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Bacterium

Bifidobacterium longum

Common name: B. longum

Beneficial Immune Gut
Beneficial
Effect
Immune
Impact
Gut
Location
Common
Prevalence
Last reviewed: April 4, 2025

Probiotic with immunomodulatory, gut-brain axis, and metabolic effects

Prevalence: One of the first colonizers of the infant gut; abundant throughout lifespan

Interacts with: Lactobacillus acidophilus, Eubacterium rectale, Faecalibacterium prausnitzii, Cross-feeding networks

Overview

Scientifically accurate microscopy-style illustration of Bifidobacterium longum showing its characteristic gram-positive elongated rod with Y-shaped or V-shaped bifurcations at the ends

Bifidobacterium longum is a Gram-positive, anaerobic, rod-shaped bacterium and one of the most extensively researched probiotic species. It is among the first colonizers of the infant gut and remains a key beneficial bacterium throughout the lifespan, with documented effects on digestive health, immune function, mental wellbeing, and metabolic health.[1]

Key Strains and Their Applications

BB536

One of the most extensively studied strains, effective for constipation, ulcerative colitis, allergies, and metabolic health.[2]

NCC3001

Psychobiotic strain with documented effects on depression, stress, and the gut-brain axis.[1]

35624 (B. infantis 35624)

Strain with potent immunomodulatory properties, particularly effective for IBS through normalization of IL-10/IL-12 cytokine ratio.[3]

1714

Translational psychobiotic for stress reduction, cognitive enhancement, and sleep quality improvement.[4]

EVC001

Infant-specialized strain that metabolizes human milk oligosaccharides (HMOs) and prevents necrotizing enterocolitis (NEC).

Mechanisms of Action

Immunomodulation

  • Upregulation of regulatory T cells (Tregs) expressing Foxp3
  • Normalization of IL-10/IL-12 cytokine ratio (anti-inflammatory to pro-inflammatory)
  • Reduction of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, IL-8, IL-17)
  • Modulation of Th1/Th2 and Th17/Treg balance

Gut Barrier Enhancement

  • Upregulation of tight junction proteins (ZO-1, occludin, claudin-1)
  • Reduction of intestinal permeability
  • Activation of TLR2 and NOD2 pathways
  • Maintenance of mucus layer integrity

Metabolite Production

  • Short-chain fatty acids: Acetate, lactate, and cross-feeding support for butyrate production
  • Tryptophan metabolites: Indole-3-lactic acid (ILA), indole-3-carbaldehyde (I3C)
  • Biotin synthesis: Produces biotin and pimelate through microbial crosstalk

Gut-Brain Axis Modulation[4]

  • Regulation of hypothalamic-pituitary-adrenal (HPA) axis
  • Reduction of serum corticosterone and ACTH levels
  • Increased Brain-Derived Neurotrophic Factor (BDNF) expression
  • Modulation of brain wave activity (theta and alpha bands)

Clinical Evidence

Irritable Bowel Syndrome (IBS)

The strain B. infantis 35624 demonstrated significant reduction in all cardinal IBS symptoms including abdominal pain, bloating, and bowel movement difficulty. The mechanism involves normalization of the IL-10/IL-12 cytokine ratio.[3]

Depression and Anxiety

A landmark 2017 study in Gastroenterology showed that B. longum NCC3001 reduced depression scores in IBS patients with comorbid anxiety/depression. fMRI revealed reduced limbic reactivity to negative emotional stimuli in the amygdala and frontolimbic regions.[1]

Stress Response

B. longum 1714 attenuated cortisol output and subjective anxiety in response to acute stress, while improving hippocampus-dependent visuospatial memory and enhancing frontal midline EEG mobility.[4]

Chronic Constipation

BB536 significantly improved bowel movement frequency and reduced failure of evacuation in elderly individuals with chronic constipation. Mechanisms include SCFA production (acetic and butyric acid) and suppression of microinflammation.[2]

Atopic Dermatitis

B. longum CCFM1029 alleviates atopic dermatitis through conversion of tryptophan to indole-3-carbaldehyde (I3C), activating the aryl hydrocarbon receptor (AhR) signaling pathway and suppressing Th2-type immune responses.[5]

Infant Health

A meta-analysis of 15 RCTs (3,152 infants) found B. longum supplementation significantly reduces risk of necrotizing enterocolitis (RR=0.539). The strain metabolizes HMOs to produce lactic and acetic acids, lowering intestinal pH to inhibit pathogens.[6]

B. longum and B. infantis: Understanding the Relationship

One of the most common points of confusion in probiotic research involves the relationship between Bifidobacterium longum and Bifidobacterium infantis. Taxonomic reclassification has clarified that what was historically called B. infantis is actually a subspecies of B. longum—formally designated Bifidobacterium longum subsp. infantis.

