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What are Prebiotics?

Written by Charlotte Green

what are prebiotics?

In recent years, it has become increasingly clear that looking after our gut health is not only important for our digestion but our overall health as well. In fact, it is thought that the health of our gut could impact our weight (1), immune function (2) and even our mood (3).

This is largely due to the influence of the gut microbiota, the community of trillions of microorganisms that live along the digestive tract. The composition of the gut microbiota can be influenced by a variety of lifestyle-related factors including diet, sleep, and stress. It is thought that dysbiosis, an imbalance of the “good” and “bad” bacteria, can contribute to the emergence of a variety of diseases including obesity, IBS and autoimmune diseases such as coeliac disease (4). However, there are simple changes that can be made to improve gut health, including adding in sources of prebiotics to your diet.

What are Prebiotics?

The term “prebiotic” has become increasingly popular, particularly in food marketing, but it can be difficult to navigate the facts from the fads. Essentially, prebiotics are a source of food for the “good” bacteria in the large intestine. They are a type of plant-based fibre, obtained from the diet, that are broken down by the gut microbiota. The most beneficial prebiotics are inulin, fructo-oligosaccharides (FOS) and galacto-oligosaccharides (GOS) (5).

Where can you find Prebiotics?

Prebiotics are found in plant-based foods. Good sources of prebiotics include:

  • Leeks

  • Oats

  • Onions

  • Garlic

  • Artichokes

  • Chicory

  • Bananas (6)

Some food products, such as breakfast cereals, have also been fortified with inulin, which can act as an additional source of prebiotics (7).

How do they work?

The gut microbiota uses prebiotic fibre as an energy source, which allows the “good” bacteria to grow (5), whilst preventing the growth of harmful bacteria (8), which can have far-reaching effects to improve our overall health. This is because fermentation of prebiotics produces beneficial chemicals such as short-chain fatty acids (SCFAs). SCFAs are anti-inflammatory and can leave the digestive system and travel in the bloodstream to confer a number of health benefits around the body (8).

Health benefits of Prebiotics


Consuming foods high in prebiotics regularly to increase the number of “good” bacteria is important for effective digestion. There are certain food components, particularly dietary fibre from plant-based foods, that our body cannot digest on its own. We rely on the assistance of the gut microbiota. Therefore, a healthy gut microbiota allows us to obtain the maximum amount of energy and nutrients from the food we eat (5).

Furthermore, the gut microbiota assists in the breakdown of other important plant chemicals, such as polyphenols, found in berries, olive oil, tea, and coffee. Polyphenols are important for our health as they are potent antioxidants, preventing excessive damage to our cells (9).

Prebiotics could also be beneficial as part of the treatment of some gut disorders like IBS, although research in this area is still in its early stages (10).

Metabolic Health

Gut microbiota dysbiosis has been linked to both obesity and type 2 diabetes, largely due to increased inflammation (11). However, prebiotics have a potential role in the prevention and treatment of these conditions.

Prebiotics can increase the number of beneficial bacteria such as Bifidobacterium species (11), which may regulate appetite via various communication pathways. This was demonstrated in a study of obese children who showed reduced food consumption following treatment with the prebiotic inulin (12).

Furthermore, the increase in beneficial bacteria has been shown to improve insulin resistance, a key feature of type 2 diabetes (13). Research in this area is promising but has mostly been performed in animals, so much longer-term studies are required in humans before prebiotics are utilised for type 2 diabetes.

Brain Health

There is a two-way communication system between the gut and the brain, known as the gut-brain axis. Essentially, it means that the gut and brain can “talk” to each other via the nervous system and the transport of chemical messengers such as hormones.

Therefore, the gut microbiota has the potential to influence brain health (14). In fact, it is thought that the gut microbiota could play a role in a variety of disorders, from anxiety and depression (which we often see alongside eating disorders) to Alzheimer’s Disease.

Although research into the use of prebiotics for depression is in its early stages, it is thought that prebiotics could be helpful. They can increase the number of short-chain fatty acid producing bacteria, which could help reduce inflammation, a known risk factor for depression (15).

Similarly, early studies looking at supplementation with FOS prebiotics has been shown to reduce various markers of Alzheimer’s Disease and maintain the diversity of the gut microbiota, which is often lowered in Alzheimer’s Disease patients (16) .

What about prebiotic supplements?

In general, for those wanting to improve their gut health and general wellbeing, prebiotic supplements are not necessary. In fact, it is often more beneficial to consume prebiotics from whole foods because they contain many other vitamins, minerals and plant chemicals that are beneficial for our health. It is important to remember that no nutrient in isolation is revolutionary for health, it is all about variety and balance. Our free guide How To Build a Balanced Plate explains more on why all foods have a place in a balanced diet.

That being said, research is progressing into the use of prebiotic supplements for specific medical conditions, which could open up exciting new treatment options.

At TCN our specialist eating disorder dietitians can offer online consultations to support your health journey! Book a free 15 minute discovery call here with one of our dietitians.

Charlotte Green

Charlotte Green

Charlotte Green is a postgraduate Dietetics student at the University of Chester, after graduating with a degree in Biological Sciences from Durham University. She is passionate about the role of nutrition in health and longevity, the gut microbiome and the link between food and mood. Charlotte looks forward to supporting others live a healthier life in her future role as a registered Dietitian.



