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Lactobacillus paracasei, 

L. CASEI 431®

- a well-documented probiotic strain

Mom and child and L CASEI 431 probiotic strain
4 Min read

Lactobacillus paracasei, L. CASEI 431® (hereafter referred to by use of the trademark L. CASEI 431®) has been studied in depth and is one of the best documented probiotic Lactobacillus strains. It has been the subject of numerous studies showing its role in helping to maintain the immune system1, 2, 3, 4 and digestive health.5


High-quality, human clinical studies on Lactobacillus paracasei, L. CASEI 431® support its role in helping to maintain the immune system1, 2, 3, 4 and digestive health5

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Chr. Hansen Lactobacillus paracasei, L. CASEI 431®

L. CASEI 431® was originally isolated from a stool sample of a healthy baby. L. CASEI 431® is able to survive in the acidic digestive system, and it has been used in food and dietary supplements since 1995.

The strain L. CASEI 431® has been described in around 60 scientific publications, out of which more than 20 are publications of human clinical studies. The reports associate the probiotic strain L. CASEI 431® with support of immune health1, 2, 3, 4 in adults and digestive health5 in babies.

Immune health L CASEI 431 probiotic strain

In clinical studies, Lactobacillus paracasei, L. CASEI 431® has been associated with beneficial effects within different areas of health

Supporting the immune response

Several studies have suggested that L. CASEI 431® may be associated with a healthy immune response towards vaccine challenge models1, 3, 4. L. CASEI 431® intake is associated with increased levels of antibodies (natural chemicals that help fight viruses and infection),1, 3, 4 pointing to the potential to promote the body’s ability to produce antibodies.

Respiratory health

L. CASEI 431® intake has been associated with a reduction in; common cold and flu-like symptoms, reported doctors’ visits and use of antibiotics.2

Bowel function

L. CASEI 431®, in combination with Bifidobacterium, BB-12®, has been associated in clinical studies with improvement of the consistency of stools and the frequency of bowel movements in babies.5

Active seniors and support of immune health L CASEI 431 probiotic strain


Lactobacillus paracasei, L. CASEI 431® is safe for human consumption; it has been granted QPS (Qualified Presumption of Safety) status from EFSA in Europe.6 It has been tested in human clinical studies at levels of up to at least 50 billion CFU/day, alone and in combination with Bifidobacterium, BB-12®, with no adverse events.

L. CASEI 431® is a registered trademark of Chr. Hansen A/S. 

The article is provided for informational purposes regarding probiotics and is not meant to suggest that any substance referenced in the article is intended to diagnose, cure, mitigate, treat, or prevent any disease.

Our Chr. Hansen probiotic strains

At Chr. Hansen, our strains are backed by science. All of our probiotic strains are supported by clinical documentation. Learn more about the beneficial effects our strains have on different health areas.


References Open Close

1. Rizzardini G, et al. Evaluation of the immune benefits of two probiotic strains Bifidobacterium animalis ssp. lactis, BB-12® and Lactobacillus paracasei ssp. paracasei, L. casei 431® in an influenza vaccination model: a randomised, double-blind, placebo-controlled study. Br J Nutr. 2012;107(6):876-84. (PubMed)
2. Jespersen L, et al. Effect of Lactobacillus paracasei subsp. paracasei, L. casei 431 on immune response to influenza vaccination and upper respiratory tract infections in healthy adult volunteers: a randomized, double-blind, placebo-controlled, parallel-group study. Am J Clin Nutr. 2015;101(6):1188-96. (PubMed)
3. Trachootham, D. et al. Drinking fermented milk containing Lactobacillus paracasei 431 (IMULUSTM) improves immune response against H1N1 and cross-reactive H3N2 viruses after influenza vaccination: A pilot randomized triple-blinded placebo controlled trial. Journal of Functional Foods. 2017;33, 1–10. 
4. De Vrese, M. et al. Probiotic bacteria stimulate virus-specific neutralizing antibodies following a booster polio vaccination. European Journal of Nutrition. 2005;44(7), 406–413. (PubMed)
5. Vlieger AM, et al. Tolerance and safety of Lactobacillus paracasei ssp. paracasei in combination with Bifidobacterium animalis ssp. lactis in a prebiotic-containing infant formula: a randomised controlled trial. Br J Nutr. 2009;102(6):869-75. (PubMed)
6. EFSA Panel on Biological Hazards (BIOHAZ). Statement on the update of the list of QPS-recommended biological agents intentionally added to food or feed as notified to EFSA 3: Suitability of taxonomic units notified to EFSA until September 2015. EFSA Journal. 2015;13:4331.  

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