The Three Subspecies of B. longum

B. longum contains three recognized subspecies, each with distinct ecological niches and health applications:

Subspecies Primary Niche Key Specialty
B. longum subsp. longum Adult gut Immune modulation, IBS relief, gut-brain axis
B. longum subsp. infantis Infant gut HMO metabolism, NEC prevention, immune development
B. longum subsp. suis Animal gut Less relevant to human health

B. longum subsp. infantis: The Infant Specialist

B. infantis (now B. longum subsp. infantis) is uniquely adapted to the infant gut environment:

  • HMO metabolism: Possesses a complete enzymatic toolkit for metabolizing all human milk oligosaccharide (HMO) structures—a capability that B. longum subsp. longum lacks
  • Strain 35624: Originally classified as B. infantis 35624, this strain (now B. longum subsp. longum 35624) is one of the most studied probiotics for IBS, with documented effects on cytokine normalization[7]
  • EVC001: A B. infantis strain specifically developed for infant gut colonization; may reduce incidence of necrotizing enterocolitis (NEC) and support immune development[6]

Why This Distinction Matters

Understanding that B. infantis is a subspecies of B. longum has practical implications:

  • Product labeling: Some supplements still use the outdated name "B. infantis"—these contain B. longum subsp. infantis
  • Strain selection: Despite sharing a species name, B. longum subsp. longum and B. longum subsp. infantis have very different capabilities and optimal applications
  • Life stage relevance: B. longum subsp. infantis is most important during infancy, while B. longum subsp. longum (along with B. adolescentis/) dominates the adult Bifidobacterium population

Safety Profile

B. longum has an excellent safety record across all age groups:

  • Regulatory status: GRAS (Generally Recognized As Safe) by FDA; QPS (Qualified Presumption of Safety) in Europe
  • Adverse events: Rare and typically mild (transient GI symptoms in <5% of users)
  • Special populations: Safe in infants, elderly, pregnant women, and immunocompromised individuals
  • No antibiotic resistance transfer in safety-tested strains

Dosing Guidelines

Application Typical Dose Duration
IBS 1×10⁹ to 1×10¹⁰ CFU daily 4-8 weeks
Constipation 5×10⁹ to 5×10¹⁰ CFU daily 4 weeks
Stress/Anxiety 1×10⁹ to 1×10¹⁰ CFU daily 4-8 weeks
Atopic dermatitis 1×10⁹ CFU daily 8-12 weeks
Ulcerative colitis 2-3×10¹¹ CFU daily 8 weeks
Infant NEC prevention 1×10⁷ to 8×10⁹ CFU daily Variable

Documented Strains

BB536

Bifidobacterium longum BB536

Extensive research
ATCC BAA-999 FERM BP-6658
Seasonal allergy and hay fever reliefUpper respiratory infection preventionImmune regulation in elderlyInfant gut colonisation support

Key Findings

↑

Seasonal allergies (hay fever)

Significantly reduced nasal symptom scores during pollen season

↑

Respiratory immunity

Reduced frequency of colds and respiratory tract infections

The only B. longum strain with robust clinical evidence for reducing hay fever symptom scores in multiple double-blind RCTs — a uniquely documented allergy endpoint that distinguishes BB536 from all other Bifidobacterium longum strains

NCC3001

Bifidobacterium longum NCC3001

Moderate research
ATCC BAA-2941
Depression and anxiety reduction in IBS patientsGut-brain axis modulationQuality of life improvement in functional gut disorders

Key Findings

↑

Depression and anxiety in IBS

Significantly reduced depression scores; altered amygdala fMRI responses

The first and only probiotic strain demonstrated to reduce depression scores and measurably alter brain activity patterns (fMRI) in IBS patients — a landmark clinical finding establishing a direct gut-brain pathway for a Bifidobacterium strain

1714

Bifidobacterium longum 1714

Moderate research
DSM 33903
Stress and anxiety reduction in healthy adultsCognitive performance under stressHPA axis modulation

Key Findings

↑

Stress and cognitive performance

Reduced stress, lower cortisol awakening response, improved memory scores

The only probiotic strain shown to reduce perceived stress, cortisol awakening response, and improve memory/cognition in healthy adult males under exam stress in a double-blind RCT — establishing a uniquely documented psychobiotic profile in non-clinical populations

35624

Bifidobacterium longum subsp. longum 35624

Extensive research
NCIMB 41003 DSM 33361
IBS symptom relief across all subtypesCytokine normalization in inflammatory conditionsSystemic inflammation reduction

Key Findings

↑

IBS symptoms (all subtypes)

All four main IBS symptoms improved versus placebo in a 362-person trial

↑

Gut immune balance

Cytokine ratio normalized from inflammatory to non-inflammatory pattern within 8 weeks

