Bifidobacterium animalis subsp. lactis

What it is

Bifidobacterium animalis subsp. lactis is a species of Bifidobacterium used in probiotics; BB-12 and HN019 are two separate commercial strains with separate evidence. BB-12 was deposited in a dairy culture collection in 1983 and is used in supplements, infant formula and fermented dairy products.

What the research says

One large trial funded by the strain's maker found BB-12 raised average bowel movement frequency in adults with infrequent stools, but its pre-specified main test was not statistically significant and abdominal discomfort did not improve. For HN019, a 2024 trial found no meaningful difference from placebo for complete bowel movements in constipation. Safety studies in healthy adults found no excess adverse events, but product labels often do not match the bifidobacteria actually inside.

Evidence grade: Limited evidence.

What goes wrong

DNA testing of 16 commercial bifidobacterial probiotics found contents often differed from labels, sometimes at the subspecies level; only one matched its label in all samples. (Source 1)

• Survey study, Low certainty.
• Size: 16 products.
• Who: Commercial probiotic products.
• How long: n/a.
• Result: 1 of 16 products matched label claims across samples (per summary)
• Funding: Not stated in recorded text.

the contents of many bifidobacterial probiotic products differ from the ingredient list, sometimes at a subspecies level.

Related-species harm: bloodstream Bifidobacterium infection has been reported in very low birth weight preterm infants given a different species (B. longum subsp. infantis); cases are few, the infants recovered, and none here involved B. animalis subsp. lactis. (Source 2)

• Case report, Very low certainty.
• Size: One new case plus six in prior reports.
• Who: Extremely/very low birth weight preterm infants.
• How long: n/a.
• Result: n/a.
• Funding: Not stated.

only three previous case reports of B. longum subsp. infantis sepsis or bacteraemia have been published, comprising a total of six very low birth weight (<1500 g) preterm infants, all of whom also fully recovered.

Class caution: in the PROPATRIA trial of 298 patients with predicted severe acute pancreatitis, a multispecies probiotic given enterally did not reduce infections and more patients died (24 (16%) vs 9 (6%)); the product was a different multispecies mix, so this is a warning about critically ill patients, not evidence about this strain. (Source 3)

• Randomized trial, Moderate certainty.
• Size: 296 analysed (152 probiotic, 144 placebo)
• Who: Adults with predicted severe acute pancreatitis in Dutch hospitals.
• How long: 28 days of treatment; 90-day follow-up.
• Result: Deaths 24 (16%) vs 9 (6%); relative risk 2·53, 95% CI 1·22–5·25.
• Funding: Not stated in recorded text.

24 (16%) patients in the probiotics group died, compared with nine (6%) in the placebo group (relative risk 2·53, 95% CI 1·22–5·25)

In a study of people and mice given antibiotics, a multi-strain probiotic delayed the return of the person's own gut bacteria compared with no treatment; this was a small mechanistic study of one multi-strain product, not of this strain specifically. (Source 4)

• Randomized trial, Low certainty.
• Size: Small human cohort plus mice (exact numbers not in abstract text recorded)
• Who: Healthy human volunteers and mice after broad-spectrum antibiotics.
• How long: Weeks of follow-up after antibiotics.
• Result: Qualitative: 'markedly delayed and persistently incomplete' microbiome reconstitution with probiotics versus spontaneous recovery.
• Funding: Not stated in recorded text.

Compared to spontaneous post-antibiotic recovery, probiotics induced a markedly delayed and persistently incomplete indigenous stool/mucosal microbiome reconstitution

What the evidence supports

A small safety trial found no difference in adverse events between BB-12 yogurt and control in healthy adults taking antibiotics. (Source 5)

• Randomized trial, Low certainty.
• Size: 40 adults.
• Who: Healthy adults on antibiotics.
• How long: Not given in recorded text.
• Result: 165 non-serious adverse events, no between-group differences.
• Funding: Not stated in recorded text.

A total of 165 non-serious adverse events were reported, with no differences between the control and BB-12 groups.

What the evidence does not support

The same BB-12 trial's pre-specified defecation-frequency end point was not statistically significant. (Source 6)

• Randomized trial, Moderate certainty.
• Size: 1248 adults.
• Who: Healthy adults with low defecation frequency and abdominal discomfort.
• How long: 4 weeks.
• Result: OR 1·31 (95% CI 0·98, 1·75), P=0·071.
• Funding: Industry-funded (funded in full by Chr. Hansen A/S)

The OR for having a defecation frequency above baseline for ≥50 % of the time was 1·31 (95 % CI 0·98, 1·75), P=0·071, for probiotic treatment overall.

