What Is Your Microbiome? And Three Things That Could Change It


The microbiome could change the way we think about cancer and its treatment.

Time for a gut check: What do we know about the trillions of bacteria swarming in and around our bodies at any given moment?

The answer: not as much as we’d like. That’s why researchers at Memorial Sloan Kettering and beyond are studying the microbiome. This is the community of bacteria, viruses, fungi, and other organisms found throughout the body but especially in the digestive tract, mouth, and genitals, plus on the skin. Researchers are looking into how the contents of a person’s microbiome might influence his or her health.

“It’s a very hot topic, and I think it has the potential to answer many questions about the causes and outcomes of diseases, including cancer,” says MSK gastroenterologist Robin Mendelsohn. “It may help us understand why some people develop diseases and others don’t, and even why some people respond to treatments and others don’t.”

Having a low diversity of microorganisms has been shown to possibly be associated with different diseases, like cancer, obesity, and irritable bowel syndrome.
Robin Mendelsohn gastroenterologist

Scientists don’t yet know the exact role of the microbiome in human health. Though they have seen that a microbiome with various strains of bacteria is best.

“Having a low diversity of microorganisms has been shown to possibly be associated with different diseases, like cancer, obesity, and irritable bowel syndrome,” says Dr. Mendelsohn.

The implications for people with cancer are just scratching the surface. Immunotherapy, which harnesses a person’s own immune system to attack cancer, is revolutionizing how cancer is treated, and the microbiome may play a role, Dr. Mendelsohn says. A healthy microbiome may also help people with cancer who have recently had bone marrow transplants with their recovery.

“The microbiome might be involved in the prevention of cancer, the progression of cancer, the side effects of treatment, and long-term survival,” she says.

Changing Your Microbiome

Your microbiome changes on a day-to-day basis depending on all sorts of factors. But there are ways to change its content significantly over time. One is a fecal transplant, in which doctors transplant stool from a healthy person to an unhealthy person. Fecal transplants are currently approved for people with a Clostridium difficile infection, which wipes out the contents of the microbiome.

Not all methods for creating a more diverse microbiome are as invasive, though. Dr. Mendelsohn says modifications in the following could all play a role.

  1. Diet
    “Diet is probably the easiest way for someone to change his or her microbiome,” Dr. Mendelsohn says. But her advice goes beyond the conventional wisdom to eat more yogurt for its beneficial bacteria. “The amount of probiotics you’re getting from yogurt is questionable,” says Dr. Mendelsohn. That’s because both stomach acid and the pasteurization process kill off most of the bacteria present. You’re more likely to benefit from prebiotics, which fuel the beneficial bacteria in your body. Prebiotics are found in fiber-rich foods, like oatmeal, whole grains, fruits, and vegetables. If you’re eating a well-balanced diet, chances are you’re already getting a good amount of prebiotics.
  2. Behavior
    There are data to suggest that regular exercise, enough sleep, and a low stress level may help the bacteria in your body thrive.
  3. Antibiotics
    Each antibiotic is different, and each person’s microbiome responds differently, but even just a single dose of an antibiotic can alter the contents of the microbiome, says Dr. Mendelsohn. That’s not a reason to swear them off, though. “Antibiotics save lives and should be used when needed,” she says. “But the doctor and patient need to decide if they’re necessary.”