Based on a webinar by Professor Emeritus Atte von Wright, Scientific Advisor at Biosafe Webinar 2/3 in our microbiome series held on 19 March 2026.
If you missed the session, explore our ongoing webinar series overview and the latest webinar recordings.
Why this topic matters
In our first session of the series, we discussed how the human gut microbiota influences nutrition, physiology, immunity and even the nervous system. This naturally raises the practical question: can we shape the intestinal microbiota to support health?
Two main approaches are being used today:
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Probiotics: live microorganisms that, when administered in adequate amounts, confer a health benefit
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Prebiotics: selective substrates that feed beneficial microbes
Both aim towards a similar goal, but through different mechanisms. Probiotics act directly by adding specific strains. Prebiotics act indirectly by modulating the ecosystem through nutrition.
From Metchnikoff to modern evidence
The probiotic idea is more than a century old. Elie Metchnikoff (Nobel laureate, 1908) popularised fermented milk (yoghurt) in Western Europe after observing the diets of long‑lived Carpathian peasants. He hypothesised two broad bacterial “camps”: putrefactive species producing harmful metabolites, and fermentative species producing organic acids that support health. While modern science has refined these views, Metchnikoff’s core intuition that microbes in our gut can influence wellbeing sparked a line of research that continues today.
In the 1980s, scientific and industrial interest surged again. Researchers began to apply double‑blind, controlled study designs and to define quantitative endpoints, bringing probiotic research closer to the standards used in pharmaceuticals. For historical, technological and safety reasons, much of the work focused on lactic acid bacteria, bifidobacteria and yeasts.
A critical principle emerged: probiotic properties are strain‑specific, not species‑level generalities. Two strains from the same species can behave very differently in efficacy and mode of action. This is foundational for product development and regulation alike.
What today’s evidence shows
The strongest probiotic evidence currently relates to acute intestinal disorders. Benefits are now well documented for several well‑characterised strains, especially in certain forms of diarrhoea (e.g., viral or antibiotic‑associated).
Hallmark examples discussed in the webinar were:
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Lacticaseibacillus rhamnosus GG (LGG), arguably the best‑documented probiotic; alleviates/can help resolve viral and antibiotic‑induced diarrhoea and shows immune‑stimulatory properties.
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Saccharomyces boulardii CNCM I‑745, a yeast with a century‑long history of use; multiple studies support its role against infectious diarrhoea.
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Escherichia coli Nissle 1917, reported benefits include alleviating inflammatory bowel conditions and constipation in specific contexts.
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Other widely used strains with published evidence include Lacticaseibacillus casei Shirota, Enterococcus lactis SF68 (formerly classified as E. faecium), Lactobacillus johnsonii LA1, Limosilactobacillus reuteri (BioGaia strains), and Bifidobacterium animalis subsp. lactis BB‑12.
For chronic intestinal diseases, cancer risk reduction, cholesterol lowering, or mental health effects (anxiety/depression), evidence is still fragmentary. There are interesting signals but, echoing Prof. von Wright, the jury is still out. Any potential benefits here are also likely to be highly strain‑dependent, and claims should not be over‑generalised.
Key takeaway: Use precise strains and match them to well‑designed studies; avoid extrapolating species‑level claims to any strain.
How probiotics may work
Although many details are still being unravelled, several mechanisms have recurring support:
Immune modulation
Some probiotic strains appear to strengthen or fine-tune host immune responses. Secretory IgA is one commonly discussed marker, and some strains may act, in effect, as “live adjuvants” that fine‑tune host responses to pathogens.
Competitive exclusion
Probiotics may occupy ecological niches in the intestine and reduce pathogen colonisation in the same space.
Production of bioactive metabolites
Some strains secrete small molecules that may suppress opportunistic organisms or otherwise shape the gut environment. In many cases the chemistry often still under characterisation.
Intestinal adhesion
For some strains, intimate contact with the intestinal epithelium appears to be important. One classic case is LGG adhesion. In vivo work with colonoscopy patients showed that LGG could be detected in biopsy samples from the colonic mucosa long after it disappeared from faeces, consistent with mucosal adherence. Later, pilus proteins were identified as key factors behind this adhesive behaviour.
Formulation matters
A probiotic that cannot survive the journey through the upper gastrointestinal tract will not do much in the colon. Acid, bile, and digestive transit all work against survival. Encapsulation and slow‑release approaches can improve survivability and delivery, though these are still more common in pharmaceutical‑style products than in foods.
Prebiotics: feeding the right microbes
What they are
Prebiotics are typically fibres, oligosaccharides or sugar alcohols that are not absorbed in the small intestine but reach the colon to be fermented by resident microbes. They can be present naturally in foods or be isolated or synthesised and then added to products.
