Moderate evidenceGut health

Bifidobacterium Lactis (BB-12/HN019)

One of the most studied probiotic species. HN019 speeds up gut transit in constipated adults in dose-ranging and multicenter trials; the effect is consistent but measured in hours, not days.

Evidence last reviewed: August 2026

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What the science says

Faster colonic transit Moderate evidence
A double-blind, randomized, dose-ranging trial found that 28 days of B. lactis HN019 shortened colonic transit time in adults with functional constipation and reduced some GI symptoms. A meta-analysis of randomized trials confirms that probiotic supplementation shortens intestinal transit by roughly half a day on average, with bifidobacteria among the better performers.
Functional constipation symptoms Moderate evidence
A multi-center, triple-blind, randomized, placebo-controlled trial of 8 weeks of HN019 in functional constipation reported improvement in bowel habit outcomes, though effect sizes were modest.
Immune markers Limited evidence
Trials in older adults report increases in phagocytic activity and other laboratory immune measures, without demonstrating fewer infections.

Dosage & safety

Studied doseTransit-time trials used 1.8 billion or 17.2 billion CFU per day of HN019, with both doses working. BB-12 products typically supply 1–10 billion CFU per day.

SafetyAmong the best-documented probiotics for safety, with adverse events comparable to placebo in systematic reviews. Mild gas at the start. Standard caution applies for severely immunocompromised or critically ill patients.

Scientific references

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
Ibarra A, Latreille-Barbier M, Donazzolo Y, Pelletier X, Ouwehand AC — Gut Microbes, 2018
Probiotic supplementation decreases intestinal transit time: meta-analysis of randomized controlled trials
Miller LE, Ouwehand AC — World J Gastroenterol, 2013
Effect of an 8-Week Bifidobacterium lactis HN019 Supplementation on Functional Constipation: A Multi-Center, Triple-Blind, Randomized, Placebo-Controlled Trial
Ala-Jaakkola R, Forssten SD, Cheng J, Griffon F, Metreau I, Sturm Y, Lecerf JM, Donazzolo Y, Junnila J, Nordlund A, Hibberd A, Ouwehand AC, Ibarra A — Mol Nutr Food Res, 2025

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