The gut contains about 70%-80% of the immune cells in our body and plays an important role in regulating the immune system.
Any shift in the makeup of the gut microbial community can lead to immune dysregulation and trigger autoimmune activity.
Many lifestyle factors can help improve gut health, including reducing stress, spending time with others, eating an anti-inflammatory diet, avoiding antibiotics when possible, and taking probiotics.
Autoimmunity is when the immune system mistakenly attacks the body’s own cells. Usually, our immune system protects us from invasive pathogens such as bacteria and viruses, sending out antibodies and white blood cells to attack them. When our immune system loses the ability to differentiate between foreign cells and our own healthy cells, though, the result is autoimmune disease. (Source)
Our susceptibility to autoimmunity is controlled by genetic and environmental factors. (Source) Studies have shown that women are almost two times more likely than men to develop an autoimmune disease. (Source) Autoimmune diseases such as multiple sclerosis also tend to cluster in families. This is due to families having a similar genetic background, which may predispose members of the family to autoimmunity. However, it is important to note that autoimmune diseases are not hereditary. (Source, Source)
Environmental factors can also impact our susceptibility to autoimmunity. Throughout the 20th century, there was a rapid increase in the incidence of inflammatory disorders that include autoimmune diseases such as Type 1 diabetes and multiple sclerosis.
The “old friends hypothesis,” the reformulated version of the hygiene hypothesis, suggests that regular exposure to “friendly” microorganisms will help teach our immune system whether foreign microbes are friend or foe. (Source)
The diet we consume also can affect our susceptibility to autoimmune diseases. Western diets tend to be high in sugar, salt, and fat while being low in plant-based fiber. High-fat diets promote inflammation that could set off an immune response. (Source, Source).
The gut helps regulate the immune system, eliminating invading pathogens while recognizing that cells made by our body are not a threat. There is a growing amount of research linking autoimmune issues to the health of the gut microbiome.
The gut contains about 70%–80% of the immune cells in our body, and any change in the composition of the gut microbial community can lead to immune dysregulation. (Source) This can eventually lead to the development of autoimmune diseases. (Source)
The intestinal lining helps keep our gut microbes contained. If this lining is compromised or weakened, there is a risk of the microbes getting into our bloodstream and nearby organs, which can also lead to the development of autoimmune diseases. (Source)
Ten trillion to 100 trillion microorganisms (also known as microbes or the microbiota) reside in the gut, including bacteria, fungi, parasites, and even viruses. (Source) These microorganisms usually coexist peacefully in a symbiotic relationship in which both the human body and microbes benefit.
However, there are a small number of microbes that have a pathogenic relationship with the human body, meaning they can promote disease. If the balance between symbiotic and pathogenic microbes is disturbed, as through illnesses, certain diets, or the extended use of antibiotics, dysbiosis occurs. This disrupts the interactions the body has with the gut microbiome and can make our body more susceptible to diseases. (Source)
Each person’s gut microbiota, or flora, is unique and dynamic — it changes throughout the life of the individual. It’s been estimated the human gut hosts as many as 36,000 species of bacteria alone. (Source)
Everyone comes into the world with gut microbes already in place. The makeup of the initial microbiome depends on length of pregnancy, type of birth, and method of feeding after birth. An individual’s microbiome increases in complexity until about the age of 3 and then usually remains pretty stable into adulthood. (Source)
The typical healthy microbiome is made up primarily of three bacterial phyla, each of which includes several bacterial genera and species:
Firmicutes: e.g., Lactobacillus, Staphylococcus, Clostridium
Bacteroidetes: e.g., Bacteroides, Prevotella, Sphingobacterium
Actinobacteria: e.g., Bifidobacterium, Atopobium
The gut performs many important functions such as:
The gut also affects our brain health. A healthy gut communicates with the brain through nerves and hormones, helping to maintain our overall well-being. Researchers have found there is a bi-directional relationship between the gut and the brain, which has been dubbed the “gut–brain axis.”
The gut also produces neurotransmitters that affect gene expression in the brain, the development of the nervous system, behavior, and mood through the synthesis of serotonin. (Source, Source, Source)
Although there are bacteria everywhere, the largest colony of bacteria in our body is in our gut. Like a fingerprint, each person’s microbiome composition is unique due to their genetics and to a much greater extent, their environment. The bacteria in the gut have evolved alongside humans for thousands of years and help our bodies perform a variety of essential functions. (Source)
The intestinal mucosal barrier separates the trillions of microbes in our gut from the rest of our body. Epithelial cells that line the gut are connected together by tight junction proteins that open and close in order to allow the movement of nutrients across the lining, while preventing pathogens from leaving the gut.
