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........

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