L. casei Shirota is a specific strain of probiotic bacteria, commonly found in fermented food products. It has garnered significant attention and been extensively studied for its potential health benefits.
Understanding L. casei Shirota
L. casei Shirota is formally classified as Lacticaseibacillus casei Shirota, a lactic acid bacterium. This rod-shaped, gram-positive microorganism was first isolated in 1930 by Japanese microbiologist Dr. Minoru Shirota at Kyoto Imperial University, who named it after himself. Dr. Shirota’s work was driven by a belief in the connection between a healthy gut and overall well-being, emphasizing preventive health.
What distinguishes L. casei Shirota is its documented ability to survive the harsh conditions of the gastrointestinal tract, including stomach acid and bile. This resilience allows the live bacteria to reach the intestines and provide benefits. Its long history of research, with over 500 scientific studies, positions it as a well-examined probiotic strain globally.
Health Contributions of L. casei Shirota
L. casei Shirota supports digestive health by helping to maintain a balanced gut microbiota. It can colonize the gut, contributing to intestinal health and digestion. Studies indicate that regular intake can improve bowel habits, including stool consistency, for individuals experiencing hard stools or chronic constipation. It has also been investigated for its potential to alleviate symptoms in cases of irritable bowel syndrome (IBS) and antibiotic-associated diarrhea. The strain works by producing antimicrobial substances and competing with harmful bacteria.
The strain also influences the immune system, particularly through its interaction with the gut-associated lymphoid tissue (GALT). L. casei Shirota has been observed to enhance the activity of natural killer (NK) cells, which are lymphocytes that target abnormal or infected cells. This modulation of immune function suggests a role in strengthening the body’s defenses. Furthermore, research indicates it may help in reducing the incidence and duration of upper respiratory tract infections. The mechanisms involve modulating cytokine production and improving the intestinal barrier function.
Sources and Consumption of L. casei Shirota
The most widely recognized source of L. casei Shirota is the fermented milk drink Yakult. This product contains a substantial number of live Lacticaseibacillus casei Shirota cells, typically ranging from 6.5 billion to 10 billion colony-forming units (CFU) per 65 ml bottle. The consistent presence of this specific strain in Yakult makes it a primary way for consumers to incorporate L. casei Shirota into their diet.
While Yakult is the predominant commercial source, strains of Lacticaseibacillus casei can also be found in other fermented foods like certain yogurts and sauerkraut. Regular consumption is generally advised, as the bacteria’s presence in the gut is temporary and dependent on ongoing intake. Studies on its effect often involve daily consumption over several weeks or months.
Important Considerations for Use
L. casei Shirota is generally considered safe for consumption by the majority of the population and has been safely used for over 80 years. The United States Food and Drug Administration (FDA) has classified L. casei Shirota as “generally recognized as safe” (GRAS). Mild side effects, such as temporary gas, can occur in some individuals, particularly when first introducing probiotics. If such effects arise, reducing the intake and gradually increasing it may help.
It is important to exercise caution in certain situations. Individuals with serious medical conditions or weakened immune systems may have a greater risk of severe side effects, including infections. Consulting a healthcare professional before adding L. casei Shirota to one’s regimen is advisable, especially for those with underlying health concerns. Common products like Yakult typically recommend a daily serving of one bottle, which provides a beneficial number of live bacteria.