Understanding NHS Guidelines on Probiotics

Understanding NHS Guidelines on Probiotics

Individuals looking to improve or support their digestive health often want to know about probiotics and how to choose a product. But giving advice can be difficult because guidelines around probiotics are often conflicting. We asked Dietitian Laura Tilt to review the NHS guidance and reflect on how it aligns with current scientific thinking.
Reading: Understanding NHS Guidelines on Probiotics 13 minutes

What Does 'Probiotic' Mean?
Probiotics are defined as "live microorganisms that, when administered in adequate amounts, confer a health benefit on the host" (1). This globally accepted definition was first published in 2010 by the Food and Agriculture Organization of the United Nations and the World Health Organization. It was later reviewed in 2013 by the International Scientific Association for Probiotics and Prebiotics (ISAPP) and remained unchanged except for minor grammatical adjustments (1).

Probiotics are identified by their genus, species, subspecies (if applicable), and strain. For example, in Lactobacillus acidophilus NCIMB 30175 (found in Symprove), 'Lactobacillus' is the genus, 'acidophilus' is the species, and 'NCIMB 30175' is the strain. This information is crucial because health benefits are strain specific (1). Just because one strain within a species has a proven benefit, it doesn’t mean another strain in the same species will provide the same benefit.

Navigating Probiotic Guidelines
Given the vital role of the gut microbiome in gastrointestinal (GI) health, much of the research on probiotics has focused on their effects in GI conditions. Consequently, recommendations around probiotic appear in several GI clinical guidelines, including:

  • NICE Guidelines on the Diagnosis and Management of Irritable Bowel Syndrome in Adults (2)
  • British Society of Gastroenterology (BSG) Guidelines on the Management of Irritable Bowel Syndrome (3)
  • World Gastroenterology Organisation Global Guidelines Probiotics and Prebiotics (1)
  • The American Gastroenterological Association (AGA) Clinical Practice Guidelines on the Role of Probiotics in the Management of Gastrointestinal Disorders (4)

However, using these guidelines to inform recommendations around probiotics can be challenging, due to variation in their conclusions regarding the effectiveness and use of probiotics. For instance, the BSG guidelines state that 'Probiotics, as a group, may be an effective treatment for global symptoms and abdominal pain in IBS’ whereas the AGA guidelines recommend the use of probiotics for adults with irritable bowel syndrome only in the context of a clinical trial.

Advice on probiotics also exists for the general population. The top result when searching ‘probiotic’ is the NHS guidance (5), a sample of which is shown below. This guidance includes statements around probiotic quality and effectiveness, such as:

  • "There are many different types of probiotics that may have different effects on the body…"
  • "There's likely to be a huge difference between the pharmaceutical-grade probiotics that show promise in clinical trials and the yoghurts and supplements sold in shops"

At first read, this seems to conflict with current scientific thinking about probiotics. So how does this guidance compare to clinical guidelines and the evidence base for choosing a product? In the following sections, I will summarise the key points from the NHS and provide context for their statements.

NHS Guidance on probiotics
“Probiotics are thought to help restore the natural balance of bacteria in your gut (including your stomach and intestines) when it's been disrupted by an illness or treatment”

Research has shown that the gut microbiome is altered in a variety of conditions. For example, exposure to antibiotics rapidly changes the microbiome, and the microbiome of individuals with IBS differs significantly from healthy subjects (3).

Although normalising disturbances in gut microbiota is one mechanism by which probiotics may elicit a health benefit, it’s a common misconception that probiotics must alter resident gut bacteria to be effective (1). In general, probiotics are believed to be transient colonisers; rather than taking up permanent residence, they exert a health benefit by altering the intestinal environment while present.

Research indicates that probiotics may elicit health benefits through multiple mechanisms (1), including:

  • Normalising disturbances in gut microbiota
  • Regulating gastrointestinal transit
  • Preventing the colonisation of harmful pathogens
  • The production of metabolites like short-chain fatty acids

“There's some evidence that probiotics may be helpful in some cases, such as helping to ease some symptoms of irritable bowel syndrome (IBS)”.

To date, research has shown that certain probiotic strains or combinations of strains offer benefits for various gastrointestinal conditions. For example, there is evidence that probiotics can (1):

  • Prevent antibiotic-associated diarrhoea in children and adults.
  • Reduce abdominal bloating, alleviate pain, and provide global relief of IBS symptoms.
  • Reduce symptoms of lactose malabsorption
  • Improve symptoms of constipation
  • Induce remission in mild to moderately active ulcerative colitis (UC)

However, probiotic use does not appear to benefit all GI conditions. For instance, to date, studies evaluating probiotic effects in Crohn’s disease have not shown that they are beneficial in inducing or maintaining remission (6,7).

