IngredientsBifidobacterium adolescentis is a bacterial species formally described by Reuter in 1963 and included on the Approved Lists of Bacterial Names in 1980. Its NCBI Taxonomy ID is 1680, with the type strain deposited under accession numbers including ATCC 15703 and DSM 20083, among other international culture collections. Its full taxonomic lineage is: cellular organisms → Bacteria → Bacillati → Actinomycetota → Actinomycetes → Bifidobacteriales → Bifidobacteriaceae → Bifidobacterium.
B. adolescentis is a Gram-positive, strictly anaerobic, and non-spore-forming bacterium. Common phenotypical characteristics of bifidobacteria include being nonmotile, nonsporogenous, nonhemolytic, fructose-6-phosphate phosphoketolase (F6PPK)-positive, and negative for catalase, oxidase, and indole. The optimal growth temperature varies from 36°C to 43°C depending on the strain origin, and the species is acid-tolerant, growing optimally at pH between 6 and 7.
The genus Bifidobacterium is so designated because in the reference species, one end was rocket-shaped and the other longitudinally split, as first described by Tissier in 1900. The bifid morphology is intrinsic to B. adolescentis. The genome of Bifidobacterium adolescentis averages 2.1 Mbp in length.
Bifidobacterium adolescentis is a prominent member of the human gut microbiome, present in 60–80% of healthy adults and accounting for up to 5% of the total fecal microbiota in this population. Cell densities in healthy adults range from 109 to 1010 cells per gram of faeces. It predominantly colonizes the human intestinal tract during early to mid-adulthood, with peak abundance observed between the ages of 16 and 45. In contrast, its abundance is relatively low in children and the elderly, suggesting a specific adaptation to the adult gut environment.
Bifidobacteria enjoy a wide ecological distribution and can commonly be found in the gastrointestinal tract of many animals, including all assessed mammalian species, as well as the gut of certain insects and birds. Among the bifidobacterial species identified in primates (including humans), it is possible to distinguish bifidobacterial taxa that are typically found in adults, such as Bifidobacterium adolescentis and Bifidobacterium catenulatum.
Notably, the abundance of this bacterium is significantly elevated in centenarians, indicating a potential role in health span and longevity.
Among bacterial isolates belonging to B. adolescentis, four taxonomic subgroups not previously described can be identified by genomic and phenotypic characteristics, clearly different from the type strain (B. adolescentis ATCC 15703). These subgroups are differentiated from the type strain by specific signatures in the 16S rRNA gene sequences. Findings from genomic and phenotypic analyses reveal substantial quantitative variation in metabolic activities and production of relevant end-products across strains, highlighting the importance of strain-level differences and the health benefits they may confer.
Along with other bifidobacterial species, B. adolescentis has interested dairy manufacturers in producing "therapeutic fermented milk products" due to its higher survival rates in acidic products. Along with other beneficial intestinal bacteria such as Lactobacillus acidophilus, Lactobacillus casei, Streptococcus thermophilus, and Enterococcus faecium, bifidobacteria have been added into dairy products, most notably yogurt and milk. It is also commercially available as a lyophilized (freeze-dried) powder in oral capsule and stick-pack formulations for direct-to-consumer probiotic supplementation.
The identification of bifidobacteria was promoted by their peculiar bifurcated morphology and by their being widely found in healthy infant feces; their absence was related to cases of infant diarrhea, and they were first identified by Tissier in 1900 as Bacillus bifidus. Only over the years was the peculiar metabolic pathway used by Y-shaped bacteria for hexose fermentation discovered, defining the Bifidobacterium genus and separating them from Lactobacillus (Rogosa, 1974).
First isolated in 1963, B. adolescentis is among the earlier-characterized adult-associated species in the genus. Unlike many botanical dietary supplements with documented traditional ethnobotanical uses, B. adolescentis is a commensal microorganism with no independent pre-scientific traditional use outside of fermented food contexts. Its recognition as a health-relevant microorganism belongs entirely to the modern scientific era, beginning with Tissier's foundational observations of bifidobacterial abundance correlating with infant health in the early twentieth century, and culminating in Reuter's formal species-level characterization in the 1960s.
