You will likely have heard of probiotics. These are live microorganisms that, when consumed in sufficient amounts, can benefit health. They occur naturally in foods such as yoghurt, kefir, kimchi and sauerkraut and are also sold as supplements.
You may also know that for these probiotics to thrive, they need to be fed. That food comes in the form of prebiotics, which are non-digestible fibres found in everyday foods such as garlic, onions, leeks, bananas and oats. Prebiotics pass through the digestive system largely intact, where they become fuel for beneficial gut bacteria.
More recently, another term has begun appearing on supplement shelves: postbiotics. So what are they, and do we actually need them?
Postbiotics are the beneficial compounds produced when gut bacteria, including probiotics, break down prebiotics. In other words, they are not live bacteria themselves, but the substances those bacteria produce. These include short-chain fatty acids, enzymes, vitamins, amino acids and, in some definitions, structural components such as fragments of bacterial cell walls and parts of dead microorganisms.
Although postbiotic supplements are relatively new, postbiotics themselves are not. They have been produced in our intestines for as long as humans have had gut bacteria. What is new is the idea of consuming them directly, rather than relying on the gut microbiome to make them.
So, if postbiotics are the end product, should we skip probiotics and prebiotics and go straight to postbiotic supplements? The short answer is no. The longer answer lies in the evidence.
Postbiotics are a broad and diverse group of compounds, and research into their health effects is still at an early stage. Some studies suggest potential benefits, but the quality, strength and relevance of the evidence vary widely.
Certain postbiotics, for example, have been linked to improved mood and better sleep quality. Other findings come from laboratory studies, such as reduced invasion of colon cancer cells in cell cultures or protection against E coli infection in tightly controlled experiments. These results are interesting, but they cannot be directly applied to humans without further investigation.
Animal studies suggest some postbiotics may increase the surface area of the gut, which could improve nutrient absorption. However, results seen in animals do not always translate to people.
There is also limited evidence from human studies. One specific postbiotic, butyrate, a short-chain fatty acid produced when gut bacteria break down fibre, has been linked to potential improvements in symptoms among people with inflammatory bowel disease.
A double-blind, placebo-controlled study found that supplementation with a heat-killed strain of Lactobacillus pentosus reduced the likelihood of older adults developing the common cold. Another review concluded that a heat-killed strain of Lactobacillus acidophilus may reduce both the risk and duration of diarrhoea in children.
Read more: Gut microbiome: meet Lactobacillus acidophilus – the gut health superhero
Some postbiotics, such as exopolysaccharides, have shown promise in enhancing immune responses in cell and animal studies. However, these findings remain preliminary.
One form of postbiotic is already used in medical practice. Bacterial lysates are products made from broken-down bacteria and are prescribed in some countries to help prevent recurrent respiratory tract infections in people who are particularly vulnerable. These lysates are made from components of the bacteria that cause infection and work by stimulating the immune system. Outside of these specific clinical uses, however, evidence supporting postbiotic supplements remains limited.
Practical advantages but limited evidence
When researchers refer to advantages of postbiotics, they are usually describing practical and technical factors rather than proven health superiority. Unlike probiotics, which are live microorganisms, postbiotics are non-living compounds. This makes them more stable, easier to store, and less sensitive to heat, oxygen and time. As a result, the amount present in a supplement is more likely to match what is listed on the label.
Postbiotics may also be safer for certain vulnerable groups, such as people who are severely immunocompromised, because they do not involve ingesting live bacteria. These features make postbiotics attractive from a manufacturing and safety perspective.
However, these practical advantages do not mean postbiotics are more effective for improving health. Evidence for benefits in humans remains limited and is highly specific to individual compounds. There is also a lack of standardisation. Because postbiotics include a wide range of substances with different biological effects and dose requirements, findings for one postbiotic cannot be assumed to apply to others.
For most people, supporting the gut microbiome through a varied diet rich in fibre and fermented foods remains the most reliable way to generate postbiotics naturally, while also delivering broader nutritional benefits that supplements cannot replicate.
Perhaps most importantly, postbiotic supplements cannot replicate the wider benefits of whole foods. Eating live yoghurt, for example, provides probiotics alongside calcium and protein. Pairing that yoghurt with a banana feeds the probiotics with prebiotic fibre, while also supplying potassium and vitamin B6. Together, these foods allow the gut to produce postbiotics naturally, while delivering a broad range of nutrients at the same time.
Cost is another consideration. Supplements can be expensive, and for most people, investing that money in a varied diet rich in fibre and fermented foods is likely to deliver greater overall health benefits.
Read more: What the gut microbiome of the world’s oldest person can tell us about ageing
So where does that leave postbiotics? They are a promising area of research and may prove useful in specific clinical settings or vulnerable populations. For now, however, the evidence does not support replacing probiotics and prebiotics with postbiotic supplements for the general population.
At present, the most reliable way to benefit from postbiotics is to let your gut do what it evolved to do. Eating a diet that includes both probiotic foods and prebiotic fibres allows gut bacteria to produce postbiotics naturally. Until research on supplements becomes stronger and clearer, focusing on whole foods remains the most practical and evidence based approach.
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