Home Ingredients L. CASEI 431® (Lacticaseibacillus paracasei subsp. paracasei 431)

L. CASEI 431® (Lacticaseibacillus paracasei subsp. paracasei 431)

Lacticaseibacillus paracasei subsp. paracasei, strain L. CASEI 431® (DSM33451; formerly Lactobacillus paracasei subsp. paracasei)
Evidence Level
Limited
4 Clinical Trials
5 Documented Benefits
2/5 Evidence Score

L. CASEI 431® is a probiotic strain from Chr. Hansen, now part of Novonesis. Despite the trade name, it is classed as Lacticaseibacillus paracasei subsp. paracasei, and it has been sold in fermented milk drinks and capsules. In the largest trial, 1,104 healthy adults drinking at least 1 billion CFU a day for 6 weeks had no better flu vaccine response, the main outcome, but upper respiratory symptoms lasted slightly fewer days (6.4 versus 7.3) in the last 3 weeks, an outcome not listed in the trial registry. A smaller trial found larger vaccine antibody rises, which are markers only. Small trials after childbirth found better perineal wound scores but no change in mood scores, and one breakfast study found lower energy intake at the next meal. Both vaccine trials had Chr. Hansen authors. Many products pair 431 with other strains; results here apply to strain 431 taken alone.

Studied Dose At least 1 billion CFU a day in a fermented or acidified milk drink for 6 weeks (vaccine and respiratory trials), or one 1.5 billion CFU capsule a day for 2 to 3 weeks after childbirth. Check the CFU of strain 431 itself on blends.
Active Compound Live Lacticaseibacillus paracasei subsp. paracasei strain L. CASEI 431® (Chr. Hansen, now Novonesis; deposit DSM33451), long published as Lactobacillus casei 431 or Lactobacillus paracasei subsp. paracasei, L. casei 431. Studied in acidified or fermented dairy drinks and in capsules.

Benefits

Upper respiratory symptom duration in healthy adults

In a placebo-controlled trial in 1,104 healthy adults drinking at least 1 billion CFU a day for 42 days, upper respiratory symptoms lasted 6.4 versus 7.3 days on average in the last 3 weeks. This outcome was not in the trial registry; the main outcome, flu vaccine response, did not improve, and symptom incidence and severity did not differ. Chr. Hansen sponsored the trial and five of nine authors worked there.

Supported by Trial 1

Antibody response after a seasonal vaccine (marker studies)

In 211 healthy adults, a dairy drink with at least 1 billion CFU a day for 6 weeks gave larger rises in vaccine-specific blood IgG and saliva IgA than placebo, with no change in cytokines. The later 1,104-person trial found no change in any part of the vaccine response. Antibody levels are markers, not illness outcomes.

Supported by Trial 2, Trial 1

Perineal wound healing scores after childbirth

In 74 first-time mothers with a perineal incision, one 1.5 billion CFU capsule a day for 14 days gave better wound healing scores, the main outcome, than placebo; pain did not differ. A second paper from the same registration describes about 21 days of use, a different capsule supplier, no funding rather than university funding, and more diarrhea and bloating on the probiotic.

Supported by Trial 4

Mood scores in the weeks after childbirth

In 74 women given one 1.5 billion CFU capsule or placebo daily for about 3 weeks after delivery, scores on the Edinburgh postnatal mood questionnaire did not differ between groups at 5, 15 or 21 days. Diarrhea and bloating were reported more often on the probiotic in the first 2 weeks.

Supported by Trial 4

Energy intake at the next meal

In a crossover study in 16 healthy men, a breakfast dairy drink with the strain was followed by lower energy intake for the rest of the day than a control drink, though less than with an inulin drink. When 431 was paired with inulin for 21 days, appetite ratings, appetite hormones and body measures did not change.

