By Jim Willshire MRCVS, UK veterinary surgeon
In Part I we looked at what prebiotics, probiotics and postbiotics are and how each one supports the gut environment in a different way.
But one important question often gets overlooked: should prebiotics, probiotics and postbiotics be used together?
Each approach has real limits when used on its own. Understanding those limits is what makes the case for a combined strategy.
Prebiotics can only support bacteria that are already present. If the microbiome has lost diversity or been significantly disrupted, there may be fewer beneficial bacteria for the prebiotic to feed. Fertiliser doesn't help much if the garden is bare.
Probiotics introduce helpful strains, but most do not stay permanently. Without the right nutrition to support them, they may pass through without having much impact. Seeds need good soil.
Postbiotics deliver beneficial compounds directly, but they cannot adapt or respond to changing conditions in the way living bacteria can. They do not change microbial populations. Compost enriches the soil, but it does not plant anything new.
Each approach has value. But each also has gaps that the others can fill. On their own, they're rarely the whole picture — and that's where things get more interesting.
The gut is not a simple system with a single point of failure. It is a complex, dynamic ecosystem influenced by diet, environment, stress, medication and more.
When all three approaches are combined thoughtfully, they can complement one another. Prebiotics provide the fuel that helps beneficial bacteria — including introduced probiotics — remain active. Probiotics bring in selected strains that interact with the existing microbial community while present. Postbiotics provide microbial compounds that support the gut lining and normal immune function directly, without waiting for fermentation to occur.
The combination of prebiotics and probiotics — sometimes called a synbiotic — has been studied in both human and veterinary contexts. A fact sheet from Davies Veterinary Specialists provides a useful overview of how probiotics and prebiotics are used together in dogs and cats, and why these combinations are increasingly common in veterinary practice. Research suggests this approach may offer advantages over either component alone in certain situations.
Adding postbiotics may provide an additional layer of support, helping maintain an environment in which both resident and introduced bacteria can function effectively.
To return to the garden analogy one final time: a thriving garden needs fertiliser, seeds and compost working together. No single element does the whole job.