This post was written by one of our contributors; dietitian – Maeve Hanan
Probiotics are a popular buzzword in the health and wellness sphere, and there are countless new probiotic products being released. But it can be difficult to figure out whether it is worth adding probiotics to your diet. This article will explain what probiotics are, how they work, and who might benefit from using them.
What Are Probiotics?
Probiotics are live microorganisms (bacteria and yeast) which can pass on health benefits to us, when we consume them in the right amount (1).
Probiotics belong to different groups called ‘genus’, and within this probiotics are further classified by their ‘species’ and ‘strain’. There are hundreds of different probiotic strains, so there is a lot of variety between the various probiotic products and supplements on offer – and certain strains seem to offer benefits for specific conditions.
For example, for the probiotic Lactobacillus casei LBC80R:
- Lactobacillus = genus
- Casei = species
- LBC80R = strain
Some of the most well-researched probiotics include (1):
- Bifidobacterium Bifidum (B. bifidum)
- Bifidobacterium lactis (B. lactis)
- Bifidobacterium longum (B. longum)
- Lactobacillus casei (L. casei)
- Lactobacillus acidophilus (L. acidophilus)
- Lactobacillus plantarum (L. plantarum)
- Saccharomyces Boulardii (S. boulardii)
These can be found in probiotic supplements and yoghurts which contain live bacteria. For probiotics to actually be present in yoghurts, the product needs to specify which strain of live probiotic that it contains (as otherwise ‘made with live cultures’ may mean these were used to ferment the yoghurt, without still being present).
Fermented foods can also contain probiotics, however there is less evidence about how these impact our gut and overall health (2). Certain processes can also kills the probiotics, such as heat-treatment as part of the jarring process.
Examples of these fermented foods include:
- Kefir
- Kombucha
- Tempeh
- Kimchi
- Pickles
- Sauerkraut
- Miso
- Natto (fermented soy beans)
Kefir 
Kombucha 
Tempeh 
Kimchi 
Saurkraut 
Miso
All images: Farmdrop
Probiotics are often confused with prebiotics. Prebiotics are a type of fibre which our body can’t digest properly, so this passes to our gut where it feeds healthy gut bacteria. Prebiotics are found in certain supplements, as well as foods such as: onions, garlic, artichoke, leek, wheat bran and oats.
Synbiotics are products which contain both probiotics and prebiotics (i.e. both the healthy bacteria, and the food to encourage the growth of healthy bacteria – these are thought to work together ‘synergistically’).
In Europe the word ‘probiotic’ is officially banned from packaging. This ban is due to the fact that using the word ‘probiotic’ suggests a health benefit, but despite hundreds of applications there have been no approved health claims for probiotics by the European Food Safety Authority (EFSA) (3, 4).
How Do Probiotics Work?
Probiotics have the potential to improve our health for a number of reasons. Firstly, they can improve the overall balance of bacteria in our gut – by increasing the levels of good bacteria and reducing the ability of harmful bacteria to survive (5).
Probiotics can also improve the barrier function of the gut lining (5). Furthermore, they can stimulate production of antimicrobial substances, like bacteriocins and short chain fatty acids (SCFAs), which reduces infection and inflammation risk (5).
Beyond gut health, probiotics have been seen to impact other organs via the immune system and nervous system (e.g. via neurotransmitters such as serotonin) (5).
But it is important to remember that probiotics are only one potential piece of the puzzle.
Gut health is influenced by many factors, including:
- Diet
- Exercise
- Stress
- Age
- Medication
- Illness
- The type of environment that you live in
- Exposures during early life (such as being breastfed, or not)
It is also worth highlighting that certain probiotics may just pass through the gut rather than staying there. So research is investigating how probiotics can be developed to have a lasting impact on gut health (5, 6).
Who Might Benefit From Taking a Probiotic?
There is emerging evidence that optimising gut health can have a big impact on overall health by reducing the risk of chronic disease, improving metabolism and immune function (as more than 70% of our immune system is thought to be in our gut) (7, 8, 9). A healthy gut may also promote a healthy mind, due to the connection known as the ‘gut-brain axis’ (10).
There isn’t enough evidence to say that everybody should be taking a probiotic in order to stay healthy (5, 6). So if you don’t have any specific concerns, is better to have focus on having a balanced lifestyle and a varied diet – which includes plenty of fruit, vegetables, fibre, and possibly some of the fermented foods listed above. A recent study from America found that consuming 30 or more plant-based foods per week was significantly linked a more diverse and healthy balance of bacteria in the gut (11).
However, there are evidence-based uses for probiotics, which are always based on specific doses and strains for a specific medical issue (6). The following information is a summary of the evidence-base, and is not intended to be used as individual advice. You should seek support from a doctor or dietitian for personalised advice.
