How Gut Health and the Immune System are Connected

Science continues to reveal more about the staggering link between gut health and a strong immune system. Seventy percent of the body’s immune cells reside in the gut, and many health experts have even started to consider the gut microbiome as its own organ.

When a patient is struggling with frequent health problems or long-term discomforts, integrative doctors tend to seek underlying problems with the GI tract as a first course of action. Because the gut microbiome is teeming with trillions of bacteria, it plays a central role in healthy digestion, immunity, cognitive function, mood, and many other body systems.

When the microbiome is out of balance, the immune response is affected by increased intestinal permeability, leaving you more prone to a fungal, bacterial, or viral invaders.

root causes of poor gut health

In most cases, impaired gut health doesn’t happen overnight. Instead, it is a longer process impacted by several factors. The following are the first possibilities to consider when trying to understand and repair a damaged gut.

diet history of highly processed foods

Food is information for the body that significantly dictates the quality of your hormone, neurotransmitter, organ, and metabolism function. A current diet or diet history comprised of highly processed foods and refined sugar profoundly impacts the gut microbiome, setting the stage for the proliferation of “bad” bacteria.

Poor nutrient status from a diet lacking immune-boosting vitamins, minerals, and other compounds can also contribute to weakened immunity.

long-term stress

In times of high stress, less oxygen is delivered to the gut. Research shows that ongoing stress impacts gastric secretion, gut motility, mucosal permeability and barrier function, and mucosal blood flow.^[1] In fact, the gut microbiota seems to respond to stress signals from the body directly, indicating that long-term, high levels of stress hormones like cortisol can contribute to a heightened inflammatory response in the gut.^[2] 

overuse of antibiotics or nsaids

While there is a time and place for antibiotics and non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or aspirin, overuse can wreak havoc on the intestinal lining and contribute to increased permeability.^[3] 

blood sugar imbalances

Constant blood sugar dips and spikes can also increase gut permeability, which is largely caused by a diet high in refined carbohydrates and sugar. It appears that the blood sugar-gut connection is a two-way street; studies reveal that specific changes in intestinal bacteria can impact sugar and fat metabolism, contributing to high blood sugar levels.^[4]

gut pathogen

Ongoing gut discomforts might also point to an underlying issue, such as a fungal overgrowth, parasite, or other infection. Speak with your doctor about appropriate testing to rule out these possibilities.

the gut-immune connection

Wrapped around your small and large intestine is a layer of tissue packed with immune cells called gut-associated lymphatic tissue, or GALT. This tissue is in close contact with the gut lining and the enteric nervous system, poised to attack any dangerous microbes that make it into the intestines and multiply enough to be perceived as a threat.

Building a diverse gut microbiome is the best way to prevent this proliferation of unfriendly bacteria and help the neutral and beneficial bacteria crowd them out. With plenty of “good” bacteria, it’s more likely that the harmful ones won’t multiply enough to warrant an immune response. When the harmful bacteria increase past a certain point, the body’s immune system kicks into gear to eliminate the invaders by producing chemical messengers called cytokines. These immune cell messengers are crucial to coordinating and controlling the immune system’s inflammatory response.

An ongoing, heightened inflammatory response in the gut can damage the intestinal lining and cause increased permeability, sometimes called leaky gut. Tiny gaps in the intestinal wall called "tight junctions" are in place to allow nutrients and water to pass through. When damaged, toxins and other harmful compounds end up “leaking” through the intestinal wall into the bloodstream, prompting an immune response.

Imbalances to the gut microbiota have been linked with serious health challenges related to difficulty reaching or maintaining a healthy weight, severe blood sugar dysregulation, blood pressure issues, and other problems.^[5]

how to address gut health for better immunity

You can start addressing gut health and immune health with the following strategies.

limiting sugar and refined carbohydrates

Avoiding or limiting foods with added sugars and refined carbohydrates can significantly support gut and immune health, such as white bread, pasta, commercial cookies, and cakes. A high sugar diet can contribute to fungal proliferation and intestinal permeability in the gut.

eat a wide variety of plant foods

A colorful variety of fruits and vegetables provides a nutrient and antioxidant-rich diet and plenty of gut-supportive fiber.

drink bone broth

Rich in collagen, gelatin, and other gut-supportive minerals, bone broth is an extraordinarily healing food for the gut and immune system.

eat probiotics and prebiotics

Probiotic-rich foods include fermented varieties like raw sauerkraut and kimchi, miso, kombucha tea, and kefir. Prebiotics are non-digestible carbohydrates and are naturally present in many high-fiber foods, especially onions, garlic, asparagus, green bananas, green plantains, and Jerusalem artichokes.

find ways to manage stress

Studies show the intimate connection between stress and gut health and the positive impacts of practices like meditation.^[6] Other effective techniques include walking in nature, deep breathing, yoga, Qigong, and Tai Chi. There is no one-size-fits-all approach to stress management, so find what is doable and enjoyable in your daily life.

exercise

Physical activity can also positively change the gut microbiome’s composition. More research is needed, but evidence suggests that more exercise increases the production of short-chain fatty acid-producing microbes, reducing your risk of long-term health challenges and supporting a healthy weight.^[7]

related content: four best supplements for gut health

takeaway

A healthy gut and a robust immune system go hand in hand: having one without the other is unlikely. If you struggle with digestive discomforts or other health challenges linked to poor gut health, your immune system could suffer. Consider the diet and lifestyle strategies discussed above and speak with your integrative doctor about possible supplementation for gut and immune support.

[1] https://www.jpp.krakow.pl/journal/archive/12_11/pdf/591_12_11_article.pdf

[2] Lyte M, Vulchanova L, Brown DR. Stress at the intestinal surface: catecholamines and mucosa-bacteria interactions. Cell Tissue Res. 2011 Jan;343(1):23-32. doi: 10.1007/s00441-010-1050-0. Epub 2010 Oct 13. PMID: 20941511.

[3] Bjarnason I, Takeuchi K. Intestinal permeability in the pathogenesis of NSAID-induced enteropathy. J Gastroenterol. 2009;44 Suppl 19:23-9. doi: 10.1007/s00535-008-2266-6. Epub 2009 Jan 16. PMID: 19148789.

[4] https://www.sciencedaily.com/releases/2018/04/180410100937.htm

[5] Shanahan F, van Sinderen D, O’Toole PW, Stanton C. Feeding the microbiota: transducer of nutrient signals for the host. Gut. 2017;66(9):1709-1717. doi:1136/gutjnl-2017-313872

[6] Househam AM, Peterson CT, Mills PJ, Chopra D. The Effects of Stress and Meditation on the Immune System, Human Microbiota, and Epigenetics. Adv Mind Body Med. 2017 Fall;31(4):10-25. PMID: 29306937.

[7]Allen JM, Mailing LJ, Niemiro GM, Moore R, Cook MD, White BA, Holscher HD, Woods JA. Exercise Alters Gut Microbiota Composition and Function in Lean and Obese Humans. Med Sci Sports Exerc. 2018 Apr;50(4):747-757. doi: 10.1249/MSS.0000000000001495. PMID: 29166320.