The Connection Between Autoimmunity and Gut Health
Research has found a strong connection between autoimmunity and gut health. Lifestyle and other environmental factors can either boost or compromise gut health, helping to either prevent or increase autoimmunity. In this article we’ll look at autoimmunity, gut health, and what you can do to reduce inflammation and promote a healthy, diverse intestinal microbiome.
What Is Autoimmunity?
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)
There’s a Genetic Component to Autoimmunity
Our susceptibility to autoimmunity is controlled by genetic and environmental factors. Studies have shown that women are almost two times more likely than men to develop an autoimmune disease. 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, Source, Source)
There’s Also an Environmental Component to Autoimmunity
Environmental factors can also impact our susceptibility to autoimmunity. Throughout the 20th century there was a rapid increase in the incidence of inflammatory disorders, including 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. Diets high in processed fats promote inflammation that could set off an immune response. (Source, Source).
What Does Gut Health Have to Do With Autoimmunity?
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 Microbiome Affects Immune Function
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. This can eventually lead to the development of autoimmune diseases. (Source, Source)
Gut Permeability Is a Factor in Autoimmunity
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)
What Is the Microbiome?
Ten trillion to 100 trillion microorganisms (also known as microbes or the microbiota) reside in the gut, including bacteria, fungi, parasites, and even viruses. These microorganisms usually coexist peacefully in a symbiotic relationship in which both the human body and microbes benefit. (Source)
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 your body more susceptible to diseases. (Source)
Know Your Gut Flora
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)
What Are the Most Common Gut Bacteria?
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
- Lactobacillus bacteria have a wide variety of functions in the gut. They produce lactic acid and antibacterial peptides to prevent harmful bacteria from colonizing the gut. They behave as immunomodulators, supporting immune health by modifying the immune system’s response to threats in a beneficial manner. They have a protective effect against the overgrowth of Candida albicans, a type of yeast that is a common cause of fungal infections, and against staphylococcal (staph) infections. (Source, Source)
Lactobacillus are also often used as probiotics in supplements. A probiotic is defined by WHO as “live microorganisms which, when administered in adequate amounts, confer a health benefit on the host.” (Source)
- Staphylococcus are opportunistic pathogens that live in the gut symbiotically. However, an imbalance in the gut microbiome can lead to the overgrowth of Staphylococcus and cause a wide range of diseases, either by direct infection or by producing toxins. (Source)
- Clostridium have anti-inflammatory properties that help improve the immune function of the gut. They can help break down carbohydrates and generate short-chain fatty acids, which are used as energy by intestinal cells. (Source)
- Bacteroidetes: e.g., Bacteroides, Prevotella, Sphingobacterium
- Bacteroides help break down carbohydrates into short-chain fatty acids and help prevent infections in the gut. They are found more frequently in people who consume a more protein- and animal fat-heavy diet. (Source, Source)
- Prevotella also help digest carbohydrates into short-chain fatty acids. They tend to be more common in people who consume a lot of fiber. Since these bacteria are very genetically diverse, it’s difficult to determine their exact function in the gut microbiome. (Source, Source)
- Sphingobacterium trigger inflammatory responses from the immune system and can be used as biomarkers of infection in the body. (Source)
- Actinobacteria: e.g., Bifidobacterium, Atopobium
- Bifidobacterium break down complex carbohydrates into short-chain fatty acids as well as producing folate, which plays a key role in healthy cell growth and function. Bifidobacterium also have anti-inflammatory effects and have been shown to improve inflammatory bowel disease symptoms. (Source, Source)
- Atopobium are responsible for breaking down proteins into amino acids in the gut. (Source)
Why Does the Gut Matter?
The gut performs many important functions such as:
- digesting food to generate and deliver nutrients to our cells
- metabolizing (breaking down) enzymes, vitamins, and amino acids
- detoxifying possible carcinogens
- stimulating cell renewal in the gut lining
- activating and supporting the immune system
The Gut–Brain Axis
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)
Don’t Fear the Good Bacteria
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)
Leaky Gut Syndrome
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 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)