Lacticaseibacillus paracasei and Lacticaseibacillus casei

What it is

Lacticaseibacillus casei and L. paracasei are closely related lactic acid bacteria in the 'L. casei group', which are hard to tell apart even with genetic methods. Lactobacilli like these live in the human gut and urogenital tract and in fermented foods. The strain on the Garden of Life label, written 'Lcp-37', appears to be the commercial strain L. paracasei Lpc-37 studied in two trials funded by its maker.

What the research says

The evidence is strain-specific and limited. For Lpc-37, one trial of 120 adults missed its primary outcome but reported lower perceived stress in a per-protocol analysis. A larger 190-student trial found no effect on stress, mood or anxiety. For L. casei DN-114 001 (the Actimel strain), a trial in children found 19% fewer common infections (just significant), while a 1,127-patient trial in older hospital patients found no reduction in antibiotic-associated diarrhoea. Rarely, these species cause bloodstream infections and heart valve infections, mostly in seriously ill or immunocompromised people.

Evidence grade: Limited evidence.

What goes wrong

A review of Lactobacillus bacteraemia found L. paracasei among three probiotic organisms matched by molecular methods to blood isolates from infected patients. (Source 1)

• Systematic review, Low certainty.
• Size: Literature review (narrative)
• Who: Patients with Lactobacillus bacteraemia.
• How long: n/a.
• Result: Bacteraemia infrequent; risk factors include severe illness, immune suppression, ICU admission and central lines.
• Funding: not stated on the fetched page.

Three probiotics (Lacticaseibacillus rhamnosus GG, Lactiplantibacillus plantarum, and Lacticaseibacillus paracasei) were directly linked with blood isolates from bacteremia patients using molecular identification assays.

The Kullar et al. review cites an earlier case series by Cannon et al. in which, of 129 Lactobacillus bacteraemia cases, L. casei was the most common species (36%); the strains were not reported. (Source 2)

• Case series, Low certainty.
• Size: 129 cases (Cannon et al., as cited in the review)
• Who: Patients with Lactobacillus bacteraemia.
• How long: n/a.
• Result: L. casei 36%, L. rhamnosus 23% (Cannon et al. data, as summarised in the Kullar et al. review)
• Funding: not stated.

Cannon et al. found that in 129 cases of LB, most were due to Lcb. casei (36%) or Lcb. rhamnosus (23%), but did not report the strains involved.

A 71-year-old woman on long-term steroids who took probiotics developed L. casei endocarditis that needed valve replacement. (Source 3)

• Case report, Very low certainty.
• Size: 1 patient.
• Who: Immunocompromised 71-year-old woman taking probiotics.
• How long: n/a.
• Result: Mitral and aortic vegetations; valve replacement; six weeks of daptomycin; recovered.
• Funding: not stated.

Here we report a rare case of Lactobacillus casei endocarditis in a 71-year-old female, immunocompromised due to chronic steroid intake

A review of 82 published cases of Lactobacillus endocarditis found 17.3% had taken probiotics and overall mortality was 17.1%; L. casei and L. paracasei caused a share of cases. (Source 4)

• Expert review, not systematic, Low certainty.
• Size: 82 patients from 77 studies.
• Who: Published cases of Lactobacillus infective endocarditis.
• How long: n/a.
• Result: Prior probiotics 17.3%; surgery 53.7%; mortality 17.1%.
• Funding: not stated.

A prosthetic valve was present in 16% of patients, and 17.3% had previously been on probiotics.

What the evidence supports

The Sisu trial authors concluded Lpc-37 reduced perceived stress compared with placebo; this rests on the per-protocol population (n = 113) and a secondary outcome in a single manufacturer-sponsored trial whose primary outcome was not met. (Source 5)

• Randomized trial, Low certainty.
• Size: 113 per protocol.
• Who: Healthy adults aged 18-45.
• How long: 5 weeks.
• Result: Perceived stress reduced vs placebo (secondary outcome)
• Funding: industry-funded.

Supporting significant efficacy in the PP population (n = 113), Lpc-37 reduced perceived stress following intervention.

L. casei DN-114 001 in a fermented dairy drink was linked to 19% fewer common infectious illnesses in young children, a borderline result driven by gut infections. (Source 6)

• Randomized trial, Low certainty.
• Size: 638 children.
• Who: Children aged 3-6 in daycare or school, Washington DC.
• How long: 90 days.
• Result: Incidence rate ratio 0.81, 95% CI 0.65 to 0.99 (printed as '099' in the paper), P = 0.046; no difference in behaviour change due to illness.
• Funding: not stated on the fetched page.

