Your Body’s Bugs

Courtesy of National Institutes of Health

Microscopic bugs called microbes can be found in your eyes, mouth, gut, skin, and everywhere else. But don’t be alarmed. Most of your microbes are useful. They help you digest food. They prevent dangerous infections in your organs. And so much more. They’re vital for your health.

This collection of microbes in your body includes bacteria, fungi, and viruses. Together, it’s called the human microbiome.

“The microbiome is just as important as the brain, liver, kidney, or heart,” says Dr. Eugene Chang, who studies gut microbes at the University of Chicago.

Scientists have cataloged the types of microbes that live in the human body. They’ve found that changes in your body’s bugs are linked with many health problems. These include diabetes, obesity, inflammatory bowel diseases (IBD), and cancer. They can also cause skin disorders and tooth decay.

Certain things can harm the helpful microbes in your body. These include using antibiotics inappropriately or eating an unhealthy diet. Now, studies are starting to uncover ways to use microbes to improve your health.

Restoring Balance

One of the big jobs for our helpful microbes is to take up space. They live in places in the body that might otherwise be filled by harmful microbes that can cause disease, says Dr. Yasmine Belkaid, an immune system expert at NIH. “This is one way your microbiome prevents infection,” she says.

Your immune system normally attacks microbes that get into the body. But people grow up with their microbiome, Belkaid says. Many microbes are acquired from your mother at birth. So your immune system recognizes them as friendly and doesn’t attack them.

If these helpful microbes aren’t thriving, harmful ones can move in. But studies have shown that helpful microbes can be restored.

For example, people with a skin condition called eczema often have changes in their skin microbes. NIH researchers tested spraying a type of bacteria onto the skin of people with eczema. They found that it improved symptoms, including itching and rashes.

Your gut hosts lots of microbes. These can be thrown out of balance by many things, including antibiotics and diet. That can make room for harmful ones to grow.

One especially dangerous microbe is a type of bacteria that can grow in the intestines called Clostridioides difficile. C. difficile can cause fatal diarrhea, especially in older adults. It’s often resistant to treatment.

Researchers have developed a type of treatment for C. difficile infection called fecal microbial transplant. A patient is given microbes from the large intestine of a healthy person. This is done by transferring stool (poop) via tubes or pills.

Researchers don’t yet know exactly which of the microbes are needed for a healthy gut microbiome. So for now, they transfer the entire microbiome.

“Fecal transplants are a full-spectrum treatment. We’re just trying to change things wholesale,” says Dr. Gary Wu, a gut-health expert at the University of Pennsylvania.

Wu is part of a nationwide team that’s tracking the use of fecal transplants for C. difficile. In a nationwide study, they found that about nine out of 10 people who received fecal transplants were cured of C. difficile. “It works marvelously well for treating this infection,” Wu says.

The team continues to track people who have had fecal transplants. They want to learn more about its long-term safety.

Researchers are also testing this treatment for other conditions. These include IBD and other conditions that cause gut inflammation.

Wu says scientists are working on more targeted treatments to repair or replace a damaged gut microbiome. Different collections of microbes grown in the lab may eventually be tailored to treat different gut diseases. “That’s going to be the next generation of treatments,” he says.

Microbes and Obesity

Microbes in the gut do much more than just take up space, says Chang. “Gut microbes help regulate our metabolism—the digestion, absorption, and use of nutrients,” he explains.

His research team and others study proteins that gut bacteria release into the bloodstream. “These tell us how much we eat, when to eat, and what to eat,” he says.

This communication between our cells and our microbes seems to play a role in obesity. Chang and others have shown this in mice. They transplanted gut microbes from mice fed a high-fat diet into lean mice without any microbes. The lean mice then processed dietary fat differently and gained weight.

It’s not yet understood exactly how microbes help control metabolism. “But if we figure out how, that could be a game changer in preventing diet-induced obesity,” Chang says.

Keep Your Microbes Healthy

Researchers have started testing whether altering microbes can impact other areas of health.

Belkaid and her team found that changing the gut microbiome may improve how well a certain cancer treatment works. They’re also doing studies in mice to see if changing a female’s microbiome during pregnancy can boost her offspring’s immune system.

For now, what can you do daily to keep your helpful microbes healthy? “Diet is the major driver that shapes a person’s microbiome,” Chang says. Fortunately, your microbes respond quickly to changes in diet.

The dietary fiber found in plants is especially good for your gut bugs, says Belkaid. “One of the best things we can do for our microbes is to eat a healthy and diverse diet, and make sure it’s rich in fiber,” she explains.

Some types of foods may harm our microbiome, Belkaid adds. “These include foods high in carbohydrates, rich in sugar, or with too many artificial components,” she explains. “These can enrich for microbes that are bad for your health.”

“The microbiome is an extraordinary ally. It’s a healthy partner in helping the body function,” Belkaid says. See the Wise Choices box for other tips to help keep this partner healthy.