What makes a probiotic strain 'strain-specific'?

Evidence shows that probiotic efficacy is both strain-specific and disease-specific, so a result demonstrated for one strain cannot be extrapolated to other strains of the same species or genus. The strain, identified to strain level, is the unit that matters, not the species name.

Qualified Presumption of Safety is EFSA's generic safety pre-assessment for microorganisms in the food and feed chain, granted at the taxonomic (usually species) level with qualifications. It is a safety instrument, not a health-claim approval, and each strain still needs its own safety data package.

Why must CFU be guaranteed to the end of shelf life?

Viable counts fall over time, so a count guaranteed only at manufacture can be inadequate by the time the product is bought. CFU also measures viability and quantity, not clinical efficacy, which is strain dependent.

Can you call a product 'probiotic' in the EU?

At EU level the term probiotic is treated as an implied health claim, and because no probiotic health claim is authorized its use on labels is restricted, though national enforcement varies and several member states permit the term. VF Bioscience shares the strain science as technical information and recommends confirming wording per market.

Strain-specific probiotics: choosing a documented strain

Choosing a probiotic strain is a due-diligence exercise. For a formulator, the questions that matter are whether the strain is properly identified, whether it is safe, and whether it is clinically validated. VF Bioscience develops and characterizes probiotic strains, including Limosilactobacillus fermentum ME-3® and Lactiplantibacillus plantarum VFP46®, and supplies them with technical documentation to food supplement, functional food and pharmaceutical manufacturers worldwide.

Why is probiotic efficacy strain-specific?

Probiotics are defined as “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host” (Hill et al., 2014). A systematic review of the evidence concluded that “strong evidence was found supporting the hypothesis that the efficacy of probiotics is both strain-specific and disease-specific” (McFarland et al., Frontiers in Medicine, 2018). In practice that means a property shown for one strain cannot be assumed for another strain of the same species, let alone the same genus. Two L. plantarum strains can behave differently. This is why the species name on a label tells a formulator very little, and the strain designation tells them almost everything.

How is a probiotic strain identified and documented?

Identification runs to genus, species and strain level using validated methods. Whole-genome sequencing is now the reference method: “the ‘gold standard’ for strain identification is whole genome sequencing (WGS) including any extrachromosomal elements” (Binda et al., 2020). Beyond sequencing, the long-standing FAO/WHO guidelines require that a strain be named according to the International Code of Nomenclature and deposited in an internationally recognized culture collection, with the genus, species and strain designation carried on the label (FAO/WHO, 2002). A deposit number in a recognized collection is therefore a basic marker that a strain is real, traceable and reproducible.

What is QPS status, and what does it not mean?

Qualified Presumption of Safety is the European Food Safety Authority’s simplified, generic route for pre-assessing the safety of microorganisms used in the food and feed chain. It is granted at a taxonomic level, the species for bacteria, and any safety concerns are expressed as “qualifications” attached to that unit. QPS status says nothing about efficacy and nothing about authorized health claims.

Do CFU counts guarantee potency?

No, on two counts. First, the colony-forming-unit count measures viable cells, that is viability and quantity, not clinical effect; efficacy is strain and dose specific and has to be shown in studies on that strain. Second, viable numbers decline over storage, so the count must be guaranteed to the end of shelf life. A label should state “minimum viable numbers of each probiotic strain at the end of the shelf-life”, because a figure given “at time of manufacture” is inadequate if you purchase the product close to the end of its shelf-life” (ISAPP).

What can you claim about a probiotic in the EU?

There is no authorized EU health claim for probiotics, and the term “probiotic” by itself is seen as an unauthorized health claim in many EU countries. However, enforcement is not uniform: several member states permit the term through national guidance (FoodNavigator, 2025). The only authorized live-culture claim concerns yogurt cultures and improved lactose digestion, at a minimum of 100 million (10^8) live starter cells per gram (Regulation (EU) No 432/2012), and that is a starter-culture claim, not a probiotic one.