LACTIC ACID FERMENTS AND PROBIOTICS: THE DIFFERENCE THAT REALLY DETERMINES MICROBIOTA HEALTH (especially when antibiotics are being taken)
Yogurts that “help the flora,” supplements rich in “lactic acid ferments,” products that promise intestinal balance: commercial communication often groups together microorganisms that are actually very different from one another. Yet, if the goal is to truly protect the microbiota—particularly when it is under the stress of antibiotic therapy—what we choose makes a real difference.
Understanding the distinction between lactic acid ferments and probiotics is not a mere technicality; it means distinguishing between what simply passes through the body and what actively interacts with our health.
Lactic acid ferments: a food-related role, not a clinical one
The term originates in food technology. It refers to bacteria capable of converting sugars into lactic acid, which are essential for fermenting yogurt, cheese, and other foods. Their original function is linked to food preservation and sensory qualities, not to intestinal health.
Many lactic acid ferments do not survive gastric acidity, do not reach the colon alive, or are unable to establish meaningful interactions with the intestinal flora. Guidelines from the Italian Ministry of Health clarify that their presence in supplements does not automatically imply a health benefit.
By merely transiting through the gut without colonizing it, they do not always influence microbial balance.
Probiotics: a modern, evidence-based definition
By contrast, the definition of a probiotic is recent and rigorous. According to the WHO and the Italian Ministry of Health, probiotics are:
live microorganisms which, when administered in adequate amounts, confer a health benefit on the host.
To be defined as such, they must meet precise criteria:
- complete identification of the strain
- documented safety
- an effective dose: at least 10⁹ live cells per strain per day in Italy
- viability through to the intestinal tract
- effects demonstrated in humans
Without a clearly identified strain, an adequate dose, and clinical studies, the term probiotic is not appropriate.
Why labels still mention the “content of ferments”
Even when probiotics are involved, regulations require that the number of live microorganisms present in the daily dose be declared, expressed as colony-forming units (CFU) and guaranteed until the end of the product’s shelf life. This is a fundamental requirement to ensure that the probiotic can reach the intestine alive and in an effective quantity, in line with its scientific definition.
The use of the term “ferments” in this technical context does not refer to generic lactic acid ferments, but rather to the method used to quantify microbial viability. Probiotics are produced through controlled fermentation processes, which allow precise monitoring of the number of live cells up to the final formulation.
What might appear to be a return to generic language thus becomes a quality indicator: it guarantees that the microorganisms in the product not only belong to identified and studied strains, but are also alive—an essential condition for them to exert their function in the body.
Regulation: why “living in the gut” is not enough
In Europe, health claims are strictly regulated. According to EFSA assessments, simply increasing beneficial microflora in general does not prove a real health benefit.
To claim clinical usefulness, the following are required:
- measurable outcomes
- an impact on symptoms or complications
- studies conducted in humans
For this reason, many products, lacking sufficient evidence, use vaguer label wording such as “live lactic acid ferments,” which is less demanding from a scientific standpoint.
Where do they really act? The colon as the center of balance
The microbiota is not evenly distributed throughout the gut. The colon is where the majority of intestinal microorganisms are concentrated, within an ecosystem dominated—especially in childhood—by bifidobacteria.
These bacteria play key roles in digestion, the intestinal barrier, and immune function. However, they are also among the most vulnerable to the effects of antibiotics.
An Italian study in children treated with amoxicillin plus clavulanic acid showed a marked reduction in bifidobacterial populations compared with healthy controls. When the microbiota loses microorganisms that ensure stability, gastrointestinal disturbances and the risk of dysbiosis increase.
Probiotics during antibiotic therapy: supporting microbiota recovery
Antibiotics do not act only on the bacteria responsible for infection; they can also damage protective flora. For this reason, in many cases it is considered useful to combine antibiotic therapy with probiotics that help maintain intestinal balance.
A survey conducted among 279 Italian pediatricians shows that 63% routinely prescribe a probiotic during antibiotic therapy, with the aim of reducing gastrointestinal disturbances and supporting eubiosis in young patients. (👉 See the full analysis of the survey and the importance of probiotic strain selection.)
However, strain selection cannot be random. If a probiotic does not survive the associated antibiotic molecule, it cannot exert a real protective effect when it is most needed. Clinical evidence has shown better tolerability of therapy when strains capable of coexisting with specific classes of antibiotics are used.
The probiotic does not replace the treatment; it preserves its context, promoting a faster rebalancing of the microbiota.
Conclusion
When facing antibiotic treatment, attention is naturally focused on the infection to be cured. But it is equally important to consider the collateral effects on the microbiota, especially in children, in whom bifidobacteria represent a fundamental physiological defense.
Distinguishing between lactic acid ferments and probiotics means recognizing which microorganisms are truly able to support intestinal well-being. Choosing an appropriate probiotic must take into account the type of therapy underway, the site of microbiota action to be protected, and the available evidence for the specific strain.
When probiotics are associated with antibiotic therapy, these decisions should always be made by a physician or pediatrician, who can assess the overall clinical picture and guide the choice toward appropriate solutions.
Taking care of the microbiota does not mean interfering with therapy—it means supporting the body while it fights the infection.
* Biasucci, G.; Capra, M.E.; Giudice, A.; Monopoli, D.; Stanyevic, B.; Rotondo, R.; Mucci, A.; Neglia, C.; Campana, B.; Esposito, S. Use of Probiotics During Antibiotic Therapy in Pediatrics: A Cross-Sectional Survey of Italian Primary Care Pediatricians. Antibiotics 2025, 14, 577. https://doi.org/10.3390/antibiotics14060577