“For most people, probiotics appear to be safe. If you want to try them, and you have a healthy immune system, they shouldn't cause any unpleasant side effects”.

Most probiotic strains are derived from fermented foods or are those which colonise a healthy human gut (1). Numerous clinical trials have shown that many probiotic strains are well tolerated and safe for healthy people, with gastrointestinal side effects like bloating or increased gas tending to be mild and self-limiting (8).

However, there are some safety concerns around probiotic use in at-risk populations, namely those with compromised immune function (such as those on immunosuppressant therapy), short bowel syndrome, premature infants, and individuals with a serious underlying disease. These concerns relate to several serious adverse events, associated either with microbiological quality or infections by probiotic genera or species (8).

A recent paper describing precautions for probiotic use in at-risk populations outlines microbiological standards that probiotics should meet to protect high risk populations (8). The World Gastroenterology Organisation Global Guidelines Probiotics and Prebiotics also recommend that "probiotic use in persons with compromised immune function or serious underlying disease should be restricted to the strains and indications with proven safety and efficacy for these target patient populations." At a consumer level, the advice is that individuals talk to their doctor first if they suffer from an immune disorder or short bowel syndrome or have a serious illness.

“Because of the way probiotics are regulated, we can't always be sure that: the product actually contains the bacteria stated on the food label, the product contains enough bacteria to have an effect, the bacteria are able to survive long enough to reach your gut”.

Probiotic products are sold as dietary supplements which means they are not subject to the same manufacturing and quality control standards as medicines. This means that the quality of the product is dependent on the manufacturer (1). Issues relating to quality include:

  • Maintenance of viability (usually indicated by colony-forming units, CFU) through to the end of the shelf life - not at the point of manufacture
  • Safety (processing standards to reduce any pathogens of concern)
  • Identity (specification of genus, species, subspecies, and strain name for each strain in the product)

Each live bacteria are referred to as a CFU, and probiotic doses relate to the number of CFUs in a product. Although some publications recommend a dose of > 106–1010 CFU/day (9), there is no single dose that can guarantee a health benefit as the minimum effective dosage differs by strain. Therefore, the recommended dose should therefore be based on human studies showing a health benefit.

“There are many different types of probiotics that may have different effects on the body, and little is known about which types are best”.

Probiotic research is constantly evolving and there’s still a lot to be learned about probiotics and their potential to benefit digestive health and in recent years, other indications such as mental health disorders and cardiovascular disease.

The best approach for recommending probiotics in a clinical setting is to choose products with specific strains linked to the desired benefit in human studies. However, it can be difficult to match probiotic strains to commercial products with different names, and not all products are well-labelled. Initiatives like the US Probiotic Guide link products to evidence, but as yet this type of initiative does not exist in the UK. It’s also the case that many commercial products contain combinations of strains with documented benefits, but the products themselves have not been tested in human clinical trials.

“There's likely to be a huge difference between the pharmaceutical-grade probiotics that show promise in clinical trials and the yoghurts and supplements sold in shops”.

Products containing live microbes are generally found in two forms: supplements and foods like yoghurt, kimchi, and sauerkraut. However, only products with characterised strains which have a scientifically demonstrated effect on health can be called probiotics (1). In general, fermented foods typically do not meet the evidence level for probiotics because their health benefits have not been confirmed. Different fermented foods also contain different types of microbes, and many of these are uncharacterised. This doesn’t mean fermented foods aren’t beneficial for digestive health - a recent study found a diet rich in fermented food increased microbiome diversity (10) - but they can’t be called probiotic.

As outlined above, probiotic supplements vary in their quality and evidence. For example, many studies have shown that commercial products do not contain the stated cell numbers (9). However, several commercial products (including Symprove) have been used in clinical trials and have been shown to provide benefits for defined clinical outcomes (11). Therefore, where relevant, we should support individuals in choosing a product that contains strain(s) at the dose that has been studied and shown to provide the benefit they are looking for.

How does Symprove stack up to NHS guidance?
Taking these recommendations into consideration, how well does Symprove align with NHS guidance? Let’s look:

Symprove is clearly labelled with the four strains contained in the product:

  • Lactobacillus acidophilus NCIMB 30175
  • Lactiplantibacillus plantarum NCIMB 30173
  • Lacticaseibacillus rhamnosus NCIMB 30174
  • Enterococcus faecium NCIMB 30176

There are 10 billion CFUs per 70 ml cup of Symprove, consistent with the amount used in their human clinical research trials. This cell count is viable to the end of the shelf life, which is 6 months from the point of manufacture when stored in a cool dry place.

