What are prebiotics and how are they different from probiotics?

Prebiotics are dietary fibres that promote the growth of beneficial bacteria in your gut.

They help to restore your microbiome – a community of microorganisms living in our digestive tract. Our microbiome is the hub where all metabolic pathways in our body begin, and it is intimately connected to our immune system function. At birth we have zero microbes in our intestinal tract, and it takes us 30 years to end up with a microbiome profile that has the potential to maintain health.

We can influence – or even positively manipulate – our microbiome composition by changing what we eat. This is why you see warnings from doctors about eating too many processed foods (which don’t provide prebiotics), as well as recommendations about eating fibre-rich whole plant foods.

The following are examples of prebiotic fibres from food:

* Chicory root (inulin) – a soluble fibre that has also been shown to have cholesterol-lowering activity. It is extracted and sold as a supplement, or you can buy high strength chicory root coffee in health shops.

* Jerusalem artichoke (fructans) – another soluble fibre that also promotes the growth of beneficial bifidobacteria and lacto-bacilli species (friendly bacteria). It is supposed to be an insulin sensitiser, but I am yet to see any positive evidence for this effect.

* Psyllium husk – (is also a soluble fibre) This is the most common fibre supplement in Australia, where they have been shown to reduce cholesterol levels.

Prebiotics are different from probiotics (also known as ‘good bacteria’ supplements). Probiotics are the actual bacteria that we eat, in pill form. If you search online for prebiotics and probiotics, you will see many people recommending a mix of both to promote gut health.

Prebiotics are considered to be ‘food’ for the good bacteria in our gut, whereas probiotic supplements provide them with a home. Prebiotics make up 25-35% of chicory root; psyllium husk is about 50% soluble fibre and Jerusalem artichokes contain mostly non-soluble fibre (80%). So with these last two, the prebiotic content is relatively low.

So the question is: ‘How much prebiotic fibre do we need?’

We know that low fibre intake in adults contributes to constipation, abdominal pain and a reduced sense of wellbeing. So eating more fibre – whatever it may be – will help! There are people who struggle to tolerate higher amounts of fibre, so it is important to start small and work up.