Probiotics are increasingly cropping up in clinical consultations, by either patients or healthcare professionals (HCPs). Despite this, many HCPs don’t feel they have a strong understanding of probiotic products, as they haven’t received any formal training and hear mixed messages about the evidence base. Scientific research has often focused on the bacterial strain, but almost always overlooks the importance of the final product formulation and viability of the bacteria. So should we expect probiotic manufacturers to prove efficacy of their final product in scientific studies? (Spoiler: yes!)
By Prof Simon Gaisford, UCL School of Pharmacy
How do authorities view communication on ‘probiotics’?
As it stands, regulatory body stances on probiotic health benefits are conflicting. According to the World Health Organization (WHO) and The International Scientific Association for Probiotics and Prebiotics (ISAPP), the term ‘probiotic’ refers to live microorganisms that, when consumed (or applied), exert an effect that may be considered beneficial to overall health.1,2
However, the European Food Safety Authority (EFSA) has not approved any health claims for probiotics and so this is not able to be communicated on labels of EU-marketed products, even if the product has demonstrated significant benefit in clinical trials.3 The exception to this is when other ingredients are added to the probiotic that have approved health claims (e.g. addition of vitamin C enables a claim around ‘contributing to the reduction of tiredness and fatigue’).4 Attempting to navigate the various recommendations on probiotic use thus remains difficult and confusing.
Are HCPs getting more questions about probiotics?
A 2024 survey found that GPs, gastroenterologists and dietitians reported a growing number of patients asking about probiotics, with 77-90% of these HCPs believing probiotics have a role in managing gut health.5 However, 61% of GPs and 58% of dietitians do not feel that they have a strong enough understanding of how probiotics work and when to recommend them. At the same time, ‘clinical benefit’ and ‘evidence base’ are ranked as the most important criteria when making probiotic recommendations,5 but EFSA’s current stance prevents companies from proactively communicating precisely this , making it challenging for clinicians and consumers.
“Ultimately, to meaningfully assess clinical benefit, more attention must be paid to the product format — not just the strain”
What do we mean by ‘evidence’ in probiotics?
‘Evidence’ in this context reflects the body of findings and recommendations from research studies carried out in both laboratory settings and in human subjects to evaluate the safety and efficacy of probiotics. While the gold standard for proving efficacy might include a combination of in vitro studies, clinical trials and real-world studies, the reality is that probiotic companies don’t operate like pharmaceutical manufacturers, nor are they held to the same regulatory requirements. As a result, the existing evidence base has largely focused on specific bacterial strains rather than the final products commercially .
Why is it important to focus on the delivery system of a probiotic?
The vehicle by which the bacteria in the product are delivered also varies widely when reviewing marketed offerings – from water-based formulae to freeze-dried capsules, powders and yoghurts, amongst others. Since probiotics must survive the challenging journey through the digestive tract to provide a clinical benefit, the delivery system plays a critical role in ensuring viability and targeted delivery.
This variability has been well demonstrated in vitro under simulated gastrointestinal conditions where some powdered formulations require rehydration of the bacteria and release from the delivery system (e.g. a capsule) in order to become metabolically active, while others may be adversely affected by manufacturing processes such as pasteurisation.6 These differences make meaningful comparisons between products challenging — and reinforce the notion that not all probiotics are created equal. To put this in context, even medicinal biosimilars which are carefully engineered to mimic licensed biologic drugs must still demonstrate comparable clinical efficacy and biological activity to the reference product in robust studies to receive regulatory approval. As such, the case for product-specific evidence becomes not just important, but essential.
The World Gastroenterology Organisation (WGO) global guidelines7 suggest that the optimal dose of probiotics is both strain- and product-dependent, recommending that clinicians only advise their patients to use probiotic products that have been shown to be beneficial from in vivo studies.
Ultimately, to meaningfully assess clinical benefit, more attention must be paid to the product format — not just the strain. How a probiotic is formulated, stored, and consumed can significantly influence its viability and effectiveness in the gut. Robust, product-specific data is needed for clinicians to make informed choices about what truly works for patients.
“Ask manufacturers to provide published clinical studies conducted on the final product formulation”
What should you do about probiotics?
Given the growing public and professional interest in probiotics and the increasing appearance of these products in clinical consults, it stands that HCPs should be empowered to scrutinise the evidence available for marketed probiotics and to make the most informed decisions possible for their patients. Specifically, they should ask manufacturers to provide published clinical studies conducted on the final product formulation – not rely on evidence of the bacterial strain proven separate to the product. This is crucial because probiotic efficacy depends not only on the strain, but also on how that strain is formulated, dosed, and delivered. Without product-specific data, it is impossible to reliably assess clinical benefit.
Summary: key takeaway
Clinical evidence should go beyond strain-specific data to take account of formulation, dose, and delivery. Healthcare professionals looking to recommend probiotic products to their patients should seek product-specific evidence when evaluating probiotic options and thus be able to better navigate a market full of variability and regulatory ambiguity. By holding manufacturers to a higher standard of evidence, clinicians can be better equipped to guide informed discussions with patients.
For more support on probiotics, watch our CPD-endorsed ‘Gut Microbiome and Probiotics’ webinar.
Disclaimer: This blog was supported by an unrestricted educational grant from the healthcare professional support team at Symprove. Approval of each partnered activity is carefully assessed for suitability on a case by case basis and is independently peer reviewed Any financial support from grants does not imply any endorsement of an organisation or brand by MyNutriWeb, its organisers, its moderators or any participating healthcare professional, or their association. Funds are reinvested into the creation and promotion of professional development opportunities on MyNutriWeb.
References
- Hill C, et al. 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.
- Schlundt J. Health and Nutritional Properties of Probiotics in Food including Powder Milk with Live Lactic Acid Bacteria. 2012 Oct.
- Food and Agricultural Organization of the United Nations, World Health Organization. Food and Agricultural Organization of the United Nations and World Health Organization. Joint FAO/WHO working group report on drafting guidelines for the evaluation of probiotics in food. 2002.
- EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). (2010, October 19). Scientific Opinion on the substantiation of health claims related to vitamin C and reduction of tiredness and fatigue (ID 139, 2622) pursuant to Article 13(1) of Regulation (EC) No 1924/2006. EFSA Journal, 8(10): 1815. https://doi.org/10.2903/j.efsa.2010.1815
- Data on file, 2024. Based on external survey (n=432 healthcare professionals), conducted and independently analysed by specialist research agency, 2024.
- Fredua-Agyeman M, Gaisford S. Comparative survival of commercial probiotic formulations: tests in biorelevant gastric fluids and real-time measurements using microcalorimetry. Benef Microbes. 2015 Jan 1;6(1):141–52.
- World Gastroenterology Organisation. World Gastroenterology Organisation Global Guidelines: Probiotics and prebiotics. 2023 Feb.
Author bio:
Professor Gaisford holds a Chair in Pharmaceutics and has spent the last 15 years studying probiotics. He joined UCL School of Pharmacy in 2003, having previously been a Lecturer in Pharmaceutical Science at the University of Huddersfield. He has published 233 papers (h-index 75 with 23,000 citations), 8 book chapters and 4 books, made the Clarivate Highly Cited Researcher list in 2019, 2020, 2021, 2022, 2023 and 2024, is the Presenter of the educational YouTube channel Pharma Drama (with more than 50,000 subscribers) and is a Fellow of the Royal Society of Chemistry.