Supported by Trial 3

Mechanism of action

1

Survival and attachment in lab digestion models

In laboratory tests, the strain survived simulated stomach and intestinal conditions, attached to gut cell layers and matrix proteins, and reduced the attachment of E. coli and Salmonella to gut cells. These are lab results and do not show what happens in people.

2

Antibody markers after vaccination

In one 211-person trial, vaccine-specific IgG in blood and secretory IgA in saliva rose more than on placebo, while cytokines and innate immune measures did not change. The much larger 1,104-person trial did not confirm a change in vaccine antibodies, and how the strain might shorten symptoms was not measured.

3

Fat storage in rats (animal work)

In rats fed a high-fat diet for 10 weeks, the strain reduced fat around the testes, liver enzymes and blood triglycerides compared with untreated rats, along with changes in fat-metabolism gene markers. This is animal work and has not been tested in people.

Clinical trials

1
Healthy Adults: 42-Day Trial of Flu Vaccine Response and Respiratory Symptoms (primary outcome not met)
PubMed

Randomized, double-blind, placebo-controlled, parallel-group trial at two centers; an acidified milk drink with at least 1x10^9 CFU L. casei 431 or placebo daily for 42 days, with seasonal flu vaccination on day 21; registered ISRCTN08280229 (Jespersen et al. 2015, Am J Clin Nutr)

1,104 healthy adults aged 18 to 60 in Germany and Denmark (553 probiotic, 551 placebo).

The primary outcome, seroprotection 21 days after vaccination, did not differ, and no component of the vaccine immune response changed. Among outcomes the paper lists as other outcomes but the ISRCTN registry does not (it lists only vaccine antibody outcomes), upper respiratory symptoms lasted 6.4 versus 7.3 days on average in the last 3 weeks (P = 0.0059), while incidence and severity did not differ. The registry names Chr. Hansen A/S as sponsor and funder, and five of the nine authors were Chr. Hansen employees.

2
Healthy Adults: 6-Week Vaccine Antibody Trial (markers only)
PubMed

Randomized, double-blind, placebo-controlled, parallel-group study with separate arms: BB-12 in a capsule or L. casei 431 in a dairy drink, each at a minimum of 1x10^9 CFU once daily, against matching placebos for 6 weeks, with flu vaccination after 2 weeks (Rizzardini et al. 2012, Br J Nutr)

211 healthy adults, 56% women, mean age 33.

In the L. casei 431 arm, rises in vaccine-specific plasma IgG (P = 0.01), IgG1 and IgG3 and in saliva secretory IgA (P = 0.035) were greater than on placebo. Plasma cytokines and innate immune measures did not differ. No illness outcomes were reported. Two of the six authors were Chr. Hansen staff according to the company's 2015 trial; the abstract lists only the first author's affiliation.

3
Healthy Men: Breakfast Drink and Energy Intake (crossover phase)
PubMed

Two-phase study; phase 1 was a randomized, double-blind, placebo-controlled crossover of dairy drinks with L. paracasei subsp. paracasei 431 (more than 10^6 CFU/ml), 16 g inulin, both, or maltodextrin control at breakfast on four test days; phase 2 compared 21 days of the 431 plus inulin drink with control (NabizadehAsl et al. 2022, Appetite)

16 healthy men in phase 1; 21 in phase 2 (10 synbiotic, 11 control), in Turkey.

In phase 1, lunch energy intake differed across drinks (p = 0.017), lowest after inulin and next after the probiotic drink, and rest-of-day and 24-hour intake were lower after the inulin and probiotic drinks than control (p < 0.05). In phase 2, hunger and fullness scores, glucose, insulin, PYY, ghrelin, obestatin, adiponectin and body measures did not differ. The abstract does not name a primary outcome; the authors declared no conflict of interest.