↑

Systemic inflammation

Inflammatory markers improved across three separate conditions: ulcerative colitis, chronic fatigue, and psoriasis

The only probiotic strain with a pivotal dose-finding RCT (n=362) demonstrating that a single daily 10⁸ CFU capsule relieves all cardinal IBS symptoms simultaneously — pain, bloating, bowel dysfunction, and incomplete evacuation — while also uniquely shown to normalize the IL-10/IL-12 cytokine ratio in both gut and blood, a mechanistic profile no other B. longum strain has replicated

CECT 7347

Bifidobacterium longum CECT 7347

Moderate research
CECT 7347
Celiac disease adjunct therapyImmune modulation in inflammatory conditionsPediatric gut health

Key Findings

↑

Celiac disease (children)

Greater height growth, decreased CD3+ T cells, reduced TNF-α on GFD + CECT 7347 vs GFD alone

The only Bifidobacterium strain specifically selected and RCT-validated as an adjunct to gluten-free diet in celiac disease, targeting the TH1-biased inflammatory immune response characteristic of CD

R0175

Bifidobacterium longum subsp. longum R0175

Extensive research
Anxiety reductionPsychological stressGastrointestinal symptoms of stressGut-brain axis psychobiotic

Key Findings

↑

Psychological distress

Significantly reduced somatization, depression, anger-hostility, and anxiety in healthy volunteers

The most documented psychobiotic formulation in the world (as CEREBIOME with R0052); first demonstrated in 2008-2010 that probiotics reduce stress-induced GI symptoms and psychological distress in healthy adults — pioneering the psychobiotics field

BL999

Bifidobacterium longum BL999

Limited research
CNCM I-3470
Atopic eczema prevention in infantsAnxiety/behavior (veterinary)Immune programming in neonates

Key Findings

↑

Infant eczema prevention

Both BL999-containing formulations significantly reduced eczema risk in at-risk infants

A Nestlé proprietary strain with human infant eczema prevention data and the only probiotic strain commercially deployed for canine behavioral anxiety in a prescription veterinary product (Purina Pro Plan Calming Care)

Associated Conditions

→ Anxiety → Depression → Constipation → Allergies

Related Organisms

B
Bifidobacterium adolescentis Digestive
B
Bifidobacterium animalis subsp. lactis Digestive
B
Bifidobacterium animalis subsp. lactis Digestive
B
Bifidobacterium bifidum Digestive
B
Bifidobacterium breve Immune
B
Bifidobacterium lactis Immune

Frequently Asked Questions

What is Bifidobacterium longum?

Bifidobacterium longum is a bacterium found in the human microbiome.

Where is Bifidobacterium longum found in the body?

Bifidobacterium longum is primarily found in the Gut.

What are the health impacts of Bifidobacterium longum?

Bifidobacterium longum primarily impacts Immune and is beneficial for human health.

Research References

  1. Pinto-Sanchez MI, Hall GB, Ghajar K, et al.. Probiotic Bifidobacterium longum NCC3001 Reduces Depression Scores and Alters Brain Activity. Gastroenterology. 2017. doi:10.1053/j.gastro.2017.05.003 ↩
  2. Takeda T, Asaoka D, Nojiri S, et al.. Usefulness of Bifidobacterium longum BB536 in Elderly Individuals With Chronic Constipation. The American Journal of Gastroenterology. 2023. doi:10.14309/ajg.0000000000002028 ↩
  3. O'Mahony L, McCarthy J, Kelly P, et al.. Lactobacillus and Bifidobacterium in irritable bowel syndrome: symptom responses and relationship to cytokine profiles. Gastroenterology. 2005. doi:10.1053/j.gastro.2004.11.050 ↩
  4. Allen AP, Hutch W, Borre YE, et al.. Bifidobacterium longum 1714 as a translational psychobiotic: modulation of stress, electrophysiology and neurocognition. Translational Psychiatry. 2016. doi:10.1038/tp.2016.191 ↩
  5. Fang Z, Pan T, Li L, et al.. Bifidobacterium longum mediated tryptophan metabolism to improve atopic dermatitis via the gut-skin axis. Gut Microbes. 2022. doi:10.1080/19490976.2022.2044723 ↩
  6. Guo H, Fan M, Hou T, et al.. Efficacy and Safety of Bifidobacterium longum Supplementation in Infants: A Meta-Analysis of Randomized Controlled Trials. Foods. 2023. doi:10.3390/foods12244451 ↩
  7. Whorwell PJ, Altringer L, Morel J, et al.. Efficacy of an encapsulated probiotic Bifidobacterium infantis 35624 in women with irritable bowel syndrome. American Journal of Gastroenterology. 2006. doi:10.1111/j.1572-0241.2006.00734.x ↩