Limit of this finding: The paper prints the upper end of the confidence interval as '099'; this is almost certainly a typo for 0.99. Read that way, the interval only just excludes no effect and P = 0.046 is only just under the usual 0.05 threshold, so this is a borderline result from one trial, based on parent-reported illness, and mostly driven by gut infections.

However, the incidence rate for CIDs in the active group (0.0782) is 19% lower than that of the control group (0.0986)

What the evidence does not support

In a larger follow-up trial of 190 students facing exams, Lpc-37 had no effect on anxiety, stress or mood. (Source 7)

• Randomized trial, Moderate certainty.
• Size: 190 students.
• Who: University students aged 18-40 facing examinations.
• How long: 10 weeks.
• Result: STAI-state change vs placebo: estimate 1.03; 95% CI -1.62 to 3.67; p = 0.446; no secondary outcome significant after correction for multiplicity; exploratory (not corrected for multiplicity): Bond Lader VAS-alertness lower with Lpc-37 just before the exam (estimate -3.97; 95% CI -7.78 to -0.15; p = 0.042)
• Funding: industry-funded (Danisco Sweeteners Oy, part of IFF)

In conclusion, probiotic Lpc-37 was safe but had no effect on stress, mood, or anxiety in healthy university students

In a UK trial of hospital patients over 55 on antibiotics (reported as 1,127 randomised; the two groups add to 1,126), a drink with L. casei DN114001 plus the two yogurt cultures did not reduce antibiotic-associated diarrhoea. (Source 8)

• Randomized trial, Moderate certainty.
• Size: 1,127 patients (group sizes 549 + 577 = 1,126)
• Who: Hospital patients over 55 in UK hospitals receiving antibiotics.
• How long: Treatment during antibiotics plus 2 weeks of follow-up.
• Result: AAD 19.3% probiotic vs 17.9% placebo; OR 1.10, 95% CI 0.82-1.49, P = 0.53.
• Funding: not stated on the fetched page.

Limit of this finding: The paper says 1,127 patients were randomised, but its two groups (549 + 577) add up to 1,126, so one patient is unaccounted for in the abstract. This does not change the result (19.3% vs 17.9%, P = 0.53), but readers should treat the total as approximately 1,126 to 1,127. The authors also say changes in antibiotic stewardship and falling C. difficile rates mean the trial cannot rule out a role for the probiotic.

The proportion of patients experiencing AAD during follow-up was 19.3% (106/549) in the probiotic group vs 17.9% (103/577) in the placebo group

Where the evidence is mixed

In 120 healthy adults, Lpc-37 did not meet its primary outcome (heart rate during a stress test), but per-protocol and subgroup analyses reported lower perceived stress. (Source 5)

• Randomized trial, Low certainty.
• Size: 120 randomised; 113 per protocol.
• Who: Healthy adults aged 18-45.
• How long: 5 weeks.
• Result: Primary heart-rate hypothesis not met in ITT or PP; perceived stress lower vs placebo in PP population (n = 113)
• Funding: industry-funded (DuPont Nutrition & Biosciences, Danisco Sweeteners Oy)

The primary hypothesis was not met in either the Intention-to-Treat (ITT) or Per Protocol (PP) population

Where the research disagrees

Whether Lpc-37 reduces stress

• Patterson et al. 2020 (Sisu trial authors, sponsor-funded), RCT, n=120; primary outcome not met, secondary per-protocol result: Overall, Lpc-37 reduced perceived stress compared to placebo. (Source 5)
• Mäkelä et al. 2023 (ChillEx trial authors, sponsor-funded), RCT, n=190; primary outcome null: probiotic Lpc-37 was safe but had no effect on stress, mood, or anxiety in healthy university students (Source 7)

How much

• Reference intake: No recommended intake or upper limit exists: live bacteria are not nutrients, and no body has set an RDA, AI or UL for them. The EU (QPS list) and US (GRAS) treat this group as presumed safe in foods. (Source 9)
• Upper limit: No tolerable upper intake level has been set for any probiotic bacterium. (Source 9)
• Studied: Lpc-37: 1.75 x 10^10 CFU per day for 5 weeks (Sisu trial). (Source 5)
• Studied: Lpc-37: 1.56 x 10^10 CFU per day for 10 weeks (ChillEx trial). (Source 7)
• Studied: L. casei DN-114 001 in a fermented dairy drink daily for 90 days (DRINK trial). (Source 6)

A common belief, and what the research shows

The belief: A probiotic strain that helped stress in one trial is proven to reduce stress.

