Lactobacillus Casei

• Gut microbiome balance
• Immune system modulation
• Pathogen inhibition
• Anti-inflammatory effects

• Metabolic health support
• Cholesterol level improvement
• Antibiotic-associated diarrhea prevention
• Respiratory infection reduction
• Potential weight management support
• Oral health maintenance
• Liver function support

Lactobacillus casei exerts its beneficial effects through multiple mechanisms that contribute to gut health, immune modulation, and protection against pathogens. As a probiotic, L. casei competes with pathogenic microorganisms for adhesion sites on intestinal epithelial cells and for nutrients in the gut environment, effectively preventing colonization by harmful bacteria through competitive exclusion. This mechanism is particularly important for preventing infections by enteric pathogens.

L. casei produces lactic acid and other organic acids that lower the intestinal pH, creating an environment unfavorable for many pathogenic bacteria. It also produces specific antimicrobial compounds, including bacteriocins, hydrogen peroxide, and other antimicrobial peptides, which directly inhibit the growth of harmful microorganisms. These antimicrobial properties contribute to its effectiveness against pathogens like Helicobacter pylori, Salmonella, and Clostridium difficile.

L. casei strengthens the intestinal barrier function by enhancing tight junction proteins between epithelial cells, thereby reducing intestinal permeability and preventing the translocation of pathogens and toxins across the intestinal wall. This ‘leaky gut’ prevention is crucial for reducing systemic inflammation and endotoxemia. In terms of immune modulation, L.

casei interacts with gut-associated lymphoid tissue (GALT) and influences both innate and adaptive immunity. It enhances the activity of natural killer cells, macrophages, and dendritic cells, which are crucial components of the innate immune system. L. casei also promotes the production of secretory IgA antibodies, which provide mucosal protection against pathogens.

A particularly important aspect of L. casei’s immune modulation is its ability to balance pro-inflammatory and anti-inflammatory cytokines. It typically reduces pro-inflammatory cytokines (such as TNF-α, IL-6, and IL-1β) while increasing anti-inflammatory cytokines (such as IL-10), helping to prevent excessive inflammation in the gut. This anti-inflammatory effect extends beyond the gut and may contribute to systemic anti-inflammatory benefits, which is particularly relevant for metabolic conditions characterized by chronic low-grade inflammation.

L. casei has significant metabolic effects, including the ability to influence lipid metabolism. Some strains have been shown to reduce cholesterol levels through multiple mechanisms, including bile salt hydrolase activity, which deconjugates bile acids and leads to their excretion, forcing the body to use cholesterol to synthesize new bile acids. L.

casei also produces short-chain fatty acids (SCFAs) through fermentation of dietary fiber, which serve as an energy source for colonocytes (colon cells) and have various beneficial effects on gut health and metabolism. Butyrate, in particular, is important for maintaining the health of the intestinal lining and has anti-inflammatory properties. In the context of obesity and metabolic health, L. casei may influence energy harvest and fat storage.

Some studies suggest that it can reduce fat absorption, increase fat excretion, and modulate genes involved in lipid metabolism. It may also improve insulin sensitivity and glucose metabolism, potentially through reducing inflammation and modulating gut hormone production. L. casei also modulates the gut-brain axis through the production of neurotransmitters and neuroactive compounds, potentially affecting mood, stress response, and cognitive function.

This may explain some of its observed effects on stress-related gastrointestinal disorders. Recent research has also identified strain-specific mechanisms, particularly for well-studied strains like L. casei Shirota and L. casei DN-114 001, which have shown specific benefits for immune function and gastrointestinal health, respectively.

The Shirota strain, in particular, has demonstrated strong immunomodulatory effects and potential anti-obesity properties in both animal and human studies.

The optimal dosage of Lactobacillus casei varies depending on the specific condition being addressed, the strain used (particularly whether

it ‘s a well-studied strain like Shirota or DN-114 001), and individual factors. Generally, dosages range from 1 billion to 10 billion colony-forming units (CFU) per day for general health maintenance,

while therapeutic dosages for specific conditions may range from 10 billion to 50 billion CFU daily.

It ‘s important to note that efficacy is not solely determined by CFU count but also by strain specificity, viability at the site of action, and the particular health condition being addressed.

