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Probiotic strain · 3 human trials behind this page

B. lactis HN019: what the human trials show

Bifidobacterium animalis subsp. lactis HN019

HN019 is the probiotic strain most often sold for constipation and slow digestion. One early trial found it sped up gut transit; two larger, longer trials later missed their main goals, with benefits showing up only in people who had very few bowel movements to begin with.

The studies, one by one

  1. 2011Randomized, placebo-controlled trialFavored the strain

    100 adults with functional digestive symptoms, two doses or placebo for 14 days

    Whole-gut transit time fell in both HN019 groups (in the high-dose group from about 49 to 21 hours) and not with placebo, and most digestive symptoms became less frequent. A short trial, but the clearest positive result for this strain.

    Waller PA, Gopal PK, Leyer GJ, et al. Dose-response effect of Bifidobacterium lactis HN019 on whole gut transit time and functional gastrointestinal symptoms in adults. Scandinavian Journal of Gastroenterology, 2011. PubMed 21663486

  2. 2018Randomized, double-blind, placebo-controlled trialNo difference from placebo

    228 adults with functional constipation, two doses or placebo for 28 days

    No difference from placebo on colonic transit time, the main outcome, or on any secondary outcome. In a later look at the 65 people with three or fewer bowel movements a week, HN019 raised weekly frequency by about two. Well tolerated.

    Ibarra A, Latreille-Barbier M, Donazzolo Y, et al. Effects of 28-day Bifidobacterium animalis subsp. lactis HN019 supplementation on colonic transit time and gastrointestinal symptoms in adults with functional constipation: A double-blind, randomized, placebo-controlled, and dose-ranging trial. Gut Microbes, 2018. PubMed 29227175

  3. 2025Randomized, triple-blind, placebo-controlled trialNo difference from placebo

    Adults with functional constipation at four clinics in France, daily HN019 or placebo for 8 weeks

    HN019 did no better than placebo on complete bowel movements, stool consistency or the other symptoms measured, and stool samples showed no differences. No safety concerns.

    Ala-Jaakkola R, Forssten S, Cheng J, et al. Effect of an 8-Week Bifidobacterium lactis HN019 Supplementation on Functional Constipation: A Multi-Center, Triple-Blind, Randomized, Placebo-Controlled Trial. Molecular Nutrition & Food Research, 2025. PubMed 40320938

What the evidence doesn't show

  • The one clearly positive trial lasted 14 days and enrolled people with digestive symptoms, not diagnosed constipation.
  • The two larger trials in people diagnosed with constipation did not beat placebo on their main outcome.
  • Where HN019 did help, it was in people with three or fewer bowel movements a week, found in a later analysis rather than the planned one.
  • The 2018 trial was run by researchers employed by the strain's manufacturer.

How to find it on a label

HN019 is one strain of Bifidobacterium animalis subspecies lactis, a species found in many yogurts and supplements. The species name alone tells you little: B. lactis Bl-04, BB-12 and DN-173 010 are different strains with different studies behind them. To get the strain these trials tested, look for the code HN019 on the ingredient panel, not just "Bifidobacterium lactis."

Names you may see: B. lactis HN019 · HN019 · Bifidobacterium lactis HN019

Is it in anything we rank?

None of the products on our metabolic probiotic ranking lists this strain. Oweli Probiotic lists Bifidobacterium Lactis (Bl-04): the same species, but a different strain, so these trials don't apply to it.

Related reading

Questions

Does HN019 help constipation?

Possibly, for some people. A 14-day trial found faster gut transit, but two larger trials in adults with diagnosed constipation (28 days and 8 weeks) found no difference from placebo on their main outcome. The best signal was in people with three or fewer bowel movements a week.

How long should I try HN019?

The trials ran 2 to 8 weeks. If nothing has changed after about four weeks, the longer trials suggest more time is unlikely to help. Keep fiber and fluids in place, and see a clinician for new, severe or persistent constipation.

Is B. lactis on any label the same as HN019?

No. HN019 is one strain of B. lactis. Others, such as Bl-04, BB-12 and DN-173 010, have their own studies. Only a label that prints HN019 contains the strain these trials tested.

All probiotic strains · Strain-to-evidence lookup · Medical disclaimer

General information, not medical advice. Probiotic effects are strain-specific and modest; talk to a clinician about new, severe or persistent symptoms.