Bifidobacteria, including B. adolescentis, have been added as probiotics into dairy products, most notably yogurt and milk. These "probiotics" make suitable residents in dairy products because dairy products need to be refrigerated and have a short shelf life, enabling consumers to receive the many benefits these bacteria provide in improving gastrointestinal health.
The genus Bifidobacterium possesses a unique fructose-6-phosphate phosphoketolase pathway employed to ferment carbohydrates. Much metabolic research on bifidobacteria has focused on oligosaccharide metabolism, as these carbohydrates are available in their otherwise nutrient-limited habitats. Once internalized into the cytoplasm, hexose monosaccharides (e.g., fructose and glucose) are converted into acetate and lactate by the fructose 6-phosphate phosphoketolase pathway, also known as the bifid shunt.
Adult-associated bifidobacterial species such as B. adolescentis use plant oligosaccharides, consistent with what they encounter in the adult gut environment. The species is evolutionarily adapted to fermenting plant-derived glycans and is equipped with an extensive sugar transporter and degradation enzyme repertoire. Consequently, the species is strongly affected by dietary carbohydrates and is able to utilize a wide range of prebiotic molecules. B. adolescentis is specialized in metabolizing resistant starch and is considered a primary starch degrader, enabling growth of other beneficial bacteria by cross-feeding.
B. adolescentis strains metabolize a broad range of carbohydrates, with 26–34 carbohydrates (mean 29.5) supporting growth of individual strains. By comparison, comparator strains generally utilized fewer carbohydrates (between 3 and 39; mean: 21.9). All 15 tested B. adolescentis strains were able to grow on raffinose, lactose, galactooligosaccharides (GOS), and fructooligosaccharides (FOS), and many could utilize sorbitol, inulin, or XOS. However, few B. adolescentis strains could metabolize other sugar alcohols such as mannitol, and none could metabolize mucin, the human milk oligosaccharide 2′-FL, or the monosaccharides mannose or fucose.
Among bifidobacteria, only three species of resistant starch-degrading bifidobacteria have been reported as single isolates: B. adolescentis, B. choerinum, and B. pseudolongum. In addition to the presence of starch gene clusters, most tested B. adolescentis strains were adept at utilizing soluble starch in vitro. Putative arabinoxylan gene clusters were also identified as more common (most strains had two clusters) in B. adolescentis.
One outcome from the fermentation of prebiotics by the gut microbiota, including bifidobacteria, is the production of short-chain fatty acids (SCFAs), such as acetate, butyrate, and propionate. SCFA production in the gastrointestinal tract results in a lower pH, improved availability of calcium and magnesium, and inhibition of potentially pathogenic bacteria. Both bifidobacteria and lactobacilli produce acetate (and lactate), contributing to the SCFA-mediated health effects of prebiotics, although these two microorganisms do not produce butyrate and/or propionate directly. Importantly, through cross-feeding, acetate produced by B. adolescentis can fuel butyrate production by neighboring colonic bacteria.
The ability of B. adolescentis to restore the homeostasis of the gut microbiota, increase the abundance of short-chain fatty acid-producing flora, and alleviate inflammation is closely related to its metabolic capacity.
Gamma-aminobutyric acid (GABA) is the principal inhibitory neurotransmitter playing a key role in anxiety and depression disorders in mammals. Recent studies have revealed that members of the gut microbiota are able to produce GABA, modulating the gut-brain axis response. Among members of the human gut microbiota, bifidobacteria are well known to establish many metabolic and physiologic interactions with the host.
Bifidobacterium adolescentis taxon may represent a model GABA producer in the human gastrointestinal tract, based on genome analyses of more than 1,000 bifidobacterial strains. While bacteria can produce GABA to raise intracellular pH, they may also influence host physiology, including brain activity, mood, and sleep. A glutamate decarboxylase and transporter, encoded by gadB and gadC, respectively, are key for GABA production in many bacteria. GABA is synthesized by a pyridoxal-5′-phosphate-dependent glutamate decarboxylase (GAD) enzyme through the irreversible α-decarboxylation of L-glutamate.