Lactobacillus casei is not ‘absorbed’ in the traditional sense of dietary supplements. Instead, its bioavailability refers to the percentage of live bacteria that survive the harsh conditions of the gastrointestinal tract to reach their site of action. L. casei has relatively good survival rates compared to many other probiotic strains due to its natural acid and bile resistance.

Studies suggest that approximately 20-30% of orally administered L. casei may survive passage through the stomach and upper intestine, though this varies widely depending on formulation, strain characteristics, and individual factors such as gastric acidity and transit time. The Shirota strain, in particular, has demonstrated good survival through the GI tract in human studies. Once it reaches the intestines, L.

casei can temporarily colonize the gut mucosa, with detectable levels persisting for 1-2 weeks after discontinuation in many individuals. Some strains of L. casei have shown particularly good adhesion to intestinal epithelial cells, which enhances their residence time and functional effects in the gut. Interestingly, L.

casei delivered in fermented dairy products like yogurt or fermented milk may have enhanced survival compared to isolated supplements, as the food matrix provides protection from stomach acid and bile salts.

Enteric coating: Protects probiotics from stomach acid, increasing survival rates by 30-60%, Microencapsulation: Shields bacteria from environmental stressors, potentially improving viability by 40-70%, Delayed-release capsules: Designed to release probiotics in the intestines rather than the stomach, Buffered formulations: Include compounds that neutralize stomach acid around the bacteria, Prebiotic inclusion (synbiotics): Provides nutrients that support probiotic growth and colonization, particularly fructooligosaccharides (FOS), inulin, and specific oligosaccharides that L. casei can utilize, Higher CFU counts: Compensates for die-off during transit, though quality and strain characteristics are more important than quantity alone, Refrigerated storage: Maintains viability before consumption, Consumption with meals: Food can buffer stomach acid and improve survival, Dairy matrix delivery: Fermented milk products provide natural protection from gastric conditions, Freeze-dried preparations: Maintain stability until hydration in the digestive tract, Selection of acid-resistant strains: The Shirota strain, for example, has enhanced acid resistance

For maximum effectiveness, L. casei supplements are best taken with or just before meals, which helps buffer stomach acid and improve survival rates. When taken for antibiotic-associated diarrhea prevention, L. casei should be administered at least 2 hours before or after antibiotics to prevent direct antimicrobial effects on the probiotic.

For general digestive health, consistent daily supplementation is more important than specific timing. Morning administration may be preferable for some individuals as gastric emptying tends to be faster in the morning, potentially allowing more bacteria to reach the intestines. For metabolic health support, some research suggests taking L. casei with breakfast may be beneficial, as it can influence postprandial glucose and lipid metabolism.

For immune support, consistent daily use is more important than timing, though some practitioners recommend morning administration to align with natural circadian rhythms of immune function. When used as an adjunct to H. pylori treatment, L. casei should be taken at a different time than the antibiotic regimen, ideally with food.

For maximum colonization potential, consistent daily use at approximately the same time each day is recommended, as L. casei typically remains in the gut for only 1-2 weeks after discontinuation. L. casei in fermented dairy products like yogurt or fermented milk (particularly the Shirota strain) may have enhanced survival when consumed as part of these food matrices rather than as isolated supplements.

• Temporary digestive discomfort (gas, bloating)
• Mild abdominal cramping
• Increased thirst (rare)
• Headache (rare)
• Constipation (rare)
• Increased appetite (rare)
• Taste disturbances (rare)
• Skin rash (very rare)

• Severely immunocompromised patients (e.g., those with AIDS, lymphoma, or undergoing long-term corticosteroid treatment)
• Patients with short bowel syndrome
• Individuals with central venous catheters
• Critically ill patients in intensive care units
• Premature infants (especially very low birth weight infants)
• Patients with damaged heart valves or artificial heart valves
• Known hypersensitivity to Lactobacillus species or any components of the probiotic formulation

• Antibiotics (may reduce probiotic effectiveness; separate administration by at least 2 hours)
• Immunosuppressants (theoretical increased risk of infection)
• Antifungal medications (may reduce probiotic effectiveness)
• Medications that decrease stomach acid (may increase probiotic survival but potentially affect colonization patterns)
• Anticoagulants/antiplatelet drugs (rare case reports of increased bleeding risk with certain probiotics, though not specifically with L. casei)

No established upper limit for L. casei. Doses up to 50 billion CFU daily have been used in clinical studies without significant adverse effects in healthy individuals. However, higher doses may increase the risk of side effects such as digestive discomfort without necessarily providing additional benefits.

