Written by Barry Lees, Founder of The Health Improvers. Last reviewed 31 July 2026.
Short answer: CFU compares the declared quantity of viable live cultures, while the strain designation identifies the particular microorganism. A higher CFU count is not automatically better: check the serving size, whether the count is guaranteed through the best-before date, the full microorganism identity and the evidence for the finished product.
Commercial disclosure: We sell a live-culture supplement referenced in this guide. Product-specific statements below are limited to information currently declared on its label and product page.
| Label term | What it tells you | What to check |
|---|---|---|
| Genus and species | The microorganism’s scientific identity, for example Lactobacillus acidophilus | This is not yet a full strain designation |
| Strain designation | A more specific identifier within a species | Look for a code such as GG, BB-12 or a recognised deposit number |
| CFU | An estimate of viable microorganisms capable of forming colonies under specified test conditions | Per capsule or daily portion, and at manufacture or through shelf life |
| Storage | Conditions intended to maintain the declared count | Temperature, moisture protection and refrigeration instructions |
What is a live-culture strain?
A strain is a genetically distinct variant within a microbial species. A complete commercial designation normally includes the genus, species and strain identifier. For example, Lactobacillus acidophilus gives the genus and species only; it does not identify a particular strain.
This distinction matters because research is often strain-specific. Evidence about one strain should not automatically be transferred to every microorganism with the same species name.
You may also see older and newer names for some lactobacilli. A major taxonomic revision in 2020 divided the former Lactobacillus genus into several genera. For example, Lactobacillus rhamnosus is now generally classified as Lacticaseibacillus rhamnosus, while Lactobacillus plantarum became Lactiplantibacillus plantarum. Lactobacillus acidophilus retained its original genus.
Practical rule: genus and species are useful; a genuine strain code tells you more. “Eight species” and “eight fully identified strains” are not the same statement.
What does CFU mean?
CFU stands for colony-forming units. It is a microbiological estimate rather than a weight, and it is not necessarily a one-to-one count of individual cells.
Always put all products on the same scale:
- 100 million CFU = 0.1 billion
- 200 million CFU = 0.2 billion
- 20 billion CFU = 100 times 0.2 billion
A larger number compares declared quantity only. It does not establish that a product is more suitable or better supported.
Should the count apply at manufacture or at the best-before date?
Live microorganism counts can fall over time. A count supported through the end of shelf life is more informative than a number measured only when the product was manufactured.
Look for wording such as “guaranteed through the best-before date”. If the label does not say, ask the seller whether the figure is an end-of-shelf-life specification and whether it is supported by stability testing.
Is there an ideal CFU count?
No universal CFU number is suitable for every product. The relevant quantity depends on the microorganism, formulation, intended use and evidence. Avoid rules suggesting that every product should provide a particular number of billions.
Compare the count per recommended daily portion as well as per capsule. A front-of-pack figure spread across three capsules is not the same as that quantity in one capsule.
Do acid-resistant capsules matter?
Stomach and intestinal conditions can reduce the survival of some live cultures. Delayed-release or otherwise protective formulations can improve survival in laboratory models and some human studies, but performance depends on the exact capsule, microorganism and finished formulation.
Do not assume that every HPMC capsule is gastro-resistant. If a seller makes an acid-resistance statement, look for a capsule specification, dissolution data or finished-product survival testing. Acid-tolerant microorganisms and an acid-resistant capsule are also different claims.
Does a shelf-stable product need refrigeration?
Not necessarily. Storage needs depend on the organisms, packaging, moisture control and stability data. Follow the product’s instructions and avoid storing capsules in hot or humid conditions unless the label specifically allows it.
How our 20 Billion CFU product is currently declared
Our 20 Billion CFU Live Cultures product currently declares 20 billion viable organisms per capsule and names eight microorganisms at genus-and-species level.
The current public information does not show individual strain codes. It describes the microorganisms as selected for acid and bile tolerance and identifies the shell as vegan HPMC; it does not establish that the capsule itself is gastro-resistant. We will only describe a best-before guarantee or specific capsule performance when those points are supported by the current manufacturer specification.
Can a UK supplement call itself “probiotic”?
UK advertising regulators generally treat “probiotic” as a health-related claim. Whether it is considered general or specific depends on the presentation, but it brings the wording within the GB health-claims rules. “Live cultures” is the more cautious factual description where there is no sufficiently relevant authorised claim.
A narrow authorised claim exists for specified live yoghurt cultures in qualifying yoghurt or fermented milk. It does not apply to these capsules.
Seven checks for comparing products
- Is the CFU count per capsule or per recommended daily portion?
- Is it measured at manufacture or supported through the best-before date?
- Are genus and species identified?
- Are full strain designations provided?
- Are storage conditions clear?
- Are capsule-performance statements supported by product-specific evidence?
- Does the wording compare quantity without implying that more CFU is automatically better?
How we checked this guide
We compared the current product page and label declarations with scientific guidance on strain identification, viable counts and shelf-life quality, and with current GB advertising guidance. Product information was checked on 31 July 2026.
Sources
- ISAPP consensus statement on the appropriate use of the term probiotic
- Improving End-User Trust in the Quality of Commercial Probiotic Products
- 2020 taxonomic revision of the genus Lactobacillus
- CAP guidance on probiotic claims
- GB nutrition and health-claims guidance
This article is for general information and is not medical advice. Food supplements are not a substitute for a varied, balanced diet or a healthy lifestyle. If you have persistent symptoms, a medical condition or take medication, seek advice from an appropriate healthcare professional.
Read live cultures explained, compare UK live-culture supplements by CFU, strain identification, format and price, or browse our 20 Billion CFU Live Cultures product.
Free UK Supplement Label Checklist
CFU is one of several useful label measures. Our printable guide covers serving sizes, ingredient amounts, NRVs, specialist units, pack duration, cautions and claims.
0 comments