The Gut-Immune Link

This diverse universe, known as the microbiome, helps digest food, absorb nutrients, and regulate the immune system, among many other important functions.

Did You Know? 

More than 70% of the immune system is found in the gut, where a single layer of epithelial cells forms a barrier between gut contents and the rest of the body. 

On one side are trillions of microbes, and on the other, immune cells constantly interact with them. A major part of this defence system is the gut-associated lymphoid tissue (GALT), which houses specialised immune cells that monitor and respond to potential threats.

One way gut bacteria defend against viruses is by creating a physical barrier, making it harder for them to invade the body. Viruses must first bypass beneficial bacteria, the protective mucus they produce, and the gut lining before causing infection.

Another key defence is a balanced microbiome. In this state, the microbiome helps regulate immune responses by training the immune system to distinguish between harmful invaders and harmless microbes. It also produces short-chain fatty acids (SCFAs), which strengthen the gut barrier, reduce inflammation, and regulate immune responses. 

An imbalanced microbiome can weaken immune defences or trigger excessive immune reactions, leading to chronic inflammation and autoimmune conditions.

Several factors influence gut health. Prebiotics - found in foods like onions, garlic, leeks, asparagus, and green bananas - are a type of fibre that feeds beneficial gut bacteria, helping them thrive. Probiotics, the live bacteria found in fermented foods like yoghurt, kefir, sauerkraut, and kimchi, support a healthy microbiome. Then there are postbiotics - the beneficial by-products of bacterial fermentation, including SCFAs like butyrate, acetate, and propionate. These are produced when good bacteria ferment plant fibres that our bodies can’t digest on their own. 

While the microbiome, stomach acid, and an intact gut lining are key components of the defence system that help keep viruses at bay, daily habits also play a significant role. Stress and poor sleep can disrupt the microbiome and weaken the immune system, as can the frequent use of antibiotics, making it harder for the body to fight infections.

Eating a fibre-rich diet is one of the best ways to promote microbial diversity. 

Including a wide variety of plant-based foods ensures that the gut is consistently exposed to a range of fibres, which promotes healthy bacterial growth and strengthens the immune response. Research from the American Gut Project found that the best predictor of a healthy microbiome is a diverse diet. People who eat more than 30 different plant-based foods a week have a significantly healthier microbiome than those eating fewer than ten. 

Choosing the right carbohydrates is equally important. Simple carbohydrates, found in sugary drinks, baked goods, and processed foods, promote the growth of harmful microbes and contribute to inflammation. In contrast, complex carbohydrates - typically high in fibre - are found in fruits, vegetables, whole grains, and legumes. These feed beneficial bacteria and support SCFA production. Resistant starches, a type of complex carbohydrate, pass undigested to the colon, where gut bacteria ferment them. Foods like cooked and cooled potatoes, sweet potatoes, rice, uncooked rolled oats - commonly used in overnight oats - and chickpeas are excellent sources.

A strong gut microbiome can be the difference between fighting off a virus and getting seriously ill. By improving lifestyle habits and increasing the variety of fibre-rich, whole foods in our diet, we can support the gut-immune connection. This not only helps protect against infections but also promotes overall vitality, making it an essential part of our well-being.

ABOUT THE AUTHOR

Theresa is the Wellness Warehouse Regional Learning & Development Manager for Gauteng and KwaZulu-Natal, as well as a holistic nutritionist and health coach passionate about empowering others to live their best lives.