The appropriate dose depends on the specific condition being treated and individual factors. For general health maintenance, 1-10 billion CFU daily is typically sufficient. Individuals with compromised immune systems should consult healthcare providers before using any dose of probiotics. It’s important to note that safety concerns are more related to an individual’s health status than to specific dosage thresholds.

Lactobacillus casei has an excellent safety profile and has been consumed in fermented foods for centuries. The Shirota strain, in particular, has been extensively studied and has a strong safety record with decades of use in commercial products. L. casei has Generally Recognized as Safe (GRAS) status in the United States and Qualified Presumption of Safety (QPS) status in the European Union.

However, there have been rare cases of Lactobacillus bacteremia (bacteria in the blood) in severely immunocompromised individuals or those with serious underlying health conditions. While L. casei has a long history of safe use in foods and supplements, caution is advised in certain populations. Individuals with severe acute pancreatitis should avoid probiotics, as some studies have suggested potential harm in this specific condition.

Those with a history of endocarditis or artificial heart valves should consult healthcare providers before use. Diabetic patients should check probiotic supplement labels for added sugars, particularly in fermented dairy products containing L. casei. Individuals with milk allergies should ensure that dairy-free formulations are selected, as many L.

casei products are cultured in dairy-based media or delivered in dairy matrices. Patients scheduled for surgery should inform their healthcare providers about probiotic use, as some practitioners recommend discontinuation 1-2 weeks before major surgical procedures. While L. casei has been consumed during pregnancy in traditional foods for centuries and is generally considered safe, pregnant women should still consult healthcare providers before starting any supplement regimen.

Long-term safety studies on L. casei, particularly the Shirota strain, have shown no adverse effects with continuous use over many years, making it suitable for ongoing supplementation in healthy individuals.

In the United States, Lactobacillus casei has Generally Recognized as Safe (GRAS) status when used in traditional food applications. This GRAS status reflects its long history of safe use in fermented foods worldwide. As a dietary supplement ingredient, L. casei is regulated under the Dietary Supplement Health and Education Act (DSHEA) of 1994.

Under this framework, manufacturers are responsible for ensuring the safety of their products before marketing, but pre-market approval is not required. The FDA does not approve dietary supplements for safety or efficacy. Manufacturers of L. casei supplements may make structure/function claims (e.g., ‘supports digestive health’) but cannot make disease claims (e.g., ‘treats irritable bowel syndrome’) without going through the drug approval process.

In September 2023, the FDA issued a warning regarding the use of probiotics in hospitalized preterm infants, citing safety concerns, though this was not specific to L. casei alone. For food applications, L. casei is permitted as an ingredient in fermented foods according to the standards of identity established by the FDA.

It is also approved for use as a starter culture in various fermentation processes.

Eu: In the European Union, L. casei has Qualified Presumption of Safety (QPS) status, the European equivalent of GRAS. For use in foods, L. casei must be included on the Union list of authorized food additives. For probiotic health claims, the European Food Safety Authority (EFSA) has established strict criteria. To date, EFSA has not approved any specific health claims for L. casei, though it is permitted as a food ingredient and in food fermentation processes. In food supplements (the EU term for dietary supplements), L. casei is regulated under the Food Supplements Directive (2002/46/EC). Some member states have established national lists of permitted probiotic strains for use in food supplements. L. casei is widely used in fermented dairy products throughout the EU, which have their own regulatory frameworks.

Japan: In Japan, L. casei has a particularly strong regulatory position, largely due to the historical significance of the Shirota strain and Yakult products. L. casei can be used in Foods for Specified Health Uses (FOSHU) if approved by the Consumer Affairs Agency. Several L. casei products, particularly those containing the Shirota strain, have received FOSHU approval for specific health claims related to gastrointestinal health. It is also permitted in regular foods and as an ingredient in ‘Foods with Function Claims’ (FFC) if scientific evidence supports the claimed benefits. Japan has a long history of accepting probiotic foods, with fermented milk products containing L. casei widely available and culturally significant.

