The gut microbiome is a living ecosystem that is affected by everything from diet to stress to genetics.
Dysbiosis is a disruption in the gut's microbial ecology, which can lead to a loss of overall microbial diversity, a loss of intestinal barrier integrity, and/or an overgrowth of bacteria in the wrong place.
Dysbiosis can cause digestive symptoms, skin issues, allergies, and autoimmune disorders, as well as fatigue, depression, anxiety, and brain fog. It is also a major cause of disease.
Diet may be the most important factor in influencing the gut ecosystem, so eat fiber-rich foods to promote the good bugs in your gut, remove inflammatory foods, and consider supplementing with probiotics and prebiotics.
The belief that our gut plays a central role in disease dates back to 2500 years ago:
"All disease begins in the gut." — Hippocrates
In the last decade, advanced gene sequencing techniques have enabled us to characterize gut dysbiosis, or microbial imbalance, in hundreds of different diseases. Among others, dysbiosis has been linked to conditions including inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), celiac disease, and obesity, and the list continues to grow. Researchers have identified specific microbial profiles of dysbiosis that are shared across disease states, and are exploring therapeutic approaches that manipulate the intestinal microbiota to reverse and prevent disease.
Evidently, Hippocrates's old adage has held up to scientific scrutiny in modern times.
In this article, we’ll dive into what happens when the gut gets disrupted and how to restore it to a healthy state.
Dysbiosis occurs when the gut’s microbial ecology is thrown out of balance. A few factors that contribute to dysbiosis include:
These three factors are not mutually exclusive and can co-exist, which is most often the case. (Source)
When the gut ecosystem is disturbed, the microbiome struggles to perform essential jobs, including protecting itself from opportunistic bacteria. One bacterial colony may become dominant over another, causing a chronic imbalance that harms good gut bacteria and compromises the digestive system. This can have a profound impact on our digestion, the ability of the gut to protect itself from pathogens, and the functioning of our immune system, which is why dysbiosis tends to be associated with disease. (Source)
Dysbiosis has been implicated in a wide range of diseases including inflammatory bowel disease (IBD), diabetes, autism, and obesity in both humans and animals. That said, it's challenging to disentangle the cause-and-effect relationship here — it's unclear whether dysbiosis directly causes these disease states or if it occurs as a result of them. (Source)
One of the results of dysbiosis is a loss of intestinal barrier integrity, which can allow bacteria to infiltrate deeper into the body. This can cause chronic inflammation and impair the intestinal barrier, causing it to leak — hence the phrase “leaky gut.” Given that the intestinal tract supports the uptake of nutrients, malabsorption can occur in dysbiotic states. (Source, Source)
Microbes can also cause problems when they grow in the wrong place in the gut. This type of microbial dysbiosis typically manifests as small intestinal bacterial overgrowth, or SIBO, and occurs when the bacteria in your small intestine become overpopulated. This can lead to excess gas, severe bloating, malabsorption and other digestive issues. Treatment of SIBO often includes antibiotics, which may exacerbate the problem by opening the door to serious, hard to treat conditions such as Clostridium difficile infection. (Source, Source)
Studies show dysbiosis decreases the production of short-chain fatty acids, damages the intestinal lining, and increases inflammation. Short-chain fatty acids, in particular butyric acid, are important metabolites that prevent the growth of harmful bacteria and support gut homeostasis. (Source, Source)
One study demonstrated that feeding mice two emulsifiers used in processed foods reduced microbial communities and increased levels of Proteobacteria, which has been associated with numerous chronic diseases when found with low levels of butyrate-producing bacteria. The results from this study suggest that dysbiosis and its resultant low-grade inflammation can promote obesity and adverse metabolic effects. Furthermore, the widespread use of emulsifiers may contribute to increased incidence of obesity and other chronic inflammatory diseases. (Source, Source)
Disruptions to the human gut microbiome have been correlated with several neuropsychiatric disorders, including Parkinson’s disease, autism, schizophrenia, and depression. One recent study showed that intestinal dysbiosis contributes to amyloid pathology in mice, which may lead to the development of Alzheimer's. This is likely due to the bidirectional relationship between the brain and the gut, although the exact mechanism by which the microbiome affects neurological disease states is not yet fully understood. (Source, Source)
Research has shown a tight link between the gut and the HPA axis, which is the major neuroendocrine system that regulates our response to stress and release of cortisol. One study in mice revealed reduced relative abundance of beneficial microbes such as Lactobacillus bacteria in response to social stressors. Another study demonstrated that psychological stress may increase the risk of relapse and disease severity in IBD patients, by altering intestinal permeability and the secretion of inflammatory cytokines. (Source, Source)
Disturbances in the gut can cause digestive symptoms, including gas, bloating, cramps, diarrhea, and constipation. Dysbiosis has been implicated in GI disorders such as IBD and IBS, as well as GI-related conditions such as obesity, type 2 diabetes, and colorectal cancer. Because of the apparent connection between the gut microbiome and the brain, there are other symptoms of gut dysbiosis that do not manifest in the gut at all. These include fatigue, depression, anxiety, and “brain fog.” Dysbiosis may even contribute to skin issues, allergies, and autoimmune disorders, so you may be dealing with dysbiosis even if you don't have any noticeable digestive symptoms. (Source)
Common triggers of dysbiosis include unhealthy dietary choices, use of antibiotics and common over-the-counter medications, and stress. The effects of antibiotics have been well documented, resulting in both short-term and long-term alterations in the composition of the gut microbiome. As you may remember, your genes are not your destiny, and these kinds of environmental factors play a key role in the development of gut dysbiosis. (Source)
Studies have shown that nonsteroidal anti-inflammatory drugs (NSAIDs) impact the composition and function of the gut microbiota. NSAIDs can change the gut environment, affect intestinal permeability, and interfere with metabolism. Before popping an ibuprofen, consider a natural pain-relieving alternative like turmeric, CBD, or Boswellia. (Source, Source)
If you're interested in evaluating the state of your gut, the most commonly used diagnostics include:
As discussed in the edition about the gut microbiome, diet may be the most critical factor in shaping the gut ecosystem, so eat a fiber-rich diet to help promote the good bugs in your gut (hello resistant starch!). Beyond diet, there are a few science-backed treatments that can improve a state of dysbiosis, depending on the type and severity level, including probiotics, prebiotics, and fecal microbiota transplantation. As a first step, you should remove inflammatory foods, infections, and GI irritants like alcohol, caffeine and drugs, which can hurt the gut environment. Herbs, anti-parasite or antifungal medications, and occasionally even antibiotics, can be used to treat infections. Consult with your doctor to determine the best course of action based on your lab results. (Source)
Researchers created gutMDisorder, a comprehensive database on gut dysbiosis and specific interventions, to house all the scientific findings about dysbiosis in one place. The online repository catalogs 2000+ associations between specific gut microbes, disease states, and interventions, including drugs and foods, in humans. (Source)
In a recent opinion piece in the journal of the American Society for Microbiology, researchers postulate that overeating — particularly of easily digestible, low-fiber foods — may be responsible for the spread of dysbiosis and associated diseases. The authors hypothesize that the reduction of "natural clearing mechanisms" (e.g., starvation, diarrhea caused by pathogenic organisms) in developed countries may result in the overgrowth of bacteria (remember the hygiene hypothesis?). They suggest this increases the amount of bacterial byproducts produced in the gut and degrades the intestinal barrier, which stimulates an immune response and may promote autoimmune activity. (Source)