Bifidobacterium longum
Bifidobacterium longum (subsp. longum and subsp. infantis; strains 35624, NCC3001, BB536, 1714, R0175)
B. longum is a dominant, lifelong gut resident with strain-specific evidence for IBS symptoms (35624), depression scores in IBS (NCC3001), stress response (1714) and infant gut health (subsp. infantis).
At a Glance
- Best known for
- Reduces IBS pain, bloating and bowel symptoms (strain 35624), Lowered depression scores and altered brain activity in IBS patients (NCC3001), Reduced perceived stress and improved cortisol response (strain 1714)
- Evidence
- Moderate
- Typical dose
- 100 million CFU daily for at least 4 weeks
- Type
- Probiotic
What is Bifidobacterium longum?
Bifidobacterium longum is one of the first bacteria to colonize the newborn gut and remains one of the most abundant bifidobacteria throughout adult life, declining with age. The species is divided into subspecies: B. longum subsp. longum dominates in adults, while B. longum subsp. infantis is specialized for breastfed infants, carrying genes to digest human milk oligosaccharides. Several commercial strains have distinct research records: 35624 (formerly called B. infantis 35624, Align) for IBS, NCC3001 for gut-brain effects, BB536 (Morinaga) for immune and digestive health, 1714 for stress, and R0175 (paired with L. helveticus) for mood. B. longum is a core species in the 'gut-brain axis' research literature.
Known Health Benefits
How It Works
B. longum ferments dietary fiber and human milk oligosaccharides into acetate and lactate, lowering colonic pH, inhibiting pathogens and feeding butyrate-producing bacteria. It strengthens the epithelial barrier by upregulating tight junction proteins and mucin, and skews immune responses toward tolerance: strain 35624 normalizes the IL-10/IL-12 ratio in IBS patients and reduces systemic inflammatory markers. Gut-brain effects appear to involve vagus nerve signaling, reduced hypothalamic-pituitary-adrenal axis activation (lower cortisol with strain 1714), and metabolic products including GABA and tryptophan metabolites; the NCC3001 trial showed reduced amygdala responses to negative stimuli on functional MRI. Subsp. infantis also secretes a serpin that inhibits inflammatory proteases and reduces infant gut inflammation.
What Research Says
Evidence quality varies by strain. For IBS, a 2006 randomized trial of 362 women found B. infantis 35624 at 100 million CFU daily (but not higher doses, due to a formulation issue) significantly improved abdominal pain, bloating and bowel habit over 4 weeks; the strain is recommended in some gastroenterology guidance, though a 2018 meta-analysis found overall probiotic benefit in IBS to be modest. For mood, a 2017 pilot RCT in 44 IBS patients found B. longum NCC3001 reduced depression scores in 64% versus 32% on placebo at 6 weeks and altered brain activity on fMRI, but anxiety scores did not differ. B. longum 1714 reduced stress and cortisol output in a 22-person placebo-controlled study and improved stress-related sleep measures in a later trial. In infants, B. infantis EVC001 colonizes breastfed babies effectively and reduces gut inflammation and antibiotic-resistance genes in observational studies. BB536 has Japanese trials in bowel regularity, allergy and infection. Most trials are small and strain-specific, which keeps the overall tier at moderate.
Active Compounds
Live Bifidobacterium longum cells; exopolysaccharides, acetate and lactate, human milk oligosaccharide-degrading enzymes (subsp. infantis), serpin protease inhibitor, bile salt hydrolase, folate and B vitamins
Forms & Bioavailability
Bifidobacteria are strict anaerobes and more sensitive to oxygen, heat and stomach acid than lactobacilli, so formulation quality matters: enteric coating, oxygen-scavenging packaging and refrigeration help. Only a fraction of cells reach the colon alive, but even non-viable bifidobacteria retain some immune effects. Subsp. infantis colonizes breastfed infants durably because human milk oligosaccharides feed it; adult strains generally persist only while being taken. Pairing with prebiotic fiber (a synbiotic) improves survival and activity.
