The Connection Between Gut Health and Immunity

by | Feb 5, 2025 | Gut Health

The human body is a complex system. One interesting link is between gut health and the immune system. A well-balanced gut can strengthen your body’s defenses, while an imbalance may leave you vulnerable. So, if you want to give your immune system a boost, consider focusing your gut.

Your gut is more than just your stomach. It’s a complex system that includes the digestive tract, which goes from your mouth to your intestines. It also includes other organs like the liver, pancreas, and gallbladder. Together, they break down food, absorb nutrients, and keep your body running smoothly.

microbiome

But your gut isn’t working alone. Trillions of microorganisms, like bacteria, viruses, fungi, and other microbes, live in your intestines. This group is called the gut microbiome. Each person’s microbiome is unique and shaped by genetics, diet, lifestyle, and environmental factors (1).

A balanced microbiome does far more than aid digestion. It:

    • Produces essential vitamins
    • Helps break down dietary toxins
    • Strengthens the gut lining
    • Prevents harmful bacterial overgrowth
    • Supports the immune system

Research shows that the gut microbiome influences immune function by protecting against pathogens and reducing infection risk (1).

The Gut-Immune System Connection

The gut is often called the “second brain” because of its vast neural network, but its role in immune function is just as critical. Around 70% of the immune system resides in the gut, working closely with the trillions of microbes that make up the gut microbiome (2).

From birth, gut bacteria help shape the immune system by training it to recognise harmful invaders while tolerating beneficial microbes and nutrients. This constant interaction influences immune responses, helping the body distinguish between friend and foe (2).

How The Gut “Trains” the Immune System

Think of your immune system as a security team. It must distinguish between dangerous intruders (like harmful bacteria and viruses) and harmless visitors (like food and beneficial microbes). This training happens in the gut-associated lymphoid tissue (GALT) – a crucial part of the immune system that constantly communicates with gut bacteria to regulate immune responses (3).

Your gut microbiome also plays a direct role in the production and function of T cells and B cells – immune cells that help fight infections and prevent autoimmune diseases. When the microbiome is balanced, it helps maintain a strong and well-regulated immune system (3).

How a Healthy Gut Microbiome Boosts Immunity

A well-balanced gut doesn’t just support your immune system—it actively strengthens it. Here’s how:

    • Fewer infections – Beneficial gut bacteria suppress the growth of harmful pathogens, reducing the risk of infections (4).
    • Stronger immune responses – A healthy microbiome helps regulate immune cell production, improving your body’s ability to fight off colds, flu, and other common illnesses (5).
    • Reduced inflammation – The gut produces short-chain fatty acids (SCFAs), which help control inflammation and prevent immune overreactions linked to chronic diseases (5).

What Happens When the Gut is Imbalanced?

When the gut microbiome becomes unbalanced due to poor diet, stress, medications, or lack of sleep, it can weaken the immune system and trigger chronic inflammation. Over time, this imbalance has been linked to:

    • Autoimmune diseases
    • Obesity
    • Heart disease
    • Type 2 diabetes

The good news? Research shows that maintaining a diverse gut microbiome – through diet and lifestyle choices – can enhance immune function and reduce disease risk. By supporting your gut health, you’re also strengthening your body’s natural defenses (6).

What Weakens Your Gut and Immune System? Key Risk Factors to Know

Several factors can disrupt gut health and, in turn, weaken immunity. Key contributors include

    • Diet – Processed foods and high sugar intake harm the microbiome, while fiber-rich diets promote microbial diversity (7).
    • Chronic stress – Long-term stress can lead to gut dysbiosis, weakening immune defenses (8).
    • Medication use – Antibiotics can wipe out beneficial bacteria, creating an imbalance (9).
    • Poor sleep – A lack of sleep can negatively impact gut bacteria, while an imbalanced microbiome may further disrupt sleep (10).
    • Environmental factors – Exposure to pollutants and toxins can disturb gut health, increasing inflammation (11).

Dietary & Lifestyle Habits to Support a Healthy Gut

 

    • Eat a colourful diet – Fruit and vegetables are rich in polyphenols which feed friendly bacteria and stimulate their growth (7). Good sources of polyphenols include citrus fruit, dark leafy greens, red and purple berries, nuts and seeds, and cacao.
    • Eat more fibre – Consuming more fiber promotes healthy gut bacteria and enhances microbial diversity. This leads to increased production of short-chain fatty acids (SCFAs) that reduce inflammation (7). Aim for at least 30g/day, which you can get from vegetables, beans and pulses, and whole-grains (oats, millet, quinoa etc.).
    • Include probiotic and prebiotic foods – Foods like yogurt, kimchi, and sauerkraut provide probiotics which play an essential role in supporting a diverse microbiome. They introduce beneficial microbes into the gut. Prebiotic foods like asparagus, aubergine, endive, garlic and onions, Jerusalem artichokes, leeks, pulses and chicory, feed beneficial gut bacteria (12).
    • Consider food intolerances and allergies, such as wheat and dairy, as they create inflammation (13,14).
    • Avoid ultra-processed foods, such as sugar, which fuels unfriendly bacteria (7).
    • Avoid, as much as possible, drugs that harm gut bacteria – While necessary in some cases, antibiotics can wipe out good bacteria, weakening immune function (9). Stomach acid medication can also impact the gut microbiome (15).
    • Manage Stress – Long-term stress can greatly affect our gut and overall health. It can lead to dysbiosis, which is an imbalance in the microbiome. Our brain, microbiota and gastrointestinal tract are all connected and impact one another, so mindfulness, exercise, and sleep are key (8).
    • Get enough sleep – aim for 7-9 hours of sleep each night, as a lack of sleep can disrupt the balance of gut bacteria. An imbalanced microbiome may in turn also affect sleep quality, as certain gut bacteria produce neurotransmitters (chemicals in the brain), which play important roles in sleep regulation (10).