In an independent study conducted by the UCL School of Pharmacy, which examined various probiotics in a model simulating human gut conditions, Symprove’s bacteria were demonstrated to reach the gut, survive, and thrive. Studies show this is due to its water-based formulation, which ensures delivery of live bacteria to the colon (12).

Safety / Purity
Symprove is an ISO 9001:2015 certified company. This means their internal quality management systems are held up to internationally approved standards. The product is produced in a controlled environment and samples are sent for independent testing before being bottled.

No serious adverse events have been recorded since commercial sales began in 2010 and no serious adverse events have been recorded in any clinical trial investigating Symprove in those with pre-existing medical conditions.

Clinical evidence of benefit
Symprove has been proven beneficial in randomised controlled trials at King’s College Hospital and independent in-vitro studies at University College London. In real-world use, 92% of people report feeling the difference. You can download the full Symprove clinical research summary detailing studies and benefits here.

Probiotics can mediate digestive health benefits in several different ways. Although many probiotics may function similarly e.g., in regard to their ability to reduce colonic pH or increase short chain fatty acid production, particular gastrointestinal benefits are strain specific (11). Therefore, the most robust approach to recommending a probiotic in clinical practice is to pick a product that has been studied in humans and shown to provide the desired benefits.

When choosing a product, we should encourage looking for those that are clearly labelled with genus, species and strain, information on dosage and CFU (13). CFU should equal the amount shown to be beneficial in human studies and should last through to the use-by date.

Lastly, it's important to manage expectations around probiotic use and remind those we work with that they may not work for everyone, and may depend on their existing microbiome, diet, and physiology. The recommended approach is to try a product for between four weeks (British Dietetic Association guidelines) and twelve weeks (British Society of Gastroenterology guidelines) before deciding whether to continue, stop, or try another product.


  1. Guarner F, et al. World Gastroenterology Organisation Global Guidelines - Probiotics and Prebiotics. World Gastroenterol Organ. 2023;(February).
  2. National Institute for Health and Care Excellence (NICE). Irritable Bowel Syndrome in Adults: Diagnosis and Management. Clinical Guideline.; 2008. https://www.nice.org.uk/guidance/cg61/
  3. Vasant DH, et al. British Society of Gastroenterology guidelines on the management of irritable bowel syndrome. Gut. 2021;70(7):1214-1240. doi:10.1136/gutjnl-2021-324598
  4. Su GL, et al. AGA Clinical Practice Guidelines on the Role of Probiotics in the Management of Gastrointestinal Disorders. Gastroenterology. 2020;159(2):697-705. doi:10.1053/j.gastro.2020.05.059
  5. NHS. Probiotics. Published 2022. Accessed May 25, 2024. https://www.nhs.uk/conditions/probiotics/
  6. Bischoff SC, et al. ESPEN guideline on Clinical Nutrition in inflammatory bowel disease. Clin Nutr. 2023;42(3):352-79.
  7. Vakadaris G, et al. The Role of Probiotics in Inducing and Maintaining Remission in Crohn’s Disease and Ulcerative Colitis: A Systematic Review of the Literature. Biomedicines. 2023;11(2).
  8. Sanders ME, et al. Probiotic use in at-risk populations. J Am Pharm Assoc. 2016;56(6):680-6.
  9. Champagne C, et al. Recommendations for the viability assessment of probiotics as concentrated cultures and in food matrices. Int J Food Microbiol. 2011;149:185-93.
  10. Wastyk HC, et al. Gut-microbiota-targeted diets modulate human immune status. Cell. 2021;184(16):4137-53.e14.
  11. World Gastroenterology Organisation (WGO). WGO Practice Guideline Probiotics and Prebiotics. https://www.worldgastroenterology.org/guidelines/probiotics-and-prebiotics
  12. Fredua-Agyeman M, et al. Comparative survival of commercial probiotic formulations: tests in biorelevant gastric fluids and real-time measurements using microcalorimetry. Benef Microbes. 2015;6(1):141-151. doi:10.3920/BM2014.0051
  13. Gut Microbiota For Health. An expert panel helps end users identify high quality probiotic. Published 2019. https://www.gutmicrobiotaforhealth.com/an-expert-panel-helps-end-users-identify-high-quality-probiotics/