Probiotics and their benefits are often described as “good bacteria” that can improve digestion, strengthen the immune system and restore balance in the gut.
Some truth underlies the interest in probiotics, but the topic is more complicated than many supplement ads suggest.
Probiotics are live microorganisms that are intended to provide a health benefit when consumed in adequate amounts. You can find them in some fermented foods and dietary supplements. Importantly, different probiotic strains can have different effects, so it is not accurate to assume that one probiotic will work in the same way as another.
That is the key idea behind this article.
Probiotics may be useful in some situations.
They are not a universal treatment for every digestive problem.
What Are Probiotics?
Probiotics are live microorganisms that, when taken in adequate amounts, are intended to provide a health benefit.
The most familiar probiotic microorganisms include species from groups such as Lactobacillus and Bifidobacterium, although many other bacteria and some yeasts can also be used as probiotics. NCCIH: Probiotics
The word “probiotic” does not describe one specific organism.
That matters because the effects of probiotics can be strain-specific.
A product containing one strain of Bifidobacterium, for example, should not automatically be assumed to have the same effect as a completely different probiotic product.
The World Gastroenterology Organisation recommends linking probiotic benefits to the specific strains and doses studied rather than treating all probiotics as interchangeable. WGO: Probiotics and Prebiotics
Probiotics, Prebiotics and Your Gut Microbiome
These terms are often mixed together.
Probiotics
Live microorganisms intended to provide a health benefit when consumed in adequate amounts.
Prebiotics
Substances that are selectively used by microorganisms in ways that can benefit health.
Synbiotics
Products or combinations that contain both probiotics and prebiotics.
They are related concepts, but they are not the same thing.
Your gut also contains a large community of microorganisms of its own. These organisms interact with each other and with your body in complex ways.
A probiotic does not simply “replace bad bacteria with good bacteria”.
The reality is considerably more complicated.
How Might Probiotics Work?
Researchers have proposed several ways probiotics may influence health.
Some may interact with the microorganisms already living in the digestive tract.
Others may produce substances that affect the local environment or influence the body’s immune response.
Some may help restore parts of the microbial community after it has been disturbed.
But these mechanisms vary between organisms.
That is why the phrase “probiotics improve your gut health” is too broad to be particularly useful.
A better question is:
Which strain, at what dose, for which problem, and in which people?
That is the level at which the evidence becomes meaningful.
Are Probiotics Good for Digestion?
They may help with certain digestive problems.
The NHS says some evidence suggests probiotics may help with some symptoms of irritable bowel syndrome, but much less evidence supports many of the wider health claims often made about probiotics.
Research has also examined probiotics for antibiotic-associated diarrhoea, constipation, inflammatory bowel disease and other gastrointestinal conditions.
However, results vary depending on the condition and the probiotic used.
The World Gastroenterology Organisation emphasises that probiotic effects are strain- and dose-specific. WGO: Probiotics and Prebiotics
So there is no single probiotic that can reasonably be called “the best probiotic for digestion“.
Probiotics and Antibiotic-Associated Diarrhoea
Antibiotics can alter the microorganisms living in the digestive tract.
Researchers have investigated whether certain probiotic preparations can reduce the risk of diarrhoea associated with antibiotic treatment.
The evidence suggests that some probiotics may help in particular circumstances, but the results depend on factors such as the strain, dose, age of the person and clinical setting.
This is an excellent example of why probiotic research needs to be looked at strain by strain.
It is not enough to say “a study found probiotics worked”.
The useful question is which probiotic was studied and whether the same product is being used in practice.
Probiotics and Irritable Bowel Syndrome
IBS can involve abdominal pain, bloating, diarrhoea, constipation or changes in bowel habits.
Some studies suggest that certain probiotics may improve overall IBS symptoms or abdominal pain.
But the evidence is inconsistent, and different studies use different strains and combinations.
The NHS says there is some evidence that probiotics may help with some IBS symptoms, but also notes that there are many different types and that it is not always clear which are most effective.
