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Why do we need prebiotics?

If you have been looking into how to support your gut health, you may be familiar with the terms ‘prebiotics’ and ‘probiotics’. Although they sound the same, prebiotics have an entirely different role in your body when it comes to digestive health. 

Prebiotics are non-digestible fibre compounds found mostly in plant foods that feed certain types of bacteria in your gut, encouraging them to grow in volume. Although they are a type of dietary fibre, not all fibres are classed as a prebiotic as there is a strict criteria that must be met.

What are probiotics?

A prebiotic must: 

  • Be resistant to the acidic conditions of the stomach

  • Remain undigested until it reaches the colon

  • Be fermented by the gut microbiota.

  • Change the growth or activity of your gut bacteria

Your gut microbiota is the community of trillions of living microbes, including both beneficial and non-beneficial bacteria, that reside in your gut. It's important to nourish and support the health of good gut bacteria to keep them in balance as they perform essential functions in digestion and overall health.

It is thought that an imbalanced gut microbiota, causing a reduction in these good gut bacteria, could contribute to conditions like irritable bowel syndrome (IBS), Coeliac disease and obesity. If you want to improve your overall health, starting with your gut health is key. 

Why do we need prebiotics?

Prebiotics are a fuel and energy source for your good gut bacteria. They act like a fertiliser, feeding and stimulating the growth of important species of bacteria, including Lactobacillus and Bifidobacteria, allowing them to grow in population and thrive. These good gut bacteria have several beneficial effects on overall health, such as regulating and strengthening your immune system, inhibiting the growth of bad gut bacteria, improving digestion and producing vitamins.

The body isn’t able to break down these prebiotic fibres, so they are passed through the digestive system relatively intact to the gut microbes in your colon. Here they are digested by these microbes, and as a result produce various beneficial metabolites, including vitamins and short chain fatty acids (SCFAs). SCFAs are the end-products of prebiotic fermentation, and they play an important role in supporting gut health. 

Prebiotic benefits 

Prebiotics are not only modulators of your gut microbiota, but they are showing potential in the health of many aspects of the body. The most important benefit of prebiotics is the increased production of short chain fatty acids they cause. SCFAs play key roles in modulating your gut barrier, immune system and inflammatory response.

Why do we need prebiotics for our immune system?

Another essential benefit of prebiotics is that they can help maintain your immune system by nourishing certain types of good gut bacteria that help strengthen your body’s natural defences, including the innate immune system (your first line of defence against pathogens). SCFAs also help to balance your gut microbiota and reduce inflammation.

Why do we need prebiotics to help support our digestion?

Prebiotics promote healthy digestion in many ways - by feeding healthy bacteria and stimulating the growth of more good bacteria in the gut (2). SCFA production by these bacteria play a vital role in improving bowel movement through their stimulating and nourishing effects on epithelial cells (the cells that line your gut).  

Why do we need prebiotics to support a healthy metabolism?

An imbalance of the gut microbiota causes low-grade inflammation in the gut, which can disrupt the metabolism of glucose and the absorption of fats. Prebiotics work to modulate the gut microbiota and reduce inflammation, which in turn helps to improve glucose tolerance to support a healthy metabolism.

Prebiotics have also been linked to an increased secretion of satiety-promoting hormones, and a decreased production of ghrelin, a hormone which promotes appetite.

Can prebiotics help support healthy cholesterol levels?

The SCFAs produced by prebiotics are absorbed into the bloodstream, which allows them to travel around to various organs and exert their effects. They help fats and phospholipids get absorbed in the intestines and can bind to cholesterol, leading to a potential decrease in cholesterol in the bloodstream.

Types of prebiotics

The most beneficial prebiotics are inulin, fructo-oligosaccharides (FOS) and galacto-oligosaccharides (GOS), which can be found in a variety of plant foods. Some examples include: 

  • FOS and inulin: Jerusalem artichoke, banana, asparagus, garlic, onions and chicory.

  • GOS: Legumes, e.g. peas, lentils and beans.

Prebiotic sources

Prebiotic-rich foods 

Prebiotics are found in hundreds of plant foods, many of the foods you probably eat every day. Good prebiotic sources include: 

  • Vegetables: Artichokes, chicory, garlic, onions, leek, shallots, asparagus, beetroot, fennel, green peas, cabbage, potato and sweet potato

  • Fruit: Bananas, nectarines, apples, white peaches, watermelon, grapefruit, pomegranate and dried fruit (e.g. dates, figs, mango)

  • Legumes: Chickpeas, lentils, kidney beans, lima beans and soybeans

  • Nuts: Cashews and pistachios

  • Grains: Millet, quinoa, rye bread and oats

To have a healthy gut microbiota, you need to eat a good balance of prebiotics and probiotics as they have a highly synergistic relationship. Without prebiotics, probiotics can’t thrive, so eating probiotic foods along with prebiotic fibres helps ensure the safe delivery of healthy bacteria to your gut, and also gives them a food source to convert to many beneficial, health-promoting compounds that will support your overall health and energy levels. 

Probiotic-rich foods

  • Sauerkraut

  • Kefir

  • Kombucha

  • Yoghurt

  • Kimchi

  • Miso

  • Tempeh 

  • Pickles 

  • Sourdough bread 

  • Some cheeses

Prebiotic supplements

As mentioned above, there are many fruits, vegetables, and whole grains that contain prebiotics, so you can easily get adequate intake from a balanced diet.

If you don't regularly consume probiotic foods or need extra support, then adding a probiotic supplement to your diet might be helpful.


Although research into the full effects of prebiotics is still ongoing, they are showing to have a growing number of health benefits, reaching far wider than just digestive health. 

Many foods include natural prebiotics, so aim to include a wide variety of these foods into your diet daily, along with probiotic foods, to support your gut and overall health. 


  1. Impact of prebiotics on immune response: from the bench to the clinic

  2. Therapeutic Effects of Prebiotics on Constipation

  3. The Role of Probiotics and Prebiotics in the Prevention and Treatment of Obesity

  4. Regulation of appetite, satiation, and body weight by enteroendocrine cells

  5. Cholesterol-Lowering Effects of Probiotics and Prebiotics




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