Probiotics – Guidelines from the American Gastroenterological Association (AGA) and the European Society for Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN)

As defined by the World Health Organization (WHO), probiotics are live microbial strains—typically bacteria or yeasts—that, when administered in adequate quantities, confer measurable health benefits upon the host. The volume of scientific research exploring their potential applications continues to expand exponentially, fostering growing optimism within both the medical community and the general public. For instance, between 2007 and 2015, the United States witnessed a fourfold increase in the number of individuals regularly consuming probiotic supplements. Similarly, in Poland, data collected as part of the public awareness campaign "Probiotyk – I Choose Consciously" indicate that over half of the population now incorporates these products into their routines. Given this rapid evolution, it is prudent to examine the latest clinical guidelines, which consolidate the findings of prior studies. The American Gastroenterological Association (AGA) has issued recommendations stating that, for the majority of gastrointestinal disorders, there remains insufficient evidence to justify the routine use of probiotics. Notably, the strength of AGA’s recommendations varies significantly, as each is evaluated based on two critical parameters: first, the quality of the supporting scientific evidence (graded on a four-tier scale ranging from "very low" to "high") and second, the robustness of the recommendation itself (classified as either conditional or strong). A high quality of evidence suggests a substantial likelihood that the desired therapeutic outcome will be achieved through probiotic administration, whereas a conditional recommendation necessitates a case-by-case assessment of benefits and risks before proceeding with treatment.

The American Gastroenterological Association (AGA) provides guidelines regarding the use of selected probiotic microbial strains in infants born prior to the completion of the 37th week of gestation who exhibit reduced birth weight. The primary objective of this preventive strategy is to mitigate the risk of necrotizing enterocolitis (NEC)—a severe intestinal disorder associated with high mortality rates among preterm neonates. Optimal clinical outcomes are achieved through the concurrent administration of representatives from the *Lactobacillus* and *Bifidobacterium* genera, with specific combinations including: • *Lactobacillus rhamnosus* GG (strain ATCC 53103) combined with *Bifidobacterium longum* subspecies *infantis*; • *Lactobacillus casei* paired with *Bifidobacterium breve*; • *Lactobacillus acidophilus* alongside *Bifidobacterium longum* subspecies *infantis*; • *Lactobacillus acidophilus* with *Bifidobacterium bifidum*; • *Lactobacillus rhamnosus* GG (strain ATCC 53103) in conjunction with *Bifidobacterium longum* Reuter (strain ATCC BAA-999). These recommendations are grounded in a comprehensive synthesis of moderate- to high-quality evidence, thereby substantiating their scientific and clinical rationale.

According to the latest guidelines from the American Gastroenterological Association (AGA), the administration of probiotic supplements is not recommended for children diagnosed with bacterial gastroenteritis due to insufficient evidence supporting their efficacy. In patients who have undergone proctocolectomy—a surgical procedure involving the removal of the rectum along with pathologically altered segments of the intestine—a pouch (intestinal reservoir) is constructed to serve as a substitute for the removed rectal function. If the anal sphincter is preserved during surgery, a segment of the small intestine is anastomosed to the anal canal, thereby enabling normal fecal evacuation. In instances where patients develop pouchitis (inflammation of the intestinal reservoir), the AGA suggests considering therapeutic intervention with a combination of eight bacterial strains: *Lactobacillus paracasei*, *Lactobacillus plantarum*, *Lactobacillus acidophilus*, *Lactobacillus delbrueckii* subsp. *bulgaricus*, *Bifidobacterium longum*, *Bifidobacterium breve*, *Bifidobacterium longum* subsp. *infantis*, and *Streptococcus salivarius* subsp. *thermophilus*. It is critical to note, however, that the quality of the available scientific evidence supporting this recommendation is rated as very low.

The American Gastroenterological Association (AGA) suggests considering probiotic supplementation for adults and children undergoing antibiotic treatment, though the quality of supporting evidence remains limited. Potentially beneficial strains include *Saccharomyces boulardii CNCM I-745*, the combination of *Lactobacillus acidophilus CL1285* with *Lactobacillus casei LBC80R*, and formulations containing *Lactobacillus acidophilus* alongside *Lactobacillus delbrueckii* subsp. *bulgaricus* and *Bifidobacterium bifidum*—occasionally enriched with *Streptococcus salivarius* subsp. *thermophilus*. The decision to administer probiotics should be individualized, accounting for the risk of *Clostridioides difficile* infection (formerly *Clostridium difficile*) associated with antibiotic use. Conversely, the European Society for Paediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN) recommends *Lactobacillus rhamnosus GG* or *Saccharomyces boulardii* for preventing antibiotic-associated diarrhea in children. A 2018 study published in *„Cell“* (Suez *et al.*) demonstrated that probiotics may delay or disrupt the natural recolonization of gut microbiota post-antibiotic therapy, whereas fecal microbiota transplantation emerged as a more effective restoration method. Given the substantial interindividual variability in responses and the existing knowledge gaps, probiotic use during or after antibiotic treatment should be discussed with a physician—preferably a gastroenterologist—prior to initiation.

Current guidelines from European medical societies do not endorse the routine use of probiotic supplements for the management of infantile colic. The sole exception is the strain *Lactobacillus reuteri* DSM 17938, which has demonstrated limited efficacy in a small number of clinical trials—though the quality of evidence remains insufficient to support definitive recommendations. Should supplementation be considered, the suggested regimen involves a daily dose of 10⁸ colony-forming units (CFU) administered over a period of 21–30 days. The American Gastroenterological Association (AGA) advises that probiotics for Crohn’s disease, ulcerative colitis (UC), and irritable bowel syndrome (IBS)—in both pediatric and adult populations—should be restricted to controlled clinical trial settings. While some studies have suggested potential benefits of specific strains in IBS, these findings are derived from small, methodologically diverse samples, precluding the establishment of consistent guidelines. Caution is particularly warranted in immunocompromised individuals, those with short bowel syndrome, or patients undergoing cancer treatment. It is also critical to note that most commercially available probiotics are classified as dietary supplements, which does not ensure that their composition aligns with manufacturer claims; only a handful of probiotic products registered as pharmaceuticals in Poland undergo rigorous quality control. The decision to use probiotics should always be made in consultation with a healthcare provider, as the likelihood of achieving the desired therapeutic outcome is highest when adherence to evidence-based societal recommendations is maintained; in other contexts, results may be unpredictable.