Researchers estimate the total surface area of the human gut at 3,000 square feet — larger than a tennis court — with the number of microbes in it outnumbering human cells 10 to one.
Though words like “bacteria” and “fungi” might commonly be associated with infections or disease, the ones found in the microbiome are the peacekeepers of your body, helping digest food, fight disease and regulate the immune system.
Today, researchers at the Center for Microbiome Innovation at the University of California, San Diego are trying to map and understand this crucial component of our health through the American Gut project — a slight misnomer, as the project has collected over 10,000 samples from more than 43 countries.
“There’s more bacteria in your gut than there are stars in the universe, by a long shot,” Rob Knight, the center’s director, said as he stood next to a map of bacteria taken from people all over the globe.
The goal of his project is to identify what all of the bacteria do and how they impact your health.
The challenge is the diversity of human microbiomes and the fact that they change every day, Knight explained. We are constantly altering the makeup of our gut through what we eat, where we live and with whom we interact.
“We’re all 99.99% identical in terms of the human genome, whereas you might be 90% different from the person you’re sitting next to in terms of your microbiome,” Knight said.
Participants who send in samples also fill out detailed questionnaires to help the team identify what factors — such as sleep, environment and exercise — have the biggest impact on someone’s microbiome. Out of these influences, Knight says, long-term diet has the most profound effect.
Furthermore, “the number of different kinds of plants people eat seems to have a very big impact on the microbiome,” he said. “That seems to have a much bigger impact than whether you also eat meat occasionally or even frequently.”
But he adds that there is still so much experts don’t know and only so much his team can hypothesize based on an observational study like the American Gut Project.
“You really need to take it in to more well-defined experiments to find out what the connections are and whether the microbiome is driving the difference in lifestyle or whether the lifestyle is driving the microbiome. Sometimes, it can be a bit of both,” Knight said.
One thing researchers do know is that modernization has drastically changed the state of our microbiome through antibiotics, chemicals and diets.