Multi-Strain Probiotics: Are More Strains Better?

More probiotic strains do not automatically make a better probiotic. What matters more is which strains are included, what they have been studied for and whether they are supplied at research-relevant amounts.

A supplement containing 15 strains may sound more impressive than one containing four, but strain count alone tells us very little about the strength of the evidence behind a product.

A systematic review of 65 randomised controlled trials involving 10,863 people found that, in most of the matched comparisons available, multi-strain mixtures were not significantly more effective than single-strain probiotics.¹

What is a multi-strain probiotic?

A multi-strain probiotic contains two or more bacterial strains.

A strain is a specific, identifiable version of a bacterial species. For example, Lacticaseibacillus rhamnosus is the species, while GG identifies the specific strain.

This distinction matters because findings from one strain should not automatically be applied to another, even when they belong to the same species. Research suggests that probiotic effects can be both strain-specific and outcome-specific.²

What matters more than the number of probiotic strains?

When comparing probiotics, look beyond the number of strains on the front of the pack:

• Specific, named strains. Look for strain identifiers such as L. rhamnosus GG rather than only the species name. This allows you to identify research carried out using that particular strain.
  
  
• Relevant human research. Check whether the strain has been studied in people for the outcome you are interested in. Searching the full strain name on PubMed is a useful starting point.
  
  
• Research-relevant amounts. A higher total CFU count is not automatically better. The more useful question is whether each strain is supplied at an amount relevant to the human research behind it. There is no single ideal probiotic dose that applies to every strain.
  
  
• Transparency. A long ingredient list does not necessarily mean stronger evidence. Being able to identify the strains and understand the research behind them is more informative than strain count alone.

There is no scientifically established ideal number of probiotic strains.

Do more probiotic strains increase gut microbiome diversity?

Not necessarily. A 2026 systematic review and meta-analysis examined probiotic supplementation and gut microbiome diversity in healthy people. Across several commonly used measures of diversity, researchers found no significant difference between probiotic and control groups.³

That does not mean probiotics have no effect. It reflects an important point about how many probiotics work: taking more strains does not necessarily mean that more of those strains will permanently establish themselves in your gut.

Many probiotic strains are transient, meaning they pass through the digestive tract rather than becoming long-term members of the gut microbiome. While there, they can still exert functional effects by interacting with resident microbes, producing metabolites and influencing processes involving the gut barrier and immune system.

So, a probiotic can have biological effects without measurably increasing overall microbiome diversity and a higher number of strains does not necessarily mean a more diverse gut microbiome.

Single-strain vs multi-strain probiotics: which is better?

Neither is automatically better simply because of the number of strains it contains. A single strain may have strong human evidence for a particular outcome, while a multi-strain product needs to be assessed based on the evidence behind the strains and the amounts provided.

One issue to look out for with products containing a long list of strains is how the total CFU is divided between them. A product may advertise 20, 50 or even 100 billion CFU in total, but if that total is spread across 10 or more strains, the amount of each individual strain may be much lower than the amount used in relevant clinical studies.

Rather than asking whether a probiotic contains more strains, ask:
Which specific strains are included, how much of each is provided, and what human research supports them at those amounts?

How we approached this at EVIDOSE®

When formulating EVIDOSE® Live Biotic Daily+, our aim was not to create the longest strain list.

Instead, we selected four of the world’s most extensively researched strains: LGG, NCFM, HN019 and DSM 15954 (BB-12) and considered the human research behind each individual strain when deciding on the formulation and amounts used.

Our approach is simple: prioritise specific strains, relevant human research and research-relevant amounts over an impressive-looking strain count.

Explore Live Biotic Daily+ →

References

1. McFarland LV. Efficacy of Single-Strain Probiotics Versus Multi-Strain Mixtures: Systematic Review of Strain and Disease Specificity. Digestive Diseases and Sciences. 2021;66(3):694–704. doi:10.1007/s10620-020-06244-z.
2. McFarland LV, Evans CT, Goldstein EJC. Strain-Specificity and Disease-Specificity of Probiotic Efficacy: A Systematic Review and Meta-Analysis. Frontiers in Medicine. 2018;5:124. doi:10.3389/fmed.2018.00124.
3. Éliás AJ, Földvári-Nagy KC, Al-Gharati YZ, et al. Effect of probiotic supplementation on the gut microbiota diversity in healthy populations: a systematic review and meta-analysis of randomised controlled trials. BMC Medicine. 2026;24:71. doi:10.1186/s12916-025-04602-0.