If you have persistent or unexplained digestive symptoms, a probiotic should not be used as a reason to postpone proper medical assessment.
Can Probiotics Help With Constipation?
Some research has found possible benefits for constipation, particularly with certain strains.
However, the benefit can be modest, and the evidence is not strong enough to say probiotics are a general treatment for constipation.
If constipation is persistent, painful, associated with bleeding, unexplained weight loss or a significant change in bowel habits, seek medical advice rather than relying on a supplement.
What About Ulcerative Colitis and Crohn’s Disease?
Researchers have studied probiotics in inflammatory bowel disease.
Some evidence suggests particular probiotic preparations may help with ulcerative colitis, but this does not mean probiotics are a general treatment for inflammatory bowel disease.
Research has not shown the same consistent benefit for Crohn’s disease.
People with diagnosed inflammatory bowel disease should therefore discuss supplements with their medical team rather than attempting to manage the condition with probiotics alone.
Do Probiotics Strengthen the Immune System?
You will often see probiotic supplements promoted as immune boosters.
The science is more cautious.
Some probiotic microorganisms can interact with the immune system, and research is investigating these effects.
But that does not mean taking any probiotic supplement will automatically make you less likely to get infections.
The NCCIH notes that probiotics may influence the body’s immune response, while also stressing that much remains to be learned about their effectiveness for different health conditions.
So “supports immune health” is very different from “prevents illness”.
Probiotics and Fermented Foods
Some fermented foods contain live microorganisms.
Examples include:
- yoghurt
- kefir
- kimchi
- sauerkraut
- some fermented soya foods
But not every fermented food is a probiotic in the scientific sense.
The microorganisms may not survive processing or storage, and a food does not necessarily contain a strain shown in clinical research to provide a particular benefit.
The important point is that fermented foods can be part of a varied diet, but you should not assume that every fermented food has the same effects as a researched probiotic supplement.
Is Yoghurt a Probiotic?
Some yoghurts contain live cultures, and certain products may contain specific probiotic strains.
But yoghurt is not automatically a probiotic treatment.
Check the label if you are specifically looking for live cultures, and remember that the presence of bacteria does not prove that the product provides a clinically meaningful benefit for a particular condition.
For most people, plain yoghurt can also simply be a nutritious food that provides protein and, depending on the product, calcium.
Are Probiotic Supplements Better Than Food?
Not necessarily.
It depends on what you are trying to achieve.
A normal diet can contain fermented foods alongside plenty of fibre-rich plant foods, which may support a diverse gut environment.
A supplement, meanwhile, can provide a defined strain and dose that has been studied for a specific purpose.
The two should not be treated as direct substitutes.
The NHS notes that probiotic products are generally regulated as foods rather than medicines, and that it is not always possible to know whether a product contains the bacteria claimed on the label or whether the bacteria survive long enough to reach the gut. NHS: Probiotics
How Do You Choose a Probiotic?
There is no universally “best” probiotic.
If you are considering a supplement, look for information that identifies:
The strain
The full organism and strain designation is much more informative than a general word such as “Lactobacillus”.
The dose
Evidence from one dose cannot automatically be applied to a much smaller or larger dose.
The reason for taking it
A product studied for antibiotic-associated diarrhoea may not be the right product for IBS, constipation, or another problem.
Storage requirements
Some products require refrigeration while others are designed to remain stable at room temperature.
Evidence
Ideally, look for human studies of the specific product or strain rather than marketing claims about probiotics overall.
The World Gastroenterology Organisation stresses that probiotic recommendations should be tied to strain-specific evidence where possible.
What Does CFU Mean?
Probiotic products often advertise their strength using the abbreviation CFU, which stands for colony-forming units.
It describes the number of viable microorganisms.
A higher number is not automatically better.
A product containing billions of microorganisms is not necessarily more effective than one containing fewer if the strain, dose and condition being treated are different.
This is another reason not to judge a probiotic by the biggest number printed on the front of the bottle.
Can Probiotics Cause Side Effects?
Can Probiotics Cause Side Effects?
For healthy people, probiotics generally have a good safety record, although side effects can occur.
