Bifidobacterium longum
Bifidobacterium longum is one of the dominant bacterial species in the breastfed infant gut and a common adult gut resident. It appears in many probiotic supplements, often in multi-strain blends. Like all probiotics, the trial evidence is strain-specific and dose-specific — the species name alone does not carry the evidence of a particular branded strain.
Camden Medicals editorial · Last reviewed 27 April 2026 · Next review April 2027
- Cross-checked against
- NHS
- NICE
- BNF
- EFSA
- FSA
Camden's editorial team independently graded each health claim below on the strength of the published evidence — see the grade beside every condition.
- Class
- Probiotic
- Typical daily dose
- Most published trials use 10⁸ to 10¹⁰ CFU per day, often as part of multi-strain formulations.
- Top use evidence
- Moderate
On this page
What it is
Bifidobacterium longum is a Gram-positive, anaerobic bacterium with a characteristic Y- or V-shaped morphology (the "bifid" in Bifidobacterium). It is one of the dominant species in the breastfed-infant gut, where it metabolises human milk oligosaccharides (HMOs) — complex sugars in human milk that infants cannot digest themselves. The bacterium-mediated fermentation produces short-chain fatty acids and contributes to the development of the infant immune system.
In adults, B. longum continues to be a common — though usually minor — gut resident. Commercial supplement strains include B. longum 35624 (Procter & Gamble's Align brand; the most-trialled IBS strain), BB536 (Morinaga; included in many Japanese-origin probiotics), NCC3001 (Nestlé), and others. The 2008 reclassification of Bifidobacterium taxonomy split out three subspecies of B. longum (subsp. longum, subsp. infantis, and subsp. suis); the infantis subspecies — found in some infant probiotics — is now sometimes treated as a separate species in commercial labelling.
At a glance
- A Bifidobacterium species naturally present in the human gut from infancy onwards.
- Strain specificity matters: B. longum 35624, B. longum BB536, and B. longum NCC3001 are different strains with different published evidence.
- Best-evidenced indication: B. longum 35624 in IBS symptom management (Whorwell et al. 2006 and replications).
- No GB-authorised health claim for "B. longum" generically.
- Caution in immunocompromised, critically ill, and very young / premature infants — see safety.
What people use it for
Adults with diagnosed IBS (any subtype)
B. longum 35624 has the strongest published evidence of any specific strain for IBS symptom improvement (Whorwell et al. 2006 and follow-up). NICE CG61 lists probiotics including this strain as one option to trial for at least four weeks. [1,3]
Some evidenceModerateAdults co-supplementing with antibiotics
Some Bifidobacterium strains (often in multi-strain formulations alongside Lactobacillus) feature in the Cochrane meta-analyses on antibiotic-associated diarrhoea prevention. Talk to your pharmacist about whether your specific antibiotic course warrants probiotic co-administration. [2]
Some evidenceModerateOlder adults with reduced gut Bifidobacterium
Observational studies show Bifidobacterium counts decline with age. Whether supplementing reverses any clinically-meaningful outcome is not well-established by trial evidence; the natural-decline observation is not in itself a treatment indication.
Some evidenceLimited
How it works
B. longum produces lactic and acetic acids as primary fermentation products, and (specific strains) butyrate via cross-feeding with other gut residents. It can compete with potentially-pathogenic bacteria for binding sites and nutrients, and specific strains modulate intestinal barrier function and local immune signalling. The gut-brain axis research has highlighted some Bifidobacterium strains for vagus-nerve- mediated effects, but human translation is early and the GB-authorised health claim list does not include any cognition or mood claim for Bifidobacterium.
Common myths
Myth"B. longum is the same as B. infantis"
RealityFollowing the 2008 reclassification, what was historically called Bifidobacterium infantis is now considered a subspecies of B. longum (B. longum subsp. infantis). In commercial labelling you will see both names. They are closely related but the trial evidence is for specific strains within each subspecies, not for the species or subspecies as generic categories.
Myth"Bifidobacterium supplements rebuild the infant microbiome after C-section delivery"
RealityPopulation-level studies show C-section-delivered infants have delayed Bifidobacterium colonisation compared to vaginally- delivered infants, but the natural trajectory typically catches up by toddler age. Specific commercial probiotic formulations have been tested in this context with modest results; routine supplementation in healthy term C-section babies is not currently recommended by NHS infant feeding guidance and should be discussed with a paediatrician or health visitor.
Common online questions
Synthesised from the questions UK shoppers most often ask online about Bifidobacterium longum. Each answer is editorial and links to its evidence in the Sources list below.
Should I take Bifidobacterium longum for IBS?
