Heat-Inactivated Lacticaseibacillus casei Classification
Heat-inactivated Lacticaseibacillus casei is a postbiotic (answer b). 1
Defining Characteristics
By definition, probiotics must be live microorganisms that confer a health benefit on the host when administered in adequate amounts, as established by the Food and Agriculture Organization and World Health Organization in 2001. 1 Heat-inactivated bacteria explicitly fail to meet this fundamental criterion because the inactivation process (through heat, radiation, or other means) kills the microorganisms. 1
Why Not a Probiotic
- Probiotics require viability: The consensus definition specifically requires living microorganisms, and heat-inactivated preparations contain dead bacterial cells that cannot colonize the gut. 1
- Regulatory distinction: Guidelines clearly differentiate between bacterial cultures containing live microbes versus those inactivated by heat or radiation, with the latter classified separately and often regulated as drugs rather than probiotics. 1
Why It Is a Postbiotic
- Postbiotics are defined as preparations containing inactivated microbial cells (heat-killed, radiation-killed, etc.) and/or their metabolites that may still confer health benefits through immunomodulatory or other mechanisms. 2, 3
- Heat-killed Lacticaseibacillus species retain biological activity: Research demonstrates that heat-inactivated L. paracasei (closely related to L. casei) can activate plasmacytoid dendritic cells, induce cytokine production, and repair intestinal epithelial barriers despite being non-viable. 4, 3
- Bifidogenic effects documented: Heat-treated Lactobacillus preparations have been shown to stimulate growth of beneficial Bifidobacterium species in human fecal communities, demonstrating postbiotic functionality. 2
Why Not Other Options
- Not a prebiotic (option c): Prebiotics are non-digestible substrates (typically carbohydrates like inulin or fructooligosaccharides) that selectively promote beneficial bacterial growth. 1, 5 Heat-inactivated bacteria are cellular material, not substrate compounds.
- Not a fermented food (option a): While L. casei may be used in fermented food production, the heat-inactivated preparation itself is a processed ingredient, not a fermented food product. 1
Clinical Implications
Heat-inactivated preparations offer potential advantages in vulnerable populations (infants, immunocompromised patients) where live bacteria pose theoretical infection risks, while still providing immunomodulatory benefits through their cellular components and metabolites. 2, 3