Scientists have been studying E. coli and other bacteria dangerous to humans, but the Human Microbiome is taking a more holistic approach to understanding the trillions of microbes in our bodies.
For over a century, medical research has focused mainly on those microbes that are dangerous and deadly to human health: the E. coli and influenzas of the microscopic world. But the germ theory of disease, and the foundation of western medicine, is approaching a sea change—and rapidly so. In a word, it's expanding.
It began in 2007, when 200 scientists at 80 institutions began researching every bacteria, virus, fungi and protozoa known to man. The ongoing study, sponsored by the National Institutes of Health, is called the Human Microbiome Project, and its main goal is ambitious: to map out the DNA of the entire human microbiome, and determine the roles of different microbes on our overall health.
“This is a whole new way of looking at human biology and human disease, and it's awe-inspiring,” said Dr. Phillip Tarr, a lead researcher in the project. “These bacteria are not passengers. They are metabolically active. As a community, we now have to reckon with them like we have to reckon with the ecosystem in a forest or a body of water.”
Of course, if it were as easy as sticking some slides under a microscope, we’d have accomplished this a long time ago. The reality is more daunting, and if you’re a person that carries hand sanitizer, a little unnerving—the human body is covered, both inside and out, with trillions of living microbes. The average adult carries around a few pounds of the little guys, and about 10,000 different strains at any given time. Of course, they all have their own genes, too—which, technically speaking, makes us more microbial than human.
“The bacteria has evolved with us since we were on the plains of Africa, they've been with us for maybe one and a half million years now,” says Dr. Zen Majuk, a gastroenterologist in Santa Cruz. “They help us with vitamin K, B12 and other vitamins that they extract from the fibers in foods and share with us, that we would not get otherwise.”
While the small intestine and colon is home to the body's most diverse concentration of essential microbes, our “gut” bacteria does much more than aid in digestion and modulate our immune systems—it may hold the holy grail for medical epiphany.
“We know that bacteria in your colon could effect emotions, our state of mind, by working on the vagus nerve,” says Dr. Majuk, speaking of the nerve that runs from the brain into the abdomen, a highway of communication between the two. “People who have irritable bowel, they're more fearful, more tense, they have more panic attacks, and somehow it's related to the gastrointestinal tract. And now we think the bacteria are a big factor in this.”
A recent study by Dr. Emeran Mayer of UCLA is one of many examining this gut-brain connection. By taking MRI scans of the brains of thousands of volunteers and comparing brain structure to the types of bacteria in the digestive tract, he believes he's found a measurable correlation between how gut bacteria influences actual brain development.
But the deterioration of the “11th organ” may also correlate with an increase in certain diseases. “As organisms are being lost, a lot of diseases have just skyrocketed,” says Dr. Martin Blaser of NYU Langone's Medical Center. “Diabetes, celiac disease, asthma, food allergies, obesity, social disorders like autism. These have all gone up tremendously.”
Not surprisingly, people who live in the United States tend to have a far less diverse community of microbial flora—the result of a widespread use of antibiotics (the “neutron bomb” for microbes), and a diet rich in processed foods. A healthy microbiome requires fiber, says Dr. Majuk, who also recommends daily or weekly fermented foods and kombucha.
“So we think people in less developed countries that have more fiber in their diets are better off. Somehow that produces less asthma, less colitis, less immune diseases,” says Dr. Majuk.
In the coming months and years, we'll know more about which microbes are predominant in healthy humans, and more importantly, how to restore a healthy microbiome using probiotics and fecal transplants, which are already being performed in many parts of the world. I'll let you, um, digest that one.