Canada: Health Canada has included L. casei on its Natural Health Products Ingredients Database with approved use as a source of probiotics. It is permitted in Natural Health Products (NHPs) with specific approved claims related to gut health and immune function. Some specific strains of L. casei have been approved for health claims related to digestive health and immune support. L. casei is also permitted as a food ingredient in products like fermented dairy products. For probiotic products making health claims, pre-market approval is required through the Natural and Non-prescription Health Products Directorate (NNHPD).

Australia: In Australia, L. casei is regulated by the Therapeutic Goods Administration (TGA) when used in complementary medicines (similar to dietary supplements). It is listed in the Therapeutic Goods (Permissible Ingredients) Determination and can be used in listed medicines. For food applications, Food Standards Australia New Zealand (FSANZ) permits L. casei as a food ingredient and in food fermentation processes. Health claims are regulated under the Australia New Zealand Food Standards Code, with strict requirements for substantiation.

China: In China, L. casei is included in the list of approved probiotic strains for use in foods by the National Health Commission. For use in health foods (similar to dietary supplements), approval from the State Administration for Market Regulation (SAMR) is required. The regulatory framework for probiotics in China has been evolving, with increasing scrutiny of health claims. L. casei is widely used in fermented dairy products in China, which have their own regulatory frameworks.

India: The Food Safety and Standards Authority of India (FSSAI) permits L. casei in certain food categories, including fermented foods and dairy products. For use in nutraceuticals or health supplements, it must comply with the Food Safety and Standards (Health Supplements, Nutraceuticals, Food for Special Dietary Use, Food for Special Medical Purpose, Functional Food and Novel Food) Regulations.

The regulatory landscape for L. casei and other probiotics faces several challenges. There is significant international variation in how probiotics are regulated, creating complexity for global marketing. Strain-specific effects are not always reflected in regulatory frameworks, which may treat all L.

casei strains as equivalent despite evidence of strain-specific benefits (particularly for strains like Shirota and DN-114 001). Dosage standardization is lacking, with no consensus on minimum effective doses for different health applications. Quality control standards vary widely, with inconsistent requirements for viability testing, contamination screening, and stability assessment. Health claim substantiation requirements differ significantly between jurisdictions, with some regions (like the EU) having very stringent requirements that few probiotic products can meet.

The line between food and supplement/drug classifications is often blurry for probiotic products, creating regulatory uncertainty. This is particularly relevant for L. casei, which has a dual identity as both a traditional food component and a modern supplement ingredient. Emerging delivery formats (e.g., probiotic-infused beauty products, lozenges, or topical applications) may fall into regulatory gray areas.

Safety monitoring systems for probiotics are less developed than for conventional drugs, though adverse events appear to be rare in healthy populations. As research advances on the microbiome and probiotic mechanisms, regulatory frameworks may need to evolve to accommodate new understanding and applications. The recent taxonomic reclassification of L. casei to Lacticaseibacillus casei may create additional regulatory complexities during the transition period as labels and regulatory documents are updated.

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The cost of Lactobacillus casei supplements varies widely based on formulation, strain specificity (particularly whether it contains well-researched strains like Shirota or DN-114 001), CFU count, and additional ingredients. Basic L. casei supplements typically range from $0.10 to $0.50 per billion CFU. For a typical effective dose of 1-10 billion CFU daily for general health maintenance, this translates to approximately $0.10-$5.00 per day.

Higher potency supplements (10-20 billion CFU) generally cost $0.30-$1.50 per day. Premium formulations with verified specific strains like L. casei Shirota, advanced delivery systems, or additional ingredients can cost $1.00-$3.00 per day. Specialized therapeutic formulations for specific conditions may cost up to $3.00-$5.00 per day.

Fermented dairy products containing L. casei, such as Yakult or other probiotic drinks, typically cost $1.00-$2.50 per serving, providing approximately 6.5-10 billion CFU of the Shirota strain. These commercial fermented milk products often represent a middle-ground in terms of cost-effectiveness, providing a standardized dose of a well-researched strain in a format that may enhance probiotic survival.

The cost-effectiveness of L. casei supplementation varies by application and individual needs. For immune support, L. casei supplementation offers good value, with clinical studies showing significant benefits for preventing respiratory and gastrointestinal infections at doses costing approximately $1.00-$2.00 per day.

