The UK probiotic market is worth over £500 million — but there is something most consumers do not know
The European Food Safety Authority (EFSA) has never approved a single health claim for any probiotic product. Not one. Every application submitted — and there have been hundreds — has been rejected for insufficient evidence.
This means that in the UK and EU, no probiotic supplement can legally claim to "support gut health," "improve digestion," or "boost immunity." The word "probiotic" itself is considered an implied health claim by some EU regulators.
That does not mean probiotics are useless. It means the regulatory bar is extraordinarily high, and the evidence — while real — is more nuanced than the marketing suggests. This guide explains what probiotics are, what the clinical trial evidence actually shows, and what to look for if you decide to take one.
What are probiotics?
The internationally accepted definition comes from a joint FAO/WHO working group and was reaffirmed by an expert panel in Hill et al. (2014):
"Live microorganisms which, when administered in adequate amounts, confer a health benefit on the host."
This is a scientific definition, not a regulatory one. In the EU and UK, there is no legal definition of "probiotic" in food law, and regulators have treated the term itself as an unauthorised health claim in certain enforcement contexts.
The key elements of the definition are worth unpacking:
- Live — the organisms must be alive when consumed, which raises immediate questions about whether they survive manufacturing, shelf storage, and passage through stomach acid
- Adequate amounts — dose matters, and the effective dose varies by strain
- Health benefit — this must be demonstrated in human clinical trials for the specific strain, not assumed from the genus or species
The regulatory reality: why no probiotic claim has been approved
Between 2008 and 2012, EFSA assessed hundreds of health claim applications for probiotics. All were rejected. The EFSA Register of nutrition and health claims contains no authorised claims for any probiotic strain.
The rejections were not because EFSA concluded probiotics are ineffective. The primary reasons were:
- Insufficient characterisation — many applications did not adequately identify the specific strain being studied
- Cause and effect not established — EFSA required a clear causal mechanism linking the strain to the claimed benefit, not just an association
- Study quality — many supporting studies had methodological limitations, small sample sizes, or lacked appropriate controls
As Rijkers et al. (2013) analysed in their review of EFSA opinions, the authority applied a pharmaceutical-level evidence standard to food-category products — a standard that even some well-established nutritional science struggles to meet.
The practical consequence is stark: clinical trial evidence for specific probiotic strains exists and continues to grow, but none of it can be communicated to consumers through product marketing in the UK. This is why transparency about what the evidence does and does not show matters more than ever.
What does the clinical evidence show?
The single most important principle in probiotic research is that evidence is strain-specific. Two strains within the same species can have completely different clinical profiles. Sanders et al. (2018) reviewed the mechanisms by which probiotics may exert effects and emphasised that while some mechanisms are shared across taxa, strain-level identification is essential for clinical claims.
This means "Lactobacillus acidophilus" on a label tells you almost nothing. You need to know which Lactobacillus acidophilus — the specific strain designation — and whether that strain has been studied in clinical trials for the outcome you care about.
Areas with the strongest clinical trial evidence
The following areas have the largest body of randomised controlled trials, though the strength of evidence varies by strain and condition:
- Antibiotic-associated diarrhoea — several strains have been studied in systematic reviews, with some showing statistically significant reductions in diarrhoea incidence during antibiotic courses
- Irritable bowel syndrome (IBS) — multiple strains have been tested in RCTs. Results are mixed overall, but certain strains show consistent effects in specific IBS subtypes. Majeed et al. (2016) found that Bacillus coagulans MTCC 5856 significantly reduced clinical symptoms including bloating, abdominal pain, and stool frequency in diarrhoea-predominant IBS patients in a double-blind, placebo-controlled trial
- Functional bloating and gas — Majeed et al. (2023) conducted a randomised, double-blind, placebo-controlled trial of Bacillus coagulans MTCC 5856 (2 billion spores per day) in 66 adults with functional gas and bloating, reporting significant improvements in the probiotic group compared to placebo over four weeks
- Functional abdominal pain in children — Saneian et al. (2015) studied a synbiotic containing Bacillus coagulans Unique IS-2 with fructo-oligosaccharides in 115 children, finding a higher response rate in the treatment group (60%) compared to placebo (39.5%) at four weeks
It is important to note that these are individual study findings. They do not constitute authorised health claims, and no probiotic can legally be marketed for these outcomes in the UK.
