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The Supplement Research Compendium
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Lactobacillus paracasei

Lacticaseibacillus paracasei (Lpc-37, CNCM I-1518)

A versatile probiotic species whose effects are tightly strain-specific — immune support (CNCM I-1518), stress (Lpc-37), and allergy (LP-33)

Moderate evidence 🦠Probiotics🛡️Gut & Immune

✚ Updated · How we grade evidence

Evidence tier
Moderate
Research weight
Citations
6 verified / 6
Classification
Probiotics
❝
What the evidence says. Several controlled trials; effects real but modest or context-dependent.

What is Lactobacillus paracasei?

Lactobacillus paracasei (Lacticaseibacillus paracasei (Lpc-37, CNCM I-1518)) is a probiotic strain used for reduces the incidence of common infectious diseases (colds, gi infections) as the fermented-dairy strain cncm i-1518 — ~19% lower odds of ≥1 infection. NutriDex grades the human evidence as Moderate. Lacticaseibacillus paracasei is not one product but several well-characterized strains with divergent evidence. The strongest data is for CNCM I-1518 (the Actimel/DanActive fermented dairy strain): a 2020 meta-analysis of 9 RCTs found it modestly reduced the odds of catching common infections (OR 0.81). Strain Lpc-37 has been tested for stress with mixed results — a benefit on perceived stress in healthy adults (Sisu study) but no effect on exam anxiety in students (ChillEx), with an exploratory sleep-disturbance benefit. LP-33 improved quality of life in grass-pollen allergic rhinitis (425-subject GA2LEN trial), mainly via ocular rather than nasal symptoms. Benefits do not transfer between strains.

Purported Benefits

✓Reduces the incidence of common infectious diseases (colds, GI infections) as the fermented-dairy strain CNCM I-1518 — ~19% lower odds of ≥1 infection
✓Lowers perceived stress in healthy chronically-stressed adults (Lpc-37), with greater effect in women
✓Improves quality of life in grass-pollen allergic rhinitis on top of antihistamine (LP-33), chiefly ocular symptoms
✓May normalize evening cortisol and reduce stress-related sleep disturbance in selected populations (Lpc-37)
✓Generally well tolerated as an adjunct in immune and allergy support

Evidence by outcome

The same supplement can be well-proven for one use and unproven for another — here is the human evidence graded outcome by outcome.

OutcomeEvidenceEffectStudies
Common infectious disease incidence (CNCM I-1518)Meta-analysis of 9 RCTs (OR 0.81); strain-specific to the fermented-dairy strain, modest effect. Moderate ↑ benefit · small 1
Perceived stress (Lpc-37)One RCT (Sisu) cut perceived stress; another (ChillEx) found no effect on exam anxiety. Mixed ↔ mixed · small 2
Allergic rhinitis quality of life (LP-33)One 425-pt RCT improved RQLQ and ocular symptoms as antihistamine adjunct; nasal symptoms unchanged. Preliminary ↑ benefit · small 1
Stress-related sleep disturbance (Lpc-37)Exploratory secondary outcome in ChillEx RCT (reduced sleep-disturbance odds). Preliminary ↑ benefit · small 1

Dosing & Compounds

Typical Dose
Strain- and indication-dependent. Immune support: one ~100 mL fermented dairy drink/day delivering ~10^10 CFU CNCM I-1518. Stress (Lpc-37): ~1.5–1.75 × 10^10 CFU/day for 5–10 weeks. Allergic rhinitis (LP-33): ~10^9 CFU/day. Taken daily, often with a meal.
Active Compounds
CNCM I-1518 (Lactobacillus casei Defensis) — Actimel / DanActive fermented dairy drinkLpc-37 (Howaru Lpc-37) — capsule/sachet, stress studiesLP-33 / ST11 (CNCM I-2116) — allergic rhinitisAvailable as fermented dairy drinks, capsules, and powder sachets

Safety & Cautions

Well tolerated across trials with no serious adverse events attributable to the probiotic, including in healthy adults and students. As with all live probiotics, avoid in critically ill, severely immunocompromised, or central-venous-catheter patients, where rare bacteremia/translocation has been reported for Lactobacillus species. Fermented dairy products are not suitable for severe milk-protein allergy. Effects are strain-specific — do not assume one strain's benefit applies to another product. Educational only — always check with your doctor or pharmacist before combining Lactobacillus paracasei with any medicine.