This may represent good value compared to the costs of treating infections, including medication, lost productivity, and healthcare visits. For metabolic health support, the value proposition is less clearly established. Animal studies consistently show beneficial effects of L. casei Shirota on obesity and metabolic parameters, but human studies have shown mixed results.

The pilot study in obese children showing significant reductions in BMI with L. casei Shirota supplementation suggests potential value for this application, but more research is needed to establish consistent cost-effectiveness. For gastrointestinal health, L. casei has shown benefits for constipation, diarrhea, and inflammatory bowel conditions at doses costing approximately $0.50-$1.50 per day.

This may represent good value compared to over-the-counter medications for these conditions, which can cost $0.50-$3.00 per day and often have more side effects. For antibiotic-associated diarrhea prevention, L. casei supplementation is generally cost-effective, as the cost of supplementation ($10-$30 for a typical antibiotic course) is substantially lower than potential costs associated with treating diarrhea, including medication, lost productivity, and in severe cases, hospitalization. Commercial fermented milk products containing L.

casei Shirota (like Yakult) offer a standardized dose of a well-researched strain in a format that may enhance probiotic survival. At approximately $1.00-$2.50 per serving, these products represent reasonable value for general health maintenance, though they may be more expensive than generic supplement forms on a per-CFU basis. Generic or store-brand probiotic supplements can offer good value, but verification of strain identity is important, particularly when seeking well-researched strains like Shirota or DN-114 001. Multi-strain formulations typically cost more but may provide broader benefits than single-strain L.

casei products. The most cost-effective approach often involves targeted, time-limited use for specific conditions rather than indefinite daily supplementation without a clear indication. For individuals with chronic digestive issues or recurrent infections who respond well to L. casei, however, ongoing supplementation may represent good value compared to alternative treatments or the impact of untreated symptoms on quality of life.

The shelf life of Lactobacillus casei products varies significantly based on formulation, packaging, and storage conditions. Properly manufactured and stored freeze-dried L. casei supplements typically maintain acceptable viability for 18-24 months from the date of manufacture. L.

casei has demonstrated relatively good stability compared to many other probiotic strains, with some properly formulated products maintaining viability for up to 24-36 months at room temperature. The Shirota strain, in particular, has shown excellent stability in commercial fermented milk products, maintaining viable counts for 40-60 days under proper refrigeration. Refrigerated liquid formulations generally have a shorter shelf life of 2-3 months. Microencapsulated or specially formulated shelf-stable products may maintain viability for up to 24-36 months at room temperature.

Probiotic-fortified foods containing L. casei, such as yogurt or fermented milk, typically have shelf lives of 3-6 weeks under refrigeration, with probiotic counts gradually declining over this period.

Refrigeration (36-46°F/2-8°C) is optimal for most L. casei supplements, even those labeled as shelf-stable, as it significantly extends viability. Fermented milk products containing L. casei (particularly the Shirota strain) require consistent refrigeration to maintain probiotic viability.

If refrigeration is not possible for supplement forms, store in a cool, dry place away from direct sunlight, heat sources, and humidity. Temperature fluctuations should be minimized, as repeated warming and cooling can reduce viability. Keep containers tightly closed when not in use to prevent moisture exposure. For blister-packed probiotics, only remove capsules/tablets when ready to consume.

Liquid formulations almost always require refrigeration after opening. Follow manufacturer-specific storage instructions, as some advanced formulations may have different requirements. When traveling, consider using insulated containers with ice packs for temperature-sensitive formulations, or look for specially designed shelf-stable travel formulations. L.

casei has demonstrated relatively good stability at room temperature compared to many other probiotic strains, but refrigeration will still extend its shelf life.

Heat: Temperatures above 77°F/25°C accelerate die-off of live bacteria; exposure to temperatures above 104°F/40°C can cause rapid loss of viability., Moisture: Exposure to humidity or moisture activates freeze-dried bacteria prematurely, depleting their energy reserves and reducing shelf life., Oxygen: L. casei is microaerophilic (prefers low oxygen), and excessive oxygen exposure can reduce viability through oxidative damage., Light: Direct sunlight and UV light can damage bacterial cells through photodegradation and generation of reactive oxygen species., pH extremes: While L. casei is relatively acid-tolerant (particularly the Shirota strain), extreme pH conditions during storage can reduce viability., Freeze-thaw cycles: Repeated freezing and thawing creates ice crystals that can damage bacterial cell walls., Chemical preservatives: Many preservatives used in foods and supplements are designed to inhibit microbial growth and may affect probiotic viability., Compression and processing: Mechanical stress during manufacturing and compression into tablets can damage bacterial cells., Interaction with other ingredients: Certain active ingredients in multi-component supplements may have antimicrobial properties that reduce probiotic viability over time.

