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What is the gut microbiome? Common questions, answered by experts.

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Gut health has become a huge — and important — wellness topic, and if you've heard anything about it, chances are you've heard another keyword too: the gut microbiome.

Turns out, gut health all boils down to this more mysterious, less talked about piece of the digestive puzzle.

"When people talk about gut health, they're talking about the microbiome at large and its interactions with various bodily processes," Dr. Shilpa Ravella, a transplant gastroenterologist and assistant professor of medicine at Columbia University, recently told CBS News.

To help better understand its power and importance, we're diving deeper into the gut microbiome with some common questions: 

What is the gut microbiome?

The gut microbiome refers to the trillions of bacteria, viruses and fungi living in our intestines.

"The vast majority of the microbes that live in our bodies are actually a vital part of our ecosystem and they're essential to our health, they're not disease-causing germs like we've been taught," Dr. Robynne Chutkan, gastroenterologist at Georgetown University Hospital and author of "The Microbiome Solution: A Radical New Way to Heal Your Body from the Inside Out," previously told "CBS This Morning."

Dysbiosis, or the imbalance of our gut bacteria, have been linked to different diseases, including cancers and autoimmune diseases, Chutkan said.

"Obesity is another one," she added. "There's been a lot of really interesting research showing obese people have different microbes."

How does the gut microbiome affect our health?

One of the most important ways the microbiome affects health is through its influence on our immune system.

"What happens is, from birth onto death, our microbiome actually helps to shape our immune system," Ravella said. "This is important because we know today that inflammation is very relevant to our health. Low-level inflammation or chronic inflammation is tied to nearly all of our modern disorders. So when you have a gut microbiome that is an imbalance or dysbiosis, you tend to have more of this inflammation coursing through your body."

So if you think of the intestinal tract as simply a tube where food goes in and out, think again.

In a 2020 "60 Minutes" report, CBS News chief medical correspondent Dr. Jon LaPook spoke to Dr. Jeff Gordon, who has spent decades exploring the mysteries of the bacterial community in our gut and is recognized as "the father of the microbiome."

"(Microbes) help process the food that we consume, but they do a lot more than that. They make vitamins... they're able to produce essential amino acids, they're able to talk to our immune system and help educate the immune system," Gordon said.

How does your gut microbiome affect your mental health?

The gut doesn't just play a role in keeping us physically healthy — it also has an impact on our mental health.

"The gut and brain (connection) is really new, burgeoning scientific work that's come out over the last couple of decades — although Hippocrates eons ago spoke about it," Dr. Uma Naidoo, a nutritional psychiatrist and author of "This is Your Brain on Food," told CBS News. "But what we understand is that the gut and brain arise from the exact same cells in the human embryo, so they are connected even from our early development. Then they are connected by the vagus nerve throughout our lives."

The vagus nerve is our 10th cranial nerve, which she describes as a "text-messaging system between the brain and the gut, sending messages all the time — communicating chemical messages."

One of the things that affects these chemical messages? The food we eat.

"On days that we're eating those healthier foods, they are nurturing and taking care of the good microbes in the gut," Naidoo says, whereas when we eat processed and fast foods, the "bad microbes are taken care of," upsetting the balance in the gut.

How is your microbiome affected by your diet?

Having a happy, balanced gut microbiome has a lot to do with what we eat.

On a simple, general level, it's all about eating a "quote-unquote 'healthy' diet," explains Dr. Aditya Sreenivasan, a gastroenterologist at Lenox Hill Hospital, though he admits that it can be "hard to to meet these criteria, especially living in this country."

What exactly does this way of eating look like? The focus should be on whole plant foods, experts say.

Sreenivasan generally advises eating more fruits, vegetables and whole grains and less processed carbs like sugary drinks and processed and red meats. Recommendations may differ for people who have specific issues such as celiac disease, which could require a more specific diet.

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