What makes Bacillus coagulans different from most probiotics?
Most commercial probiotics contain strains from the Lactobacillus or Bifidobacterium genera. These are non-spore-forming organisms, which creates a fundamental problem: they are fragile.
Bacillus coagulans is a spore-forming bacterium. This distinction matters enormously for three reasons.
1. Survival through stomach acid
Non-spore-forming probiotics like Lactobacillus and Bifidobacterium species are vegetative cells — they have no protective dormant state. When exposed to the pH 1.5–3.5 environment of the stomach, a significant proportion of these organisms die before reaching the intestine. Amund (2016) reviewed the relationship between gastrointestinal stress conditions and probiotic viability, noting that acid, bile, and osmotic stresses significantly reduce the survival of non-spore-forming strains.
Bacillus coagulans forms endospores — metabolically dormant structures enclosed in a multilayered protein coat. These spores are inherently resistant to acid, heat, and bile salts. Majeed et al. (2021) demonstrated that Bacillus coagulans MTCC 5856 spores maintained substantial viability across simulated gastric conditions at multiple pH levels, significantly outperforming non-spore-forming strains.
Keller et al. (2019) studied Bacillus coagulans GBI-30, 6086 in a dynamic, computer-controlled model of the gastrointestinal tract and found high germination rates, survival, and enzyme activity — the spores not only survived stomach acid but actively germinated and became metabolically active in the intestinal environment.
2. Shelf stability without refrigeration
Because spores are metabolically dormant, they do not require refrigeration to remain viable. Many Lactobacillus and Bifidobacterium products lose significant colony counts during storage at room temperature, meaning the CFU number on the label may not reflect what you actually consume.
Bacillus coagulans spores remain stable at room temperature for extended periods. Majeed et al. (2021) confirmed exceptional thermal resistance, with the MTCC 5856 strain maintaining viability even through food processing conditions — 88.94% survival in chapati preparation and 94.56% in wheat noodle production.
3. Germination in the intestine
The spore is a delivery vehicle, not the active form. Once Bacillus coagulans spores pass through the stomach and reach the more favourable pH environment of the small intestine, they germinate into active, metabolically functioning vegetative cells. This is where they produce lactic acid and interact with the gut environment.
This mechanism — dormant transit through the stomach, active germination in the intestine — is fundamentally more reliable than hoping that enough fragile vegetative cells survive gastric acid to have an effect.
How do common probiotic strains compare?
| Strain | Spore-forming? | Survives stomach acid | Requires refrigeration | Clinical trial evidence |
|---|---|---|---|---|
| Lactobacillus acidophilus | No | Poor without enteric coating | Often yes | Moderate — many trials, but strain identification frequently lacking |
| Bifidobacterium lactis | No | Poor without protection | Often yes | Moderate — studied in immune and GI contexts |
| Lactobacillus rhamnosus GG | No | Moderate — better than most Lactobacilli | Recommended | Strong — one of the most-studied strains globally |
| Saccharomyces boulardii | No (yeast) | Good — naturally acid-resistant yeast | No | Strong for antibiotic-associated diarrhoea specifically |
| Bacillus coagulans | Yes | Excellent — spores are inherently acid-resistant | No | Growing — strain-specific trials for IBS, bloating, and functional GI symptoms |
Key observations:
- L. rhamnosus GG has the deepest evidence base among Lactobacillus strains, but survival through stomach acid remains a limitation without formulation protection
- S. boulardii is a yeast, not a bacterium, and has a strong evidence base specifically for preventing antibiotic-associated diarrhoea — it is naturally resistant to antibiotics, which is why it works in that context
- Bacillus coagulans is the only spore-forming option commonly available in consumer supplements, giving it a structural advantage in gastric survival that does not depend on coating technology
What should you look for in a probiotic supplement?
