Written by Barry Lees, Founder of The Health Improvers. Last updated 15 July 2026.
Live-culture supplements are covered in numbers and Latin names, and the marketing rarely explains them. Here's a straight guide to what actually matters on the label — so you can compare products properly. (New to the topic? Start with what probiotics and live cultures are.)
1. Strains — the names matter more than the count
A "strain" is a specific type of bacteria, usually written as three parts — genus, species and strain (for example Lactobacillus acidophilus). The families you'll see most often:
- Lactobacillus — e.g. acidophilus, rhamnosus, plantarum. Among the most-studied groups.
- Bifidobacterium — e.g. longum, bifidum, breve. Naturally common in the gut.
- Saccharomyces boulardii — a beneficial yeast rather than a bacterium.
The honest takeaway: a product that clearly names its strains is being transparent. "More strains" isn't automatically better — what matters is that they're named, so you know exactly what you're getting.
2. CFU — what the "billions" mean
CFU stands for colony-forming units — the number of live organisms per serving. You'll see figures like 4 billion, 20 billion, even 50 billion CFU. A few honest points:
- A higher CFU isn't automatically "better" — it depends on the strains and the product's purpose.
- What matters is that the CFU is guaranteed to the end of shelf life, not just "at time of manufacture" (live organisms decline over time).
- For everyday use, mid-range counts (a few billion to ~20 billion) are typical and sensible.
3. Acid resistance — helping cultures survive the journey
Stomach acid is harsh, so some products use acid-resistant capsules (or naturally robust strains) designed to help the live cultures make it through to the lower digestive tract. It's a genuinely useful feature to look for, and a sign a product has been thought through.
4. Storage — fridge or shelf-stable?
Some live cultures need refrigerating; many modern strains and packaging formats are shelf-stable. Neither is inherently better — just check the storage instructions match how you'll actually keep it.
5. The rest of the label
- Vegan/vegetarian capsule shell, if that matters to you.
- UK manufacture to GMP standards.
- Honest wording — responsible brands describe strains and CFU rather than promising to "cure" digestive issues, because those claims aren't authorised.
Putting it together
A trustworthy live-cultures supplement names its strains, guarantees its CFU to end of shelf life, and — ideally — uses acid-resistant capsules. Our own 20 Billion CFU 8-Strain Live Cultures is built on those principles: eight named strains, 20 billion CFU per capsule, in acid-resistant vegan capsules. For the wider picture read what probiotics are, and to compare products, our Best UK Probiotic Supplements 2026 guide.
Disclaimer: This article is for general information only and is not medical advice. Food supplements are not a substitute for a varied, balanced diet or a healthy lifestyle, and are not intended to treat, cure or prevent any disease. If you have ongoing digestive symptoms, please consult your GP. Always read the label.
Explore more in our Digestion & Gut Health range.
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