The human body is an intricate network where various systems interact closely, and none more so than the gut and the immune system. This relationship, deeply embedded in the gastrointestinal tract, plays a pivotal role in maintaining overall health and well-being. The concept of gut health has expanded beyond digestion to include its significant influence on the immune system. Among the factors contributing to this beneficial interaction, postbiotics have emerged as a key player. Let's delve into the gut-immune system connection and explore how postbiotics can enhance this vital relationship.
The Gut-Immune System Connection
The gastrointestinal tract is home to a complex community of microorganisms known as the gut microbiota. This microbiota consists of bacteria, viruses, fungi, and other microbes that coexist in a delicate balance. The gut microbiota is crucial for several functions, including digestion, vitamin synthesis, and protection against pathogens. However, one of its most critical roles is in regulating the immune system.
The gut is the largest immune organ in the body, containing approximately 70% of the body's immune cells. These immune cells are in constant communication with the gut microbiota, learning to distinguish between harmful and harmless organisms. This interaction helps the immune system respond appropriately to infections while maintaining tolerance to beneficial or benign microbes (1).
The gut is like a big control center that talks to the immune system through different channels, creating what's called the gut-immune system connection. Gut microbiome plays a crucial role in this link, as it has a direct influence on how the immune system operates. Keeping our immune system in balance is important. It needs to fight off germs that try to invade our bodies while also making sure not to attack our own cells, which could lead to autoimmune diseases. The good bacteria living in our guts are really helpful for keeping everything in check. They play a big role in making sure our immune system works the way it should, keeping us healthy. Lately, scientists have found out that if the mix of these gut bacteria gets dysregulated, it can throw our immune system off balance and lead to problems where the body starts attacking itself, like in autoimmune diseases (2).
To better understand this relationship, it’s important to understand the foundational basics of this system and how it works.
What is the immune system?
The immune system is a network made up of various organs, cells and proteins and it has an important role. It protects you from harmful substances, germs, and cell changes that could make you sick. Its main jobs include fighting off disease-causing germs like bacteria, viruses, parasites, or fungi, and getting rid of them. It also recognizes and neutralizes harmful substances from our environment and battles against changes in the body that could lead to diseases, such as cancer cells. Without an immune system, we'd have no defense against these threats, leaving us vulnerable to everything harmful that comes from outside or even changes that happen inside our bodies.
Many things that the body sees as unfamiliar can trigger the immune system. These foreign substances, known as antigens (like the proteins found on the surfaces of bacteria, fungi, and viruses), latch onto specific receptors on immune cells. This attachment sets off a chain of reactions within the body. After the body encounters a germ that causes disease for the first time, it often keeps a record of the germ and the best way to defeat it. This means if the body encounters the germ again, it quickly recognizes it and begins to fight it faster.
The immune system is divided into two subsystems: the innate (non-specific) immune system and the adaptive (specific) immune system, which work together to respond to germs or harmful substances. The innate immune system acts as the body's general defense, primarily using cells like natural killer cells to fight germs that breach barriers such as the skin or digestive system. On the other hand, the adaptive immune system creates antibodies to fight specific pathogens the body has encountered before. This system is also referred to as the "acquired" immune response, highlighting its ability to learn and remember specific threats (3).
Gut Microbiome’s Role in Immunity
When your immune system is functioning well, you hardly realize it's at work. However, if it becomes compromised, either from being weakened or facing unusually strong pathogens, you become sick. The microbes in your gut play a significant role in ensuring your immune system works as it should.
The way our gut bacteria interact with our body's natural defense systems, both the innate (non-specific) and the adaptive (specific) immune systems, is really important for keeping our intestines healthy and preventing swelling or inflammation. Our gut bacteria do lots of work like breaking down proteins and complex sugars, making vitamins, and creating lots of different substances that help the cells lining our gut talk to our immune cells. To keep things in order, the cells lining our gut form a protective barrier that keeps our gut bacteria separate from our immune cells and makes it harder for unwanted stuff to get through.