For folate, of 148 B. adolescentis genomes analyzed, 74% contained the full complement of genes known to produce folate de novo. There was wide variation in the amount of extracellular folate produced by different strains in vitro, ranging from 23 to 180 ng/mL, but all strains produced folate. B. adolescentis also produces several bioactive compounds including γ-aminobutyric acid (GABA), folate, and antimicrobials.
Some strains of B. adolescentis are adept at metabolizing lactose and may reduce symptoms associated with lactose intolerance. Through genomic and phenotypic analyses, B. adolescentis has been found to possess properties associated with improving lactose tolerance, metabolic health, and mood, as well as supplying vitamins and inhibiting pathogens.
Treatment with B. adolescentis can reduce intestinal permeability and improve the intestinal barrier to reduce lipopolysaccharide (LPS) passage across the intestinal barrier, and suppress the NF-κB pathway and IL-6 generation. Bifidobacteria more broadly have been shown to relieve intestinal inflammation by repairing the intestinal barrier, changing the gut microbiota, and altering cytokine levels.
The immunomodulatory potential of B. adolescentis includes promoting regulatory T-cell (Treg) differentiation and suppressing Th2 responses. Bifidobacterium adolescentis P2P3 efficiently degraded resistant starch and demonstrated immunomodulatory activity through stimulated secretion of Th1-type cytokines from mouse macrophages.
Strains of B. adolescentis have been shown to potentially protect against or improve recovery from several diseases, including liver-related, metabolic, allergic airway, colitis, arthritis, and bacterial infections. Strains have also been demonstrated to possess anti-inflammatory, anxiolytic, antioxidant, antidepressant, and/or antiviral activity. Moreover, B. adolescentis has been proven to have antiviral potential via its Mx GTPase pathway.
B. adolescentis, one of the most abundant Bifidobacterium species in the human colon, is commonly applied in the treatment of constipation, irritable bowel syndrome (IBS), and inflammatory bowel disease (IBD).
A notable human clinical trial examined B. adolescentis PRL2019 directly in a pediatric IBS population. This multicentric, randomized, double-blind, placebo-controlled, parallel-arm trial aimed at evaluating the effectiveness of Bifidobacterium adolescentis PRL2019 in children with IBS. IBS children diagnosed according to Rome IV criteria were enrolled and randomized into two groups to receive one stick containing 20 × 109 colony-forming units of B. adolescentis PRL2019 or an equivalent placebo once a day, in a 1:1 ratio, for 12 weeks. Seventy-two subjects (mean age 12.2 ± 1.8 years, 30 males) were enrolled and randomized. No significant differences were observed between the two groups at baseline. The proportion of patients achieving complete remission was significantly higher in the treatment group (19/36; 52.8%) than in the placebo group (7/36; 19.4%, p = 0.003). Both groups obtained a reduction in Total IBS Symptom Severity Scale (IBS-SSS), Pain Intensity Score, Pain Frequency Score, and Life Interference Score from baseline to week 12. Upon intergroup comparison, only the treatment group showed significant improvements in all these scores.
A broader systematic review of Bifidobacteria in IBS corroborates these findings. Probiotics, specifically Bifidobacteria, may improve abdominal pain in patients with IBS; however, results from randomized controlled trials are conflicting. A systematic search was conducted of MEDLINE, EMBASE, and the Cochrane Controlled Trials Register from inception to May 2019. A total of 8 RCTs involving 1,045 patients with Rome-diagnosed IBS were included; the dose of total Bifidobacteria ranged from 106 to >1011 CFU, and duration of supplementation ranged between 2 and 8 weeks. The overall evidence for Bifidobacteria in IBS must therefore be characterized as preliminary and mixed, with the species-specific PRL2019 trial being among the only trials to test a single B. adolescentis strain prospectively in a controlled human setting.
The depletion of B. adolescentis in individuals with IBD suggests its significance for intestinal health. B. adolescentis shows differential abundance in IBD patients compared to healthy individuals. Genomic and animal model studies have been conducted, but large controlled human trials in IBD populations using B. adolescentis as a single intervention remain limited. The evidence at this stage is largely observational and mechanistic. New treatments such as probiotics and prebiotics have been shown in previous studies to effectively mitigate the occurrence of IBD with fewer side effects than conventional treatments, and Bifidobacterium has been shown to relieve intestinal inflammation by repairing the intestinal barrier, changing the gut microbiota, and altering cytokine levels.
