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Not medical advice. The Atlas is not a substitute for a clinician who can examine you.

B. infantis 35624

Bifidobacterium · The IBS Strain (Align)

Evidence grade 3 of 5, Mixed. Read how the Atlas grades evidence.

6 human trials, about 70 studies, ~4,000 participants. The written rationale for this grade is still being prepared.

FDA
GRAS; Align
WADA
Not prohibited

Reference only. Not medical advice.

What can go wrong

The IBS strain 35624 is generally regarded as well tolerated in adults, with transient and individual effects. Infant use is a different and sensitive matter. Live probiotics given to preterm or hospitalized infants have been associated with serious invasive infection: in 2023 the FDA linked a hospital probiotic to an infant death and warned against such use, and the EVC001-containing product Evivo with MCT Oil was recalled. Any consideration of a probiotic for an infant, especially one born preterm or medically fragile, should be discussed with a pediatrician or neonatologist before use, and should not be started on the basis of marketing or general adult probiotic evidence.

'B. infantis' names two different probiotic stories that are easy to blur and worth keeping apart. The first is strain 35624 (Bifantis, the strain in Align), which carries among the better single-strain trial records for irritable bowel syndrome, anchored by Whorwell et al. (2006) in 362 IBS patients where benefit appeared only at a specific 1x10^8 cfu dose. The second is strain EVC001, studied in breastfed infants, where it colonizes durably, consumes human milk oligosaccharides, and is associated with lower gut inflammation and fewer potential-pathogen and antibiotic-resistance genes. A taxonomic twist sits underneath: whole-genome sequencing in 2016 showed the IBS strain 35624 is actually B. longum subsp. longum, while EVC001 is genuinely B. longum subsp. infantis, so the two strands are not even the same subspecies. Infant use is a sensitive pediatric domain and should be routed through a qualified provider.

The single strain with the strongest IBS evidence. The strain inside Align.

What people take it for

These are the reasons people give for taking it. They are not effects it has been shown to have.

  • IBS symptom relief (strain 35624): abdominal pain, bloating, bowel-habit normalization across subtypes
  • Infant gut colonization and human-milk-oligosaccharide utilization (strain EVC001)
  • Association with reduced enteric inflammation in breastfed infants (strain EVC001, mechanistic/surrogate)
  • Association with fewer potential-pathogen and antibiotic-resistance gene signatures in the infant gut (strain EVC001)
  • Immune and inflammatory modulation (mechanistic, strain-dependent)

What people get wrong

  • Often said'B. infantis' is one strain with one job

    ActuallyThe name covers at least two distinct commercial strains with separate evidence: strain 35624 studied for adult IBS (Whorwell 2006), and strain EVC001 studied in the infant gut (Frese 2017, Henrick 2019). Benefits shown for one do not transfer to the other.

  • Often saidThe IBS strain in Align really is B. infantis

    ActuallyWhole-genome sequencing in 2016 (PLOS One) reclassified strain 35624 as B. longum subsp. longum, not subsp. infantis. The original 'infantis' label came from partial 16S rRNA analysis. Marketing keeps the historic name, but the two streams are not the same subspecies.

  • Often saidAny Bifidobacterium works for IBS

    ActuallyMeta-analyses and the 2020 AGA guideline stress that probiotic effects are strain-specific. The 35624 designation, not the species, is what carries the IBS trial data; generic Bifidobacterium products do not inherit it.

  • Often saidMore probiotic means more benefit

    ActuallyIn Whorwell 2006 the middle dose (1x10^8 cfu) beat placebo while both a lower (1x10^6) and a higher (1x10^10) dose did not, so dose response was not linear.

Who profits, and who pushes back

  • American Gastroenterological Association (2020 guideline panel)

    Pushes backProfessional-society clinical practice guideline (Gastroenterology)

    The AGA guideline made 'no recommendation' on probiotics for adults and children with IBS, concluding that the available evidence was insufficient and suggesting patients consider stopping probiotics given the associated costs.

  • Alexander C. Ford and colleagues (IBS meta-analysts)

    Pushes backSystematic-review and meta-analysis authors in functional GI disorders

    Pooled probiotic trials in IBS sit against a placebo response near 37%, with several studies underpowered or showing baseline imbalances, so strain-level benefit signals should be read cautiously rather than as settled efficacy.

  • US Food and Drug Administration

    Pushes backFederal regulator, 2023 safety communication and warning letters

    The FDA stated that probiotic products given to preterm infants carry a risk of invasive, potentially fatal disease and that it was investigating the role of an EVC001-containing product in the death of a preterm infant who developed sepsis.

  • IBS / gastroenterology clinicians

    Promotes itClinical

    35624 is among the few strains with credible IBS RCT support; commonly recommended.

  • Align (Procter & Gamble)

    Sells this. Has a commercial interest in a product sold as this compound, as of July 2026.

    Promotes itMass-market brand

    Sells the 35624 strain; genuine IBS evidence behind a consumer product.

Where the research comes from

Share of published research by country of origin.
PlaceShare of published research
USA38%
Ireland24%
Europe22%
Other16%

Research published from: Ireland, USA, Global.

How we got here

Bifidobacterium longum subsp. infantis is described as a specialist of the breastfed infant gut, adapted to digest human milk oligosaccharides, sugars the infant cannot use directly. That adaptation was mapped in the genome sequence work led by researchers including those at UC Davis (Sela et al., PNAS 2008), a program with deep roots in the study of human-milk glycobiology. The taxonomy itself was reworked outside a purely Western frame of reference by an international committee: Mattarelli and colleagues (2008) folded the old species B. infantis, B. longum, and B. suis into one species, B. longum, with three subspecies. Separately, the IBS strain 35624 came out of the Alimentary Pharmabiotic Centre in Cork, Ireland, with the Whorwell 2006 trial establishing its dose-specific IBS signal. In 2016, genome sequencing corrected 35624's own label from subsp. infantis to subsp. longum, a reminder that strain identity, not species names, carries the evidence.

  1. 2006Whorwell IBS trial of strain 35624 (Am J Gastroenterol), 362 patients, benefit only at 1x10^8 cfu
  2. 2008Mattarelli et al. reclassify B. infantis as B. longum subsp. infantis (three subspecies of B. longum)
  3. 2008Sela et al. sequence B. longum subsp. infantis genome, revealing human-milk-oligosaccharide utilization (PNAS)
  4. 2016Whole-genome sequencing reclassifies the IBS strain 35624 as B. longum subsp. longum, not subsp. infantis (PLOS One)
  5. 2017Frese et al. show EVC001 durably colonizes breastfed infants (mSphere)
  6. 2019Henrick et al. associate EVC001 colonization with lower enteric inflammation in breastfed infants (Pediatric Research)
  7. 2023FDA issues warning letter to Infinant Health (formerly Evolve BioSystems) over Evivo with MCT Oil for preterm infants; product recalled

At a glance

Strain
35624 (Bifantis)
Best for
IBS, all subtypes
Brand
Align (P&G)
Origin
Cork, Ireland research

What this entry does not yet cover

What follows is unfinished work on our side, not a finding about B. infantis 35624. A short entry is not a safe entry.

  • Cost and market. We have not documented what it sells for or who sells it.
  • Supply chain. We have not mapped where it is made.
  • Who uses it. We have not documented the user groups.
  • What could change. No forward-looking summary yet.
  • How it compares. We have not set it against the alternatives.
  • Children and teenagers. We have not checked what is known about younger people.

Sources