Some people notice gas, bloating or other mild digestive symptoms after starting a probiotic.
The safety picture is less reassuring for people who are severely ill or have compromised immune systems.
The NCCIH reports that serious infections have occurred in some high-risk situations and advises people with serious underlying health problems to discuss probiotics with a healthcare professional.
Who Should Be Especially Careful?
Speak with a doctor before taking probiotic supplements if you:
- have a weakened immune system
- are seriously ill
- have a major underlying medical condition
- are considering probiotics for a baby or medically vulnerable person
NCCIH highlights particular safety concerns in high-risk patients, including premature infants.
More generally, a supplement should not be assumed to be harmless simply because it is described as “natural”.
Do Probiotics Need to Be Taken Forever?
Usually there is no reason to assume that taking a probiotic indefinitely is necessary.
The right duration depends on why you’re taking it and the evidence for that particular strain.
Limited information also remains about the long-term effects of many commercial probiotic products.
If a clinician recommends a specific probiotic for a particular condition, follow that advice.
If you are taking one simply because it is advertised as a general health booster, there is less reason to assume permanent use is beneficial.
What About Probiotics for Children?
Researchers have studied probiotics in children for several conditions, but the evidence varies.
Healthy children may tolerate many probiotic products without serious problems, but high-risk children are a different matter.
Do not give probiotic supplements to a medically fragile child without discussing the product with their healthcare professional.
The same principle applies particularly strongly to premature babies because serious infections have been reported in this group.
Can Probiotics Replace Medical Treatment?
No.
A probiotic may be useful as part of a particular treatment strategy, but it should not replace an established treatment because a supplement advertisement promises a “natural cure”.
The NHS specifically advises against using probiotics as a reason to postpone medical care.
Persistent diarrhoea, blood in the stool, unexplained weight loss, ongoing abdominal pain or other concerning symptoms deserve appropriate medical assessment.
A Better Way to Think About Gut Health
It is tempting to imagine your gut as a simple battle between “good bacteria” and “bad bacteria”.
It is not.
The gut microbiome is a complex community influenced by diet, medicines, illness, age and many other factors.
A healthy eating pattern that regularly includes fibre-rich plant foods can support the environment in which many beneficial microorganisms live.
Useful foods include:
- vegetables
- fruit
- beans and lentils
- oats and other whole grains
- nuts and seeds
Fermented foods can also be part of a varied diet.
This is one reason why focusing only on a probiotic capsule can miss the bigger picture.
The Bigger Picture
Probiotics are neither miracle cures nor useless.
Genuine evidence shows that particular probiotic strains can help in some circumstances.
But the benefits are not universal, and the evidence is much weaker for many of the broad claims made in advertising.
The most useful questions are:
What problem am I trying to solve?
Which probiotic strain has been studied for that problem?
What dose was used?
How strong is the evidence?
Is it appropriate for me?
That is a much better way to think about probiotics than simply choosing the bottle with the largest number of bacteria.
For practical information about foods containing probiotics, see Probiotic Foods: Which Fermented Foods Actually Contain Probiotics?
For help choosing a supplement, see How to Choose a Probiotic Supplement: Strains & CFUs.
For a wider look at healthy eating and the nutrients your body needs, see Balanced Diet: The Evidence Based Guide to Healthy Eating.
Medical Disclaimer
This information is provided for general educational purposes only. It is not intended to diagnose, treat or prevent any medical condition and should not be considered a substitute for advice from a qualified healthcare professional.
The effects of probiotics can differ between strains, doses, health conditions and individuals. A probiotic that has been studied for one condition should not automatically be assumed to work for another.
People with serious underlying health conditions or weakened immune systems should speak with a healthcare professional before taking probiotic supplements.
Do not use this article as a substitute for individual medical assessment or professional guidance.
Sources
- NHS — Probiotics
- NCCIH — Probiotics: Usefulness and Safety
- NCCIH — 5 Things to Know About Probiotics
- World Gastroenterology Organisation — Probiotics and Prebiotics