Bifidobacterium infantis, longum, lactis and breve: Evidence Profiles
Strain-by-strain look at Bifidobacterium longum, infantis, lactis and breve: who was studied, what trials and reviews found, and why one strain's result does not carry to another.
Content last updated . This page has not been medically reviewed.
What is Bifidobacterium (infantis, longum, lactis, breve) good for?
What the body uses it for, and how strong the evidence is. A normal job in the body is not proof that extra supplements add benefit; each card says which.
Irritable bowel syndrome symptoms (B. infantis 35624)
Preliminary or mixedIn a trial of 362 women with IBS, one strain (B. infantis 35624, now called B. longum 35624) at one tested amount beat placebo for abdominal pain and a symptom score over 4 weeks.
Supplements: Result belongs to this strain, population and amount. NCCIH says definite conclusions on strains for IBS are not possible.
Stool frequency in chronic constipation (B. lactis)
Preliminary or mixedA meta-analysis of 30 trials in adults with chronic constipation found B. lactis significantly increased stool frequency.
Supplements: Authors urge caution because of high heterogeneity and risk of bias; it does not show which product or amount works.
Memory test scores in older adults (B. breve A1)
Preliminary or mixedIn one 16-week trial of 80 older adults with suspected mild cognitive impairment, B. breve A1 improved a memory test score more than placebo.
Supplements: Single small trial; not enough to say it helps memory in general.
Living organisms that pass through the gut
Not enough evidenceBifidobacterium is a genus of bacteria used in probiotic products; each strain has its own research.
Supplements: No general benefit of the genus is established.
Immune or general gut health claims
Not enough evidenceMarketing often says bifidobacteria boost immunity or gut health in general.
Supplements: NHS says the evidence for probiotics is limited and there is little evidence for many health claims.
Connected topics
Open a group to see how each topic connects and how strong the evidence is.
Health goals (2)
- Digestive SupportPreliminary or mixed
B. lactis increased stool frequency in a meta-analysis of adults with chronic constipation, with high heterogeneity and risk of bias. This does not apply to other strains or to a product that was not tested.
- Gut HealthPreliminary or mixed
Some Bifidobacterium strains have been tested for bowel symptoms: B. infantis 35624 in women with IBS and B. lactis for stool frequency in adults with constipation. Results depend on the strain, and the evidence is mixed and limited.
Body systems (3)
- Digestive SystemPreliminary or mixed
Bifidobacterium lactis showed an effect on stool frequency in adults with constipation, and B. infantis 35624 helped IBS symptoms at one tested amount in women. Evidence is limited and strain-specific.
- Gut HealthPreliminary or mixed
The trials of Bifidobacterium strains are about bowel symptoms (IBS pain, constipation). Findings are strain-specific and mixed.
- Immune SystemDocumented risk
People with weakened immunity or severe illness have a higher chance of serious side effects from probiotics, and severe or fatal infections have been reported in premature infants. Ask a clinician first.
Body parts (1)
- GutPreliminary or mixed
Bifidobacterium strains are used in the gut, where small trials looked at IBS symptoms and constipation. Results are strain-specific and mixed.
Functional actions (1)
- Digestive SupportPreliminary or mixed
B. lactis increased stool frequency in adults with chronic constipation in a meta-analysis, with high heterogeneity and risk of bias. Other strains were not shown to do the same.
Conditions & symptoms (3)
- Chronic ConstipationPreliminary or mixed
The meta-analysis covered adults with chronic constipation; benefit was for B. lactis only and quality was limited.
- ConstipationPreliminary or mixed
B. lactis increased stool frequency in adults with chronic constipation in a meta-analysis, with high heterogeneity and risk of bias.
- Irritable Bowel SyndromePreliminary or mixed
B. infantis 35624 helped abdominal pain at one tested amount in 362 women in one trial; NCCIH says definite conclusions on which strains help are not possible.
Documented risks and interactions (2)
- Caution with weakened immunity, severe illness and premature infants. People with weakened immune systems or severe illness should ask a doctor first, and severe or fatal infections have been reported in premature infants given probiotics.
- Product contents may differ from the label. Some probiotic products contain organisms not listed on the label, and NHS notes that labels may not reliably reflect the bacteria or amount.
Names you will see
A probiotic strain is identified by genus, species, subspecies (if any) and a letter-and-number strain code. [2] Names have moved over time:- A 2026 review writes Bifidobacterium longum (formerly Bifidobacterium infantis) 35624. [3] WGO calls the same code B. longum subsp. longum 35624. [2] Older papers still say B. infantis 35624.
- WGO writes B. animalis subsp. lactis where trials and reviews often say B. lactis. [4][5]
For the wider naming picture see strain names and taxonomy changes.
Evidence labels used below: promising but limited, mixed, insufficient evidence, preclinical. Each label is our plain summary of the source, not the source's own grade.
