So What Exactly is the Microbiome?

What if I told you that you have a second genome? This genome is much larger than your human genome, having 6-7 million genes as compared to your measly 25,000 human genes. This genome is 300,000 years older than us and we could not survive without it. This genome is our microbiome and, unlike your and my DNA, which are 99.9% similar, our microbiomes are drastically different.

Our bodies are covered in trillions of these microbial inhabitants—bacteria, fungi, viruses, and archaea—that far exceed the number of our own human cells. Every second of every day you exchange 38-million of these microbes with your environment: you leave a trail of them everywhere you go, vacuum them in with every breath, and provide a home for them all over your body. You may think this is gross, but that is a dangerous misconception. We no longer want to kill 99.9% of germs; we want 99.9% of them to thrive.

The microbiome industry is one of the fastest growing realms of the life sciences with venture-capital investments expected to reach 658 million dollars in 2023. And after attending the 3rd Annual Translational Microbiome Conference in Boston this month and learning about the many new clinical trials, products, services, and routes that will change the dynamic surrounding microbes and antibiotic usage in medicine, I am confident that the industry will reach and exceed these estimates.

Nonetheless, we still have a lot to learn about the microbiome and that is what I’m here to tell you about. Each day there are new claims, many of which are dichotomous, and with all the circulating excitement about the field, a question still stands: what exactly do we know about the microbiome?

Thus far we have made significant findings regarding human nutrition, immunology, and psychiatry. And this list is growing fast with research and development in dermatology, oncology, surgery, dentistry, and more.

Many dietitians and nutritionists are now looking to the microbiome to figure out why certain populations have very few diabetic and obese people, why unexpected food allergies develop, and why diets do not work for everyone. We should no longer ask what the best diet is for humans; we should instead ask what diet is best for you, the individual.

We presently know that certain foods, such as yogurt and fermented products like kimchi, seem to improve our gut health by promoting microbial diversity. However, we also know that, due to the varying microbial compositions of each of our guts, these health benefits differ from person to person. And, as a result, we now welcome the idea of personalized nutrition. In a 2015 study at the Weizmann Institute of Science in Israel in which 800 people had their blood glucose levels monitored in response to 46,898 meals, they found that each individual’s response to an identical food item varied greatly and was dependent on the microbial composition of their gut. One of the most striking differences is when those in the cohort consumed rice and ice cream, 65% had higher blood glucose level spikes when eating the rice. Acknowledging how dangerous this can be for those with diabetes and obesity, the study undermines much of what we know about human nutrition and warrants more research.

By investigating and making strides to harness the potential of the microbiome, we have also found new ways to treat things like Clostridium difficile (C. diff.) infections, which is the most common hospital-acquired infection worldwide. Strikingly, 1 in every 5 patients with C. diff. is unresponsive to antibiotics. This major gap in recovery contributed to the development of the fecal microbiota transplant (FMT), a treatment in which bacteria from a healthy person’s gut are transferred to that of a sick person, by organizations such as OpenBiome. Unlike antibiotics which may cause more damage than improvement and are not effective in preventing recurrence of C. diff. infections, FMT recolonizes the patients gut with a healthy set of microbes and cures recurrent C. diff. in over 90% of the cases.

In terms of psychiatry, the many connections between our gut and brain are presently being explored. There are ongoing, microbiome-related clinical trials looking at anorexia, PTSD, anxiety, Alzheimer’s, Parkinson’s, and even alcoholism. We are only scraping the surface of this connection and still have made profound findings. In the case of Alzheimer’s disease, which affects 1 in every 3 people over the age of 85 in the United States and is predicted to bankrupt Medicare if unresolved, studies have found that probiotic supplementation leads to moderate, yet significant, improved cognitive function in those diagnosed. More remarkably, when the gut of a healthy mouse is colonized by microbes taken from the gut of a mouse with Alzheimer’s, the formerly healthy mice develop Alzheimer’s.

These are only a few studies from thousands in the field and, although they seem promising, it is important to recognize the limitations. We still know very little about the role of the microbes that cover our bodies: most microbiome research is still in a nascent stage and explores the fundamental biology of these invisible occupants that make home on us walking petri dishes.

In the meantime, you have an important role to fill! We ask that you keep track of new happenings in science. Our knowledge of the microbiome is very dynamic—and bacteria evolve quickly. These bacteria were originally viewed as life-threatening organisms, but we now know they are essential to our survival. I implore you to stay educated and protect the integrity of the word “microbe.” Through this, you are protecting both yourself and those around you, including these little friends that ride along with us every day.

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