Lactobacillus casei

bacteriapantetheine

What is it

Lactobacillus casei (recently reclassified as Lacticaseibacillus casei) is a probiotic bacterium widely used in fermented dairy products and probiotic supplements. It is closely related to L. paracasei and L. rhamnosus and is studied for digestive, immune, and metabolic health.

How it works

L. casei is a transient inhabitant of the human gut that ferments lactose and other carbohydrates to produce lactic acid. This lowers intestinal pH, creating an environment less favorable for many pathogenic bacteria. It competes with potentially harmful organisms for binding sites on intestinal cells and for available nutrients. It interacts with the gut-associated immune system, modulating cytokine production and supporting regulatory immune responses. Certain L. casei strains have been shown to strengthen intestinal barrier function by upregulating tight junction proteins and to influence the composition of the broader gut microbiota by supporting beneficial bacterial populations. Strain-level effects vary considerably. Strain Shirota (used in Yakult) has been studied for digestion, immune function, and mood. Strain DN-114001 (used in some commercial yogurts) has been studied for cold and gastrointestinal symptoms in older adults. Strain LC-11 is common in multi-strain supplement blends.

Evidence for 4 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Antibiotic-associated diarrhea prevention

Grade B

Good evidence

L. casei, often in multi-strain probiotic formulas, reduces incidence of antibiotic-associated diarrhea. Some trials of L. casei DN-114001 in older adults show reduced diarrheal duration.

Constipation in older adults

Grade C

Moderate evidence

Trials of fermented dairy containing L. casei Shirota suggest modest improvement in stool frequency and consistency in elderly people with chronic constipation.

Common cold duration and severity

Grade C

Moderate evidence

Some trials show modest reductions in cold duration or severity with L. casei consumption, often in combination with other strains. Effect sizes are small.

Irritable bowel syndrome

Grade C

Moderate evidence

L. casei has been included in multi-strain IBS probiotic trials with modest benefit. Isolated strain effects are harder to characterize.

3 commercial forms

L. casei Shirota

Strong gastric acid survival, well-studied

Found in Yakult fermented milk drinks. Has the most extensive research on digestive and immune outcomes.

L. casei DN-114001 (also called L. paracasei Defensis)

Used in fermented dairy products

Studied for cold prevention and gastrointestinal symptoms in older adults.

L. casei LC-11

Standard supplement-grade strain

Common in multi-strain capsule probiotic products.

Dosage

There is no RDA for probiotics. Clinical studies of L. casei typically use 1 to 100 billion CFU per day, with single-strain trials often in the 5 to 30 billion CFU range. Yakult-style fermented milk drinks typically contain about 10 billion CFU per bottle. Capsule supplements commonly provide 1 to 20 billion CFU per dose.

When and how to take it

L. casei can be taken with or without food. Taking with a small meal or with dairy may improve survival through the stomach by buffering acid. Consistency is more important than precise timing: take at the same time each day to maintain steady gut exposure. Separate from antibiotic doses by at least 2 hours. Refrigeration extends shelf life for most strains.

Food sources

Food	Amount	%DV
Yakult and similar fermented milk drinks	Approximately 10 billion CFU per bottle	—
Some yogurts (with added L. casei culture)	Varies; check label	—
Aged cheeses (variable)	Variable presence; not standardized	—

Safety

L. casei is generally well tolerated. Mild bloating, gas, or stool changes can occur initially. Serious adverse events are rare in healthy people. As with other live probiotics, immunocompromised individuals face a small but documented risk of bacteremia. No established Tolerable Upper Intake Level. Long-term consumption of fermented L. casei products has a strong safety record.

Who should be cautious

People who are severely immunocompromised, organ transplant recipients on immunosuppression, those with central venous catheters, and critically ill patients should consult their physician before taking live probiotic supplements. Pregnant and breastfeeding women generally tolerate L. casei well. People with severe milk allergies should check labels, as many commercial L. casei products are dairy-based.

Interactions

Antibiotics can kill probiotic organisms; separate doses by at least 2 hours. Immunosuppressive medications increase the small risk of bacterial translocation. No well-documented interactions with most supplements or medications. Combining with other probiotic strains is generally considered safe but has not been thoroughly evaluated for additive effects.

Frequently asked questions

What's the difference between L. casei, L. paracasei, and L. rhamnosus?⌄

They are closely related species (now grouped under Lacticaseibacillus). Genetic reclassification has shuffled some strains between these names. They have overlapping but distinct documented effects.

Is Yakult a good source of L. casei?⌄

Yes. Yakult contains L. casei Shirota, the most-studied strain, at approximately 10 billion CFU per bottle. It also contains added sugar, which is worth considering.

Can L. casei help with constipation?⌄

Trials in older adults suggest modest improvement in stool frequency. Effects are not as strong as targeted fiber interventions but may complement other approaches.

How long until I notice effects?⌄

For acute conditions like antibiotic-associated diarrhea, effects appear within days. For chronic concerns, several weeks of consistent use are typical.

Can children take L. casei?⌄

Yes, L. casei has been used in many studies in children and is generally well tolerated. Discuss with your pediatrician for specific applications.

References

ChEBI: pantetheine — ChEBI Database link
Wikidata: Lacticaseibacillus casei — Wikidata link

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Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you're pregnant, breastfeeding, on medications, or managing a chronic condition.