Understanding the Species and Strain Difference
Many people are confused by probiotic names, especially when a famous brand name is involved. The question of "Is Lactobacillus casei the same as Shirota?" is a classic example. The simplest way to understand this relationship is to think of it in terms of biological classification: a species is a broad category, while a strain is a more specific sub-group within that species. For example, a Golden Retriever is a specific breed (analogous to a strain) of the domestic dog species (Canis familiaris) (analogous to the species). In the same way, Shirota is a specific, proprietary strain of the bacterial species Lactobacillus casei.
The Name Change: Lactobacillus to Lacticaseibacillus
Adding to the confusion, the scientific naming convention for some bacteria was updated in April 2020. What was formerly known as Lactobacillus casei has been officially reclassified as Lacticaseibacillus casei. This change was made based on more precise genetic sequencing, which showed that the large Lactobacillus genus needed to be split into several smaller, more accurate genera. While the new name, Lacticaseibacillus, is technically correct, many labels and consumers still use the older, more familiar name. The full name of the specific strain is therefore Lacticaseibacillus casei strain Shirota, but it is still widely known and referred to as Lactobacillus casei Shirota, or simply LcS.
The Characteristics of Lactobacillus casei
As a species, Lactobacillus casei is a type of lactic acid bacteria (LAB) found widely in nature. It is present in the human digestive system, oral cavity, and also in various fermented foods. Its defining characteristics include:
- Acid Tolerance: It can survive in a variety of acidic environments, including the human stomach.
- Versatility: The species is commonly used in industrial fermentation processes for dairy products like yogurt and cheese, as well as olives.
- Probiotic Potential: Numerous strains within the L. casei species have been identified as having probiotic properties and have been investigated for a wide range of potential health benefits, including supporting digestion and immunity.
What Makes the Shirota Strain Unique?
So, if Shirota is just one type of L. casei, what makes it so special? The key is strain-specific research. While the L. casei species as a whole has certain general properties, the specific Shirota strain has been extensively studied and documented for over 80 years since its discovery by Dr. Minoru Shirota. Its unique properties and clinically proven benefits are what distinguish it.
Key characteristics and benefits of the Shirota strain include:
- Robust Survival: It is a highly acid-resistant strain, ensuring that billions of live bacteria reach the intestines after ingestion.
- Immune System Enhancement: Research shows that the Shirota strain can increase the activity of natural killer (NK) cells, an important part of the body's immune system.
- Digestive Regulation: Clinical trials have linked LcS consumption to improved bowel movements, including alleviating constipation and managing loose stools.
- Infection Protection: It has been studied for its potential in preventing infectious diarrhea and suppressing harmful bacteria like H. pylori.
- Proprietary Strain: It is the exclusive strain used in the popular fermented milk drink, Yakult.
Comparison Table: L. casei vs. Shirota Strain
| Characteristic | Lactobacillus casei (Species) | Shirota (L. casei Strain) |
|---|---|---|
| Classification | Broad species containing many strains. | Specific, patented strain within the species. |
| Origin | Found in various natural sources, including humans and fermented foods. | Isolated and cultured by Dr. Minoru Shirota in 1930. |
| Commercial Products | Used in many probiotic supplements and fermented foods globally. | Exclusively used in the Yakult brand product. |
| Health Effects | Varies by strain; general benefits may differ. | Clinically proven for specific effects on immunity and intestinal regulation. |
| Research | Research findings apply to the species as a whole, not specific strains. | Extensive research supports its targeted health benefits. |
| Resilience | Variable; different strains have different levels of acid and bile resistance. | Highly acid-resistant, confirmed to survive passage through the gut. |
Why Strain Specificity Matters for Probiotics
The most important takeaway is that probiotic benefits are strain-specific. You cannot assume that just because a product contains L. casei, it will have the same effects as the Shirota strain. Different strains of the same species can have different genetic makeups and different impacts on the human body. This is why scientific studies and product labels should always specify the particular strain used. A product containing "Lactobacillus casei" might be helpful, but only a product with "Lactobacillus casei strain Shirota" has the specific, scientifically-backed benefits associated with Shirota. When choosing a probiotic, always check the label for the full strain name, which is often listed after the species name, such as Lactobacillus casei Shirota.
For more detailed information on specific probiotic strains and their documented effects, you can consult authoritative databases like the Optibac Probiotics Strain Database.
Conclusion: Not the Same, but Related
In summary, the key to the question "Is Lactobacillus casei the same as Shirota?" is understanding the species-strain relationship. No, they are not the same; rather, the Shirota strain is a specific, well-researched, and proprietary subtype of the broader Lactobacillus casei species. The specific health benefits and survival characteristics of the Shirota strain, as found in Yakult, are not generalizable to all bacteria within the L. casei species. Always look for the specific strain name when evaluating a probiotic product to ensure you are receiving the particular benefits you expect.
Key Takeaways
- Species vs. Strain: Lactobacillus casei is a bacterial species, while Shirota is a specific, patented strain within that species.
- Taxonomic Update: The official name for the species is now Lacticaseibacillus casei, although the older name is still widely used.
- Brand Association: The Shirota strain is famously associated with the Yakult fermented milk drink.
- Strain Specificity Matters: The health benefits attributed to a probiotic are dependent on the specific strain, not just the species.
- Research Focus: The Shirota strain has been extensively researched, with studies supporting its targeted effects on immunity and intestinal health.