Final Thoughts

Understanding the link between gut health and immunity is crucial for overall well-being. A healthy gut microbiome can enhance immune function and protect against illnesses.

Simple lifestyle changes can make a big impact. Embrace a balanced diet rich in fiber, probiotics, and prebiotics to boost your gut health.

Regular exercise and quality sleep also play roles in maintaining a resilient immune system. These habits support both your physical and mental well-being.

If you think your immune system needs some help and want a personalised health plan, why schedule a free 20-minute consultation with me? During this call you can learn how nutritional therapy can support you. Just reach out to me here to schedule it.

Please note: this information is for general use only. It should not replace advice from your doctor or health care professional. If you have any health concerns, please reach out to your local health care provider.

References

    1. Zmora N, Suez J, Elinav E. You are what you eat: diet, health, and the gut microbiome. Nature Reviews Gastroenterology & Hepatology. 2019;16(1): 35–56
    2. Wiertsema SP, van Bergenhenegouwen J, Garssen J, Knippels LMJ. The interplay between the gut microbiome and the immune system in the context of infectious diseases throughout life and the role of nutrition in optimizing treatment strategies. Front Immunol. 2020;11: 364
    3. Honda K, Littman DR. The microbiota in adaptive immune homeostasis and disease. Nature. 2016;535(7610): 75–84.
    4. Pickard JM, Zeng MY, Caruso R, Núñez G. Gut microbiota: Role in pathogen colonization, immune responses, and inflammatory disease. Nat Rev Immunol. 2017;17(12):721-735. doi: 10.1038/nri.2017.107.
    5. Belkaid Y, Hand T. Role of the microbiota in immunity and inflammation. Cell. 2014;157(1): 121-31.
    6. Spragge F, Bakkeren E, Jahn MT, Araujo EB, Pearson CF, Wang X, Pankhurst L, Cunrath O, Foster KR. Microbiome diversity protects against pathogens by nutrient blocking. Science. 2022;378(6617): 1572-1578. doi: 10.1126/science.adj3502.Wang M, Tao Y, Zhang Y, et al. The role of diet in shaping gut microbiota. International Journal of Food Sciences and Nutrition. 2021;72(1): 16–26.
    7. Zhang P. Influence of foods and nutrition on the gut microbiome and implications for intestinal health. Front Nutr. 2021;8: 709827. doi: 10.3389/fnut.2021.709827.
    8. Karl JP, Hatch AM, Arcidiacono SM, et al. Effects of psychological, environmental and physical stressors on the gut microbiota. Front Microbiol. 2018;9:2013. doi:10.3389/fmicb.2018.0201
    9. Patangia DV, Anthony Ryan C, Dempsey E, Paul Ross R, Stanton C. Impact of antibiotics on the human microbiome and consequences for host health. MicrobiologyOpen. 2022 Jan 13;11(1). doi:10.1002/mbo3.1260
    10. Wang Z, Wang Z, Lu T, Chen W, Yan W, Yuan K, et al. The microbiota-gut-brain axis in sleep disorders. Sleep Medicine Reviews. 2022 Oct;65:101691. doi:10.1016/j.smrv.2022.101691
    11. Koenig JE, Spor A, Scalfone N, Fricker AD, Stombaugh J, Knight R, et al. Succession of microbial consortia in the developing infant gut microbiome. Proceedings of the National Academy of Sciences. 2010 Jul 28;108(supplement_1):4578–85. doi:10.1073/pnas.1000081107
    12. İnce Palamutoglu M, Köse G, Bas M. Probiotics and prebiotics affecting mental and Gut Health. Healthcare. 2024 Feb 21;12(5):510. doi:10.3390/healthcare12050510
    13. Cenni S, Sesenna V, Boiardi G, Casertano M, Russo G, Reginelli A, et al. The role of gluten in gastrointestinal disorders: A Review. Nutrients. 2023 Mar 27;15(7):1615. doi:10.3390/nu15071615
    14. Szilagyi A, Ishayek N. Lactose intolerance, dairy avoidance, and treatment options. Nutrients. 2018 Dec 15;10(12):1994. doi:10.3390/nu1012199
    15. Bruno G, Zaccari P, Rocco G, Scalese G, Panetta C, Porowska B, et al. Proton pump inhibitors and dysbiosis: Current knowledge and aspects to be clarified. World Journal of Gastroenterology. 2019 Jun 14;25(22):2706–19. doi:10.3748/wjg.v25.i22.2706