Antibiotic Associated Diarrhoea
There is good evidence that using saccharomyces, lactobacillus, or mixed probiotics during and after a course of antibiotics reduces the risk of developing antibiotic associated diarrhoea and a clostridium difficile (C.Diff) infections for both adults and children (12, 13). Although it is advised to take antibiotics and probiotics a few hours apart, so that the probiotic isn’t destroyed by the antibiotic. If probiotics are being used to prevent antibiotic associated diarrhoea in children it is advised to try lactobacillus rhamnosus GG or saccharomyces boulardii (12). Whereas for preventing C.Diff infections in children saccharomyces boulardii is recommended (12).
Traveller’s Diarrhoea
Saccharomyces boulardii or a mixture of lactobacillus acidophilus and bifidobacterium bifidum have also been seen to reduce the risk of traveller’s diarrhoea (14). These are usually taken for 2-7 days before travelling, then every day while you are travelling.
The European Society for Paediatric Gastroenterology Hepatology and Nutrition (ESPGHAN) also recommends considering a probiotic alongside rehydration for the treatment of acute gastroenteritis in children (15). The types of probiotics recommended for this include: lactobacillus rhamnosus GG, saccharomyces boulardii or lactobacillus reuteri DSM 17938 (although lactobacillus reuteri DSM 17938 has less supporting evidence than the other two) (15).
Inflammatory Bowel Disease
Inflammatory bowel diseases (IBD) include ulcerative colitis and Crohn’s disease. As these conditions are associated with inflammation and disturbance of gut microbiota probiotics may have a role in the management of these conditions. Research has found that probiotics can be useful in both the treatment of mild to moderate ulcerative colitis, and in preventing relapses – these include: saccharomyces boulardii lyo CNCM I-745, E. coli Nissle 1917 and VSL#3 (16, 17, 18). However, there is less evidence for the use of probiotics in the management of Crohn’s disease.
Pouchitis is a condition that can occur in some patients who have undergone bowel surgery for IBD, this is when inflammation occurs in pouch in the small intestine which has been formed. In the UK the probiotic VSL#3 is used in the treatment and prevention of pouchitis (19, 20). This is currently the only case when a probiotic is currently approved for prescription in the UK.
Irritable Bowel Syndrome
There is also some evidence that certain strains from the lactobacillus, bifidobacterium and saccharomyces genus may be useful in managing symptoms related to irritable bowel syndrome (IBS) (21). This should be trialled one at a time for at least 4 weeks to see if any changes in symptoms occur (22). More research is needed to discover the most effective strains in terms of IBS management (22). One study from the UK also found that taking a multi-strain probiotic helped to increase levels of healthy bifidobacteria in the gut in patients who were following a low FODMAP diet (23).
H.Pylori Infection
Helicobacter pylori (H. pylori) is a type of bacteria that can cause a stomach infection or ulcer. Some studies have found that using saccharomyces boulardii or lactobacillus reuteri alongside standard medical treatment can reduce the length of illness (24).
Lactose Intolerance
There is emerging evidence about the role of probiotics in the treatment of lactose intolerance. A recent systematic review found that bifidobacterium animalis was the most effective strain to use in this context, but there was also some evidence for fermented dairy products as well as: lactobacillus rhamnosus, lactobacillus reuteri and bifidobacterium longum (25).
Eczema
The World Allergy Organisation (WAO) recommends that pregnant women, and breastfeeding women who have a family history of eczema, should consider taking a probiotic in order to to reduce the infant’s risk of developing eczema (26). Although, there isn’t strong evidence to suggest that probiotics should be used in the management of eczema, which has already been diagnosed (27). However two small studies have found that a combination of Lactobacillus salivarius LS01 and Bifidobacterium breve BR03, or a combination of Salivarius LS01 and S. thermophilus ST10, may have a role alongside other treatments for eczema 28, 29).
Mental Health
Probiotics may also play a role in mental health, although this is quite a new area so more research is needed (11, 30). What we do know, however, is that there is a strong link between the gut and the brain (known as the ‘gut-brain axis’) so looking after your gut health is likely to have a knock-on, positive effect on your brain health.
Summary
Probiotics are living microorganisms which have a beneficial role in our gut, and also have wide-reaching implications for overall health. Eating a balanced diet which includes a wide variety of plants is a great way of improving the diversity of our gut microbiome. Consuming fermented foods may also help, but the evidence is less clear about this.
If you are healthy, there currently seems to be no extra benefit in taking a probiotic. But there are a number of medical conditions where it may be useful to take a specific dose of a specific probiotic strain. This is a complicated and evolving area, so if in doubt you can seek support and individualized advice from a Registered Dietitian.
Reference
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