Probiotics, particularly strains of Bifidobacterium animalis subsp. lactis, show some evidence of improving digestive comfort and gastrointestinal symptoms in adults without diagnosed GI disorders. Evidence for other gut health benefits across various conditions is limited or uncertain.
What the research shows
High-quality evidence from randomized controlled trials and systematic reviews indicates that fermented milk containing Bifidobacterium animalis subsp. lactis can improve digestive comfort and reduce digestive symptoms in adults with minor digestive complaints. Meta-analyses and systematic reviews in other populations, such as solid organ transplant recipients and chronic kidney disease patients, show very low certainty evidence and no clear benefits of synbiotics, prebiotics, or probiotics on gut health outcomes. Evidence for probiotic support improving cognitive function in Alzheimer's disease is promising but requires further high-quality studies. In children and adolescents with neuropsychiatric disorders, Bifidobacterium supplementation shows potential but evidence is limited. Gut microbiome-based interventions for obesity in children and adolescents show very low certainty evidence with minimal effects. Probiotic interventions with Lactobacillus in liver transplant patients have not demonstrated clear benefits in preventing infections or complications. Overall, safety profiles are good with minimal adverse events reported. More rigorous, strain-specific, and adequately powered studies are needed to confirm benefits and clarify effective strains and populations.
Best studied probiotic strains
Bifidobacterium animalis subsp. lactis (including CNCM I-2494 and DN-173 010)
Evidence is strongest for digestive comfort in adults without diagnosed GI disorders; effects in other populations or conditions are less certain.
Lactobacillus (general)
No specific strain identified; benefits uncertain and further research needed.
Bifidobacterium (general)
Strain-specific effects not well defined; more research needed.
Who may benefit
Safety
Probiotic and synbiotic interventions are generally safe with minimal and mild adverse events reported, such as flatulence, nausea, diarrhea, abdominal pain, and mild digestive discomfort. No serious adverse events related to probiotic use were reported in the reviewed studies.
Limitations
Most studies have small sample sizes, short durations, and heterogeneous interventions. Many systematic reviews report very low certainty evidence due to risk of bias, unclear strain identification, and inconsistent outcomes. There is a lack of high-quality, adequately powered randomized controlled trials with standardized probiotic strains and doses. Evidence is often mixed or uncertain, especially in populations with chronic diseases or complex conditions. More research is needed to clarify strain-specific effects and long-term benefits.
PubMed sources
| Study | Type | Year | PMID |
|---|---|---|---|
| Synbiotics, prebiotics and probiotics for solid organ transplant recipients. The Cochrane database of systematic reviews |
Systematic Review | 2022 | 36126902 |
| Intestinal Flora Balance Therapy Based on Probiotic Support Improves Cognitive Function and Symptoms in Patients with Alzheimer's Disease: A Systematic Review and Meta-analysis. BioMed research international |
Meta-analysis | 2022 | 36017397 |
| A systematic review of microbiome changes and impact of probiotic supplementation in children and adolescents with neuropsychiatric disorders. Progress in neuro-psychopharmacology & biological psychiatry |
Systematic Review | 2021 | 33271210 |
| Synbiotics, prebiotics and probiotics for people with chronic kidney disease. The Cochrane database of systematic reviews |
Systematic Review | 2023 | 37870148 |
| Gut microbiome-based interventions for the management of obesity in children and adolescents aged up to 19 years. The Cochrane database of systematic reviews |
Systematic Review | 2025 | 40637175 |
| Common mechanisms of Gut microbe-based strategies for the treatment of intestine-related diseases: based on multi-target interactions with the intestinal barrier. Cell communication and signaling : CCS |
Research Study | 2025 | 40528179 |
| Fermented milk containing Bifidobacterium lactis DN-173 010 improved self-reported digestive comfort amongst a general population of adults. A randomized, open-label, controlled, pilot study. Journal of digestive diseases |
Randomized Controlled Trial | 2009 | 19236549 |
| Methods of preventing bacterial sepsis and wound complications after liver transplantation. The Cochrane database of systematic reviews |
Meta-analysis | 2014 | 24599680 |
| The Urinary Tract Microbiome in Health and Disease. European urology focus |
Systematic Review | 2018 | 28753805 |
| A randomized, double-blind, controlled study and pooled analysis of two identical trials of fermented milk containing probiotic Bifidobacterium lactis CNCM I-2494 in healthy women reporting minor digestive symptoms. Neurogastroenterology and motility |
Randomized Controlled Trial | 2013 | 23480238 |