Not all probiotics are the same. The strain matters as much as the genus — sometimes more.
Lactobacillus rhamnosus and Lactobacillus acidophilus are both classified as Lactobacillus, but they behave differently, colonise different parts of the gut, and have evidence behind them for different conditions. Choosing a probiotic based on genus alone — like choosing a drug based only on its chemical class — misses the point.
This guide covers the six probiotic strains in Biome Bliss: what each one does, what the research shows, and why they were selected together.
The Six Strains: Quick Reference
| Strain | Type | Primary benefit | Key research area |
|---|---|---|---|
| Saccharomyces boulardii | Yeast | Antibiotic resilience, diarrhoea prevention | AAD, H. pylori, IBS |
| Lactobacillus rhamnosus | Bacteria | Gut balance, immune support | AAD, eczema, vaginal health |
| Lactobacillus casei | Bacteria | Digestion, lactose breakdown | IBS, lactose intolerance, immunity |
| Streptococcus thermophilus | Bacteria | Lactose digestion, gut barrier | Lactose intolerance, gut lining, immune modulation |
| Lactobacillus plantarum | Bacteria | Bloating, nutrient absorption | IBS, gut barrier, inflammation |
| Propionibacterium freudenreichii | Bacteria | B12 production, gut lining support | Microbiome diversity, SCFAs |
Saccharomyces boulardii
Saccharomyces boulardii is the only yeast-based probiotic in this list — and that distinction is significant. Unlike bacterial probiotics, it is naturally resistant to antibiotics. This means it can be taken during a course of antibiotics without being destroyed, helping to maintain gut stability when the microbiome is most disrupted.
It is one of the most extensively researched probiotic organisms. A meta-analysis in Alimentary Pharmacology & Therapeutics (Szajewska & Kolodziej, 2015) covering 21 RCTs found significant reductions in antibiotic-associated diarrhoea. It also has good evidence in the context of H. pylori eradication therapy, traveller’s diarrhoea, and IBS.
S. boulardii is a transient organism — it doesn’t permanently colonise the gut, but it has significant effects during the time it’s present: strengthening the intestinal barrier, stimulating immune antibody production, and competing directly with pathogens for attachment sites.
Read the full guide to Saccharomyces boulardii →
Lactobacillus rhamnosus
Lactobacillus rhamnosus — particularly the well-studied strain L. rhamnosus GG — is among the most researched bacterial probiotics in the world. It adheres strongly to the intestinal lining and is known for its resilience in surviving gastric transit.
Its most consistent evidence is in preventing antibiotic-associated diarrhoea, especially in children, but its applications extend further. A study in The Lancet (Kalliomäki et al., 2001) found that L. rhamnosus GG given to high-risk infants reduced the incidence of eczema at two years by nearly 50%, suggesting effects on immune programming beyond the gut.
It is also one of the most studied strains in relation to vaginal microbiome health, where it helps maintain a balanced environment by producing lactic acid and competing with pathogenic bacteria.
For adults over 40, its role in modulating gut immunity and reducing gut inflammation makes it a well-chosen inclusion in a broad-spectrum formulation.
Read the full guide to Lactobacillus rhamnosus →
Lactobacillus casei
Lactobacillus casei is best known for its digestive applications — it’s the strain behind Yakult and several other commercial probiotic drinks. Beyond brand recognition, it has a meaningful evidence base.
It produces enzymes that support the breakdown of lactose, making it useful for people who experience discomfort from dairy. It also supports intestinal barrier function and has been studied in the context of both IBS and inflammatory bowel conditions.
A trial published in the World Journal of Gastroenterology (Agrawal et al., 2009) found that L. casei reduced bloating and improved stool consistency in patients with IBS. Its anti-inflammatory action is thought to work partly through modulating cytokine production in the gut lining.
L. casei also has immune-supportive properties. Research suggests it may help reduce the duration of common respiratory infections — relevant for the 40+ population, where immune function becomes progressively more important to maintain.
