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Bifidobacterium longum

Bifidobacterium longum

Probiotics & Gut

What bifidobacterium longum may help with

Ranked by how strong the human evidence is — best supported first.

Best supportedBowel regularityLimited evidence· 4 sources

Then, in order

About Bifidobacterium longum

A bifidobacterium that dominates the infant gut and persists into adulthood. Commercial strains include BB536, studied for bowel habit and respiratory symptoms, and 1714, studied for stress markers.

B. longum illustrates how far apart two strains of one species can sit. BB536 has decades of Japanese research behind it on bowel habit and seasonal respiratory symptoms; strain 1714 has been studied in small neuroimaging and stress trials that are far more preliminary than the "psychobiotic" framing suggests. Neither body of work supports a generic claim for the species, and most retail products name the species alone. The infant subspecies, B. longum subsp. infantis, is a distinct organism with its own literature and is listed separately.

Sold as
Capsule, Sachet, Fermented milk, Multi-strain blend component
Standardised to
CFU of the named strain; BB536 and 1714 are the designations with published trials — a product without this marker may not resemble what was studied.
Also known as
B. longum, BB536, B. longum 1714

Regulation: Sold as a dietary or food supplement with no pre-market efficacy review, and no authorised health claims in the EU.

What the research used

The amounts, forms and durations published trials of Bifidobacterium longum actually administered.

These are the amounts published trials administered — not a recommendation, and not a dose to copy. Trial participants were screened, supervised and given a characterised preparation. What is in a retail bottle is frequently not what was studied, and the amount that suits one person is not general advice.

  • Studied for Bowel habit (strain BB536)

    2–10 billion CFU

    Limited

    Capsule or fermented milk, daily · 2–12 weeks

    Doses from Japanese trials, most conducted or supported by the strain owner, with self-reported stool frequency as the endpoint.

  • Studied for Stress and cortisol (strain 1714)

    1 billion CFU

    Not enough

    Capsule, daily · 4 weeks

    From small trials in healthy volunteers using cortisol output and electroencephalography as endpoints. Preliminary work in a few dozen people, not a demonstrated clinical effect.

This is general information about food, not medical advice. It cannot diagnose, treat or replace guidance from a clinician who knows your history.

When it was taken

Each window says whether a trial compared it against an alternative, or whether it is convention and pharmacology. Most timing advice is the second kind.

None of the timings below were directly compared in a trial. They reflect how the research happened to dose, or what the pharmacology implies — which is not the same as a timing being better.

  • With food

    Not enough

    Bifidobacteria are relatively acid-sensitive, so taking them with a meal or with a buffering food is the usual practice. It has been examined in laboratory survival work rather than in a clinical comparison.

    Timing was not directly compared. This reflects convention or how the compound behaves in the body, not a trial showing this window works better.

The evidence in depth

Best supported: Limited

What each association actually rests on, and the papers behind it. A rating describes the state of the research, not how promising the supplement sounds. How we rate evidence.

Bowel regularity

Gut & Digestive Health
Limited evidence

Trials of BB536 report modest improvements in stool frequency and consistency, particularly in older adults and people with constipation. The literature is dominated by one manufacturer and uses self-reported endpoints.

Limited evidence. Early human work, or mostly lab and animal research.

View the 4 sources

Deep research mode adds each paper’s own conclusion and stated limitations.

Immune function

Immune Health
Not enough evidence

Studies of BB536 and seasonal allergic symptoms or influenza in older adults exist but are small and largely from one research programme. There is not enough independent evidence to support an immune claim.

Not enough evidence. Not enough human research to say anything useful yet.

View the 3 sources

Deep research mode adds each paper’s own conclusion and stated limitations.

Stress and anxiety

Mental Wellbeing
Not enough evidence

Small trials of B. longum 1714 report reduced cortisol output and changes in brain electrical activity during stress tasks in healthy volunteers. These are early mechanistic studies in small groups, not evidence that the supplement changes anxiety.

Not enough evidence. Not enough human research to say anything useful yet.

View the 3 sources

Deep research mode adds each paper’s own conclusion and stated limitations.

Things to know

Interactions, contraindications and dose limits, most serious first. Concentrated extracts interact with medication in ways the whole plant does not, so this section carries more weight here than it does on a food page.

  • Avoid

    Immunocompromise, central lines and critical illness

    Bifidobacterium bacteraemia is rarer than lactobacillus bacteraemia but has been reported, including in preterm infants and immunosuppressed patients. Live cultures in these groups are a specialist decision.

  • Worth knowing

    Strain designations carry the evidence

    BB536 and 1714 have separate literatures and neither transfers to an unnamed B. longum product. The species name on a label is not a claim about what was tested.

  • Too much

    Gas and bloating on starting

    Common and usually transient. Bifidobacteria ferment carbohydrate, so some gas production is expected rather than a sign of a problem.

Evidence ratings on this page: 1 limited evidence, 2 not enough evidence.

Supplements are sold in the US without pre-market review of efficacy or safety. Nothing on this page is a recommendation to take Bifidobacterium longum, or a dose to follow.