Bifidobacterium lactis: What It Is & What Research Shows
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Bifidobacterium lactis: What It Is & What Research Shows
Key Takeaways
- Bifidobacterium lactis (full name Bifidobacterium animalis subsp. lactis) is a rod-shaped gut bacterium and one of the most widely used and studied probiotic organisms.
- It copes with acid and oxygen better than most bifidobacteria, making it practical to add to yoghurts and supplements.
- Research is strain-specific. A result from one B. lactis strain does not automatically apply to another.
- Placebo-controlled trials have looked at three areas: gut transit time, upper respiratory illness in active adults and bloating.
- Results from individual studies are promising but are not proof that any product will work for you. Speak to a GP or pharmacist if you have ongoing gut symptoms.
What is Bifidobacterium lactis?
Bifidobacterium lactis is a friendly, lactic-acid-producing bacterium that lives naturally in the human large intestine. It belongs to the Bifidobacterium genus, one of the main groups of bacteria in a healthy adult and infant gut.
Scientists first described it in 1997 after isolating it from fermented milk. In 2004 it was reclassified as a subspecies of Bifidobacterium animalis. That is why you will see it written as Bifidobacterium animalis subsp. lactis, B. animalis lactis or simply B. lactis on labels and in research. All three names refer to the same organism.
Under a microscope it is a small, rod-shaped bacterium that does not move or form spores. Like other bifidobacteria, it breaks down carbohydrates in the gut and produces lactic acid and acetic acid.
Why is B. lactis so widely used?
B. lactis is one of the most commonly used bifidobacteria because it is unusually hardy. Most bifidobacteria are sensitive to oxygen and acid, which makes them hard to keep alive in foods and capsules. B. lactis tolerates both better, so it survives manufacturing, storage and the journey through the stomach more reliably.
That robustness is also why it has been studied so extensively. Several individual B. lactis strains have each been tested in multiple human clinical trials, building a body of evidence that few other probiotic species can match.
Is Bifidobacterium lactis a probiotic?
B. lactis is a bacterium, not automatically a probiotic. Scientists use the word "probiotic" for live microorganisms that have been shown to benefit health when taken in adequate amounts, and that evidence belongs to specific strains. Many B. lactis strains are used in food supplements and fermented foods because individual strains have been tested in this way.
Why does the strain matter?
In probiotic research the strain, not the species, is what gets tested. A study result describes one specific strain at one specific dose, in one group of people.
"Think of it like dog breeds. A greyhound and a bulldog are both dogs, but you would not expect them to run the same race. Strains of B. lactis share a name but can differ in their genes, in how they interact with the gut, and in what they have been studied for."
This matters when you read health headlines or product labels. Before assuming a finding applies to you, ask:
- Which strain was tested? Look for the strain code after the species name.
- At what dose? Doses are given in colony-forming units (CFU), often billions per day.
- For how long, and in whom? A 2-week study in healthy adults tells you something different from a 6-month study in people with a diagnosed condition.
- Was it compared with a placebo? Randomised, double-blind, placebo-controlled trials give the most reliable answers.
What has research on B. lactis found?
Three placebo-controlled trials of B. lactis strains have examined gut transit time, colds in active adults, and bloating. Each found a measurable difference compared with placebo.
| Area | Who took part | Duration | Key finding |
|---|---|---|---|
| Gut transit time (Waller et al., 2011) | 100 adults, avg age 44 | 14 days | Transit time 25% to 33% faster than at the start; no change with placebo |
| Active lifestyles (West et al., 2014) | 465 physically active adults, avg age 35 | 150 days | 27% lower risk of upper respiratory illness vs. placebo |
| Bloating (Ringel-Kulka et al., 2011) | 60 adults with functional bowel disorders | 8 weeks | Lower bloating scores than placebo at 4 and 8 weeks |
Gut transit time: does B. lactis help digestion move along?
In a 2011 trial, adults taking a B. lactis strain had a faster whole-gut transit time after 14 days, and the effect was larger at the higher dose. Transit time is how long food takes to travel from mouth to exit; slow transit is linked with constipation and feeling sluggish.
Waller et al. (2011) — Gut Transit Time
Three groups: high-dose (17.2 billion CFU/day), low-dose (1.8 billion CFU/day), or placebo. Neither participants nor researchers knew who was taking what.
- Transit time improved by 33% in the high-dose group and 25% in the low-dose group. No change in the placebo group.
- Participants in both probiotic groups also reported fewer occasional digestive symptoms, including abdominal pain, flatulence and constipation.
- Some symptoms also improved in the placebo group, which is common in gut studies and is why a placebo comparison matters.
A 2021 review of the same strain found shorter transit in several trials but mixed results in others, and called for larger studies (Cheng et al., 2021).
Active lifestyles: can B. lactis support you through training?
In a 150-day trial, physically active adults taking a B. lactis strain had a 27% lower risk of an upper respiratory illness (such as a cold) than those taking a placebo. Regular hard training can leave people more prone to these illnesses, so this group is often studied.
West et al. (2014) — Active Adults & Upper Respiratory Illness
Researchers at Griffith University in Australia randomly assigned participants to one of three daily interventions:
- A single B. lactis strain (2 billion CFU)
- A combination of a different B. lactis strain with Lactobacillus acidophilus (5 billion CFU)
- A placebo
The single B. lactis strain cut the risk of an upper respiratory illness by 27% compared with placebo. This result was statistically significant. The combination showed a 19% lower risk, but this did not reach statistical significance. In both probiotic groups, the first illness tended to arrive later than with placebo: about 0.7 months later for the single strain and 0.9 months later for the combination.
