. It is also noted that in these in vivo studies, there are changes noted in characterization of bacteria often considered as pathogens. The authors comment that these microorganisms are present in healthy animals. Therefore, just because a presumed pathogenic organism is present, this does not mean the organism is causing clinical disease. Attempts to treat animals in these situations might well be ill-advised. Also, in testing for viability of organisms in feces, the presence of nonviable organisms does not imply lack of effect so one cannot necessarily extrapolate data from healthy patients to a clinical setting.
Evidence for use of probiotics in cat with gastrointestinal tract (GIT) illness:
(Acute enteropathy)- For cats, it was noted that administration of E faecium SF68 to shelter cats demonstrated a lower percentage of cats with diarrhea for > 2 days versus the percentage of cats administered a placebo. Overall, the authors state that studies of small animals with acute diarrhea provide weak evidence for the exclusive use of probiotics. Yet, the studies do provide considerable evidence for the prevention of stress-induced diarrhea (likely caused by housing in shelters, significant physical exercise, or antimicrobial administration). Evidence based medicine is lacking for using probiotics in cats with naturally occurring acute diarrhea.
(Chronic enteropathy)- In this situation, it was stated that with client-owned cats with undefined (> 3 weeks duration) diarrhea, fecal firmness did increase in almost 72% of the cats given a synbiotic product when the synbiotic capsule was opened and mixed with the food. Due to a number of limitations related to studies of sick pets, comparisons regarding probiotics and their use in animals with chronic GIT illness are inadequate. However, as with healthy animals, no adverse effects were reported with probiotic administration.
Evidence of use of probiotics in kittens: In one study of an acute outbreak of diarrhea in kittens, only 9.5% of kittens that received E faecium SF68 required other medical treatment, compared to 60% of the control kittens that did not receive the probiotic. There was also more rapid resolution of signs in kittens that received the probiotic compared to those kittens that did not. There were still concerns that there were similar limitations to the studies available in kittens as in adult cats. The authors state that it is important to remember that there are significant species differences in the response to probiotics and probiotics are likely to have different effects in immature animals than in adult animals due to transitions in the GIT microorganisms during development.
The evidence for probiotic use in non-GIT illness (atopic dermatitis, genitourinary tract infection, respiratory tract disease) is limited to a few studies with limited numbers of animals.
In the long run, results were variable among studies and some studies indicated no effect of probiotics. Since there were no substantial adverse effects noted in any of the studies after probiotic administration, this suggests the relative safety of their use over a short period. Further consistent microbiome and metabolome assessment will better assist our understanding of the mechanisms of response and GIT influences in GIT and non-GIT diseases. Part Two. (VT)