Several technologies have been developed to enhance the stability of L. casei products. Microencapsulation protects bacteria with a protective coating that shields them from environmental stressors and controls their release. Freeze-drying (lyophilization) removes water while preserving the cellular structure, significantly extending shelf life.

Addition of cryoprotectants like trehalose, sucrose, or glycerol helps protect bacterial cells during freeze-drying and storage. Specialized packaging such as nitrogen-flushed bottles, blister packs, or aluminum foil sachets reduces exposure to oxygen and moisture. Some formulations include prebiotics that not only support growth in the gut but may also enhance stability during storage. Advanced formulations may incorporate acid-resistant strains (the Shirota strain is naturally relatively acid-resistant) or add buffering agents to protect against pH fluctuations.

Vacuum-sealed packaging removes oxygen that could damage sensitive probiotic strains. Cold-chain management throughout manufacturing, distribution, and retail ensures optimal temperature conditions are maintained. Some manufacturers use overages (adding more CFUs than stated on the label) to compensate for expected die-off during shelf life, ensuring that the product contains at least the labeled amount of viable probiotics through the expiration date. Dairy matrices have been shown to enhance the stability of L.

casei, which is why many commercial products (particularly those containing the Shirota strain) are delivered in fermented milk or yogurt formats.

Synthesis Methods

Natural Sources

Quality Considerations

Lactobacillus casei has a long history of human use, primarily through its presence in traditional fermented foods consumed across diverse cultures for thousands of years. While the bacterium itself wasn’t identified until modern times, its effects have been utilized throughout human history through the consumption of fermented dairy products and other fermented foods. L. casei is naturally present in many fermented dairy products, including traditional yogurts, fermented milks, and certain cheeses, which have been staples in various cultures for millennia.

The fermentation of milk for preservation and enhanced digestibility is one of the oldest food processing techniques, dating back to at least 10,000-15,000 years ago with the domestication of cattle. These fermentation practices, which naturally cultivate L. casei and other lactic acid bacteria, spread throughout Europe, Asia, and eventually worldwide. In Asia, fermented milk products containing L.

casei have been consumed for thousands of years. In Eastern Europe and the Mediterranean, various fermented dairy products that naturally contain L. casei have been part of the traditional diet for centuries. The scientific identification and study of L.

casei began in the early 20th century. The species was first isolated and described in 1919 by Orla-Jensen from cheese, though it was initially classified under different taxonomic designations before being recognized as a distinct species. The name ‘casei’ refers to its common occurrence in cheese (from the Latin ‘caseus’ meaning cheese). Throughout the mid-20th century, microbiologists began to understand the role of L.

casei in various fermentation processes, particularly in dairy fermentations. Its ability to produce lactic acid and antimicrobial compounds was recognized as crucial for food preservation and safety. A significant milestone in the modern history of L. casei came in 1935 when Dr.

Minoru Shirota at Kyoto Imperial University in Japan isolated a specific strain of L. casei from the human intestine. This strain, later named L. casei Shirota, was selected for its ability to survive passage through the digestive system.

In 1935, Dr. Shirota used this strain to develop a fermented milk product called Yakult, which became one of the first commercial probiotic products in the world and is still widely consumed today. Another important strain, L. casei DN-114 001 (marketed as L.

casei Defensis or L. casei Immunitas), was developed in the late 20th century and has been extensively studied for its immune-enhancing properties. In the 1980s and 1990s, scientific interest in L. casei as a probiotic grew significantly, with research expanding beyond its traditional role in food fermentation to explore its potential health benefits.

Clinical studies began to investigate its effects on conditions ranging from gastrointestinal disorders to immune function. In recent decades, L. casei has become one of the most widely studied and used probiotics, with applications in both food products and supplements. The Shirota strain, in particular, has been the subject of hundreds of scientific publications and is one of the most extensively researched probiotic strains worldwide.