1. Strain identification, not just species
A label that says "Lactobacillus acidophilus" without a strain designation (such as NCFM, La-5, or a specific ATCC number) is telling you almost nothing. The clinical evidence is strain-specific. If the manufacturer does not identify the exact strain, you cannot verify whether it has been studied.
2. CFU count at time of expiry, not time of manufacture
Colony-forming units (CFU) tell you how many live organisms are in the product. But CFU at time of manufacture is meaningless if significant die-off occurs during storage. Look for products that guarantee CFU at the end of shelf life. Spore-forming strains like Bacillus coagulans have an inherent advantage here because spores do not die off during storage the way vegetative cells do.
3. Evidence of survival to the intestine
A probiotic that does not reach the intestine alive is not a probiotic — it is an expensive powder. For non-spore-forming strains, this means asking whether the product uses enteric coating, delayed-release capsules, or other gastric protection technology. For spore-forming strains, survival is built into the organism's biology.
4. Storage requirements
If a probiotic requires refrigeration, consider whether the entire supply chain — from manufacturer to warehouse to delivery to your home — maintained cold chain integrity. A product that sat in a warm delivery van for hours may have lost a significant proportion of its viable organisms. Shelf-stable formulations eliminate this variable.
5. Clinical evidence for the specific strain
Ask whether the named strain (not just the species) has been tested in human clinical trials published in peer-reviewed journals. Not in vitro studies, not animal studies, not trials on a different strain within the same species — human trials on the exact strain in the product.
Why PARTICULAR chose Bacillus coagulans Unique IS-2
PARTICULAR's approach to ingredients is consistent: choose the form with the best evidence for actually working in the human body, not just the cheapest or most recognisable option. For probiotics, that philosophy led to Bacillus coagulans Unique IS-2 (ATCC PTA-11748).
Spore-forming aligns with the microgranule philosophy
PARTICULAR's microgranule technology is built around a core principle: nutrients need to survive the stomach to be absorbed in the intestine. Each nutrient is individually coated in gastric-resistant microgranules designed to protect it through stomach acid and release it where it can be absorbed.
Bacillus coagulans spores achieve something similar through their own biology. The spore coat is nature's version of gastric protection — a dormant structure that resists acid, bile, and heat, then germinates into an active organism in the intestinal environment. Choosing a probiotic strain whose survival mechanism mirrors the delivery system's design philosophy was a deliberate decision.
The IS-2 strain is clinically studied
Bacillus coagulans Unique IS-2 has been the subject of multiple published studies:
- Genome characterisation confirming its identity and probiotic gene profile (Upadrasta et al., 2016)
- A clinical trial in children with functional abdominal pain showing higher response rates vs placebo (Saneian et al., 2015)
- A study on protein utilisation demonstrating improvements in branched-chain amino acid absorption and lower-body muscle power in resistance-trained males (Tarik et al., 2022)
- Preclinical research on gut-brain axis modulation (Satti et al., 2023)
The closely related strain MTCC 5856 — studied by Majeed et al. in multiple RCTs for IBS and functional bloating — adds further evidence for the B. coagulans species in gastrointestinal contexts.
Shelf-stable and vegan
As a spore-forming organism, B. coagulans Unique IS-2 does not require refrigeration. The spores remain viable at room temperature throughout the product's shelf life, stored within PARTICULAR's pouch alongside the other personalised microgranules.
B. coagulans is produced by bacterial fermentation, not derived from animal sources. It is fully compatible with PARTICULAR's vegan formulation.
Works alongside other nutrients
Because PARTICULAR combines your probiotic with personalised doses of nutrients like vitamin C and zinc — each in independently coated microgranules — there is no need for a separate probiotic supplement. One daily scoop from your pouch delivers everything together, with each component protected and released appropriately.
Take the PARTICULAR questionnaire to find out whether Bacillus coagulans IS-2 is included in your personalised blend.