Main groups and sources:
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Fructooligosaccharides (FOS) and inulin: abundant in artichoke, chicory, onion, asparagus, banana
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Glucooligosaccharides (GOS): naturally present in legumes and dairy
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Human milk oligosaccharides (HMOs): specialised compounds, increasingly used in infant nutrition
What they do
A well‑known effect is bifidogenesis (promoting Bifidobacterium), often accompanied by increases in lactic acid bacteria.
Reported or proposed outcomes include improved barrier function, laxation or better bowl function, better lipid profiles in some settings, enhanced mineral absorption of calcium and magnesium, satiety effects and, depending on the substrate, changes in short‑chain fatty acid (SCFA) production. Butyrate is of particular interest because of its role in gut physiology and host metabolism.
That said, not all findings are uniform across studies, and dose tolerance varies. Excessive intake can cause indigestion in some individuals.
Ingredients such as inulin are attractive because they offer both functional (prebiotic) and technological benefits. They are widely used across categories like bakery, beverages, and reduced-calorie products, where they contribute to texture and mouthfeel as well as microbe modulation.
Postbiotics and synbiotics are gaining ground
The webinar also covered two related categories.
Postbiotics
Postbiotics are heat‑inactivated or dead microbes or their components interact with their host by modulating host responses. Even without viability, cell‑surface structures and other components may influence epithelial or immune responses. Early products exist and this area is developing quickly.
Synbiotics
Synbiotics combine a probiotic and a prebiotic in the same product. In experimental settings, synbiotics often outperform probiotics alone, and multiple commercial preparations in the market already use this approach.
What we can conclude (so far)
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Probiotics have documented, practical benefits in certain acute intestinal disorders, especially when well-characterised strains are used. For chronic diseases and extra‑intestinal outcomes, evidence is interesting but not yet convincing. More strain‑specific, well‑controlled studies are needed.
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Prebiotics can consistently modulate the microbiota in directions generally considered beneficial, but individual tolerance can limit use at higher doses.
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Future progress depends on precision: selecting the precise strain or substrate, designing robust clinical studies, and matching the product to the appropriate regulatory pathway.
Personalisation may be the future, but we are not there yet
Looking ahead, Prof. von Wright’s offered an optimistic yet measured view. As we improve our characterisation of host–microbiota interactions, and of how the modes of action of specific strains and substrates actually work, more personalised probiotic, prebiotic, and synbiotic strategies may become possible. In time, we may be able to design targeted interventions for specific complaints, risk groups, or physiological goals.
That vision is plausible. It is not here yet.
For now, bringing a successful probiotic product to market is a long project with scientific, technological and regulatory workstreams moving in parallel. The more novel the product and the stronger the intended claims, the more demanding the journey becomes.
These regulatory questions will be the focus of our final webinar in the series.
Q&A highlights from the webinar
Do you personally “self‑medicate” with probiotics?
Prof. von Wright said that he occasionally uses them for specific issues and has had positive experiences, though not as part of any long-term longevity strategy.
Do milk‑based and plant‑based probiotic products differ?
Comparative studies are still limited. Plant-based substrates often carry naturally occurring prebiotics, which means some products could function as “natural synbiotics.” Dairy has historically dominated because many strains grow well in milk and fermentation may improve digestibility, for example through lactose breakdown. In practice, the best choice depends on tolerance, diet, and the specific product.
What regulatory strategy does Biosafe recommend for probiotic projects?
That depends on product type and intended claims. Foods with vague, non‑specific messaging face lighter requirements than products making explicit health claims. Novel foods and pharmaceutical‑style forms raise their own additional issues. Many of the underlying studies, including safety, characterisation, and efficacy, are relevant across microbial product categories both in foods and feeds. Biosafe supports both regulatory pathway planning and the design or coordination of needed studies.
How many probiotics actually survive to the colon?
The upper gastrointestinal tract is a hostile environment. Acid and bile reduce viability, so formulation becomes important. Encapsulation and slow‑release systems can improve survival and delivery, though they are still more common in pharmacy‑style products than foods.
What about probiotics in cosmetics or cleaning solutions?
Many so-called probiotic cosmetics actually use inactivated microbes, which places them closer to postbiotics. Claims and evidence levels vary widely, and regulatory guidance is less developed than in food and feed. In cleaning products, there is experimental work with Bacillus, though authorised product frameworks are still being developed in many jurisdictions.
Is Biosafe involved in advocacy around the terms “probiotic” and “prebiotic” on EU labels?
Biosafe is not an advocacy organisation as such. However, we participate in industry working groups, e.g. via associations, and support clients with the regulatory and scientific processes behind the scenes.