4
New Mothers: Capsules After Childbirth (wound scores improved, mood scores unchanged)
PubMed

Triple-blind randomized placebo-controlled trial registered as IRCT20170506033834N7 and reported in two papers; one 1.5x10^9 CFU L. casei 431 capsule or a maltodextrin placebo daily from the day after birth, for 14 days in the wound paper and about 21 days in the mood paper (Abdollahpour et al. 2023, BMC Complement Med Ther)

74 women who gave birth at a hospital in Tabriz, Iran; the wound paper enrolled first-time mothers with a mediolateral episiotomy.

The wound paper's primary outcome, a REEDA healing score, favored the probiotic (adjusted mean difference -0.50, 95% CI -0.96 to -0.05, P = 0.03), while pain did not differ (P = 0.66) and no side events were reported. The 2025 mood paper found no difference in Edinburgh depression scores (p = 0.71) and reported more diarrhea and bloating on the probiotic in the first 2 weeks. The two papers disagree on several details: 14 versus about 21 days of use, capsules from Tak Gen Zist versus Bio Fermentation, funding from Tabriz University of Medical Sciences versus no funding, and no side events versus more diarrhea and bloating on the probiotic (each 4 of 34, versus 2 and 1 of 35 on placebo, at day 15). Neither reports maker funding.

Side effects and drug interactions

Common Potential side effects

In a trial after childbirth, diarrhea and bloating were reported more often on L. CASEI 431® capsules than on placebo at 5 and 15 days (at day 15, diarrhea in 4 of 34 versus 2 of 35 and bloating in 4 of 34 versus 1 of 35), with none by 21 days; an earlier paper from the same registration reported no side events.
The vaccine and respiratory trials gave the strain in acidified or fermented milk drinks; check the label if you avoid dairy.
The NIH notes that few studies have looked at probiotic safety in detail, so there is little solid information on how often side effects occur.
The NIH notes that the risk of harmful effects from probiotics is greater in people with severe illnesses or compromised immune systems; check with a doctor first in these situations.
The published trials of the strain alone lasted 6 weeks or less, so longer use is not well studied.
Both vaccine trials had Chr. Hansen authors, so independent confirmation of the respiratory result is limited.
Many products combine 431 with LGG, BB-12, LA-5 or other strains; results for those blends cannot be assigned to 431 alone.

Important Drug interactions

Antibiotics: no cited trial tested the strain alone during an antibiotic course; ask a pharmacist about timing.
Immunosuppressants or other medicines that weaken the immune system: talk with your doctor before taking live probiotics.
Flu vaccine: in the 1,104-person trial the strain did not change the antibody response to flu vaccination; a smaller trial found larger antibody rises.

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Frequently asked questions about L. CASEI 431® (Lacticaseibacillus paracasei subsp. paracasei 431)

Is L. CASEI 431® a Lactobacillus casei or a Lactobacillus paracasei?

Despite its trade name, the strain is classed as Lacticaseibacillus paracasei subsp. paracasei, and studies call it L. paracasei subsp. paracasei, L. casei 431. Chr. Hansen papers give its deposit as DSM33451. Its results do not carry over to L. casei strains or to other L. paracasei strains such as Shirota.

Does L. CASEI 431® help with upper respiratory symptoms?

In one large trial in healthy adults, symptoms lasted slightly fewer days (6.4 versus 7.3) over the last 3 weeks, but this was not the main outcome or a registered outcome, and how often symptoms occurred did not change. Chr. Hansen staff were among the authors. See a doctor for a high fever, trouble breathing or symptoms that last.

How much L. CASEI 431® was used in studies?

The vaccine and respiratory trials used at least 1 billion CFU a day in a milk drink for 6 weeks. Trials after childbirth used one 1.5 billion CFU capsule a day for 2 to 3 weeks. Many products blend 431 with other strains, so check how much of strain 431 itself is listed.

Is L. CASEI 431® safe to take?

Trials lasting up to 6 weeks did not report serious problems, although one trial after childbirth found more diarrhea and bloating in the first 2 weeks. The NIH notes that probiotic safety is little studied and that risk is greater in people with severe illnesses or weakened immune systems, who should ask a doctor first.