In 2020, taxonomic revisions led to the reclassification of many Lactobacillus species into new genera, with L. casei being reclassified as Lacticaseibacillus casei. However, the name Lactobacillus casei remains in common use in both scientific and commercial contexts. Today, L.

casei is recognized not only for its historical role in food fermentation but also as a scientifically validated probiotic with specific health benefits, representing a bridge between traditional food practices and modern evidence-based supplementation.

Zhang Y, et al. Effects of probiotic type, dose and treatment duration on irritable bowel syndrome diagnosed by Rome III criteria: a meta-analysis. BMC Gastroenterol. 2016;16(1):62., Goldenberg JZ, et al. Probiotics for the prevention of Clostridium difficile-associated diarrhea in adults and children. Cochrane Database Syst Rev. 2017;12:CD006095., Hao Q, et al. Probiotics for preventing acute upper respiratory tract infections. Cochrane Database Syst Rev. 2015;2:CD006895., Guo Q, et al. Probiotics for the prevention of pediatric antibiotic-associated diarrhea. Cochrane Database Syst Rev. 2019;4:CD004827., Sun J, Buys N. Effects of probiotics consumption on lowering lipids and CVD risk factors: a systematic review and meta-analysis of randomized controlled trials. Ann Med. 2015;47(6):430-440.

Lactobacillus casei Shirota for Prevention of Antibiotic-Associated Diarrhea in Hospitalized Elderly Patients (ClinicalTrials.gov Identifier: NCT04091451), Effects of Lactobacillus casei on Metabolic Parameters in Patients with Type 2 Diabetes (ClinicalTrials.gov Identifier: NCT03956056), Lactobacillus casei Shirota as an Adjunct to Standard Therapy for Helicobacter pylori Eradication (ClinicalTrials.gov Identifier: NCT03902561), Effects of Lactobacillus casei on Cognitive Function in Older Adults (ClinicalTrials.gov Identifier: NCT04153214), Lactobacillus casei for Prevention of Necrotizing Enterocolitis in Very Low Birth Weight Infants (ClinicalTrials.gov Identifier: NCT03755934)

Lactobacillus casei has a substantial body of scientific evidence supporting several of its health benefits, with the strongest evidence for specific strains like Shirota and DN-114 001. The evidence for L. casei in immune function is relatively strong, with multiple clinical trials showing benefits for preventing respiratory and gastrointestinal infections, particularly in children and elderly populations. The DN-114 001 strain has shown particular efficacy in this area.

For metabolic health, the evidence is mixed but promising. Animal studies consistently show beneficial effects of L. casei Shirota on obesity, lipid profiles, and liver function. Human studies have shown some positive results, particularly in children, but not all trials have demonstrated significant benefits.

A pilot study in obese children showed significant reductions in BMI and waist circumference with L. casei Shirota supplementation, but a study in adults with metabolic syndrome found no significant changes in gut microbiota or metabolic parameters. For gastrointestinal health, L. casei has shown benefits for constipation, diarrhea, and inflammatory bowel conditions in several clinical trials.

The Shirota strain, in particular, has demonstrated efficacy for improving bowel movements and stool consistency in constipated individuals. There is moderate evidence supporting the use of L. casei for preventing antibiotic-associated diarrhea, though it may be less effective than some other probiotic species like Saccharomyces boulardii or certain Lactobacillus rhamnosus strains. The evidence for L.

casei in liver health is primarily from animal studies, which show protective effects against non-alcoholic fatty liver disease and improvements in liver function markers. Human studies in this area are limited but suggest potential benefits. For cholesterol reduction, several studies have shown modest improvements in lipid profiles with L. casei supplementation, though the effects are generally small and may not be clinically significant for all individuals.

The quality of evidence varies across different applications, with the strongest evidence coming from well-designed randomized controlled trials for immune function and certain gastrointestinal conditions. For other applications, the evidence may be limited by smaller sample sizes, heterogeneity in study designs, or inconsistent results across studies. It’s important to note that the effects of L. casei are strain-specific, with strains like Shirota and DN-114 001 having the most extensive research support.

Other strains may have different effects and levels of evidence. Future research directions include larger, longer-term clinical trials, studies on specific mechanisms of action, exploration of strain-specific effects, and investigation of potential applications in metabolic and neurological disorders.