The Low Down on Prebiotics

Probiotics are live microorganisms that when consumed, provide health benefits to the host. So, what’s a prebiotic? It’s the new buzz word in digestive health and in case you’ve wondered, no, they’re not the same thing.  

In 2008, the International Scientific Association of Probiotics and Prebiotics (ISAPP) defined prebiotics as ‘a selectively fermented ingredient that results in specific changes in the composition and/or activity of the gastrointestinal microbiota, thus conferring benefit(s) upon host health’.  Let’s break this down: 

Changes in the composition: 

Prebiotics go on to stimulate the growth of certain bacterial strains in the colon – think of it as food for beneficial bacterial strains, the equivalent of bacterial cryptonite. Take the strain Akkermansia Municiphilia for example, evidence suggests that low levels are associated with poor health outcomes such as type two diabetes and obesity and that higher levels are supportive of short chain fatty acid production and metabolic health. Science can’t yet help to package Akkermansia Municiphilia into a probiotic capsule however we can support its’ proliferation through diet. 

Activity of the gastrointestinal microbiota: 

Given the right food, commensal bacteria go on to work in our favour. When given access, they ferment prebiotics, leading to the production of short chain-fatty acids: butyrate, acetate and propionate, which in turn act as fuel for the cells lining the wall of the colon. This offers protection against cancers of the colon, poor nutrient status and the proliferation of pathogenic bacteria and parasites. Conversely, when starved of the right substrate (fuel), bacterial metabolites such as histamine, ammonia and hydrogen sulphide can have negative implications. These metabolites also don’t just directly impact in the gut, they can go on to influence the immune system, metabolic system and nervous system.

Are prebiotics beneficial for all?

Though they’re all around us in the form or fruits, vegetables, nuts, seeds and resistant starch (RS), there are many cases in which prebiotics aren’t well tolerated. In fact, in cases of dysbiosis, SIBO, constipation, IBS and parasitic infections prebiotics may make symptoms worse because rapid fermentation can cause gas, bloating diarrhea and/or constipation. This sort of reaction may lead to a diet low in prebiotics which, in the long term, will perpetuate further dysbiosis.  

If you’ve been diagnosed with one of the above then treatment may require removal of certain prebiotic fibres for a period of time, however after such time the gradual increase in prebiotic rich foods will be needed. 

Please work with a professional to guide your prebiotic intake in these cases. In clinic I often see a lack of prebiotic intake as the barrier between the status quo (or infection) and developing a thriving digestive system. If you need help determining whether this is you or if you need help navigating any of the above conditions, please get in touch and book your complimentary consult.  

Food as medicine: 

There is the temptation to look to supplements for prebiotics and there are some great options, however there is also ample opportunity within the diet to load up on prebiotics and really, unless working with a professional for guidance, food should be your source. Some recommended dietary sources included: 

  • Crushed raw garlic: a beautifully rich source of inulin and Fructooligosaccharides (FOS). It also has natural anti-microbial properties making it the ideal inclusion in cases of dysbiosis. Try adding ½ teaspoon to this Avocado and Spinach Dip
  • Blueberries: a rich source of prebiotics, polyphenols, antioxidants and vitamin C.  They’re known to promote growth of 20 bacterial species and the combination of the above makes blueberries ideal in most gut healing protocols. Try this Mixed Berry and Tahini Smoothie
  • Green banana flour: a rich source of RS and pectins. A practical means for getting more prebiotics in when you consume things like smoothies and chia puddings as all you need to do is stir it in. Try green banana flour in this beautiful Mango Chia Pudding
  • Leeks, onions, asparagus and spring onions: rich sources of inulin and FOS.
  • Cooked and cooled potato, sweet potato and basmati rice: a source of resistant starch and the preferred means for including higher carbohydrate foods during a gut healing protocol. RS are discussed in detail in the Low Down on Resistant Starch

In Summary: 

Probiotics confer huge health benefits for the human host – a concept now widely accepted. However, as consumers we tend to think of probiotics as being limited to the eight (or 2 – 15) strains listed on the back of a probiotic bottle.  The reality is, we don’t even know yet how many strains and species of bacteria live in our colon. What we do know is that diversity in bacterial strains is hugely beneficial to health and that not all of these strains can be packaged in a simple capsule. So, the natural solution is to consume a diet high in fibre with an array of prebiotic fibres and allow these to support the diversity of our microbiome for us. 


Davani-Davari D et al., 2019. Prebiotics: Definition, Types, Sources, Mechanisms, and Clinical Applications. Foods, 8, 3, 92.

Salvin J. 2013. Fiber and prebiotics: mechanisms and health benefits. Nutrients, 5, 4, 1417-35.

Dao MC et al., 2016. Akkermansia muciniphila and improved metabolic health during a dietary intervention in obesity: relationship with gut microbiome richness and ecology. British Medical Journal, 65, 426-436.

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