Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host. These beneficial bacteria play a role in maintaining a balanced gut microbiome. Lactobacillus casei Shirota is a well-researched strain, commonly found in fermented dairy products and available as a dietary supplement.
Understanding Lactobacillus casei Shirota
Lactobacillus casei Shirota (LcS) is a distinct strain. As of April 2020, Lactobacillus casei was reclassified as Lacticaseibacillus casei, so the strain may also be called Lacticaseibacillus casei Shirota. This bacterium is gram-positive, rod-shaped, non-spore-forming, and facultatively anaerobic, meaning it can survive in environments with or without oxygen. LcS produces lactic acid by fermenting sugars, which helps to lower the pH in its surroundings.
The “Shirota” designation refers to the scientist, Dr. Minoru Shirota, who isolated this unique strain in 1930. Dr. Shirota’s goal was to identify a lactic acid bacterium capable of surviving the harsh conditions of the digestive tract, including stomach acids and bile, to reach the intestines alive and exert beneficial effects. This strain was incorporated into a fermented milk drink, introduced in Japan in 1935, which became widely known as Yakult. The ability of LcS to survive transit through the gut has been confirmed in human studies.
Strain specificity is a significant aspect of probiotics, as health benefits are often unique to individual strains, not just the species or genus. While Lacticaseibacillus casei as a species is found in various fermented foods, the Shirota strain has been extensively researched for its particular effects on human health. Its resilience and survival in the gut contribute to its efficacy as a probiotic.
Health Advantages of Lactobacillus casei Shirota
Lactobacillus casei Shirota has been extensively investigated, revealing several health benefits, particularly for digestive and immune system support. One primary advantage is its positive influence on digestive health. Studies have shown that consuming LcS can help improve gut motility and alleviate symptoms of chronic constipation, leading to softer and easier-to-pass stools. Regular intake of LcS-fermented milk also improves bowel habits in individuals with conditions like Parkinson’s disease.
Beyond constipation, LcS reduces the incidence and duration of various types of diarrhea. This includes infectious diarrhea, traveler’s diarrhea, and diarrhea associated with antibiotic use. For instance, it has been investigated for easing diarrhea caused by specific infections such as Clostridium difficile and Helicobacter pylori, as well as viruses like norovirus and rotavirus. Consumption of LcS has been shown to reduce the antibiotic-induced decrease in the abundance of beneficial gut bacteria, such as Bifidobacterium, while also increasing levels of Lactobacillus bacteria.
The immune system also benefits from Lactobacillus casei Shirota consumption. LcS has been shown to modulate the human innate immune system and increase the activity of natural killer (NK) cells. NK cells are white blood cells that play a role in the body’s defense against infections and abnormal cells. Studies indicate that daily intake of LcS-fermented milk may reduce the risk of upper respiratory tract infections (URTIs), such as the common cold, in healthy middle-aged office workers. This benefit is mediated through immune system modulation and the inhibition of increases in salivary cortisol levels, a stress marker.
LcS contributes to balancing the gut microbiota composition. It supports the growth of beneficial microbes and helps maintain gut homeostasis by displaying antimicrobial activity against pathogenic bacteria. This includes gram-positive and gram-negative bacteria, as well as antibiotic-resistant strains. By enhancing gut barrier function, LcS helps prevent impaired barrier function of intestinal epithelial cells, which can otherwise lead to an imbalance in the gut environment.
Incorporating Lactobacillus casei Shirota into Your Diet and Safety
Lactobacillus casei Shirota can be incorporated into your diet through specific fermented dairy products and dietary supplements. The most well-known source is a fermented milk drink that specifically contains this strain. When choosing a supplement, it is important to read labels carefully to ensure it contains the Lactobacillus casei Shirota strain, as probiotic benefits are strain-specific.
Dosage varies by product, but many studies on LcS have involved daily intake of fermented milk containing 1 billion to 100 billion colony-forming units (CFUs). For instance, one study observed an increase in Lactobacillus counts in feces with consumption of 100 ml of LcS-fermented milk containing 1 billion CFUs, three times daily for four weeks. While no definitive dosage guidelines exist, following the product’s recommended serving size is advised. Consistency is important for maintaining beneficial effects, as levels of LcS in the gut may revert to pre-intervention states within two weeks after stopping consumption.
Lactobacillus casei Shirota is generally considered safe for most individuals. Mild side effects such as temporary gas or bloating can occur, especially when first introducing probiotics. If these symptoms appear, reducing the dose and gradually increasing it might help. Studies have reported no serious side effects or adverse events associated with LcS consumption. There have also been no reports of LcS acquiring transferable antibiotic resistance genes.
Caution is advised for certain populations. Individuals with severely weakened immune systems or serious underlying medical conditions should consult a healthcare professional before taking any probiotic, including LcS. While rare, some probiotics have been linked to serious infections, particularly in immunocompromised individuals or those with damaged heart valves. Discuss probiotic use with a healthcare provider to ensure it is appropriate for your specific health situation.