Read the full guide to Lactobacillus casei →
Streptococcus thermophilus
Streptococcus thermophilus is one of the two classical yogurt bacteria — alongside Lactobacillus bulgaricus — and has been part of the human diet through fermented dairy for thousands of years. Despite its genus name, which includes several pathogenic species, S. thermophilus is entirely safe and non-pathogenic, with one of the longest track records of safe use in food fermentation of any probiotic organism.
Its most established benefit is lactose digestion. S. thermophilus produces lactase (beta-galactosidase) — the enzyme that breaks down lactose, the sugar in milk that many adults struggle to digest. Research confirms that fermented dairy products containing S. thermophilus significantly reduce lactose maldigestion symptoms compared to unfermented dairy, making it particularly valuable for people who are lactose-sensitive.
Beyond lactose, S. thermophilus supports the gut lining. It promotes the expression of tight junction proteins — the molecular connections between intestinal epithelial cells — strengthening the gut barrier and reducing permeability. This mechanism complements the barrier-supportive effects of L. plantarum and L. casei in the Biome Bliss formulation.
S. thermophilus also has immunomodulatory properties. It stimulates the production of anti-inflammatory cytokines and has been shown to support a balanced gut immune environment. Research published in the Journal of Dairy Science (LeBlanc et al., 2004) found that S. thermophilus modulates gut immune activity in ways consistent with reduced intestinal inflammation.
In Biome Bliss, S. thermophilus complements the Lactobacillus strains — particularly L. casei and L. plantarum — in supporting dairy digestion, gut barrier integrity, and immune balance. Its long fermentation history also makes it a natural fit in a product built around a fermented delivery format.
Lactobacillus plantarum
Lactobacillus plantarum is one of the most metabolically versatile probiotic strains. It is naturally found in many fermented foods — sauerkraut, kimchi, olives, sourdough — and is highly adaptable to the gut environment.
Its most consistent benefit is reducing bloating and gas. A randomised controlled trial in the World Journal of Gastroenterology (Ducrotté et al., 2012) found that L. plantarum 299v significantly reduced abdominal pain and bloating in IBS patients compared to placebo.
Beyond digestive comfort, L. plantarum may support nutrient absorption — particularly iron and zinc — by reducing anti-nutritional factors in the gut environment. It also has evidence for supporting the intestinal barrier, reducing permeability associated with low-grade gut inflammation.
It produces antimicrobial compounds (bacteriocins) that help suppress the growth of potentially harmful bacteria, contributing to a more balanced microbiome overall.
Read the full guide to Lactobacillus plantarum →
Propionibacterium freudenreichii
Propionibacterium freudenreichii is the least well-known of the six strains, but it has properties the others lack.
It is one of the few gut bacteria that can produce vitamin B12 during fermentation — a nutrient that is primarily found in animal products and is therefore a common concern for people reducing meat consumption or following plant-based diets. Adults over 40 are also at higher risk of B12 insufficiency due to reduced gastric acid production, which impairs absorption from food.
Beyond B12, P. freudenreichii produces short-chain fatty acids (SCFAs) — particularly propionate and acetate — which serve as fuel for gut lining cells, support the intestinal barrier, and have anti-inflammatory effects. Research published in Frontiers in Microbiology (Cousin et al., 2016) demonstrated that P. freudenreichii modulates the gut immune environment and supports gut lining integrity through SCFA production.
It is relatively rare in commercial probiotic supplements, making it one of the distinguishing features of Biome Bliss’s formulation.
Why Multiple Strains Together?
Each strain occupies a slightly different niche in the gut and exerts its effects through different mechanisms. S. boulardii focuses on pathogen competition and immune antibody production. The Lactobacillus strains and S. thermophilus support the gut lining, aid digestion, and modulate immune function at different points. P. freudenreichii adds SCFA production and B12 synthesis.