What is L. CASEI 431?

L. CASEI 431® is a probiotic strain from Chr. Hansen, now part of Novonesis. Despite the trade name, it is classed as Lacticaseibacillus paracasei subsp. paracasei, and it has been sold in fermented milk drinks and capsules.

What is L. CASEI 431 used for?

NutraSmarts does not list L. CASEI 431 under a health category. What the research covers: In a placebo-controlled trial in 1,104 healthy adults drinking at least 1 billion CFU a day for 42 days, upper respiratory symptoms lasted 6.4 versus 7.3 days on average in the last 3 weeks.

Does L. CASEI 431 interact with any medications?

Possible interactions include: Antibiotics: no cited trial tested the strain alone during an antibiotic course; ask a pharmacist about timing. Immunosuppressants or other medicines that weaken the immune system: talk with your doctor before taking live probiotics. If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for L. CASEI 431?

NutraSmarts rates the evidence for L. CASEI 431 as Limited (2 out of 5). It is backed by 4 study summaries and 12 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(12 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Jespersen L, Tarnow I, Eskesen D, Morberg CM, Michelsen B, Bügel S, Dragsted LO, Rijkers GT, Calder PC. 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. doi: 10.3945/ajcn.114.103531.PubMedUsed to support: Randomized, double-blind, placebo-controlled, parallel-group trial at two centers in Germany and Denmark: 1,104 healthy adults aged 18 to 60 drank an acidified milk drink with at least 1x10^9 CFU L. casei 431 (n = 553) or placebo (n = 551) for 42 days, with seasonal flu vaccination on day 21. The primary outcome, seroprotection 21 days after vaccination, did not differ, and no component of the vaccine immune response changed. Among other outcomes, upper respiratory symptoms lasted 6.4 vs 7.3 days (P = 0.0059) in the last 3 weeks; incidence and severity did not differ. Registered ISRCTN08280229; the registry lists HI titers as the primary outcome and antigen-specific antibody response as the only secondary outcome, with no symptom outcome, and names Chr. Hansen A/S as sponsor and funder. Five of the nine authors (Jespersen, Tarnow, Eskesen, Morberg, Michelsen) were at Chr. Hansen A/S.
  2. Rizzardini G, Eskesen D, Calder PC, Capetti A, Jespersen L, Clerici M. 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. doi: 10.1017/S000711451100420X.PubMedUsed to support: Randomized, double-blind, placebo-controlled, parallel-group study in 211 healthy adults (mean age 33): at least 1x10^9 CFU BB-12 in a capsule or L. casei 431 in a dairy drink, each against its own matching placebo, once daily for 6 weeks, with flu vaccination after 2 weeks. In the L. casei 431 arm, rises in vaccine-specific plasma IgG (P = 0.01), IgG1 and IgG3 and in saliva secretory IgA (P = 0.035) were greater than on placebo; plasma cytokines and innate immune measures did not differ. Antibody markers only; no illness outcomes. The abstract lists only the first author's affiliation; Eskesen and Jespersen are listed as Chr. Hansen staff in the company's 2015 trial.
  3. NabizadehAsl L, Sendur SN, Ozer B, Lay I, Erbas T, Buyuktuncer Z. Acute and short-term effects of Lactobacillus paracasei subsp. paracasei 431 and inulin intake on appetite control and dietary intake: A two-phases randomized, double blind, placebo-controlled study. Appetite. 2022;169:105855. doi: 10.1016/j.appet.2021.105855.PubMedUsed to support: Two-phase study in healthy men. Phase 1: randomized, double-blind, placebo-controlled crossover in 16 men drinking a dairy drink with L. paracasei subsp. paracasei 431 (more than 10^6 CFU/ml), 16 g inulin, both, or a maltodextrin control with a standard breakfast. Energy intake at an ad libitum lunch differed across drinks (p = 0.017; lowest with inulin, then the probiotic drink), and rest-of-day and 24-hour intake were lower with the inulin and probiotic drinks than control (p < 0.05). Phase 2: 21 days of the synbiotic (431 plus inulin, n = 10) or control (n = 11) changed no appetite score, hormone or body measure. The authors declared no conflict of interest.