What the research shows: The first Lpc-37 trial missed its primary outcome ('The primary hypothesis was not met in either the Intention-to-Treat (ITT) or Per Protocol (PP) population'), and the larger follow-up found Lpc-37 'had no effect on stress, mood, or anxiety in healthy university students'.

Questions and answers

What is it?

These are lactic acid bacteria from the 'L. casei group'. They are so closely related that telling the species apart is difficult. Lpc-37 is one commercial strain of L. paracasei. (Source 10)

What does it do in the body?

Effects depend on the strain. For Lpc-37 the trials conflict: a 190-student trial found no effect on stress, mood or anxiety. For L. casei DN-114 001, results ranged from a borderline reduction in children's infections to no effect on antibiotic diarrhoea in older patients. (Source 7)

Is it good or bad for you?

Trials in healthy people report side effects similar to placebo. In seriously ill or immunocompromised people these species occasionally cause bloodstream infections, and L. paracasei is one of three probiotic organisms genetically matched to such infections. (Source 1)

How do you get more of it?

In studies, people got these bacteria from fermented dairy drinks and from capsules. The group also occurs naturally in fermented foods. (Source 9)

If it is harmful, what reduces it?

Generally does not apply, because these bacteria are not harmful in healthy people. When they cause bloodstream or heart valve infection, doctors treat it with antibiotics; in the published endocarditis cases, aminoglycosides and penicillin were used most often. (Source 4)

Why might someone be low in it or missing it?

No study we found links low levels of L. casei or L. paracasei in particular to a cause. Lactobacilli normally live in the gut and urogenital tract, but the literature we searched does not say what depletes these species specifically. (Source 9)

We searched: WebSearch on L. paracasei ecology and the L. casei group review; no human study on causes of depletion of these species was found

Which whole foods contain it or feed it?

Lactobacilli occur in fruit and vegetables and in naturally fermented foods. Commercial fermented milk drinks carry specific strains such as DN-114 001. (Source 9)

What happens if you do not have it?

No study we found shows harm from not carrying these species. Supplementing Lpc-37 in healthy students changed neither stress nor gut microbiota diversity compared with placebo. (Source 7)

We searched: Searched for consequences of absence of L. casei/paracasei; none found

How can you test for it?

Consumer stool tests can report lactobacilli, but a US government lab (NIST) study found that the same reference stool gave very different results across seven companies. Even the species are hard to separate with standard methods. (Source 11)

References

1. Microorganisms (MDPI). Lactobacillus Bacteremia and Probiotics: A Review. 2023. DOI 10.3390/microorganisms11040896. Read the source
2. Microorganisms (MDPI). Lactobacillus Bacteremia and Probiotics: A Review. 2023. DOI 10.3390/microorganisms11040896. Read the source
3. Cureus. A Case of Lactobacillus casei Endocarditis Associated With Probiotic Intake in an Immunocompromised Patient. 2023. DOI 10.7759/cureus.38049. Read the source
4. Antibiotics (MDPI). Infective Endocarditis by Lactobacillus Species—A Narrative Review. 2024. DOI 10.3390/antibiotics13010053. Read the source
5. Neurobiology of Stress. Lacticaseibacillus paracasei Lpc-37® improves psychological and physiological markers of stress and anxiety in healthy adults: a randomized, double-blind, placebo-controlled and parallel clinical trial (the Sisu study). 2020. DOI 10.1016/j.ynstr.2020.100277. Read the source
6. European Journal of Clinical Nutrition. Use of a fermented dairy probiotic drink containing Lactobacillus casei (DN-114 001) to decrease the rate of illness in kids: the DRINK study. 2010. DOI 10.1038/ejcn.2010.65. Read the source
7. Brain, Behavior, & Immunity - Health. Efficacy and safety of Lacticaseibacillus paracasei Lpc-37® in students facing examination stress: A randomized, triple-blind, placebo-controlled clinical trial (the ChillEx study). 2023. DOI 10.1016/j.bbih.2023.100673. Read the source
8. Journal of Hospital Infection. Do probiotics prevent antibiotic-associated diarrhoea? Results of a multicentre randomized placebo-controlled trial. 2020. DOI 10.1016/j.jhin.2020.01.018. Read the source
9. Frontiers in Microbiology. The Lactobacillus casei Group: History and Health Related Applications. 2018. DOI 10.3389/fmicb.2018.02107. Read the source
10. Frontiers in Microbiology. The Lactobacillus casei Group: History and Health Related Applications. 2018. DOI 10.3389/fmicb.2018.02107. Read the source
11. Communications Biology. Evaluating the analytical performance of direct-to-consumer gut microbiome testing services. 2026. DOI 10.1038/s42003-025-09301-3. Read the source