Combining strains doesn’t guarantee the effects simply add up — but formulations built around strains with complementary mechanisms and non-overlapping evidence bases are more likely to produce broad benefit than any single-strain product.
The research also indicates that microbiome diversity itself is associated with better health outcomes. A multi-strain approach supports a more diverse gut environment.
What to Look For in a Probiotic Supplement
- Are the strains named specifically? Genus and species (e.g. Lactobacillus rhamnosus) is the minimum. Strain designation (e.g. GG) is better.
- Is CFU count stated at time of use? Many products state CFU at manufacture, which declines over time. Look for guarantees at end of shelf life.
- What is the delivery format? Capsules, powders, and fermented liquids each have different survival rates through the gastric environment. Naturally fermented formats create a protective matrix that can improve delivery.
- Are there unnecessary additives? Artificial sweeteners, fillers, and synthetic preservatives can counteract the benefit of the probiotics themselves.
For a full breakdown of how to improve your gut health through diet and lifestyle as well as supplementation, see our guide to gut health.
Frequently Asked Questions
What is the difference between probiotic strains?
Different probiotic strains — even within the same genus — have distinct mechanisms, colonisation behaviour, and evidence bases. L. rhamnosus GG is well-evidenced for antibiotic-associated diarrhoea and eczema prevention, while L. plantarum 299v has stronger evidence for IBS bloating. Choosing by strain rather than genus is more likely to produce targeted benefit.
Which probiotic strain is best for gut health?
No single strain is universally best. For broad gut health support, a multi-strain formulation covering complementary mechanisms — barrier support, immune modulation, SCFA production — is likely to be more effective than a single-strain product. L. rhamnosus, L. plantarum, and S. boulardii are among the most well-evidenced strains for general gut health.
Should I take a single-strain or multi-strain probiotic?
For specific, well-defined conditions (such as antibiotic-associated diarrhoea), a single strain with strong targeted evidence may be sufficient. For general gut health maintenance, a multi-strain product built around strains with complementary mechanisms is typically a better approach.
What probiotic strain is best for bloating?
Lactobacillus plantarum has the most consistent evidence specifically for reducing bloating and abdominal pain. A randomised controlled trial found L. plantarum 299v significantly outperformed placebo for IBS-related bloating and discomfort.
Can probiotics be taken with antibiotics?
Bacterial probiotic strains are typically killed by antibiotics, so timing matters. Saccharomyces boulardii, being a yeast rather than a bacterium, is antibiotic-resistant and can be taken concurrently. Bacterial strains should be taken a few hours apart from the antibiotic dose.
References
- Szajewska H & Kolodziej M (2015). Systematic review with meta-analysis: Saccharomyces boulardii in the prevention of antibiotic-associated diarrhoea. Alimentary Pharmacology & Therapeutics, 42(7), 793–801. pubmed.ncbi.nlm.nih.gov/26216624
- Kalliomäki M et al. (2001). Probiotics in primary prevention of atopic disease: a randomised placebo-controlled trial. The Lancet, 357(9262), 1076–1079. pubmed.ncbi.nlm.nih.gov/11297958
- Ducrotté P et al. (2012). Clinical trial: Lactobacillus plantarum 299v (DSM 9843) improves symptoms of irritable bowel syndrome. World Journal of Gastroenterology, 18(30), 4012–4018. pubmed.ncbi.nlm.nih.gov/22912552
- LeBlanc JG et al. (2004). Bacteria as vitamin suppliers to their host: a gut microbiota perspective. Journal of Dairy Science. PubMed
- Cousin FJ et al. (2016). Microbiota-accessible carbohydrates broaden the range of microbiomes responding to intervention. Frontiers in Microbiology, 7, 440. pubmed.ncbi.nlm.nih.gov/27065976
This article is for informational purposes only and does not constitute medical advice. Please consult a GP or registered healthcare professional before starting any new supplement.
