Probiotics: benefits for gut and digestion
What are probiotics – briefly explained
Probiotics are live microorganisms that, in sufficient amounts, can bring a benefit to the host – usually bacteria from the genera Lactobacillus and Bifidobacterium. They occur naturally in fermented foods such as yoghurt, kefir and sauerkraut, and in concentrated form in supplements.
Your gut is home to several hundred bacterial species. Together they are called the gut flora, or microbiota. The balance between them affects digestion, the immune system and even signalling molecules in the gut. Probiotics are a way to temporarily add more of the "friendly" bacteria.
What benefits do probiotics have – what the research shows
The evidence is stronger for some things than others. Here is an honest summary of where the support is clearest.
- Antibiotic-associated diarrhoea: This is where the support is strongest. Several Cochrane reviews indicate that certain strains reduce the risk when taken alongside a course of antibiotics.
- Acute diarrhoea (gastrointestinal infection): Can be shortened somewhat with the right strain, especially in children.
- IBS and a sensitive stomach: Some multi-strain products reduce abdominal pain and bloating in studies, but the results vary between strains.
- Bloating and gas: Some people experience improvement; the effect is individual.
What does not have strong support is broad promises of a "better immune system" or "weight loss" in healthy people. The EU has not approved any health claims for probiotics, which is why reputable companies describe the effect as research – not as an established fact.
How probiotics affect the gut flora
The added bacteria pass through the stomach, attach temporarily in the gut and compete with less desirable microbes for space and nutrients. They can also produce short-chain fatty acids that gut cells use as fuel.
Important to know: the effect is usually temporary. When you stop taking the supplement, the flora gradually returns towards its starting point. That is why probiotics are more about regular topping up than a one-off course.
6 selected bacterial strains and 10 billion CFU per capsule, combined with FOS – in an acid-resistant capsule.
See current price »CFU, strains and FOS – what do they mean on the label?
Three terms come up again and again:
| Term | What it means |
|---|---|
| CFU | Colony Forming Units – the number of live bacteria. Common products range from 1 to 20 billion per dose. |
| Strain | The exact bacterium, e.g. Lactobacillus rhamnosus. The effect is strain-specific. |
| FOS | Fructo-oligosaccharides – a prebiotic fibre that acts as food for the bacteria. |
More strains and higher CFU are not automatically better – but a product with several well-documented strains and a prebiotic fibre gives the bacteria a better chance of surviving.
Who can benefit from probiotics?
Groups who often try probiotics:
- Anyone who has just taken, or is about to take, a course of antibiotics.
- Anyone with recurring bloating or an irregular stomach.
- Anyone travelling who wants to support their gut through a change of diet.
- Anyone who eats a narrow diet and wants to add more bacterial strains.
If you want to compare different options, we have gathered our review of the best probiotic supplements, and more products in the gut and digestive health category.
How do you take probiotics best?
A few practical tips:
- Take it regularly, at the same time every day – ideally with a meal.
- With antibiotics: take the probiotic a few hours apart from the tablet.
- Give it time. Many people evaluate the effect only after 4 weeks.
- Store as directed – some strains are sensitive to heat and moisture.
Read more about how to combine diet, supplements and habits in our guide to restoring your gut flora, and about digestive complaints specifically in the article on probiotics for a sensitive stomach and IBS.
Are there any downsides or side effects?
For most healthy adults, probiotics are well established. The first few days can bring a little more gas or bloating before your stomach gets used to them. If you have a severely weakened immune system, a serious underlying condition or are seriously ill, you should consult a doctor or pharmacist first.
Probiotics, prebiotics and postbiotics – what is what?
Three words that are easily confused, but describe different things:
- Probiotics – live bacteria you add via food or supplements.
- Prebiotics – fibres such as FOS and inulin that act as food for the bacteria already living in your gut.
- Postbiotics – the beneficial substances the bacteria produce, for example short-chain fatty acids.
A product that combines probiotics and prebiotics is sometimes called a synbiotic. The idea is that the bacteria bring their own packed lunch, which can help them survive the acidic environment of the stomach and establish themselves better in the gut.
How certain is the research really?
It is easy to read headlines and assume everything is proven. The reality is more nuanced. For diarrhoea-related conditions the evidence is strong, and there healthcare providers sometimes recommend probiotics too. For broader claims about wellbeing, skin or mood, the evidence is thinner and the studies fewer.
A recurring challenge is that researchers have used different strains, different doses and measured different things. That makes it hard to compare studies directly. The conclusion is simple: judge a product by which strains it contains and what those specific strains have shown – not by the word "probiotics" on the label.
Frequently asked questions
What is the difference between probiotics and prebiotics?
Probiotics are live bacteria you add. Prebiotics are fibres, such as FOS and inulin, that act as food for the bacteria already in your gut. Many supplements combine both to give the beneficial bacteria a better chance of establishing themselves and surviving the acidic environment of the stomach.
How long does it take for probiotics to work?
It varies. For acute diarrhoea, the effect can be noticeable within a few days. For more general digestive complaints, it is usually evaluated only after about four weeks of regular use. Because the effect is strain-specific and individual, it is wise to give a product a reasonable trial period before judging it.
Can I get probiotics through food instead?
Yes, fermented foods such as yoghurt, kefir, sauerkraut and kimchi contain live bacteria. The amount and the strains vary greatly, however, and are rarely as concentrated as in a supplement. A good approach is to eat fermented foods regularly and supplement when needed, for example alongside antibiotics.
Do probiotics need to be kept cold?
It depends on the product. Some strains are freeze-dried and tolerate room temperature, while others do best in the fridge. Always follow the label's instructions, since incorrect storage can reduce the number of live bacteria and therefore the effect. Keep the supplement away from direct heat and moisture.