Dosage Guidance
| Use Case | Dosage |
|---|---|
| IBS (strain 35624) | 100 million CFU daily for at least 4 weeks |
| Mood in IBS (NCC3001) | 1 billion CFU daily for 6 weeks |
| Stress / sleep (strain 1714) | 1 billion CFU daily for 4–8 weeks |
| Infants (subsp. infantis) | 8 billion CFU daily mixed with breast milk |
| General digestive support | 1–10 billion CFU daily |
Always consult a healthcare provider for personalized dosing.
Natural Food Sources
- Human breast milk fosters B. longum subsp. infantis in infants
- Fermented dairy products labeled with B. longum (BB536 in some yogurts)
- Prebiotic fibers (inulin, GOS, resistant starch) increase native B. longum
- Not naturally present in significant amounts in most fermented foods
Potential Side Effects
Transient gas or bloating; rare bacteremia in severely immunocompromised or premature infants; otherwise one of the best-tolerated probiotic species
Who Should Avoid It
- Severe immunosuppression without medical supervision
- Central venous catheter or critical illness
- Premature infants (only NICU-approved strains and products)
- Short bowel syndrome (rare bacteremia reports)
Pregnancy & Lactation
B. longum strains (including BB536 and combination products) have been used in pregnancy trials to reduce infant allergy and in lactating mothers without safety issues. Bifidobacteria are normal residents of the maternal gut and the breastfed infant's gut. Use is generally considered safe, though evidence of benefit in pregnancy itself is limited.
Known Drug Interactions
Antibiotics reduce viability (separate by 2 hours); may improve tolerance of antibiotic regimens; theoretical caution with immunosuppressants; no significant drug interactions documented
Evidence Classification
Supported by cohort studies, case-control studies, or multiple observational studies with consistent findings.
Frequently Asked Questions
Can B. longum help depression or anxiety?
Small trials show reductions in depression scores (NCC3001 in IBS patients) and in perceived stress and cortisol (strain 1714), with brain-imaging changes supporting a real effect. These are pilot-scale studies, and the effects are modest. B. longum is a reasonable low-risk adjunct to, not a replacement for, treatment of depression or anxiety.
Why is the IBS dose so low?
In the key trial, 100 million CFU daily worked but 10 billion did not, which investigators attributed to the higher-dose capsule forming a gel that prevented release. The marketed product (Align) uses 1 billion CFU. The lesson is that more is not always better and that the studied formulation matters.
Is B. infantis for babies the same as B. longum?
Yes, B. infantis is now classified as a subspecies of B. longum. It is uniquely able to digest human milk oligosaccharides and dominates the gut of breastfed infants in traditional settings, but is often absent in babies born by cesarean or exposed to antibiotics in high-income countries. Supplementing it in breastfed infants restores colonization and lowers gut inflammation in studies, though long-term health benefits are still being established.
Do bifidobacteria decline with age and should older adults supplement?
Yes, bifidobacteria including B. longum fall markedly in later life, alongside increased gut inflammation. Trials of BB536 and other strains in older adults show improvements in bowel regularity and some immune markers. Eating more fiber and prebiotics, which feed native bifidobacteria, is a well-supported first step, with supplementation a reasonable addition.
References
- Probiotic Bifidobacterium longum NCC3001 Reduces Depression Scores and Alters Brain Activity: A Pilot Study in Patients With Irritable Bowel Syndrome. Pinto-Sanchez MI, Hall GB, Ghajar K, et al.. Gastroenterology (2017)
- Efficacy of an encapsulated probiotic Bifidobacterium infantis 35624 in women with irritable bowel syndrome. Whorwell PJ, Altringer L, Morel J, et al.. Am J Gastroenterol (2006)
- Probiotics — Health Professional Fact Sheet. NIH Office of Dietary Supplements. NIH ODS (2023)View study
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This entry is for educational purposes only. It is not medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement regimen, especially if you take medications or have health conditions.