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Nutrition, Science

The Science Behind Gut Health

Written by: Phoebe Cottle
Dietitian, Swisse Science Team

There is an abundance of conversation on the topic of gut health, your gut microbiome and why it is important. It can sometimes be complicated, making it hard to understand the role of the gut in overall health, particularly when the research in this area is growing and constantly evolving. Being such a complex system, it may not be widely known that the gut is a crucial part of our immune system! It participates in many functions that have an effect on the entire body.1

The “gut” and immune health

The gastrointestinal tract or “gut” has many different functions. It digests foods, absorbs fluid and nutrients as well as providing a physical and immunological barrier.1 This means that it is able to act as a protective “wall” to microorganisms, foreign material and potential pathogens (microbes that can infect the body and cause illness) that enter the body1.

The attachment of pathogens to the inside surface of the gut is an essential initial step in order for an infection to occur.2 When this happens, the gut’s defence mechanism is activated and the epithelium (tissue and cells lining the surface of the intestine) produces mucus and antimicrobial molecules to help prevent pathogen invasion (e.g. the bad things that can make us sick).2

It is estimated that 70-80% of our immune cells are located in the gut, making it one of the largest immune organs in the body.3

The gut microbiome in the immune system

The gut microbiome has also been found to play an important role in the immune system. The term, gut microbiome, describes the vast and diverse community of microorganisms that live inside our intestinal tract.4 These microorganisms help in contributing to the production of antimicrobial molecules by epithelial cells that line the small and large intestine.4

The gut microbiome also supports our overall health through the by-products produced when the bacteria in the gut ferment dietary substances (more on this later!). For example, when certain carbohydrates are fermented by bacteria, Short Chain Fatty Acids (SCFA’s) are created, which are an extremely important food or energy source for the cells of your gut and ensure that it is able to function and remains healthy.4 They can also circulate in the body to the liver and other tissues for further metabolism.4 It is clear that our gut microbiome not only influences the health of our GI tract but our entire body.

How to support our gut

As we can see, it is important to support and maintain our intestinal health, to ensure that the integrity of our “gut barrier” is strong and able to function as a protective wall (preventing leakage of sometimes harmful toxins into the blood stream.)4 This immune response that takes place in our gut is dependent upon the presence of both macro and micronutrients for optimal functioning.4 We can support this with the help of pre and probiotics.

Pre and Probiotics

The community of microorganisms that make up our gut microbiome is estimated to include thousands of species.1 These “gut bugs” can be enhanced and kept happy through diet, prebiotics and probiotics in order to help maintain overall health.5

Probiotics are concentrates of live organisms that contribute to a healthy microbial environment 1 There are many different strains of probiotics, all of which have differing actions, however research has found some to enhance the barrier function of the GI tract.6 You can find probiotics (live bacteria) in fermented foods such as yoghurt, sauerkraut, kefir, miso and tempeh, just to name a few.

Prebiotics are non-digestible (they don’t break down straight away) carbohydrate components of the diet that are the preferred energy substrates of the “friendly” microbes in the gut. They stimulate the growth or activity of specific bacteria which are beneficial for us.1,5

So basically, probiotics are the live bacteria that are good for your gut and prebiotics can be thought of as the food that helps to keep these beneficial “gut bugs” happy.

What foods can help our gut and immune system?

To help support our gut and therefore our immune system, we should look towards including a variety of foods in our diet and plenty of fresh fruit and vegetables.

An issue with a typical Western diet (high in fat and digestible carbohydrates) is that it often lacks the prebiotics to feed our good bacteria. This can lead to impairment of the gut microbiota (or dysbiosis) which can increase our susceptibility to disease.6

Foods that are rich in dietary fibre (that can be digested by the healthy bacteria) include plant foods, such as fruit and vegetables, lentils and legumes, and fermented foods (sauerkraut, kimchi). These will enable our “good” gut bugs to keep our gut barrier (and ourselves) healthy!6


  1. Mahan, K.L & Raymond, J.L (Ed.). (2017) Krause’s Food & The Nutrition Care Process. Elsevier.
  2. Kamada et al, Role of the gut microbiota in immunity and inflammatory disease. Nature reviews. Immunology 2013.
  3. Langkamp-Henken et al. NCP 1992.
  4. Practice-Based Evidence in Nutrition (PEN) Gastrointestinal System – Microbiota
  5. Lin et al, Impact of the Gut Microbiota, Prebiotics, and Probiotics on Human Health and Disease, Biomed J, 2014.
  6. Lomer, M (Ed.). (2014) Advanced Nutrition and Dietetics in Gastroenterology

Phoebe Cottle - Dietitian, Swisse Science Team

Nutrition, Science