If this layer of cells is compromised, permeability in the gut barrier may be increased, allowing the microbes in our gut to “leak” into the bloodstream. This increase in permeability is a condition called leaky gut syndrome, and it can significantly affect our digestion and immune system. (Source)
The gut microbiome composition can be affected by a variety of lifestyle factors. Stress has been shown to increase the permeability of the gut barrier, allowing bacteria to cross and activating an inflammatory immune response that alters the composition of the microbiome.
The “stress hormone,” cortisol, has been shown to suppress the response of tight junction proteins in the gut lining. Chronic stress induces a decrease in the number of tight junction proteins, causing the lining to become more permeable and allowing pathogens to move out of the gut.
The body’s response to stress can also increase circulating levels of pro-inflammatory proteins called cytokines, causing inflammation in the gut. This decreases the abundance of several beneficial gut bacteria, which changes the composition of the microbiome and reduces its diversity. (Source)
Researchers have also found that people who have large social networks tend to have more diverse microbiomes compared to those who don’t. Specific bacterial genera, such as Akkermansia, Lactococcus, and Oscillospira, have been found to be more abundant in people who are very social.
Research into possible effects of bacterial diversity on behavior may help guide the development of new probiotic and prebiotic therapies for treating mental health conditions such as anxiety and depression. (Source)
Over the last few decades, the prevalence of autoimmune diseases such as celiac disease has risen and has been linked to increased consumption of gluten, which is very common in Western diets.
Some research suggests that gliadin, the component of gluten that stimulates an immune response, increases permeability across the gut barrier. (Source) Research has also found that gluten-containing diets can alter the gut microbiome and contribute to dysbiosis. (Source)
Chronic inflammation is closely linked with many autoimmune diseases. (Source) Food allergies, sensitivities, or intolerance may cause inflammation in the gut lining and lead to a multitude of symptoms. Exclusion diets are often recommended to confirm an allergy, sensitivity, or intolerance, and identified foods are then avoided.
Food sensitivities cause immune reactions that may be uncomfortable but not life-threatening. This kind of reaction to food may resolve over time as the composition of the gut microbiome evolves.
Symptoms of food sensitivity include:
Food intolerance is when the digestive system is unable to digest or break down food. Food intolerances are typically related to the amount of a particular food you eat — some people may be able to avoid digestive reactions when a small amount of a problem food is consumed, but will experience symptoms of food intolerance if they eat a larger amount.
Symptoms of food intolerance include:
A food allergy is an inappropriate immune response to something most people eat with no problem. The immune response can be uncomfortable and, in some cases, severe or even life-threatening.
Symptoms of food allergy include:
Our gut microbiome is exposed to antibiotics not only from medical use, but also from their use on crops and farm animals. Antibiotic use can drastically alter microbiome composition and provide opportunities for bacteria that cause diseases. (Source)
Exposure to antibiotics causes the loss of some important species of gut bacteria. Typically, it takes about a month to restore microbial diversity in the gut after antibiotic treatment and an additional 2 weeks for the baseline composition of microbiota to be restored. However, several common species may not be detected for around 6 months.
Antibiotic use can also disrupt the balance established by gut microbes. Since antibiotics cause a decrease in microbiome diversity, this can lead to the overgrowth of pathogens that usually coexist symbiotically with other bacteria present in the gut under normal circumstances.
Some antibiotics can even cause the mucus layer in the gut to thin, which makes the gut lining more susceptible to damage and inflammation from opportunistic pathogens like H. pylori that colonize the gut microbiome. In some people, H. pylori infections in the gut can lead to gastric and duodenal ulcers, intestinal metaplasia (where cells that line the stomach are replaced or changed), and gastric cancer. (Source, Source)
Some researchers recommend reestablishing the gut microbiota with probiotics. (Source) One cost-effective way of reversing intestinal permeability, strengthening the intestinal barrier, and reducing inflammation is by incorporating some gut-healing foods into your diet, such as kimchi, pickles, or yoghurt.
Autoimmunity is when our body’s immune system mistakenly attacks the healthy cells in our body. Genetic and environmental factors affect our susceptibility to autoimmunity. About 70%–80% of the immune cells in our body are the gut, so any changes to the composition of the gut microbiome can lead to immune dysregulation and the development of autoimmune diseases.
Autoimmune diseases can be managed by promoting gut health. Researchers have found that changes in lifestyle and diet can help reduce gut inflammation, which is closely linked with many autoimmune diseases.
Each person has a unique gut microbiome composition. This article breaks down the variety of species that are typically present in the gut, and how the environment, diet, and disease can influence the makeup of the microbiome. (Source)
The bacteria in our gut have a symbiotic relationship with the body. They play a key role in the development of immunity in the gut, but are also able to trigger inflammation. The pathways of communication and inflammation between the gut bacteria and the intestinal barrier is explained in this article. (Source)