  4. Abdollahpour D, Homayouni-Rad A, Nourizadeh R, Hakimi S, Mehrabi E. The effect of probiotic supplementation on episiotomy wound healing among primiparous women: a triple-blind randomized clinical trial. BMC Complement Med Ther. 2023;23(1):149. doi: 10.1186/s12906-023-03980-3.PubMedUsed to support: Triple-blind randomized trial in 74 first-time mothers with a mediolateral episiotomy at Alzahra Hospital, Tabriz: one capsule of L. casei 431 (1.5x10^9 CFU) or a maltodextrin placebo daily for 14 days from the day after birth, capsules supplied by Tak Gen Zist Pharmaceutical Company. The primary outcome, a wound healing score (REEDA), favored the probiotic (adjusted mean difference -0.50, 95% CI -0.96 to -0.05, P = 0.03); pain, the secondary outcome, did not differ (P = 0.66). No side events were reported in either group. Funded by Tabriz University of Medical Sciences. Registered IRCT20170506033834N7.
  5. Abdollahpour D, Homayouni-Rad A, Nourizadeh R, Hakimi S, Mehrabi E. The effect of Lactobacillus casei on postpartum depression: a randomized controlled trial. BMC Psychiatry. 2025;26(1):5. doi: 10.1186/s12888-025-07658-7.PubMedUsed to support: Randomized controlled trial in 74 postpartum women at Al-Zahra Hospital, Tabriz, under the same registration (IRCT20170506033834N7) as the wound healing paper: a 500 mg capsule of L. casei 431 (dose printed as 1.5x10^9 cfu/ml) or an identical placebo once daily from the day after delivery to about 21 days. Edinburgh depression scores did not differ between groups (p = 0.71). This paper names a different capsule supplier (Bio Fermentation Pharmaceutical Company, versus Tak Gen Zist in the wound paper), states no funding, and reports diarrhea and bloating more often on the probiotic at days 5 and 15, with none by day 21.
  6. Pørksen CJ, Keller MK, Damholt A, Frederiksen AKS, Ekstrand KR, Markvart M, Larsen T, Bakhshandeh A. The effect of a lozenge combining prebiotic arginine and probiotics on caries increment in children during 10-12 months, a randomized clinical trial. J Dent. 2023;135:104599. doi: 10.1016/j.jdent.2023.104599.PubMedUsed to support: Other-product reference (BLEND): placebo-controlled, double-blind randomized trial in 343 children aged 5 to 9 (288 completed) of a lozenge with 2% arginine, LGG (DSM33156) and L. CASEI 431 (DSM33451) for 10 to 12 months; caries increment was lower on the lozenge (p = 0.007), with no change in plaque or gingivitis. Two authors were Chr. Hansen employees and one a former employee; Chr. Hansen sponsored a PhD student, supplied the product and paid for monitoring and data management. Cited for the strain's deposit number (DSM33451); the effect cannot be assigned to 431 alone.
  7. Rubin IMC, Mollerup S, Broholm C, Baker A, Holm MKA, Pedersen MS, Pinholt M, Westh H, Petersen AM. Synbiotic Intervention with Lactobacilli, Bifidobacteria, and Inulin in Healthy Volunteers Increases the Abundance of Bifidobacteria but Does Not Alter Microbial Diversity. Appl Environ Microbiol. 2022;88(19):e0108722. doi: 10.1128/aem.01087-22.PubMedUsed to support: Other-product reference (BLEND): single-group study in 15 healthy volunteers taking LGG, LA-5, L. CASEI 431 and BB-12 with 20 g chicory inulin daily for 4 weeks. No adverse effects; stool consistency and frequency were almost unchanged and gut microbial diversity did not change, while bifidobacteria rose. Two authors were employed or financially supported by Chr. Hansen, which markets the product. No placebo group.