Key takeaways
- No probiotic health claim has ever been approved by EFSA. Clinical trial evidence exists, but the regulatory bar for authorised health claims has not been met — be sceptical of any probiotic product making explicit health claims in the UK
- Probiotic evidence is strain-specific — "Lactobacillus acidophilus" on a label tells you almost nothing without a strain designation and supporting clinical trials for that exact strain
- Most commercial probiotics use non-spore-forming strains (Lactobacillus, Bifidobacterium) that are vulnerable to stomach acid and require refrigeration to maintain viability
- Bacillus coagulans is spore-forming: its endospores survive stomach acid naturally, remain shelf-stable without refrigeration, and germinate into active organisms in the intestine
- Look for strain identification, CFU guaranteed at expiry, evidence of gastric survival, and published human clinical trials on the specific strain
- PARTICULAR chose Bacillus coagulans Unique IS-2 because its spore-forming survival mechanism aligns with the microgranule gastric protection philosophy — both designed to ensure what you swallow actually reaches where it needs to work
- The honest position: choose a probiotic based on clinical evidence for the specific strain, not marketing claims that the regulations do not permit
Sources cited in this article:
- Hill C, Guarner F, Reid G, et al. "Expert consensus document. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic." Nat Rev Gastroenterol Hepatol. 2014;11(8):506-14.
- Binnendijk KH, Rijkers GT. "What is a health benefit? An evaluation of EFSA opinions on health benefits with reference to probiotics." Benef Microbes. 2013;4(3):223-30.
- Sanders ME, Benson A, Lebeer S, et al. "Shared mechanisms among probiotic taxa: implications for general probiotic claims." Curr Opin Biotechnol. 2018;49:207-216.
- Majeed M, Nagabhushanam K, Natarajan S, et al. "Bacillus coagulans MTCC 5856 supplementation in the management of diarrhea predominant Irritable Bowel Syndrome: a double blind randomized placebo controlled pilot clinical study." Nutr J. 2016;15:21.
- Majeed M, Nagabhushanam K, Paulose S, et al. "The effects of Bacillus coagulans MTCC 5856 on functional gas and bloating in adults: A randomized, double-blind, placebo-controlled study." Medicine (Baltimore). 2023;102(9):e33109.
- Saneian H, Pourmoghaddas Z, Roohafza H, et al. "Synbiotic containing Bacillus coagulans and fructo-oligosaccharides for functional abdominal pain in children." Gastroenterol Hepatol Bed Bench. 2015;8(1):56-65.
- Amund OD. "Exploring the relationship between exposure to technological and gastrointestinal stress and probiotic functional properties of lactobacilli and bifidobacteria." Can J Microbiol. 2016;62(9):715-25.
- Majeed M, Majeed S, Arumugam S, et al. "Comparative evaluation for thermostability and gastrointestinal survival of probiotic Bacillus coagulans MTCC 5856." Biosci Biotechnol Biochem. 2021;85(4):962-971.
- Keller D, Verbruggen S, Cash H, et al. "Spores of Bacillus coagulans GBI-30, 6086 show high germination, survival and enzyme activity in a dynamic, computer-controlled in vitro model of the gastrointestinal tract." Benef Microbes. 2019;10(1):77-87.
- Upadrasta A, Pitta S, Madempudi RS. "Draft Genome Sequence of the Spore-Forming Probiotic Strain Bacillus coagulans Unique IS-2." Genome Announc. 2016;4(2).
- Tarik M, Ramakrishnan L, Bhatia N, et al. "The effect of Bacillus coagulans Unique IS-2 supplementation on plasma amino acid levels and muscle strength in resistance trained males consuming whey protein: a double-blind, placebo-controlled study." Eur J Nutr. 2022;61(5):2673-2685.
- Satti S, Palepu MSK, Singh AA, et al. "Anxiolytic- and antidepressant-like effects of Bacillus coagulans Unique IS-2 mediate via reshaping of microbiome gut-brain axis in rats." Neurochem Int. 2023;163:105483.