What was found, strain by strain
| Strain (as named in the source) | Who and how long | What the source found | Label |
|---|---|---|---|
| B. infantis 35624 (now B. longum 35624) | 362 women with IBS in primary care; 4 weeks; three amounts against placebo | At 1 x 10^8 the strain beat placebo for abdominal pain and the composite score; the 1 x 10^6 and 1 x 10^10 amounts did not differ from placebo. [6] | Mixed |
| Same strain, pooled | Five trials, meta-analysis (2017) | Single-strain B. infantis did not change pain, bloating or bowel-habit satisfaction; products that combined it with other organisms did. [7] | Mixed |
| B. lactis (group) | 30 trials of probiotics in adults with chronic constipation, review of trials to 2022 | B. lactis had a significant effect on stool frequency; mixtures of probiotics did not. The authors cautioned about high heterogeneity and risk of bias. [5] | Promising but limited |
| B. animalis subsp. lactis HN019 | One trial, adults with fewer than 3 bowel movements a week | WGO lists increased bowel-movement frequency (single trial, its level 3). [4] | Promising but limited |
| B. longum BB536 | 80 older adults (mean age 77.9), chronic constipation, up to 4 weeks, 5 x 10^10 CFU | The main score was not significant (P = 0.074); the stool-frequency subscale was better than placebo. [8] | Mixed |
| B. breve Bif195 | Healthy volunteers taking low-dose aspirin | WGO lists fewer small-bowel injuries (single trial). [4] | Promising but limited |
| B. breve A1 (MCC1274) | 80 older adults with suspected mild cognitive impairment, 16 weeks | A memory test score improved against placebo. This is outside the gut, from one trial. [9] | Promising but limited |
A strain's result stays with that strain. Many positive trials used mixtures that include a bifidobacterium; those results belong to the mixture. WGO warns against combining different strains without a reason when making recommendations. [2]
Why certainty is modest
- The American Gastroenterological Association (AGA, 2020) said that for IBS trials of individual probiotics the certainty of evidence was low or very low. [10]
- WGO's tables list only positive trials; null trials were not included. [4] A table of "what worked" therefore overstates the picture.
- WGO notes there is no comparative evidence to rank products. [2] Proper evidence not found for a head-to-head ranking of bifidobacteria strains (searched: WGO guideline, AGA review, PubMed).
Amounts used in studies
The IBS trial above tested 1 x 10^6, 1 x 10^8 and 1 x 10^10; the highest amount did no better than placebo and had formulation problems. [6] WGO says no general dose can be stated and that dose should rest on human studies of the specific product. [2] These are study amounts, not advice.Frequently asked questions
Is Bifidobacterium infantis the same as Bifidobacterium longum?
For the 35624 strain, a 2026 review calls it B. longum (formerly B. infantis) and WGO calls it B. longum subsp. longum. [3][2] Other B. infantis strains are different strains and need their own evidence.
Does Bifidobacterium lactis help constipation?
A 2022 review found a significant effect of B. lactis on stool frequency in adults, with high heterogeneity and risk of bias. [5] It does not say which product or amount suits any person.
Do all bifidobacteria work the same way?
No. NCCIH and WGO both say effects depend on the specific strain. [1][2]
Are bifidobacteria safe?
WGO describes a good safety record for Bifidobacterium species in generally healthy people, with caution for weakened immunity and serious illness. [2]
Can babies take Bifidobacterium?
Infant use is a separate question. NCCIH reports FDA's 2023 warning about premature infants, so ask the baby's pediatric team. [1]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Safety and who should ask first
- WGO describes the safety record of Bifidobacterium species as similar to lactobacilli, but says people with weakened immunity or serious illness should use only strains and indications with proven safety for them. [2]
- NCCIH says the risk of harm is greater in severe illness or weakened immunity, that severe or fatal infections were reported in premature infants (FDA warned clinicians in 2023), and that some products contain organisms not on the label. [1]
- The NHS advises talking to a doctor first if you have an existing condition or a weakened immune system. [11]
- Medicine interactions, pregnancy, kidney or liver disease and surgery are not described for these strains in the sources we read. Ask a clinician or pharmacist; see medication interactions, pregnancy and breastfeeding and supplements before surgery.
- Product quality varies; see quality testing and certifications.
- Bloody diarrhea, diarrhea lasting more than 7 days, signs of dehydration or a sick infant need medical care first. [12]
References
- NCCIH (US National Center for Complementary and Integrative Health). Probiotics: Usefulness and Safety. Read 2026-10-22.
- World Gastroenterology Organisation. WGO Global Guideline: Probiotics and prebiotics. February 2023. Read 2026-10-22.
- Strain-Specific Systematic Review with Meta-Analysis of Probiotics Efficacy in the Treatment of Irritable Bowel Syndrome (J Clin Med 2026). PMID 41682832. Read 2026-10-22.
- World Gastroenterology Organisation. WGO Global Guideline: Probiotics and prebiotics, 2023 PDF edition, Tables 7 to 9. February 2023. Read 2026-10-22.
- Probiotics and synbiotics in chronic constipation in adults: A systematic review and meta-analysis of randomized controlled trials (van der Schoot A et al. Clin Nutr 2022). PMID 36372047. Read 2026-10-22.
- Efficacy of an encapsulated probiotic Bifidobacterium infantis 35624 in women with irritable bowel syndrome (Whorwell PJ et al. Am J Gastroenterol 2006). PMID 16863564. Read 2026-10-22.
- Efficacy of Bifidobacterium infantis 35624 in patients with irritable bowel syndrome: a meta-analysis (Yuan F et al. Curr Med Res Opin 2017). PMID 28166427. Read 2026-10-22.
- Usefulness of Bifidobacterium longum BB536 in Elderly Individuals With Chronic Constipation: A Randomized Controlled Trial (Takeda T et al. Am J Gastroenterol 2023). PMID 36216361. Read 2026-10-22.
- Probiotic Bifidobacterium breve in Improving Cognitive Functions of Older Adults with Suspected Mild Cognitive Impairment: A Randomized, Double-Blind, Placebo-Controlled Trial (Xiao J et al. J Alzheimers Dis 2020). PMID 32623402. Read 2026-10-22.
- Preidis GA et al. AGA Technical Review on the Role of Probiotics in the Management of Gastrointestinal Disorders. Gastroenterology 2020 (full text read via PMC8018518). PMID 32531292. Read 2026-10-22.
- NHS (UK). Probiotics. Page last reviewed 24 November 2022. Read 2026-10-22.
- NHS (UK). Diarrhoea and vomiting. Read 2026-10-23.