Buying Probiotics: Strains, CFU & What to Look For

The market for products containing live bacterial cultures has become difficult to navigate: capsules, powders, and drops advertise high numbers, exotic strain names, and plenty of promises. Anyone looking to buy probiotics is left wondering how to recognise a genuinely well-formulated product in the first place, and which claims on the label are just marketing. This guide sorts through the key terms objectively, explains the central figures, and shows step by step what to look for when comparing products – deliberately without any promises of a curative effect, and why that has to be the case becomes clear further below.

What Is Meant by "Probiotics" and Cultures

In everyday usage, "probiotics" refers to products or foods that contain live microorganisms – usually specific lactic acid bacteria (for example from the genera Lactobacillus and Bifidobacterium) or yeasts such as Saccharomyces. The same cultures also occur naturally in fermented foods such as yoghurt, kefir, sauerkraut, or kimchi. The underlying idea is an old one: fermented food has been a fixed part of the diet in many food cultures for centuries. The difference between a food and a supplement lies mainly in standardisation – a dietary supplement contains defined strains in a documented amount, whereas yoghurt or sourdough naturally varies.

A sober assessment of the term matters here. In the European Union, "probiotic" is considered a health claim and, as such, is not authorised. Suppliers are therefore not free to simply advertise a dietary supplement as "probiotic" or attribute specific effects to it. On labels, you'll increasingly find neutral wording such as "with live cultures" or "bacterial cultures" instead. That's not a lack of quality — it's simply the current legal situation, and if anything, a sign that a supplier is complying with the rules. If you'd like to understand the difference from fibre as "food" for bacteria, you'll find it in our guide on Probiotics or Prebiotics.

Important Bacterial Strains and What CFU Means

Cultures act – if they act at all – not as an abstract group, but always as a specific strain. A strain is a precisely defined variant within a species, comparable to a particular cultivar within a plant species. It's identifiable by a three-part designation: genus, species, and a strain identifier made up of letters and numbers. Examples of clearly named strains are Lactobacillus rhamnosus GG or Bifidobacterium animalis subsp. lactis BB-12. If this identifier is missing and the label simply says "Lactobacillus" or "various lactic acid bacteria," there's no way to determine what's actually contained – and any research on a specific strain can't be matched to the product.

The second key figure is CFU – colony-forming units (in German, KBE). It indicates how many viable, reproducible microorganisms are contained in one serving. Figures often fall in the range of several billion CFU per daily dose. One detail that many people overlook is crucial here: the CFU count should refer to the end of shelf life, not the time of manufacture. Live cultures decline in number over time – a product that only states the amount "at the time of manufacture" can contain significantly less by its use-by date. Paying close attention to this helps you avoid one of the most common disappointments. More on how these figures interact is available in the guide Probiotics and Gut Flora: Strains, CFU, and Selection.

A higher CFU count isn't automatically better, either. More sensible than sheer billion-count records is a product whose strains are clearly named and whose dosage is comprehensibly justified. A quantity only becomes truly meaningful once there's a defined strain behind it that the figure can actually be attributed to.

What to Look For When Buying

The points above translate into several concrete criteria that can be checked on the label and product page. They help distinguish a genuinely well-formulated product from sheer numbers marketing.

Strain diversity, used thoughtfully. Some products rely on a single, well-characterised strain, others on combinations of several strains. Having many different names isn't a goal in itself – what matters more is that each individual strain is cleanly named and present in a meaningful amount, rather than listing a dozen names that are only present in trace amounts. A long list looks impressive but says nothing about the actual composition.

A traceable CFU count. Look for a clearly stated amount per daily dose – ideally with an explicit note that it holds true through the best-before date. If the reference point is missing, the figure stays vague and is hard to compare with other products. A trustworthy statement gives the amount and the reference point in the same sentence.

