Recognising Probiotic Quality: CFU, Strains & Gastric Resistance

Live bacteria in a capsule that are meant to survive the journey through aggressive stomach acid - preparations with bacterial cultures are a small logistical marvel. And that is precisely why the quality varies so widely. The direct answer up front:

You can recognise good preparations with bacterial cultures by three things: a clear CFU figure that refers to the best-before date (not just to production), precisely named bacterial strains (genus, species and strain) and protection through gastric-acid-resistant capsules or robust cultures.

One important note for context: in the EU, no health claim is currently approved for probiotics - even the term "probiotic" is regarded as a claim of effect. Here we therefore assess exclusively the quality features of preparations with defined live cultures, not any effects.

CFU: how many live microbes are in there?

The amount of live bacteria is stated in CFU (colony-forming units), often in billions per serving. The most important point that many overlook: a higher number is not automatically better - what matters is whether the stated amount reliably arrives.

So pay close attention to what the CFU figure refers to: the time of production or the best-before date. Live cultures decline over time - the statement "until the end of the shelf life" is therefore more honest and more meaningful. A preparation that advertises huge production figures but only contains a fraction by the end of its shelf life is worth less than it looks.

The bacterial strains: precision counts

Bacteria are named by genus, species and strain - for example Lactobacillus (genus) rhamnosus (species), followed by a strain designation. This is not a detail for nerds: only the complete designation makes a preparation verifiable. A high-quality label names the strains fully and precisely, instead of speaking only vaguely of "lactic acid bacteria".

Many products combine several strains (multi-species). Whether more strains or a targeted single strain is a better fit depends on the intended use - more on that shortly.

Why is the exact strain designation so important? Because two strains of the same species can differ markedly from one another - just as two dogs of the same breed can have completely different characters. A preparation that promises only "Lactobacillus cultures" leaves you in the dark about what is actually in it. Only the complete identification down to the strain makes a product properly comparable and verifiable.

One strain or many? Mono-species vs. multi-species

Some preparations contain a single, deliberately selected strain (mono-species), others combine many different ones (multi-species). Both approaches have their logic:

• Mono-species: a well-documented, precisely definable strain.
• Multi-species: covers a broader spectrum.

More strains are not automatically better. What matters is that the cultures are clearly named and present in a sensible amount. A good label lists each strain with its respective CFU amount, instead of just giving a total figure - that is a genuine quality signal.

Gastric-acid resistance and processing

For live cultures to reach the gut at all, they must survive the stomach acid - an environment specifically designed to kill microorganisms. This is why many preparations rely on gastric-acid-resistant capsules or on particularly robust strains.

Production and storage are important too: some products must be kept refrigerated, others are shelf-stable. Freeze-dried cultures are considered comparatively robust. Sometimes a prebiotic is added - a dietary fibre as "food" for the cultures; this is then referred to as a synbiotic. You can read more about the difference in Probiotics vs. Prebiotics.

Storage and shelf life: the often-overlooked factor

With hardly any other preparation is storage as decisive as here - after all, we are talking about living organisms. Heat and moisture take their toll on bacterial cultures. So here are a few practical points:

• Refrigerated vs. shelf-stable: some products belong in the fridge, others are shelf-stable thanks to processing (e.g. freeze-drying) and packaging. The pack tells you what applies.
• Avoid moisture: blister packs or capsules with a desiccant offer better protection than open tins in a damp bathroom.
• In summer: do not store in a hot car or on the windowsill - heat can lower the microbe count. For everything about correct storage, see Storing supplements correctly in summer.

The best-before date has a special meaning here too: it marks not only the chemical stability but ideally the point up to which the stated microbe count is still guaranteed.

Form and intake

Preparations with bacterial cultures come as capsules, powder (also in sachets) and drops. Powder is suitable when capsules are not to be swallowed - for children or older people, for example. For intake, many manufacturers recommend a fixed time of day; the details depend on the particular product. What matters with all forms is the microbe count and recommended intake stated on the pack. Nutrients and digestion puts the topic into further context.

What the research is looking into

Research into bacterial cultures and the gut microbiome is a very active field. Among other things, it is examining how differently individual strains behave, how many live microbes actually reach the gut, and what role the interplay of bacterial cultures and dietary fibres (synbiotics) plays. The enormous diversity and individuality of the human microbiome is also the subject of many studies. However, there are currently no robust, EU-approved health claims for probiotics - we therefore describe the preparations neutrally via their defined cultures and quality features, without claiming any effects.

How do I recognise good quality? The checklist

Honestly put into perspective

Objectively verifiable and established are the quality features: CFU amount (ideally until the best-before date), strain precision, gastric-acid resistance and storage notes. These criteria help you compare preparations properly. What we may not tell you are specific health effects - for that, there is no approved claim in the EU whatsoever, even the term "probiotic" counts as a claim of effect. So a high CFU number is an indication of many live microbes, not a promise of effect. For persistent digestive complaints, please turn to qualified medical professionals.

Suitable products from Scheunengut

You will find preparations with live cultures in the category Bacterial Cultures, and complementary products around digestion in Gut & Digestion.

Read on: Gut, Microbiome & Probiotics, Probiotics: Capsule or Powder?, Inulin as a Prebiotic, Supplements and Antibiotics and Psyllium Husk: Effect & Use.

Frequently Asked Questions (FAQ)

How do I recognise good probiotics or preparations with bacterial cultures?

By a clear CFU figure that refers to the best-before date, by precisely named strains (genus, species, strain) and by protection through gastric-acid-resistant capsules or robust cultures. Ideally the CFU amount per strain is stated and the product is lab-tested.

What does CFU until the best-before date mean?

Live cultures decline over time. A CFU figure at the time of production says less than one that guarantees how many microbes are still present by the end of the minimum shelf life. The latter is more honest and more meaningful.

Are more bacterial strains better?

Not automatically. Multi-species preparations cover a broader spectrum, while a single, well-documented strain is precisely definable. What matters is that the cultures are clearly named and present in a sensible amount, ideally with CFU per strain.

Why is gastric-acid resistance important?

Stomach acid is an acidic environment that can kill microorganisms. For live cultures to reach the gut, gastric-acid-resistant capsules or particularly robust, often freeze-dried strains help.

How we at Scheunengut ensure tested purity from raw material to tin is explained on our page about the Clean Earth Badge.