For antibiotic-associated diarrhoea and traveller's diarrhoea: S. boulardii wins — it's the only probiotic that cannot be killed by antibiotics. For long-term gut health maintenance, IBS management, and immune modulation: Lactobacillus strains have broader evidence. Most people benefit from using both strategically.
Overview
Saccharomyces boulardii and Lactobacillus species are the most clinically studied probiotics, but they are fundamentally different organisms — one is a yeast, the other a bacterium. This distinction has major practical consequences for how and when to use them.
What Is Saccharomyces Boulardii?
A beneficial yeast (Saccharomyces cerevisiae var. boulardii) isolated from lychee and mangosteen in Southeast Asia. Unlike bacterial probiotics, it cannot be killed by antibiotics — making it uniquely valuable during antibiotic courses. Produces proteases that destroy C. difficile toxins and reduces gut inflammatory cytokines.
Best for: Antibiotic-associated diarrhoea prevention, C. difficile infection recurrence prevention, Traveller's diarrhoea prevention and treatment, Acute infectious diarrhoea.
Standard dose: 250–500 mg 2× daily; take 2 hours away from antibiotics.
Side effects: Generally excellent tolerance. Not suitable for severely immunocompromised individuals (theoretical fungal infection risk). May cause mild gas initially..
What Is Lactobacillus Strains?
Gram-positive lactic acid bacteria — the most studied probiotic genus. Hundreds of strains exist with different clinical applications. Key strains include L. rhamnosus GG (diarrhoea), L. acidophilus (IBS), L. reuteri (cholesterol, H. pylori), and L. crispatus (vaginal health). The strain matters enormously — 'Lactobacillus' alone is not specific enough.
Best for: IBS management (specific strains), Long-term gut health maintenance, Vaginal health (L. crispatus, L. rhamnosus GR-1), Immune modulation.
Standard dose: 5–50 billion CFU/day depending on strain and indication.
Side effects: Initial gas and bloating (1–2 weeks). Not suitable for severely immunocompromised. Antibiotic-sensitive — take 2 hours away from antibiotics..
Evidence & Absorption Scores
We scored both on four dimensions: quality of clinical evidence, bioavailability, GI tolerance, and value for money. Scores are out of 10:
Head-to-Head Comparison
| Category | ▲ Saccharomyces Boulardii | ▲ Lactobacillus Strains |
|---|---|---|
| Antibiotic Resistance | Yes — antibiotics cannot kill it (yeast) | No — killed by broad-spectrum antibiotics |
| Take During Antibiotic Course | Yes — ideal use case | Yes — but take 2+ hours after antibiotics |
| Antibiotic-Associated Diarrhoea | Gold standard — 61% risk reduction | Helpful (L. rhamnosus GG) but less robust |
| C. difficile Prevention | Excellent — destroys C. diff toxins | Helpful as adjunct |
| IBS Management | Moderate evidence | Strong evidence for specific strains |
| Long-Term Gut Health | Not designed for ongoing use — use situationally | Ideal for ongoing gut microbiome support |
| Vaginal Health | No specific evidence | Excellent — L. crispatus, L. rhamnosus GR-1 |
| Immune Modulation | Good — via gut barrier protection | Strong — direct immune cell interaction |
| Immunocompromised Safety | Avoid in severe immunocompromise | Avoid in severe immunocompromise |
Best Uses for Each
✅ Saccharomyces Boulardii — Best For
- Antibiotic-associated diarrhoea prevention
- C. difficile infection recurrence prevention
- Traveller's diarrhoea prevention and treatment
- Acute infectious diarrhoea
✅ Lactobacillus Strains — Best For
- IBS management (specific strains)
- Long-term gut health maintenance
- Vaginal health (L. crispatus, L. rhamnosus GR-1)
- Immune modulation
Who Should Choose Saccharomyces Boulardii?
▲ Choose Saccharomyces if:
Anyone on antibiotics (start immediately, take 2h after each antibiotic dose, continue 2 weeks post-course), travellers to high-risk areas, people recovering from C. diff, or those with acute diarrhoea.
▲ Choose Lactobacillus if:
People wanting long-term gut microbiome support, IBS management, vaginal health, cholesterol reduction, or immune modulation. Choose strain-specific products for your indication, not generic 'Lactobacillus.'
Can You Take Both?
Yes — and this is strongly recommended during and after antibiotic courses. S. boulardii protects against antibiotic-associated diarrhoea during the course; Lactobacillus strains help restore the microbiome after. Continue S. boulardii for 2 weeks post-antibiotics, then transition to a Lactobacillus/Bifidobacterium-dominant probiotic.
Frequently Asked Questions
The Bottom Line
For antibiotic-associated diarrhoea and traveller's diarrhoea: S. boulardii wins — it's the only probiotic that cannot be killed by antibiotics. For long-term gut health maintenance, IBS management, and immune modulation: Lactobacillus strains have broader evidence. Most people benefit from using both strategically.