Prebiotics: Food for a thriving gut


  • Human diet is the main source of energy for the growth of gut microbes and can have profound effects on balance of good vs bad bacteria in the gut.
  • Prebiotics are group of nutrients that bacteria in the gut can breakdown and use to provide energy.
  • Prebiotics are typically derived from otherwise indigestible dietary materials like resistant starch and dietary fibres found in fruit and vegetables.
  • Digestion or breakdown of prebiotics by gut microbes produces important by-products.
  • These by-products not only nourish the gut thereby maintaining optimal health and function but also have beneficial effects on other organs.


Gut health and microbiota

Having a healthy gut is a hot topic these days.

Words like probiotics, prebiotics, fermented foods, microbiome, microbiota and gut bacteria are being incorporated into our everyday chat!

And for an extremely powerful reason.

Research has shown that a healthy gut microbiome has amazing health benefits, beyond just helping with digestion.

Having a healthy gut is essential to your overall health and wellbeing.

So what do all these terms mean?

Gut microbiota are the microorganisms including bacteria, virus and fungi that reside in the gut whereas the microbiome includes all the genetic makeup of these microorganisms including gut bacteria. Bacteria make up most of the microbiome.

Fermentation is a process that occurs without the requirement of oxygen but requires important microorganisms like bacteria to break down food components producing the desired food products and taste, texture, or aroma.


Prebiotics are defined as “a substrate that is selectively utilized by host microorganisms conferring a health benefit”. Host refers to organism that the microorganism resides in, in our case humans. Beneficial effects of prebiotics include defence against pathogens, immunity, bowel function, mineral absorption, metabolism and satiety.

What roles do prebiotics and probiotics play in improving gut health?

Prebiotics can have profound effects on both the composition (good vs bad) and function of gut microbes. Importantly, prebiotics stimulate the growth or activity of good gut bacteria. Thereby providing optimal environemnet to provide health benefit.

Traditionally prebiotics included non-digestible carbohydrates with high insoluble fiber content.

Recently this classification has been extended to the above definition due to non-carbohydrate food sources like polyphenols and flavanols (eg. cocoa) and polyunsaturated fatty acids having beneficial effects on gut health also.

Prebiotics naturally occur in dietary food products including asparagus, garlic, sugar beet, onion, chicory, Jerusalem artichoke, wheat, banana, honey, barley, tomato, rye, soybean, human and cow’s milk, peas, beans, seaweeds and microalgae.

Prebiotics feed the gut microbiota, and their broken-down products are short-chain fatty acids (SCFAs).

SCFAs are released into blood circulation, consequently, affecting not only the cells and function of the gut but also other distant organs.

SCFAs are used in many metabolic processes by cells of the gut and strengthen the gut function.

Other functions include supporting immune system.

In chronic diseases like Inflammatory Bowel Disease (IBD) and Colitis, SCFA production is impaired. This restricts energy supply to important cells of the gut.

And can contribute to inflammation of the gut lining.

In addition to SCFAs, production of other important nutrients like vitamins (e.g. vitamin K and folic acid) and amino acids, which humans are unable to produce themselves are also generated.

Adjusting the microbiota using prebiotics can increase SCFAs producing bacteria and enriche microbiome diversity. Greater microbial diversive is protective against disease.

Take-home message

  • Prebiotics feed the bacteria already in your gut.
  • Incorporate more foods naturally high in prebiotics into your diet.
  • Prebiotics produce short chain fatty acids that have beneficial effects on gut and overall health.
  • Foods naturally high in prebiotics include Jerusalem artichokes, chicory, garlic, onion, leek, shallots, spring onion, asparagus, beetroot, fennel bulb, green peas, snow peas, sweetcorn, savoy cabbage.
  • If you have IBD consider a low FODMAP diet and try incorporating a prebiotic. However, individual results may vary and side effects of abdominal pain, bloating and flatulence and diarrhea may be experienced.