Gastric resistance. Live cultures need to survive the acidic environment of the stomach. Some manufacturers address this with gastro-resistant (enteric-coated) capsules, others with particularly robust strains or a recommendation to take the product with a meal. Information on this shows that the supplier has actually thought the issue through. Whether a capsule or loose powder is the more practical form is explored in the comparison Probiotics: Capsule or Powder?

Storage and refrigeration. Some products require refrigeration, others are stable at room temperature. Either can be fine – what matters is that the requirement is stated on the pack and fits your everyday routine. If you travel a lot or want to take the product at work, a room-stable version is often simpler. Heat and moisture generally take a toll on live cultures, so storage near a stove or windowsill should be avoided.

A proper strain designation with an identifier. This is probably the single most reliable criterion. Complete strain names including an identifier signal that defined, documented cultures are being used and that the manufacturer knows exactly what it's using.

Purity and lab testing. Reputable suppliers provide information on quality controls, such as independent lab testing for viable count, purity, and contaminants. Transparency about origin and production is a good sign. For an overview of how to read such documentation, see the guide Recognising Probiotic Quality.

Price in proportion. The price per daily dose says more than the price per pack. Very cheap products sometimes skimp on strain definition or documentation, while very expensive ones aren't automatically higher quality. Work out the price per daily serving and compare what you're getting for it – that's what makes packs of different sizes genuinely comparable.

Buying Checklist

• Are the strains contained fully named – genus, species, and strain number?
• Is the CFU count per daily dose stated, ideally referenced to the end of shelf life?
• Is there guidance on surviving stomach acid – such as gastro-resistant capsules or an intake recommendation?
• Is the storage requirement clearly stated on the pack (refrigerated or room-stable), and does it fit your routine?
• Does the supplier provide information on purity, lab testing, and origin?
• Is the ingredient list concise, without unnecessary fillers?
• Does the price per daily dose hold up in comparison?
• Does the product description stay factual, rather than advertising with claims of a curative effect?

On Taking Probiotics

There's no universally valid rule for how to take probiotics – the recommendation on the specific pack is always what counts. A daily serving is typical, often taken with or shortly before a meal, because food buffers the stomach environment somewhat. Powders can be stirred into cold or lukewarm water; hot drinks aren't suitable, since heat damages live cultures. Capsules are swallowed whole with enough liquid. Taking them consistently over a period of time is more common than a one-off dose, though here too the manufacturer's instructions apply. Newcomers often start with a smaller serving and observe their individual tolerance before working up to the full daily dose.

Dietary supplements don't replace a varied diet or medical advice. Anyone with a pre-existing condition, a weakened immune system, who is pregnant, or who takes medication should get medical clearance before taking them. Fermented foods, incidentally, also provide cultures and can easily be worked into your diet – how a supplement compares with everyday food is shown in Probiotic Supplement or Yoghurt?

An Honest Assessment

As present as bacterial cultures are on the shelf, a realistic view is part of the picture. In the EU, the term "probiotic" isn't authorised as a health claim, and no health claims are currently officially approved for such products. That doesn't mean the products are worthless – it means that blanket claims of an effect on gut, digestion, or immune system aren't legally backed and aren't blanket scientifically proven. Effects, where they exist, are generally strain- and person-specific: what has been studied for one particular strain can't simply be transferred to any other.

For your purchasing decision, that means two things. First: be sceptical of suppliers who promise specific curative effects – that's more of a warning sign than a quality marker. Second: judge a product by verifiable facts – named strains, a transparent CFU statement, documented quality – rather than by bold marketing claims. A thoughtfully formulated product can be a sensible part of a conscious diet; it is not a miracle cure. If you'd like to read more broadly on the topic, you'll find the bigger picture in Gut and Microbiome.

Bottom line: when buying, it's worth taking an objective look at the label rather than the advertising: clearly named strains with a number, an honest CFU figure that holds through the end of shelf life, traceable information on storage and purity, and a fair price per daily dose. Anyone who works through these points in turn makes an informed decision – regardless of which brand advertises the loudest or prints the highest number on the pack.