Strains and CFU
The names on a probiotic label can look daunting, yet they tell you exactly which microbes are in the pack. This guide explains probiotic strains, from the difference between lactobacilli and bifidobacteria to strain codes and the 2020 name changes, so you can compare labels with confidence.
Species table
Many Lactobacillus species were renamed in 2020, so labels may show either the new or the old name. The table gives current names with former names in brackets. It describes where each species usually appears, not what it does.
| Species | Group | Typically found in | Notes |
|---|---|---|---|
| Lactobacillus acidophilus | Lactobacilli | Capsules, powders | Kept its name in 2020 and appears in many multi-strain blends |
| Lacticaseibacillus rhamnosus (formerly L. rhamnosus) | Lactobacilli | Capsules, powders, drops | Many different strains are sold under this species |
| Lacticaseibacillus paracasei (formerly L. paracasei) | Lactobacilli | Capsules, powders | Common in multi-strain products |
| Lactiplantibacillus plantarum (formerly L. plantarum) | Lactobacilli | Capsules, powders, sachets | Comparatively tolerant of processing |
| Limosilactobacillus reuteri (formerly L. reuteri) | Lactobacilli | Drops, chewables | Often supplied in oil-based drops |
| Lactobacillus gasseri and L. crispatus | Lactobacilli | Capsules | Both kept the Lactobacillus name in 2020 |
| Bifidobacterium longum, B. breve, B. bifidum | Bifidobacteria | Capsules, powders, drops | Sensitive to oxygen, so packaging matters |
| Bifidobacterium animalis subsp. lactis | Bifidobacteria | Capsules, powders, chewables | Often shortened to B. lactis on labels |
| Streptococcus thermophilus | Lactic acid bacteria | Powders, capsules | Also one of the cultures used to make yoghurt |
| Saccharomyces boulardii | Probiotic yeast | Capsules, sachets | A yeast rather than a bacterium, usually listed separately |
| Bacillus coagulans (now Heyndrickxia coagulans) | Spore-formers | Gummies, chewables, capsules | Spores tolerate heat |
| Bacillus subtilis | Spore-formers | Capsules, gummies | Forms hardy spores |
The basics
Lactobacilli and bifidobacteria are the two groups you will see most often on probiotic labels. Lactobacilli are lactic acid bacteria, familiar from fermented foods such as yoghurt and sauerkraut, and many of them cope reasonably well with processing. Bifidobacteria are more sensitive to oxygen, so products that contain them tend to rely on protective packaging such as foil blisters or sealed sachets.
Neither group is better than the other. Research is specific to individual strains, so a finding about one strain does not automatically apply to another strain of the same species, let alone to a whole group. Many products combine species from both groups, and the label should list each one.
A full strain name has a genus, a species and a strain code. The genus and species tell you what kind of microbe it is, and the code, a short run of letters or numbers, identifies one particular strain within that species. A label that lists only species names makes it hard to compare products or to look up what has been published about the strains inside.
In 2020 the old Lactobacillus genus was split into several new groups after genetic analysis showed it held very different bacteria. Lactobacillus rhamnosus became Lacticaseibacillus rhamnosus, for example, and Lactobacillus plantarum became Lactiplantibacillus plantarum. The microbes themselves did not change, so a product using the old name is not out of date, and some labels print both.
Beyond lactobacilli
S. boulardii is a yeast rather than a bacterium, and labels sometimes call it Saccharomyces cerevisiae var. boulardii. It is usually sold in capsules or sachets and is often listed separately from bacterial cultures, sometimes with its own count. Our guide on how to read a probiotic label shows where to find it.
Species such as Bacillus coagulans and Bacillus subtilis form spores, a dormant state with a tough outer coat. Spores tolerate heat far better than most cultures, which is why they suit probiotic gummies and chewables.
Synbiotics and added ingredients
Some products pair live cultures with a prebiotic fibre, and these are often called synbiotics. Others add heat-treated cultures or vitamins and minerals. Each of these appears in the ingredients list, so it helps to know what they are.
Powders tend to carry the most fibre, as our page on probiotic powders and sachets explains.
No health claims are currently authorised for probiotics in Great Britain. When a pack says "vitamin D contributes to the normal function of the immune system", the claim belongs to the vitamin, not to the cultures.
Our probiotic quality checklist covers other wording to watch for.
Comparing products
When you compare two products, line up the full strain names first, then check the CFU and the date it applies to. Products that share a species may contain quite different strains, so matching the codes is the only way to tell whether two labels describe the same culture. The guide on how to choose a probiotic supplement puts these checks in order.
Format matters too, because not every strain survives every format. Most lactobacilli and bifidobacteria are found in probiotic capsules, powders and drops, while gummies mostly rely on spore-formers. If a name on a label is unfamiliar, ask us a question and Probiotic Supplements UK will explain it.
FAQs
Neither group is better in general. Research is specific to individual strains, so the full strain name tells you more than the group it belongs to. Many products combine species from both.
Many Lactobacillus species were renamed in 2020, so you may see Lacticaseibacillus rhamnosus where you expected Lactobacillus rhamnosus. The microbe is the same, and some labels print both names to help shoppers.
Not automatically. A product with a few clearly named strains and a count stated until the best-before date can tell you more than a long list with no strain codes. Follow the label for how much to take.
Many are, but not all, because some cultures are grown on dairy-based media. Look for a vegan or vegetarian statement on the pack, and check the capsule shell too, as some are made from gelatine.
Send us the strain names from a label and we will explain what each part means and whether it was renamed. We answer by email and do not recommend brands.