This is one of the larger B. lactis trials in everyday healthy adults. The result came from one strain, in one population, over five months.
Bloating: what did the research find?
In an 8-week trial, adults with functional bowel complaints who took a B. lactis strain combined with Lactobacillus acidophilus rated their bloating as milder than those on a placebo. Bloating is one of the most common gut complaints and often has no single clear cause.
Ringel-Kulka et al. (2011) - Bloating in Functional Bowel Disorders
Researchers at the University of North Carolina recruited adults with functional bowel disorders including IBS, but without constipation. Half took the two-strain combination (200 billion CFU/day); half took a placebo. Participants scored their bloating on a seven-point scale.
- Bloating scores were lower in the probiotic group than in the placebo group at 4 weeks and again at 8 weeks.
- The benefit appeared early and lasted to the end of the study.
This was a small study that tested two strains together, so the effect cannot be put down to B. lactis alone. It is still one of the few trials to make bloating its primary outcome.
What else is B. lactis being studied for?
Beyond these three trials, researchers are exploring B. lactis strains in several other areas. The evidence here is earlier-stage or mixed, so treat it as "being explored" rather than "established".
- The gut microbiome. Some strains have been linked to higher levels of other beneficial bacteria, such as bifidobacteria and lactobacilli, in older adults.
- Gut barrier and infections. Laboratory and animal studies, plus one large trial in India, suggest some strains may help the gut lining resist harmful microbes.
- Ageing and immunity. Some trials in older adults have examined markers of immune function, which naturally decline with age.
- IBS symptoms and body composition. Other individual strains have been studied for IBS symptom severity and abdominal fat.
Most of these areas still need larger, independent trials before firm conclusions can be drawn.
Where can you get Bifidobacterium lactis?
You can find B. lactis in some fermented dairy foods and in food supplements. It also lives naturally in many people's guts. It grows well in milk, which is why it is a common culture in "bio" yoghurts and other fermented dairy products.
Foods that may contain B. lactis:
- Live or "bio" yoghurts, including some Greek-style yoghurts
- Buttermilk
- Some cheeses and cottage cheese
- Some kefirs and fermented milk drinks
Not every yoghurt or kefir contains it. Check the label for "Bifidobacterium lactis", "B. lactis" or "bifidus". Food labels rarely give the strain or the amount, which makes it difficult to compare with the doses used in studies.
How can you increase bifidobacteria in your gut?
The most reliable everyday way to support bifidobacteria is to feed them fibre. Bifidobacteria thrive on prebiotic fibres such as inulin and fructo-oligosaccharides (FOS). These are found in onions, garlic, leeks, asparagus, chicory root, bananas, oats and pulses. A varied, plant-rich diet, alongside fermented foods, gives your gut bacteria more to work with.
What to look for in a B. lactis supplement
Supplement checklist
- The strain is named, not just the species, so you can see which research applies to it
- The CFU count is stated and guaranteed until the end of shelf life, not just at manufacture
- The dose is in the range used in studies (the trials above used 1.8 billion to 200 billion CFU/day)
- Storage instructions are clear (some products need refrigeration; others are shelf-stable)
- There is information on testing and quality, such as where it is made and to what standards
Explore our probiotic supplements
The NDS probiotic range includes a variety of multi-strain formulations containing Bifidobacterium lactis alongside other well-researched strains, manufactured to GMP standards.
View the rangeIs Bifidobacterium lactis safe?
B. lactis has a long record of safe use in foods and is well tolerated by most healthy people. The European Food Safety Authority includes B. animalis on its Qualified Presumption of Safety (QPS) list for use in the food chain. A 2021 review of one widely studied strain found no safety concerns across 42 published studies.
Possible side effects. When people start a probiotic, some notice mild wind, bloating or a change in bowel habit for the first few days. This usually settles as the gut adjusts.
Speak to a GP or pharmacist before taking a probiotic if you:
- Have a weakened immune system, for example from chemotherapy or immunosuppressant medicines
- Are seriously ill, recovering from surgery, or have a central line or catheter
- Are pregnant or breastfeeding
- Want to give a probiotic to a baby, especially one born prematurely
- Take regular medicines or have a long-term condition
Do not use a supplement to manage persistent symptoms. See your GP if you have a change in bowel habit lasting more than three weeks, blood in your stool, unexplained weight loss, or ongoing abdominal pain.
Frequently Asked Questions
References
- 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. Scand J Gastroenterol. 2011. doi:10.3109/00365521.2011.584895
- West NP, Horn PL, Pyne DB, et al. Probiotic supplementation for respiratory and gastrointestinal illness symptoms in healthy physically active individuals. Clinical Nutrition. 2014. doi:10.1016/j.clnu.2013.10.002
- Ringel Y, Ringel-Kulka T, Maier D, et al. Probiotic bacteria Lactobacillus acidophilus NCFM and Bifidobacterium lactis Bi-07 versus placebo for the symptoms of bloating in patients with functional bowel disorders: a double-blind study. J Clin Gastroenterol. 2011. doi:10.1097/MCG.0b013e31820ca4d6
- Cheng J, Laitila A, Ouwehand AC. Bifidobacterium animalis subsp. lactis HN019 effects on gut health: a review. Front Nutr. 2021;8:790561. doi:10.3389/fnut.2021.790561
- Bifidobacterium animalis subsp. lactis. Wikipedia, accessed 25 October 2026. View article