Probiotics are live microorganisms that, when consumed in adequate amounts, may provide health benefits by supporting the balance of the intestinal or other microbiota.
What the research shows
Probiotics classically include strains of Lactobacillus and Bifidobacterium, which have been studied for their potential to support human health by modulating the gut microbiota. High-quality evidence from systematic reviews and meta-analyses shows that probiotics can influence microbiome composition, improve infant gut health when given maternally, support cognitive function in Alzheimer's disease, and help maintain gut flora during antibiotic use. Probiotics may also improve symptoms in functional constipation and modulate immune-inflammatory responses. Evidence supports strain-specific effects, with Lactobacillus and Bifidobacterium strains frequently studied. Safety profiles are generally favorable, with no significant increase in adverse events reported. However, some studies have low evidence levels or heterogeneity, and more high-quality, long-term research is needed to confirm benefits and clarify strain-specific effects.
Best studied probiotic strains
Lactobacillus
Effects are strain-specific; benefits observed mainly in maternal-infant health and gut microbiota preservation during antibiotics.
Bifidobacterium
Often studied alongside Lactobacillus; benefits include microbiome modulation and potential symptom improvement.
Bacillus subtilis
Evidence moderate; used in combination with lactulose for constipation.
Who may benefit
Safety
Probiotics are generally safe with no significant increase in adverse reactions reported in clinical trials and meta-analyses. However, safety may depend on the strain and population. More long-term safety data are needed.
Limitations
Some studies have low evidence levels or significant heterogeneity. Effects are strain-specific and not all strains have been equally studied. More high-quality, long-term randomized controlled trials are needed to confirm benefits and clarify mechanisms. Evidence for some conditions remains preliminary.
PubMed sources
| Study | Type | Year | PMID |
|---|---|---|---|
| Microbiota-Focused Dietary Approaches to Support Health: A Systematic Review. The Journal of nutrition |
Systematic Review | 2025 | 39486521 |
| Effects of maternal probiotic supplementation on breast milk microbiome and infant gut microbiome and health: a systematic review and meta-analysis of randomized controlled trials. American journal of obstetrics & gynecology MFM |
Meta-analysis | 2023 | 37660760 |
| The interaction between the gut microbiota, nutrition, and human health. Journal of the science of food and agriculture |
Research Study | 2026 | 41414728 |
| 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 |
| [Lactulose plus live binary Bacillus subtilis in the treatment of elders with functional constipation]. Zhonghua yi xue za zhi |
Clinical Trial | 2012 | 23328284 |
| Effect of Probiotic-Assisted Eradication of +/ on Intestinal Flora. BioMed research international |
Randomized Controlled Trial | 2022 | 35528160 |
| Reversible aberrancies in gut microbiome of moderate and late preterm infants: results from a randomized, controlled trial. Gut microbes |
Randomized Controlled Trial | 2023 | 38010080 |
| The gut microbiome, symptoms, and targeted interventions in children with cancer: a systematic review. Supportive care in cancer : official journal of the Multinational Association of Supportive Care in Cancer |
Systematic Review | 2018 | 29168036 |
| [The role of probiotics in oral health.]. Orvosi hetilap |
Research Study | 2023 | 37330980 |