A study focused on the relieving effects of 16 strains of two dominant Bifidobacterium species (B. bifidum and B. adolescentis) on type 2 diabetes (T2D). The results indicated that more B. adolescentis strains appeared to be superior in alleviating T2D symptoms than B. bifidum strains. This effect was closely related to the ability of B. adolescentis to restore the homeostasis of the gut microbiota, increase the abundance of short-chain fatty acid-producing flora, and alleviate inflammation in mice with T2D. This evidence is currently from animal models; it has not yet been confirmed in prospective human clinical trials focused solely on B. adolescentis.
In prebiotic supplementation studies, B. adolescentis, B. longum, and B. pseudocatenulatum were found to be the most affected Bifidobacterium species after prebiotic administration. However, different dosage (15 g/day vs. 5.5 g/day) and study populations could be responsible for contrasting results, and evidence from human studies with prebiotics involving NAFLD or metabolic syndrome patients is scarce.
Previous studies of Bifidobacterium adolescentis, a species of Bifidobacterium that is common in the human intestinal tract, have demonstrated that it can alleviate liver steatosis and steatohepatitis. In an animal study, male C57BL/6J mice on a choline-deficient high-fat diet (CDHFD) were treated with drinking water supplemented with B. adolescentis for 8 weeks. B. adolescentis supplementation reversed the CDHFD-induced liver steatosis and steatohepatitis, as evaluated on the NAFLD activity score, reduced liver enzymes, and lipid accumulation. Further studies demonstrated that B. adolescentis supplementation preserved the gut barrier, reduced gut microbiota-derived LPS, and inhibited the hepatic TLR4/NF-κB pathway. This was accompanied by elevated expressions of FGF21 receptors (FGFR1 and β-klotho) in the liver. The supplementation was found to alleviate FGF21 resistance. This mechanistic evidence is derived from animal models and has not yet been replicated in human clinical trials for NAFLD.
Bifidobacterium adolescentis CGMCC15058 demonstrated preventive as well as therapeutic effects against liver failure. Administration of this bacterial strain significantly reduced elevated levels of alanine aminotransferase, lipopolysaccharide-binding protein, and total bile acid in serum. It also exhibited anti-inflammatory properties by decreasing the levels of inflammatory cytokines and increasing anti-inflammatory cytokines. Again, this is animal-model data.
A murine study specifically examined how strain origin affects metabolic outcomes. Four B. adolescentis strains were isolated from the feces of newborn and elderly humans and used to investigate whether supplementation could alleviate obesity in mice. Male C57BL/6J mice fed a high-fat diet (60% energy as fat) received one of four 14-week interventions with different strains or phosphate-buffered saline control. The B. adolescentis strains isolated from elderly humans decreased body weight or weight gain of mice, while the strain isolated from newborns increased body weight. The elderly-derived strains also increased serum leptin concentrations and induced expression of thermogenesis- and lipid metabolism-related genes in brown adipose tissue. All B. adolescentis strains alleviated inflammation in the spleen and brain and modified the cecal and colonic microbiota. These findings are limited to animal models and highlight that strain origin is a material variable in outcomes.
Preventive and therapeutic treatment with Bifidobacterium adolescentis on collagen-induced arthritis in an animal model revealed that early administration (before disease induction) performed better than late administration in terms of reduced clinical symptoms, rebalanced pro- and anti-inflammatory responses, maintained fecal short-chain fatty acid concentrations, and restored intestinal dysbiosis. This evidence is animal-model only, and no human clinical trials are currently published on this indication.
In preclinical studies, Bifidobacterium adolescentis treatment reduced ear and skin thickness and suppressed eosinophil and mast cell infiltration. Its immunomodulatory potential promoted Treg differentiation and suppressed Th2 responses. It also altered gut microbial colonization by increasing the proportion of Lactobacillus, which was positively correlated with increased propionic acid production. The human evidence for this application is observational only.
