When we talk about gut health, probiotics, or fermented foods, the term bacterial strains often arises. But what does it mean, and why is it critical?

What Are Bacterial Strains—and Why They Matter

Bacteria are microscopic organisms residing throughout our bodies—especially in the gut—where they support digestion, immunity, nutrient synthesis, and skin health. Bacteria are classified by genus, species, and strain. For instance, Bifidobacterium longum denotes the species, while strains like B. longum BB536 or 35624 represent genetically distinct variants (1).

Strain specificity is vital because different strains—even within the same species—can have profoundly different effects: some produce beneficial metabolites, others modulate immunity, and a few may be neutral or potentially harmful.

Strain Specificity: Not All Bacteria Are Created Equal

Clinical research links specific health outcomes to individual strains:

• longum BB536 improved bowel movements in elderly adults with chronic constipation (2).
• The same strain promoted healthier stool frequency in elderly patients receiving enteral feeding (3).
• Extracellular vesicles (EVs) from B. longum help cells bind mucus and modulate immunity, indicating strong gut interaction and colonization potential (4,5).
• EVs from B. longum NSP001 reduced inflammation and enhanced gut barrier integrity in murine colitis models (6).

These findings underscore the importance of strain-level specificity.

Probiotics vs. Postbiotics: A Shift in Focus

Probiotics are live microorganisms that deliver health benefits when consumed in adequate amounts.

Postbiotics are non-living derivatives—like short-chain fatty acids (SCFAs), peptides, or cell fragments—that retain functional effects even when the bacteria are not alive (7).

Because postbiotics don’t require bacteria to survive digestion, they offer advantages in stability and safety (8).

Does More Mean Better? Not in Postbiotics

Marketing often suggests that more strains are better. However, formulations with multiple unvalidated strains can lead to metabolic competition, reduced potency, and unpredictable outcomes.

Evidence shows that a few well-researched strains—particularly B. longum—can deliver strong, targeted effects:

BB536 supports regularity and immune modulation in older adults (2,3,6).

EVs from B. longum facilitate gut barrier reinforcement and inflammation reduction (4,6).

Concentrating on high-evidence strains yields better results than scattering focus across many unproven ones (9).

What to Look for in a High-Quality Postbiotic

When evaluating a postbiotic supplement, check for:

• Precise strain notation, for example B. longum BB536 or 35624.
• Clinical evidence, demonstrated in randomized controlled trials (2,3,6).
• Known mechanisms, such as SCFA production, gut barrier enhancement, or cytokine regulation (7,9).
• Stability and purity, ensuring room-temperature shelf life without harmful additives (8).

Conclusion: Small Details, Big Differences

In gut health, precision trumps quantity. Instead of opting for a product with “15+ strains,” choose supplements containing a few clinically proven strains like Bifidobacterium longum BB536. Postbiotics aren’t about more—they’re about the right strains, formulated for reliability, research-backed effectiveness, and biological impact.

Connect with us on:

 

Available at:

 

References

1. O’Callaghan, A. and Van Sinderen, D. (2016) ‘Bifidobacteria and their role as members of the human gut microbiota,’ Frontiers in Microbiology, 7. https://doi.org/10.3389/fmicb.2016.00925.
2. Sugahara, H. et al. (2015) ‘Probiotic Bifidobacterium longum alters gut luminal metabolism through modification of the gut microbial community,’ Scientific Reports, 5(1). https://doi.org/10.1038/srep13548.
3. Kondo, J. (2013) ‘Modulatory effects of Bifidobacterium longumBB536 on defecation in elderly patients receiving enteral feeding,’ World Journal of Gastroenterology, 19(14), p. 2162. https://doi.org/10.3748/wjg.v19.i14.2162.
4. Nishiyama, K. et al. (2020) ‘Extracellular Vesicles Produced by Bifidobacterium longum Export Mucin-Binding Proteins,’ Applied and Environmental Microbiology, 86(19). https://doi.org/10.1128/aem.01464-20.
5. Nie, X. et al. (2025) ‘Bifidobacterium longum NSP001-derived extracellular vesicles ameliorate ulcerative colitis by modulating T cell responses in gut microbiota-(in)dependent manners,’ Npj Biofilms and Microbiomes, 11(1). https://doi.org/10.1038/s41522-025-00663-4.
6. Roberfroid, M. et al. (2010) ‘Prebiotic effects: metabolic and health benefits,’ British Journal of Nutrition, 104(S2), pp. S1–S63. https://doi.org/10.1017/s0007114510003363.
7. Wegh, C. a. M. et al. (2019) ‘Postbiotics and their potential applications in early life nutrition and beyond,’ International Journal of Molecular Sciences, 20(19), p. 4673. https://doi.org/10.3390/ijms20194673.
8. Aggarwal, S. et al. (2022) ‘Postbiotics: From emerging concept to application,’ Frontiers in Sustainable Food Systems, 6. https://doi.org/10.3389/fsufs.2022.887642.
9. Salminen, S. et al. (2021b) ‘The International Scientific Association of Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of postbiotics,’ Nature Reviews Gastroenterology & Hepatology, 18(9), pp. 649–667. https://doi.org/10.1038/s41575-021-00440-6.