The human intestine is home to trillions of bacteria. While most people think of bacteria in a negative light, the bacteria that reside in our gut from birth are far from bad. These bacteria are known as our “gut microbiota” and serve an important role in protecting our bodies from invading pathogens. Similar to an army protecting a castle, the gut microbiota in our large intestine is the defensive barrier against the “bad” bacteria that attempt to invade and cause infection.
While the specific composition of bacteria in our gut differs between individuals, there are a core set of bacteria from a variety of species that are common to everyone. When our gut is filled with a rich, diverse population of bacteria, it is said to be in balance. When this composition is altered through exposure to environmental factors (i.e. diet, toxins, drugs), the gut is said to be in dysbiosis – an imbalance of bacteria.
The role of intestinal dysbiosis on human disease has been widely studied, and it has now been shown that intestinal microbial dysbiosis is linked to inflammatory bowel disease, obesity, type 2 diabetes, non-alcoholic fatty liver disease, and cardiovascular disease. So how exactly do the trillions of bacteria present in our gut cause disease?
Some diseases such as inflammatory bowel disease are due to dysbiosis of the gut microbiota that results in infection by incoming pathogens such as E. coli or Salmonella. However, some diseases are caused by the dysbiosis of the gut microbiota that results in an altered representation of bacterial genes that are involved in metabolic pathways. Our gut microbiota not only forms a protective barrier to block out incoming pathogens, they are also key players in the breakdown of nutrients that are not fully broken down in the small intestine. When the bacteria in our gut encounter these nutrients, they break them down even further into small products that can be absorbed into the body. During a state of dysbiosis, the altered representation of bacterial genes involved in this process can lead to the formation of products that are not always beneficial to our body’s health. The absorption of these products into our body can in turn lead to disease such as non-alcoholic fatty liver disease.
Now that we know how changes in our gut microbiota can cause disease, how exactly do we stop it? There is no easy way to prevent this, however, there are two current approaches to help reverse this imbalance of gut microbes. The first, the use of probiotics, is a well-known method to help constantly repopulate our gut with the good bacteria. Probiotics are the good or helpful bacteria that can be found in foods such as yogurt or in supplement form, and serve to replenish the intestinal tract with these beneficial bacteria. The second method, fecal transplantation, is used for patients who suffer from a severe imbalance of gut bacteria and involves taking fecal matter containing a healthy gut microbiota population from a donor and administering it to the patient.
With this in mind, remember that not all bacteria are bad bacteria, and it is vital to eat a balanced diet and avoid toxins that could alter the protective ability of our good bacteria!
Carding, S., Verbeke, K., Vipond, D., Corfe, B., & Owen, L. Dysbiosis of the gut microbiota in disease. Microbial Ecology in Health and Disesase, 2015. 26: 26191.