Genome analyses of more than 1,000 bifidobacterial strains revealed that the B. adolescentis taxon might represent a model GABA producer in the human gastrointestinal tract. In silico screening of human/animal metagenomic datasets showed an association between B. adolescentis load and mental disorders such as depression and anxiety. In vitro screening of 82 B. adolescentis strains identified two high GABA producers: B. adolescentis PRL2019 and B. adolescentis HD17T2H. Feeding rats with a supplementation of these B. adolescentis strains confirmed their ability to stimulate in vivo production of GABA, highlighting their potential implication in gut-brain axis interactions. Evidence in this area is currently restricted to in silico genomic analyses, in vitro experiments, and animal (rat) studies; no human RCTs on mood or anxiety with B. adolescentis alone have been published.
Through genomic and phenotypic analyses, B. adolescentis has been found to possess properties associated with improving lactose tolerance. Bifidobacteria inhabiting the gastrointestinal tract are well known for their ability to produce short-chain fatty acids, enhance gut barrier function, protect the host against infection, and modulate the host's immune responses. The evidence for direct lactose intolerance improvement from B. adolescentis supplementation in humans is currently at the mechanistic and genomic analysis stage.
B. adolescentis combined with inulin-type fructans increased butyrate production by 180% compared to either component alone, according to a 2021 study. Bifidobacterial promotion through prebiotics, including inulin, arabinoxylans, galactooligosaccharides, and fructooligosaccharides, has been correlated with a greater Lactobacillus–Bifidobacterium to Enterobacteriaceae ratio and modulated short-chain fatty acid production.
Bifidobacterium adolescentis is a gut commensal prevalent among healthy adults and centenarian populations, potentially contributing to host health through diverse functional properties. Genomic and phenotypic analyses have advanced understanding of the prevalence of multiple potentially beneficial properties of B. adolescentis, including those associated with improving lactose tolerance, metabolic health, and mood, and supplying vitamins and inhibiting pathogens. A registered double-blind, randomized controlled clinical trial has been designed to assess the effects of B. adolescentis on aging-related functional indicators, intestinal flora, DNA methylation, and other aging characteristics in middle-aged and elderly people aged 45–65 years. Results from this trial are not yet published.
Because B. adolescentis is a living organism, dosages are expressed in colony-forming units (CFU) rather than milligrams.
No single standardized dose or formulation has been established across human clinical studies. Dose ranges across research are wide and highly strain-specific; translating animal model doses directly to humans is not scientifically validated.
Bifidobacteria are generally recognized as safe (GRAS) organisms with probiotic properties. The GRAS classification in the United States and the Qualified Presumption of Safety (QPS) status granted by the European Food Safety Authority to the Bifidobacterium genus reflect their established history of safe use in food products. B. adolescentis has a documented long history of commensal residence in the human gut, and no specific toxigenic or virulence factors have been identified for the species as a whole.
Antibiotic resistance is a nuanced safety consideration for B. adolescentis. A multidrug resistance gene (ErmX) has been detected in some strains, which confers resistance to macrolide antibiotics, lincosamide antibiotics, streptogramin antibiotics, streptogramin A antibiotics, and streptogramin B antibiotics. Some studies have shown that the erm(X) gene is quite common in Bifidobacterium strains, and the resistance level is directly proportional to gene expression.
Separately, bifidobacteria have demonstrated resistance to antitubercular drugs (pyrazinamide, isoniazid, streptomycin) at high concentrations. These results indicate that bifidobacteria have resistance to tuberculosis drugs and can adapt. B. adolescentis can be considered for antibiotic and probiotic therapy due to its intrinsic resistance to antitubercular drugs and its probiotic properties. Regulatory frameworks for probiotic safety typically require that antibiotic resistance genes be non-transferable (i.e., not located on mobile genetic elements) to avoid horizontal gene transfer to pathogenic bacteria. Strain-specific genomic assessment is therefore recommended before clinical deployment.
There are ample documented evidences of safe use of Lactobacillus and Bifidobacterium; however, few cases of bacteraemia and endocarditis have also been reported among patients with severe diseases such as short gut syndrome, heart valve transplantation, and severe, active ulcerative colitis. This risk, while rare, underscores the need for individual assessment in critically ill or severely immunocompromised patients.
