Why Your Immune System Depends on Your Gut Health

immune system | Probiotic America

What comes to mind when you envision your immune system? You might see it as a sort of armor, surrounding your body and keeping harmful microorganisms from penetrating the skin and assaulting your organs.

But you’d be wrong.

The human immune system isn’t an external barrier at all. Rather, it’s a complex internal network of microbe-fighting energy production. And it’s capable of manufacturing the ammunition necessary to attack and destroy potentially harmful invaders. Whether it’s healing a paper cut or fighting off a serious illness, your immune system is always at work.

This hub of defensive activity is centered within the digestive system. In fact, up to 80 percent of a person’s immunity can be found in the gut. The population of microbes living in the digestive tract, collectively known as the gut microbiota, is where microscopic gladiators are produced. They are then distributed throughout the body, where they fight to maintain maximum immunity against disease, viruses, and other maladies.

Gut: The Immunity Nerve Center

Inside the large intestine, there is an inner barrier which protects against potentially harmful agents. This is called the mucosa, and its surface membranes constitute an adaptive immune system – which, as its name implies, constantly changes to defend against various foreign microbes as they attack the gut. The lymphoid tissue in these membranes makes up the largest single mass of such tissue in the entire body. Because the gut microbiota continuously “communicates” with the immune system, the two work together to identify and combat pathogens which live in the digestive tract.

When a pathogenic invader is detected, cells located in the wall of the intestine produce and secrete antibodies that specifically target the unwanted microbe. This is how pathogens get destroyed by the immune system while the beneficial microbes in the gut remain protected. And, when this lymphoid tissue in the intestine’s mucosa initiates this type of immune response, other areas of lymphoid tissue throughout the body often follow suit, repelling similar attacking organisms elsewhere.

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Probiotics: Immunity Soldiers

One of the key components of the gut microbiota and its support of the immune system is the trillions-strong group of so-called “healthy” bacteria known as probiotics. Though researchers are still trying to figure out precisely how probiotics work, the end result is that these bacteria contribute greatly to optimal health – including providing a stronger level of immunity.

Probiotics protect the body not only against harmful bacteria, but also from viruses, infections, toxins, and other disease-causing parasites. In addition, probiotics facilitate the absorption of important minerals like iron and magnesium, while producing essential B-vitamins and pathogen-destroying enzymes.

Probiotics and Good Health: Benefits on Several Fronts

Microbiologists and physicians are just starting to understand the complete range of benefits that probiotics provide with regards to immunity.

Battling the Common Cold

A 2011 study published in the European Journal of Nutrition revealed that taking probiotics reduced both the probability of contracting the common cold and the duration of the illness itself.1 Similar results were achieved when researchers examined the effects of probiotic supplementation on 30 elite rugby players from New Zealand.2

Easing Digestive System Disorders

Currently, the largest body of research into the effectiveness of probiotics centers around its impact on the digestive system itself. For example, there is a growing body of evidence to support using probiotics to treat acute, infectious diarrhea.3 This is especially prevalent in hospitalized young children, who are susceptible to diarrhea caused by Rotavirus, which is commonly found in healthcare settings.4

Probiotics for Antibiotic Issues

Perhaps unsurprisingly, the administration of probiotics is being recommended for hospitalized patients and nursing home residents who are taking antibiotic medications and/or are at greater risk of being infected with the superbug known as Clostridium difficile (or C. difficile). This antibiotic-resistant bacterium, which can trigger severe diarrhea and colonic inflammation, has reportedly caused a half million infections and 14,000 deaths in a single year.5

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Fighting Inflammation

Moreover, scientists are beginning to learn about the strong relationship between the gut microbiota and a wide range of inflammatory diseases and disorders. It is thought that when the balance between probiotics and unhealthy bacteria is upset, the likelihood of the person suffering from inflammation-related symptoms increases.

In contrast, when probiotics are introduced into the digestive system, there is a corresponding reduction in the amount of inflammatory mediators (substances that transmit energy between nerve cells or from a nerve ending to an organ) secreted in the digestive tract, which in turn normalizes the equilibrium of intestinal microflora so that gut homeostasis is achieved.6

Be Good to Your Gut

Researchers don’t yet know what the precise balance between probiotics and other bacteria in the gut should be, nor are they certain which strains of probiotics are necessary for gut homeostasis. The good news, though, is that for everyone (excluding some patients who suffer from autoimmune disorders), the supplementation of probiotics is safe and free of side effects.7 Most importantly, physicians are starting to recognize the necessity of strong gut health in protecting their patients from colds, infections, and any other illnesses that target the human immune system.

Dr. Cary Nelson


1. Berggren, Anna et al. “Randomised, Double-Blind And Placebo-Controlled Study Using New Probiotic Lactobacilli For Strengthening The Body Immune Defence Against Viral Infections”. N.p., 2011. Print.
2. Black, Katherine. “Probiotic Supplementation Reduces The Duration And Incidence Of Infections But Not Severity In Elite Rugby Union Players”. Sciencedirect.com. N.p., 2014. Web. 25 Feb. 2017.
3. Allen, Stephen. “Probiotics For Treating Infectious Diarrhoea”. Onlinelibrary.wiley.com. N.p., 2003. Web. 25 Feb. 2017.
4. Szajewska, H., M. Wanke, and B. Patro. “Meta-Analysis: The Effects Of Lactobacillus Rhamnosus GG Supplementation For The Prevention Of Healthcare-Associated Diarrhoea In Children”. N.p., 2011. Print.5. https://www.cdc.gov/drugresistance/biggest_threats.html
6. Isolauri, Erika et al. Ajcn.nutrition.org. N.p., 2001. Web. 25 Feb. 2017.
7. Al-Salami, Hani et al. “Probiotics Applications In Autoimmune Diseases”. N.p., 2012. Print.