However, if this teamwork between our gut bacteria and the gut's protective immune system isn't working well, it can lead to an increase in bad bacteria that can break down this protective barrier, making it easier for infections to happen. When the balance of good and bad bacteria in our gut is off, it can mess with our immune system, leading to inflammation, stress on our cells, and even resistance to insulin, which is a precursor for diabetes. Over time, if our gut isn't balanced right, there's a higher risk of developing serious health issues like type 2 diabetes, heart disease, bowel problems, autoimmune diseases, and even some types of cancer (4).
We can improve the balance of bacteria in our gut microbiome through dietary strategies, which can support your immune health as a result. One of the strategies we can utilize to optimize our gut microbiome and immune health is postbiotics.
3 Ways Postbiotics Can Help
Postbiotics are bioactive compounds produced by probiotic bacteria during the fermentation of prebiotics in the gut. Unlike probiotics, which are live organisms, postbiotics can exert their beneficial effects without the need to survive the gastrointestinal tract's harsh environment. This makes them a promising and efficient way to modulate the gut microbiome and, by extension, the immune system. Here are three ways postbiotics can support the gut-immune system connection (5).
Strengthening Gut Barrier Integrity
Postbiotics are crucial in maintaining the integrity of the gut barrier. This barrier is the body's first line of defense against pathogens and harmful substances. By strengthening the gut barrier, postbiotics prevent the translocation of harmful bacteria and toxins into the bloodstream, thereby reducing inflammation and the risk of immune-mediated diseases. This effect directly supports the immune system by ensuring that it does not become overburdened or triggered by unnecessary stimuli, allowing it to respond more effectively to genuine threats.
Modulating Immune Responses
Postbiotics are important because they help control how our immune system responds, making sure there's a good balance between signals that cause inflammation and signals that calm it down. They work with immune cells to help them work better and teach them to be more tolerant. This control is really helpful because it stops our immune system from overreacting, which can cause problems like autoimmune diseases and allergies. By keeping the immune response balanced, postbiotics make sure that our body fights off pathogens the right way, without causing too much inflammation or harming our tissues.
Defense against Pathogens
Postbiotics have the ability to fight off bad bacteria and help protect your body from getting sick. They do this in a couple of ways. First, by making special substances that stop harmful germs from growing, and second, by giving a boost to the immune cells that hunt down and get rid of these germs. Also, postbiotics are great at making sure good bacteria can live and grow in your gut by winning the battle over who gets the food and the best spots to live. This not only helps keep infections away but also makes your gut a better place for friendly bacteria to thrive, making your gut's defense system even stronger.
Conclusion
The connection between the gut and the immune system is really important for staying healthy, and postbiotics are key in making this connection even stronger. They help by supporting gut barrier integrity, modulating immune responses and defending against pathogens postbiotics. Eating foods or taking supplements with postbiotics can make our gut and immune system work better together, which is great for keeping us healthy over time. As scientists learn more about how our gut bacteria work, they're finding out how useful postbiotics can be for our immune health, making it a very interesting area in nutrition studies.
References
- Vighi, G., Marcucci, F., Sensi, L., Di Cara, G., & Frati, F. (2008). Allergy and the gastrointestinal system. Clinical and experimental immunology, 153 Suppl 1(Suppl 1), 3–6. https://doi.org/10.1111/j.1365-2249.2008.03713.x
- Wu, H. J., & Wu, E. (2012). The role of gut microbiota in immune homeostasis and autoimmunity. Gut microbes, 3(1), 4–14. https://doi.org/10.4161/gmic.19320
- InformedHealth.org [Internet]. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. How does the immune system work? [Updated 2020 Apr 23]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK279364/
- Yoo, J. Y., Groer, M., Dutra, S. V. O., Sarkar, A., & McSkimming, D. I. (2020). Gut Microbiota and Immune System Interactions. Microorganisms, 8(10), 1587. https://doi.org/10.3390/microorganisms8101587
- Liu, Y., Wang, J., & Wu, C. (2022). Modulation of Gut Microbiota and Immune System by Probiotics, Pre-biotics, and Post-biotics. Frontiers in nutrition, 8, 634897. https://doi.org/10.3389/fnut.2021.634897