Tested strains of B. adolescentis showed different effects on lipid metabolism and immunity regulation, with these effects related to whether they had been isolated from the feces of newborn or elderly humans. This indicates that B. adolescentis from different sources may have disparate effects on host health possibly due to the transmission of origin-specific functions to the host. This finding has direct implications for safety and efficacy comparisons: individual strain characterization is indispensable, and results from one strain cannot be freely extrapolated to another.
There is no specific published human clinical data on drug-drug or drug-probiotic interactions unique to B. adolescentis compared to other Bifidobacteria. TB drug treatment leads to a significant decline in important commensal bacteria such as Lactobacillus, Bifidobacterium, Coprococcus, and Ruminococcus, with this phenomenon persisting for at least 1.2 years after treatment. This is accompanied by a sharp decline in SCFA-producing bacteria, which are important for intestinal health and general health. This suggests that antibiotic courses — particularly prolonged antitubercular regimens — deplete endogenous B. adolescentis populations, which may be a rationale for probiotic adjunctive use, though human trial evidence in this specific context is lacking.
The pediatric IBS trial using 20 × 109 CFU/day for 12 weeks did not report significant adverse events attributable to the probiotic intervention, consistent with the broader safety profile of Bifidobacterium species in clinical research populations. The safety of potential probiotics should not be overlooked. Probiotic effects are strain-specific, and introducing a new probiotic strain demands that it is at least as safe as its conventional counterparts. Hence, safety assessment is required before probiotics are used for human applications.
The overall evidentiary landscape for B. adolescentis as a dietary supplement can be characterized as follows: the mechanistic and genomic evidence is robust and growing rapidly, particularly for SCFA production, GABA biosynthesis, carbohydrate fermentation, and gut barrier function. Preclinical (mouse and rat) evidence exists for metabolic disease (obesity, T2D, NAFLD), arthritis, and atopic dermatitis. Human clinical evidence is limited but emerging: the best-controlled human trial to date is a multicenter pediatric RCT in IBS demonstrating clinically significant symptom improvement with 20 × 109 CFU/day of strain PRL2019 for 12 weeks. Broader systematic review data on Bifidobacteria in IBS confirm potential but note conflicting results across trials. Human evidence for most other proposed applications (metabolic disease, liver health, mood, longevity, arthritis) remains absent or preliminary. Strain-level variation is a critical consideration: findings from one strain cannot be extrapolated to the species as a whole.
Health conditions that Bifidobacterium adolescentis may help support.
Bifidobacterium adolescentis is a naturally occurring gut commensal that becomes increasingly relevant in the digestive microbiome of children as they transition to solid foods. It contributes to prebiotic fermentation and SCFA production. It is noted in the pediatric probiotic literature as part of the broader Bifidobacterium genus evidence base for gut health.
Bifidobacterium adolescentis is a common adult gut Bifidobacterium species whose reduced abundance is associated with constipation. As part of the Bifidobacterium evidence base for constipation, it is included in the scientific rationale for prebiotic and probiotic supplementation. FOS supplementation in RCTs significantly increased fecal Bifidobacterium counts alongside improved bowel frequency and stool consistency.
Bifidobacterium adolescentis is a human gut commensal that ferments dietary fibers including arabinoxylan and resistant starch, producing acetate and supporting cross-feeding of butyrate-producing bacteria. It has been identified as a keystone species linking prebiotic intake to SCFA production and microbiome composition improvements in adult humans.
Bifidobacterium adolescentis is a GABA-producing gut bacterium with demonstrated relevance to the gut-brain axis. It contributes to GABAergic signaling in the gut that can influence brain function and has been shown to affect mental health markers through gut microbiota modulation. It is one of several Bifidobacterium species identified as capable of direct neurotransmitter production.
Bifidobacterium adolescentis is a major butyrate-producing Bifidobacterium species that is depleted in IBD patients. Its supplementation has been studied in clinical IBD contexts, with evidence supporting gut microbiota restoration and anti-inflammatory effects.
Body systems that Bifidobacterium adolescentis may help support.
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