Key Studies

meta-analysis Poon et al. 2020 ✓ PubMed
Meta-analysis of 9 RCTs: fermented dairy with CNCM I-1518 reduced odds of ≥1 common infectious disease (OR 0.81, 95% CI 0.66–0.98, p=0.029) and mean infections per subject (-0.09, 95% CI -0.15 to -0.04, p=0.001).
randomized controlled trial Mäkelä et al. 2023 (ChillEx) ✓ Full text
Triple-blind RCT, 190 students: Lpc-37 had no effect on exam-related state anxiety (diff 1.03, 95% CI -1.62 to 3.67, p=0.446) but reduced sleep-disturbance odds (OR 0.30, 95% CI 0.11–0.82, p=0.020).
RCT Olivares-Galvan 2025 (Nutrients) ✓ Full text
15-day exploratory intervention in healthy adults showed L. paracasei CNCM I-1518 enhanced cellular and humoral immunity (increased B lymphocytes, monocytes, IgG1/IgG2/IgG4 and complement C3/C4) and raised the gut Lactobacillus/Clostridium ratio.
randomized controlled trial Patterson et al. 2020 (Sisu) ✓ Full text
RCT, 120 healthy adults: Lpc-37 (1.75×10^10 CFU/day, 5 wk) decreased perceived stress 6.4% vs +4.1% placebo (p=0.048), with a larger effect in women (p=0.049).
RCT Zhang 2020 (Nutrients) ✓ Full text
RCT in 898 cold-prone adults: daily L. plantarum HEAL9 plus L. paracasei 8700:2 for 12 weeks reduced incidence, duration, and severity of community-acquired common colds versus placebo.
randomized controlled trial Costa et al. 2014 (GA2LEN) ✓ PubMed
Double-blind RCT, 425 grass-pollen allergic rhinitis patients: LP-33 added to loratadine improved RQLQ quality-of-life and ocular symptoms vs placebo, while nasal symptoms were unchanged.
6 sources cited · 6 verified Search all studies on PubMed ↗

Common questions about Lactobacillus paracasei

What is Lactobacillus paracasei used for?

Lactobacillus paracasei is most often taken for Reduces the incidence of common infectious diseases (colds, GI infections) as the fermented-dairy strain CNCM I-1518 — ~19% lower odds of ≥1 infection, Lowers perceived stress in healthy chronically-stressed adults (Lpc-37), with greater effect in women, Improves quality of life in grass-pollen allergic rhinitis on top of antihistamine (LP-33), chiefly ocular symptoms, May normalize evening cortisol and reduce stress-related sleep disturbance in selected populations (Lpc-37). A versatile probiotic species whose effects are tightly strain-specific — immune support (CNCM I-1518), stress (Lpc-37), and allergy (LP-33)

Does Lactobacillus paracasei work — what does the evidence say?

Moderate evidence. Several controlled trials; effects real but modest or context-dependent. Lacticaseibacillus paracasei is not one product but several well-characterized strains with divergent evidence. The strongest data is for CNCM I-1518 (the Actimel/DanActive fermented dairy strain): a 2020 meta-analysis of 9 RCTs found it modestly reduced the odds of catching common infections (OR 0.81). Strain Lpc-37 has been tested for stress with mixed results — a benefit on perceived stress in healthy adults (Sisu study) but no effect on exam anxiety in students (ChillEx), with an exploratory sleep-disturbance benefit. LP-33 improved quality of life in grass-pollen allergic rhinitis (425-subject GA2LEN trial), mainly via ocular rather than nasal symptoms. Benefits do not transfer between strains.

What is the typical dose of Lactobacillus paracasei?

Strain- and indication-dependent. Immune support: one ~100 mL fermented dairy drink/day delivering ~10^10 CFU CNCM I-1518. Stress (Lpc-37): ~1.5–1.75 × 10^10 CFU/day for 5–10 weeks. Allergic rhinitis (LP-33): ~10^9 CFU/day. Taken daily, often with a meal.

Is Lactobacillus paracasei safe? Any cautions or side effects?

Well tolerated across trials with no serious adverse events attributable to the probiotic, including in healthy adults and students. As with all live probiotics, avoid in critically ill, severely immunocompromised, or central-venous-catheter patients, where rare bacteremia/translocation has been reported for Lactobacillus species. Fermented dairy products are not suitable for severe milk-protein allergy. Effects are strain-specific — do not assume one strain's benefit applies to another product.

How many studies support Lactobacillus paracasei?

NutriDex cites 6 sources for Lactobacillus paracasei, graded "Moderate".

Cite this page
APA

Peh, D. (2026). Lactobacillus paracasei (Lacticaseibacillus paracasei (Lpc-37, CNCM I-1518)): Benefits, Dosage, Side Effects & Evidence. NutriDex — The Supplement Research Compendium. Retrieved 26 Jun 2026, from https://nutridex.info/s/l-paracasei

BibTeX
@misc{nutridex_l_paracasei,
  author       = {Peh, Daryl},
  title        = {Lactobacillus paracasei (Lacticaseibacillus paracasei (Lpc-37, CNCM I-1518)): Benefits, Dosage, Side Effects \& Evidence},
  year         = {2026},
  howpublished = {NutriDex --- The Supplement Research Compendium},
  url          = {https://nutridex.info/s/l-paracasei},
  note         = {Reviewed by Dr Daryl Peh, MBBS Singapore, MMed FM. Accessed 2026-06-26}
}

For medical claims, citing the underlying primary studies linked above is preferred. NutriDex is an educational reference, not medical advice.

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