  8. Zhang H, Yeh C, Jin Z, Ding L, Liu BY, Zhang L, Dannelly HK. Prospective study of probiotic supplementation results in immune stimulation and improvement of upper respiratory infection rate. Synth Syst Biotechnol. 2018;3(2):113-120. doi: 10.1016/j.synbio.2018.03.001.PubMedUsed to support: Other-product reference (BLEND): single-center, double-blind, randomized controlled trial in adults with four or more colds in the past year, comparing a drink with L. paracasei, L. casei 431 and L. fermentum PCC against a placebo drink for 12 weeks. Upper respiratory infection incidence (p < 0.023) and flu-like episodes with fever (p < 0.034) were lower on the drink. Two authors were at the R&D center of Hangzhou Weiquan Foods. The effect cannot be assigned to 431 alone.
  9. Alikamali M, Shahnazi M, Mirghafourvand M, Mostafa-Gharehbaghi M, Homayouni-Rad A, Fardiazar Z, Mohammad-Alizadeh-Charandabi S. Effect of Maternal Probiotic Supplementation During Breastfeeding on Postpartum Depression and Bilirubin Levels in Low-Birth-Weight (1000-2000 G) Infants: A Randomized Controlled Trial. Health Promot Perspect. 2026;16(2):272-281. doi: 10.34172/hpp.45313.PubMedUsed to support: Other-product reference (BLEND): randomized, double-blind, placebo-controlled trial in 122 breastfeeding mothers of infants weighing 1,000 to 2,000 g, given L. paracasei 431 and B. lactis BB-12 (1x10^9 CFU/day each) or placebo for 42 to 45 days. Neither primary outcome, maternal depression score or infant total serum bilirubin, differed between groups; one infant death and two positive blood cultures occurred in each group. Registered IRCT20100414003706N42.
  10. Leboš Pavunc A, Penava L, Čuljak N, Banić M, Novak J, Butorac K, Ceilinger M, Miličević J, Čukelj D, Šušković J, Kos B. Evaluation of the Probiotic Properties of Lacticaseibacillus casei 431(®) Isolated from Food for Special Medical Purposes(§). Food Technol Biotechnol. 2023;61(4):418-429. doi: 10.17113/ftb.61.04.23.8045.PubMedUsed to support: Laboratory study: L. casei 431 (Lacticaseibacillus paracasei ssp. paracasei), both freeze-dried and recovered from a food for special medical purposes, survived simulated stomach and intestinal conditions, adhered to extracellular matrix proteins and Caco-2 cells, and reduced the binding of E. coli and Salmonella Typhimurium to Caco-2 cells by about 1.8 log units. No human outcomes.
  11. Shin YJ, Bae JM, Cho HR, Mahoro P, Kim HH, Kim SH, Kim TH, Bae MJ. Antiobesity Effects of Lactobacillus paracasei Subsp. paracasei, L. casei 431 on High-Fat Diet-Induced Obese Rats. J Med Food. 2023;26(7):445-453. doi: 10.1089/jmf.2022.K.0144.PubMedUsed to support: Animal study: rats fed a high-fat diet and given L. casei 431 for 10 weeks had less epididymal fat, lower serum ALT, AST and triglycerides, and smaller fat cells than untreated high-fat controls, with changes in lipid metabolism gene and protein markers. No human data.
  12. National Center for Complementary and Integrative Health. Probiotics: Usefulness and Safety NCCIH (National Institutes of Health). 2019;Last updated August 2019; accessed 2026..SourceUsed to support: Not PubMed-indexed. NIH page on probiotics: few studies have looked at probiotic safety in detail, so there is a lack of solid information on the frequency and severity of side effects; the risk of harmful effects is greater in people with severe illnesses or compromised immune systems.