If you have a confirmed IBS diagnosis and have read NICE CG61, a probiotic trial of at least 4 weeks at the manufacturer- recommended dose is one option on the NICE pathway. For B. longum specifically, the strain with the strongest evidence is B. longum 35624 (Align brand internationally; not always available under the same name in the UK). Talk to your GP or pharmacist about fitting it into your wider IBS plan. [3,1]
B. longum vs B. infantis — which should I pick for my baby?
For routine supplementation in healthy term breastfed or formula- fed infants, NHS infant feeding guidance does not recommend either. For specific clinical situations (preterm infants in NICU, infants with severe colic), the evidence base is for specific named strains under specialist supervision — not for consumer-grade supplements. Talk to your health visitor or GP before giving a probiotic to a baby.
Will B. longum boost my immunity?
There is no GB-authorised health claim for B. longum — or any Bifidobacterium species — as an immune booster. Some specific strains have shown immune-marker changes in trials, but those marker changes do not translate reliably to clinical outcomes like fewer colds or shorter illnesses. The labelling rule is the same as for vitamin C: "contributes to normal function" is about adequacy, not about supplementation producing a supra-normal effect. [5]
Does B. longum survive freezer / shelf storage?
Most commercial Bifidobacterium products are freeze-dried and have shelf-life ratings — check the label for the CFU at end of shelf life (NOT at manufacture). Cold-chain shipping is relevant for some products and not for others; the manufacturer is the right source of confirmation.
Is B. longum safe in pregnancy?
Some research-context use of Bifidobacterium in pregnancy exists (allergy-prevention trials, gestational-diabetes trials). For routine use in pregnancy, talk to your midwife or pharmacist — the substance itself has a favourable safety profile, but any supplement during pregnancy should be discussed first.
Camden guides citing Bifidobacterium longum
Editorial pieces from the Camden blog that reference Bifidobacterium longum. Each guide cites the evidence it draws on.
🔬 Camden’s evidence review
The research Camden reviewed, graded on its strength. This is our own appraisal — it sits beneath the official guidance above, never above it.
Irritable bowel syndrome (IBS) — B. longum 35624
ModerateEvidencemoderateWhorwell et al. (Am J Gastroenterol 2006, N=362) reported B. longum 35624 (then named Bifidobacterium infantis 35624; reclassified per 2008 taxonomy) at 1 × 10⁸ CFU/day for 4 weeks improved composite IBS symptoms versus placebo. Effect sizes are modest but consistent across follow-up trials. [1,6]
Antibiotic-associated diarrhoea (AAD) prevention
ModerateEvidencemoderateThe Cochrane review of probiotics for paediatric AAD prevention (Guo et al., CD004827.pub5, 2019) covers multiple Bifidobacterium-containing formulations alongside Lactobacillus. Moderate-quality evidence for the category; specific strain-level data for B. longum alone is more limited than for Lactobacillus rhamnosus GG. [2]
Inflammatory bowel disease (IBD) maintenance therapy
InsufficientEvidenceinsufficientSome early trials with B. longum-containing formulations (e.g. VSL#3 / De Simone Formulation) in ulcerative colitis maintenance have shown effects, but the evidence base is small, the products used in trials are specific multi-strain formulations not equivalent to single-strain B. longum supplements, and clinical guidelines do not recommend probiotics as primary IBD therapy.
Safety
Bifidobacterium longum has a long safety record at typical food-supplement doses for most healthy adults. Not appropriate for everyone — see scenarios below.
Talk to your pharmacist or GP first if you:
- You are immunocompromised, on chemotherapy, or have HIV with a low CD4 count.
- You are critically ill, in intensive care, or have a central venous catheter.
- You have severe acute pancreatitis.
- You are buying for a premature or unwell newborn (specialist supervision required).
- You are pregnant or breastfeeding.
- You are starting a course of antibiotics.
Common side effects: Mild bloating or wind in the first few days; settles with continued use. Rare in healthy adults.
Pregnancy and breastfeeding
Used in some research-context trials in pregnancy (allergy and gestational diabetes prevention work). Talk to your midwife or pharmacist before routine use.
Used in some research-context trials in breastfeeding women. Talk to your pharmacist or GP.
Talk to your GP, midwife, or pharmacist before starting any supplement during pregnancy or breastfeeding.
More clinical detail (for clinicians and informed readers)
Contraindications
- Severe immunocompromise.
- Critical illness with central venous access.
Drug interactions
- Antibiotics — separate doses by at least 2 hours.
- Immunosuppressants — caution as for the contraindications.
This is not an exhaustive list. Always tell your prescriber and pharmacist about every supplement you take.
Common side effects
- Mild bloating or flatulence in the first 1-2 weeks.
Rare side effects
- Bacteraemia in immunocompromised or critically-ill patients (rare).
How to take it
- Typical supplemental range
- Most published trials use 10⁸ to 10¹⁰ CFU per day, often as part of multi-strain formulations.
- Timing
- For antibiotic co-administration, separate the probiotic dose from the antibiotic by at least 2 hours.
