Compare probiotic supplements by CFU count, strain diversity, and use-case match. A 50-billion-CFU product is not automatically better than a 10-billion one — strain identity matters more than dose. Math + product knowledge, not medical advice.
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Side-by-side comparison
| Product | CFU at manufacture | Strains | Storage | Use-case match | Trade-offs |
|---|
Highlighted rows = best fit for selected goal. Doesn’t constitute clinical recommendation.
What CFU actually means (and what it doesn’t)
CFU = Colony-Forming Units. It’s a count of live bacteria capable of replicating, measured by plating an aliquot of the product on growth media and counting colonies that grow. Key caveats:
- “At manufacture” vs “through expiration”: Federal regulators don’t require either. Brands that label “guaranteed through expiration” have done stability studies; brands that label “at manufacture” might lose 50-90% potency before you buy it.
- 10 billion vs 50 billion: Most successful RCTs used 10-25 billion CFU/day. Higher doses (50-100B) are marketing-led — there’s no consistent dose-response above 25B for most indications.
- Strain identity matters more than total CFU: “Lactobacillus rhamnosus GG” (one strain) has Cochrane-level evidence for acute infectious diarrhea. “Lactobacillus rhamnosus” (no strain ID) on a label means you don’t know what you’re getting.
- Diversity isn’t always good: Multi-strain products (10-15 strains) sound impressive but most clinical evidence is for single-strain or dual-strain combinations. Diversity is reasonable for general use; for specific conditions, look for the specific strain that was studied.
Strain-condition evidence summary
| Condition | Best-evidence strain(s) | Typical CFU/day |
|---|---|---|
| Antibiotic-associated diarrhea | Saccharomyces boulardii (CNCM I-745); Lactobacillus rhamnosus GG | 5-10B |
| IBS overall symptoms | Bifidobacterium infantis 35624 (Align); multi-strain VSL#3 / Visbiome | 1-4B (B. infantis); 450B (Visbiome) |
| Acute infectious diarrhea (children) | Lactobacillus rhamnosus GG; Saccharomyces boulardii | 10B |
| Bacterial vaginosis recurrence (adjunct to antibiotics) | Lactobacillus crispatus; L. rhamnosus GR-1 + L. reuteri RC-14 | 1-10B |
| Infant colic (breastfed) | Lactobacillus reuteri DSM 17938 (BioGaia) | 100M (0.1B) |
| Travel diarrhea | Saccharomyces boulardii; L. rhamnosus GG | 5-10B |
| H. pylori adjunct (with PPI + antibiotics) | Lactobacillus reuteri; Saccharomyces boulardii | 5B |
Storage requirements explained
- Refrigerated required: Some Lactobacillus + Bifidobacterium strains are temperature-sensitive. Brands like Visbiome and certain Florastor variants need cold-chain from manufacturer to your fridge.
- Shelf-stable: Saccharomyces boulardii (yeast, not bacterium) is heat-stable. Some lyophilized (freeze-dried) Lactobacillus formulations are stable at room temp through expiration if dose was over-formulated to account for loss.
- Time-released / acid-resistant capsules: Brands like Culturelle and Align use enteric coatings or delayed-release capsules so bacteria survive stomach acid. Without this, much of the dose dies before reaching the colon.