In the same trial, BB-12 did not significantly improve abdominal discomfort. (Source 6)

• Randomized trial, Moderate certainty.
• Size: 1248 adults.
• Who: Healthy adults with low defecation frequency and abdominal discomfort.
• How long: 4 weeks.
• Result: No significant difference.
• Funding: Industry-funded (Chr. Hansen A/S)

GI well-being, defined as global relief of abdominal discomfort, did not show significant differences.

In a 2024 triple-blind trial of 229 people with constipation, complete spontaneous bowel movements improved in both the HN019 and placebo groups, with no meaningful difference between them. (Source 7)

• Randomized trial, Moderate certainty.
• Size: 229 randomised (117 placebo, 112 HN019)
• Who: Adults with functional constipation.
• How long: 8 weeks.
• Result: No meaningful difference between groups in CSBMs (the Key Points give no numbers)
• Funding: Not stated in recorded text.

demonstrated that CSBMs were improved in both the placebo and HN019 groups, with no meaningful differences between groups.

A review by the strain maker's scientists reports that BB-12 alone had no effect on cholesterol in young healthy adults or in people newly diagnosed with type 2 diabetes or pre-diabetes. (Source 8)

• Systematic review, Low certainty.
• Size: Not given.
• Who: Young healthy adults.
• How long: Not given.
• Result: No impact on cholesterol.
• Funding: Industry authors (Novonesis)

In the clinical studies where individuals were supplemented with the BB-12 strain alone, no impact was seen on the cholesterol levels of young healthy adults or in newly diagnosed individuals with type 2 diabetes or pre-diabetes.

Where the evidence is mixed

In a large trial fully funded by the strain's maker, 4 weeks of BB-12 did not significantly improve the pre-specified defecation-frequency end point, though average weekly defecation frequency was higher than with placebo and a stricter post hoc responder analysis was positive. (Source 6)

• Randomized trial, Moderate certainty.
• Size: 1248 adults.
• Who: Healthy adults with low defecation frequency and abdominal discomfort.
• How long: 4 weeks.
• Result: Primary responder end point OR 1·31 (95% CI 0·98, 1·75), P=0·071 (not significant); average defecation frequency P=0·0065; post hoc stricter responder OR 1·55 (95% CI 1·22, 1·96), P=0·0003.
• Funding: Industry-funded (funded in full by Chr. Hansen A/S)

Limit of this finding: The trial's pre-specified main test (a defecation frequency above baseline for at least half the time) was not statistically significant: OR 1·31, 95% CI 0·98 to 1·75, P=0·071. The often-quoted OR 1·55 (P=0·0003) comes from a stricter responder definition that the paper's results section describes as a post hoc analysis, and the authors' 'clinically relevant benefit' conclusion leans on that and on average weekly frequency. Read this as a possible small effect on how often people open their bowels, from one trial fully funded by the strain's maker, not as a proven benefit.

A treatment effect on average defecation frequency was found (P=0·0065), with the frequency being significantly higher compared with placebo at all weeks for probiotic treatment overall (all P<0·05).

Where the research disagrees

Does B. animalis subsp. lactis help constipation?

• Eskesen et al. 2015 (BB-12; funded by Chr. Hansen), RCT, 1248 adults; pre-specified primary defecation end point not significant (OR 1·31, P=0·071); authors' conclusion rests on average frequency and a post hoc responder analysis: 4 weeks' supplementation with the probiotic strain BB-12® resulted in a clinically relevant benefit on defecation frequency. (Source 6)
• Cheng et al. 2024 (HN019), triple-blind RCT, 229 adults: Daily consumption of B lactis HN019 at the tested dose of 4.69 × 10⁹ CFU did not outperform placebo to increase CSBMs. (Source 7)

How much

• Reference intake: No recommended intake exists; this is not a nutrient. In the US, BB-12 has GRAS status; in the EU the species has QPS status (a safety presumption, not an intake). (Source 8)
• Upper limit: No upper limit has been set by any body we found. (Source 8)
• Studied: BB-12: 1 or 10 billion CFU a day in capsules for 4 weeks. (Source 6)
• Studied: HN019: at least 4.69 × 10⁹ colony-forming units a day for 8 weeks. (Source 7)

A common belief, and what the research shows

The belief: Any B. lactis product works the same way, and the label tells you what's inside.