How to spot quality
Look for
- Named strain identifier on the label (e.g. "Bifidobacterium longum 35624", "B. longum BB536").
- CFU per dose stated AT END OF SHELF LIFE.
- GMP-certified manufacture; cold-chain shipping where relevant.
Red flags
- Generic "Bifidobacterium" without a strain identifier.
- Marketing claims about "boosting immunity", "improving mood", or "treating depression".
- CFU stated only at manufacture.
Commonly combined with
Other ingredients that share a biological pathway, cofactor relationship, or evidence-backed protocol with this one. Mechanisms below cite primary physiology — not folk pairing. Doses are literature ranges, not recommendations. Talk to your pharmacist or GP before changing your stack, especially if you take prescription medication.
Lactobacillus rhamnosus
Moderate evidenceB. longum and L. rhamnosus are the two most-studied genera in the probiotic literature; commonly co-formulated for general gut and immune support.
Bifidobacterium longum dominates the infant colon and remains a significant component of the adult gut microbiome; it ferments oligosaccharides to short-chain fatty acids (acetate, lactate) that modulate gut pH and act as substrates for downstream butyrate-producing bacteria. Lactobacillus rhamnosus GG occupies different niches, produces antimicrobial peptides, and has the strongest individual evidence base for antibiotic-associated and acute infectious diarrhoea. The combination is mechanistically complementary (different niches, different metabolic outputs) rather than directly synergistic.
Evidence: Goldenberg 2017 (Cochrane CD006095) covers multi-strain probiotic evidence in adults and children. Multi-strain products including B. longum and L. rhamnosus are heavily represented in the trial pool but the meta-analysis did not find a definitive advantage of multi-strain over single-strain formulations for the primary outcome (CDAD prevention). Other endpoints (general gut comfort, immune signalling, mood — see Pinto-Sanchez 2017 for B. longum mood data) have variable individual evidence. [7]
Doses studied: Multi-strain products typically deliver 5-20 billion CFU per strain per day. No definitive clinical-outcome dose-response established.
Akkermansia muciniphila (next-generation probiotic)
Limited evidenceMulti-strain microbiome support — Akkermansia (mucus-layer) + B. longum (broad-spectrum bifidobacterium) combination addresses different microbiome axes.
Akkermansia thickens mucin layer + reduces LPS translocation; B. longum produces SCFAs + supports colonic barrier through different pathway. Mechanism-complementary across barrier + SCFA axes.
Evidence: Each component has individual trial body; combination not directly trialled in human studies.
Doses studied: Pasteurised Akkermansia 10⁹-10¹⁰ CFU/day + B. longum 10⁹-10¹⁰ CFU/day capsule.
Bifidobacterium animalis subsp. lactis (BB-12, HN019, DN-173 010)
Limited evidenceSister species combination — broad bifidobacterium coverage across the two human-resident species.
B. longum dominant in adult gut; B. animalis lactis dominant in commercial products. Combination extends bifidobacterium genus coverage. Mechanism complementary on Bifidobacterium-enrichment axis.
Evidence: Each component has individual trial body; combination trials small.
Doses studied: B. longum 10⁹-10¹⁰ CFU + B. animalis lactis 10⁹-10¹⁰ CFU/day capsule combination or multi-strain product.
Faecalibacterium prausnitzii (next-generation butyrate-producing probiotic)
Limited evidenceMulti-strain microbiome support — established + next-generation.
B. longum carbohydrate-fermenting + SCFA production; F. prausnitzii butyrate-specific. Mechanism complementary on microbiome diversity.
Evidence: Mechanism complementary; combination evidence limited.
Doses studied: Multi-strain product including F. prausnitzii + B. longum.
Lactobacillus plantarum / Lactiplantibacillus plantarum (299v / CECT 7484/7485)
Limited evidenceLactobacillus + Bifidobacterium cluster — most-common multi-strain combination.
L. plantarum + B. longum — different genera with complementary niche distribution. Universal combination in multi-strain probiotic products.
Evidence: Multi-strain microbiome support.
Doses studied: 10⁹-10¹⁰ CFU each daily.
Lactobacillus reuteri
Limited evidenceMulti-strain microbiome cluster — Lactobacillus + Bifidobacterium genus complementarity.
L. reuteri small-intestinal colonisation; B. longum colonic colonisation. Different gut-region niche distribution; mechanism complementary.
Evidence: Multi-strain microbiome support.
Doses studied: 10⁹-10¹⁰ CFU each strain daily.
Roseburia intestinalis (next-generation butyrate-producing probiotic)
Limited evidenceMicrobiome diversity cluster.
B. longum carbohydrate fermenter + Roseburia butyrate producer. Different mechanisms; complementary on microbiome diversity + SCFA production.
Evidence: Mechanism complementary.
Doses studied: Multi-strain product including Roseburia + B. longum.