As we head into the colder months, cold and flu season has immunity on everyone’s minds. Being in the middle of a global pandemic makes the topic even more relevant; people are constantly asking what they can do to improve their immune system. Ongoing research on the microbiome suggests that it plays an important role in immune system development and maintenance (1, 2). Let’s look at the role of the microbiome in immune health.
The microbiome, a collection of organisms living primarily in our digestive tract, has been shown to play a role in the development and support of the immune system. First, the bacteria can influence normal and healthy gut development by impacting the proliferation or death of various cells in the digestive tract to improve gut function (2).
Also, the bacteria in the gut microbiome have been shown to form short chain fatty acids (SCFAs) through the metabolism of undigestible fibers from the diet. These SCFAs are known to have an anti-inflammatory role and can support intestinal repair by encouraging the renewal of damaged cells. SCFAs also serve as energy for the cells of the lower digestive tract (the colon), allowing the walls of this section of the gut to stay healthy and well-functioning (3, 4). Keeping the digestive tract in good condition is essential to maintaining biochemical processes that uphold the body’s immune response.
In addition to these actions, the microbiota (or the collection of bacteria in the microbiome) acts as an anti-infectious barrier by keeping dangerous bacteria or other pathogens from attaching to the intestinal wall and replicating (2, 5). This means that a healthy microbiome reduces the chances of getting sick from various pathogens. It is important to note that the bacteria of the digestive tract also have mechanistic roles that impact the pathways for immune responses in the body. These roles are numerous and impacts how well the body can ward off or react to potential diseases.
It is clear that the microbiota plays a big role in immune and gut health. However, it is important to specify that these beneficial interactions work best when the bacteria of the gut are in a balanced equilibrium. This ideal equilibrium is likely different for each of us. When this equilibrium is disrupted (something known as dysbiosis), it could increase the likelihood for both infectious and non-infectious disease (6). Inflammatory disorders could also be promoted by a disrupted microbiome, including type 1 diabetes, rheumatoid arthritis, irritable bowel disease, non-alcoholic fatty liver disease, obesity, heart disease, and cancer (7).
Interestingly, it seems that there are certain microbiome signatures that mark the dysbiosis associated with various disease states. Research is continuously showing more microbiome profiles that have been identified as potential markers for risk or presence of disease (6). This is an extremely interesting area of ongoing research and will help medical professionals to better diagnose disease and target individualized treatment.
While we don’t yet know what makes an “ideal” microbiome (most likely it is different for everyone), we do know that there are some factors associated with bacterial diversity and resilience which are important qualities for health. Bacterial diversity is associated with a widely diverse diet, increased plant products like fruit, vegetables and whole grains, high fiber, and low fat. Avoiding a typical western-style diet which is high in animal products, sugar, additives, fats, and low in fiber can also drive diversity in the microbiome (9, 10, 11). We also know that maintaining the necessary balance of the microbiota is key to avoiding dysbiosis, which can lead to increased risk for disease. Dysbiosis can be caused by medications like antibiotics, an unbalanced/unhealthy diet, or various illnesses or diseases.
It’s important to note that though the microbiome seems like a self-running entity, 20% of the diversity of the microbiome is directly influenced by diet and lifestyle (8). This is great news- it means that we have the potential to make changes to our microbiome by implementing lifestyle changes. We are continuing to learn more about how to optimize those changes to improve each person’s individualized microbiome profile to achieve better health.
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