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.
What Is Dysbiosis and Why Should I Care?
Dysbiosis is defined as an altered state of the intestinal microbiome
Dysbiosis occurs when the gut’s microbial ecology is thrown out of balance. A few factors that contribute to dysbiosis include:
- Loss of beneficial organisms
- Overgrowth of pathogenic or opportunistic organisms
- Loss of overall microbial diversity
These three factors are not mutually exclusive and can co-exist, which is most often the case. (Source)
It prevents the microbiome from functioning properly
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)
It's strongly linked to chronic disease
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)
It can promote “leaky gut”
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)
It can cause SIBO
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)
What Does the Research Show About Dysbiosis?
Dysbiosis depletes protective acids
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)
Food additives can disrupt the gut
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)
It's linked to brain disorders
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)
Stress can promote gut dysbiosis
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)