One of the most fascinating recent developments in medicine is our discovery of the importance of the microbiome in health and disease. What is this microbiome and how does it affect our lives?
Over the last few years researchers have begun to discern the role of the microbiome in maintaining health and its alteration in causing many illnesses.
It is well known that we harbor many microorganisms within our digestive tract. In fact, it is estimated that our gut contains over ten trillion microbes, most of which reside in our colon. These include vast numbers of bacteria, but also fungi, viruses and protozoa. These microorganisms comprise the microbiota and their genetic material is called the microbiome.
The microbiota has evolved in a Darwinian fashion to relate to us—their host—in various ways. Most live as commensals. These organisms thrive in our gut but do not affect our health in any meaningful way. Many others, however, are symbionts. These not only grow and multiply within our digestive tract, but also provide benefits to us by assisting in digestion and promoting a healthy immune status to maintain our good health. Finally, there are microbes that are pathobionts. These invade our gut and lead to various infections such as traveler’s diarrhea, gastroenteritis or colitis. But they can also cause or aggravate many systemic diseases.
The intestinal microbiota is intimately involved with the maturation of our gut after birth. Experiments in mice have demonstrated that altered microbiota may have a detrimental effect on the intestinal surface, lymphoid function, motility, metabolic processes and mucosal immunity of our digestive tract.
Normally, these microorganisms defend us against pathogens. They assist in energy utilization and the digestion and absorption of nutrients. They also play an important role in drug metabolism. However, when the microbiome is altered, a dysbiosis develops. When this occurs, a derangement in the number and kind of microbiota leads to various diseases. Small bowel bacterial overgrowth, Clostridium difficile colitis, inflammatory bowel disease and irritable bowel syndrome are prime examples that have been shown to be affected and perhaps caused by this dysbiosis. Even chronic constipation has been attributed to an altered microbiome.
Moreover, malignancies both within the gut and in other parts of our bodies have been linked to alterations in our microbiome. One example of this is the development of gastric cancer from chronic Helicobacter pylori infection. Importantly, many other serious illnesses are also associated with this modification in our gut flora. These include: arthritis, asthma, autism, diabetes mellitus, fibromyalgia, coronary heart disease, metabolic syndrome, mood disorders, fatty liver disease and even such neurologic diseases such as multiple sclerosis and Parkinson’s disease. Obesity itself has also been said to be a product of this dysbiosis. It has been demonstrated that antibiotic use in infants prior to age two contributes to obesity in later life. Experiments in mice have confirmed this observation.
It is well known that chronic irritable bowel syndrome can follow an attack of acute gastroenteritis. It is possible that change in the microbiota alters the normal function of the bowel to affect motility and visceral sensitivity. Once this process occurs, it may be difficult to correct. Current studies suggest a possible role for probiotics in preventing and treating this illness.
Ironically, the tremendous medical and scientific advancements of the 20th century in understanding and treating diseases, such as the use of antibiotics and better sanitation, have possibly led to causing new illnesses or aggravating other pathologic conditions. We have disturbed the unique balance of symbiosis with our microbiota which nature created over millennia.
Now, the 21st century holds out the promise to cure or prevent many of these diseases by identifying and correcting alterations in our microbiome. We are learning about the effects on our macro or external environment from manufacturing and pollution in causing global warming. It is our task to discover more about the relationship with our microbiome and how it affects our lives and health. Antibiotics, other medications and even the processed foods we eat have disrupted and damaged our micro or internal environment. Nature rewards diversity.
Just as a nation, political party or financial portfolio is stronger with diversity, so too is our microbiome. We must find ways of reversing this change in order to enhance our long term health. This challenge of restoring the balance of our microbiome is one of the most important ones facing us today.