  1. Cuevas-Sierra A, Ramos-Lopez O, Riezu-Boj JI, Milagro FI, Martinez JA. Diet, Gut Microbiota, and Obesity: Links with Host Genetics and Epigenetics and Potential Applications. Adv Nutr [Internet]. 2019 Jan 1 [cited 2022 Sep 28];10(suppl_1):S17–30. Available from:

  2. Yoo JY, Groer M, Dutra SVO, Sarkar A, McSkimming DI. Gut Microbiota and Immune System Interactions. Microorganisms [Internet]. 2020 Oct 1 [cited 2022 Sep 28];8(10):1–22. Available from:

  3. Osadchiy V, Martin CR, Mayer EA. The Gut–Brain Axis and the Microbiome: Mechanisms and Clinical Implications [Internet]. Vol. 17, Clinical Gastroenterology and Hepatology. W.B. Saunders; 2019 [cited 2021 Jun 15]. p. 322–32. Available from:

  4. Carding S, Verbeke K, Vipond DT, Corfe BM, Owen LJ. Dysbiosis of the gut microbiota in disease. Microb Ecol Heal Dis [Internet]. 2015 Feb 2 [cited 2021 Aug 17];26(0). Available from:

  5. Davani-Davari D, Negahdaripour M, Karimzadeh I, Seifan M, Mohkam M, Masoumi SJ, et al. Prebiotics: Definition, types, sources, mechanisms, and clinical applications [Internet]. Vol. 8, Foods. MDPI Multidisciplinary Digital Publishing Institute; 2019 [cited 2021 Jun 17]. Available from: /pmc/articles/PMC6463098/

  6. Functional foods - British Nutrition Foundation - Page #2 [Internet]. [cited 2022 Sep 28]. Available from:

  7. Brownawell AM, Caers W, Gibson GR, Kendall CWC, Lewis KD, Ringel Y, et al. Prebiotics and the health benefits of fiber: Current regulatory status, future research, and goals. J Nutr [Internet]. 2012 May 1 [cited 2021 Jun 17];142(5):962–74. Available from:

  8. Simon E, Călinoiu LF, Mitrea L, Vodnar DC. Probiotics, Prebiotics, and Synbiotics: Implications and Beneficial Effects against Irritable Bowel Syndrome. Nutrients [Internet]. 2021 Jun 1 [cited 2022 Sep 20];13(6). Available from:

  9. Sakkas H, Bozidis P, Touzios C, Kolios D, Athanasiou G, Athanasopoulou E, et al. Nutritional status and the influence of the vegan diet on the gut microbiota and human health [Internet]. Vol. 56, Medicina (Lithuania). MDPI AG; 2020 [cited 2021 Jun 16]. Available from:

  10. Guarino MPL, Altomare A, Emerenziani S, Di Rosa C, Ribolsi M, Balestrieri P, et al. Mechanisms of Action of Prebiotics and Their Effects on Gastro-Intestinal Disorders in Adults. Nutrients [Internet]. 2020 Apr 1 [cited 2022 Sep 30];12(4). Available from: /pmc/articles/PMC7231265/

  11. Li HY, Zhou DD, Gan RY, Huang SY, Zhao CN, Shang A, et al. Effects and Mechanisms of Probiotics, Prebiotics, Synbiotics, and Postbiotics on Metabolic Diseases Targeting Gut Microbiota: A Narrative Review. Nutrients [Internet]. 2021 Sep 1 [cited 2022 Sep 24];13(9). Available from:

  12. Hume MP, Nicolucci AC, Reimer RA. Prebiotic supplementation improves appetite control in children with overweight and obesity: a randomized controlled trial. Am J Clin Nutr [Internet]. 2017 Apr 1 [cited 2022 Sep 24];105(4):790–9. Available from:

  13. Chen K, Xie K, Liu Z, Nakasone Y, Sakao K, Hossain A, et al. Preventive Effects and Mechanisms of Garlic on Dyslipidemia and Gut Microbiome Dysbiosis. Nutrients [Internet]. 2019 Jun 1 [cited 2022 Sep 24];11(6). Available from:

  14. Dinan TG, Cryan JF, Dinan TG, Cryan JF, Physiol J. Gut instincts: microbiota as a key regulator of brain development, ageing and neurodegeneration. J Physiol [Internet]. 2017 Jan 15 [cited 2022 Jan 13];595(2):489–503. Available from:

  15. Methiwala HN, Vaidya B, Addanki VK, Bishnoi M, Sharma SS, Kondepudi KK. Gut microbiota in mental health and depression: role of pre/pro/synbiotics in their modulation. Food Funct [Internet]. 2021 May 25 [cited 2022 Sep 23];12(10):4284–314. Available from:

  16. Kang JW, Zivkovic AM. The Potential Utility of Prebiotics to Modulate Alzheimer’s Disease: A Review of the Evidence. Microorganisms [Internet]. 2021 Nov 1 [cited 2022 Sep 23];9(11). Available from:


Talia Cecchele Nutrition is a team of registered dietitians that specialise in eating disorders, disordered eating, digestive issues and sports nutrition. We aim to bring balance back to nutrition, help you to break free from food rules and find food freedom. We offer virtual consultations and group programs so whether you are based in London, the United Kingdom or around the world we would love to support you. To enquire about a private consultation please fill out a contact form.

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