What the research shows: The two main strains have different results (BB-12 mixed in one industry-funded trial whose main pre-specified test was not significant; HN019 null in a 2024 trial), and a DNA study found that 'the contents of many bifidobacterial probiotic products differ from the ingredient list, sometimes at a subspecies level.'

Questions and answers

What is it?

A probiotic bacterium; BB-12 and HN019 are separate named strains. BB-12 came from a dairy culture collection and is used in supplements, infant formula and fermented dairy. (Source 8)

What does it do in the body?

In one large trial funded by its maker, BB-12 raised average weekly bowel-movement frequency in people with infrequent stools, but the trial's pre-specified main test was not statistically significant and discomfort did not improve. HN019 did not beat placebo in a 2024 constipation trial. (Source 6)

Is it good or bad for you?

Generally regarded as safe for healthy people: US GRAS status for BB-12 and EU QPS status for the species. Benefits are modest and strain-specific; caution about probiotics in critically ill people applies across the class. (Source 8)

How do you get more of it?

In studies, people took capsules (BB-12, 1 or 10 billion CFU a day for 4 weeks) or ate BB-12-supplemented yogurt. This describes what was studied only. (Source 6)

If it is harmful, what reduces it?

Does not apply for healthy people; it is not considered harmful, and a 40-person safety study in healthy adults taking antibiotics found no excess adverse events. (Source 5)

Why might someone be low in it or missing it?

These are commercial strains, so most people only carry them after consuming them. Antibiotics disturb gut bacteria generally; one study found a multi-strain probiotic slowed recovery of the native microbiome afterwards. (Source 4)

Which whole foods contain it or feed it?

BB-12 is added to some fermented dairy products and infant formula as well as supplements. (Source 8)

What happens if you do not have it?

No study we found shows harm from lacking these specific strains. (Source 8)

We searched: Searched for consequences of absence of BB-12/HN019; none found. Closest source is the Collins 2025 review.

How can you test for it?

No validated consumer test was found. Labs can check strain identity in products with DNA methods, and such checks show labels are often wrong. (Source 1)

References

1. Pediatric Research. Validating bifidobacterial species and subspecies identity in commercial probiotic products. 2016. DOI 10.1038/pr.2015.244. Read the source
2. Anaerobe. Bifidobacterium bacteraemia is rare with routine probiotics use in preterm infants: A further case report with literature review. 2023. DOI 10.1016/j.anaerobe.2023.102713. Read the source
3. The Lancet. Probiotic prophylaxis in predicted severe acute pancreatitis: a randomised, double-blind, placebo-controlled trial. 2008. PMID 18279948, DOI 10.1016/S0140-6736(08)60207-X. Read the source
4. Cell. Post-Antibiotic Gut Mucosal Microbiome Reconstitution Is Impaired by Probiotics and Improved by Autologous FMT. 2018. PMID 30193113, DOI 10.1016/j.cell.2018.08.047. Read the source
5. Gut Microbes. Safety of Bifidobacterium animalis subsp. lactis (B. lactis) strain BB-12-supplemented yogurt in healthy adults on antibiotics: a phase I safety study. 2015. PMID 25569274, DOI 10.1080/19490976.2015.1005484. Read the source
6. British Journal of Nutrition. Effect of the probiotic strain Bifidobacterium animalis subsp. lactis, BB-12, on defecation frequency in healthy subjects with low defecation frequency and abdominal discomfort: a randomised, double-blind, placebo-controlled, parallel-group trial. 2015. PMID 26382580, DOI 10.1017/S0007114515003347. Read the source
7. JAMA Network Open. Eight-Week Supplementation With Bifidobacterium lactis HN019 and Functional Constipation: A Randomized Clinical Trial. 2024. PMID 39356506, DOI 10.1001/jamanetworkopen.2024.36888. Read the source
8. Frontiers in Microbiology. Understanding the probiotic health benefits of Bifidobacterium animalis subsp. lactis, BB-12. 2025. DOI 10.3389/fmicb.2025.1605044. Read the source