The majority of what comprises our bodies is not human at all—indeed, the majority of the body’s composition are microbial, tiny living things, invisible to the naked eye, like fungi, viruses, and bacteria. Where do most of the bacteria live? Deep in our bowels—or our guts—where these microbes outnumber all the cells in our body.
The collection of these tiny organisms is called the microbiome, and it’s key to understanding both what it means to have a healthy gut, as well as scores of possible health solutions. Scientists have been curious about the human microbiome as far back as the 17th century, but it’s only in the past decade that genetic sequencing technology has allowed researchers the techniques to study, and start to understand, microbes in greater detail.
“The microbiome is a fascinating new frontier of medicine that’s really making us think of medicine differently,” says naturopathic doctor and nurse practitioner Erica Matluck, who studies gut health. “There’s a lot we know, and a lot we do don’t know. And it’s as unique to us as our DNA.”
What we do know is that the microbes and bacteria in our guts are essential to our general well-being, especially when it comes to influencing conditions such as heart disease, obesity, diabetes—and our mental health.
In her practice, Matluck asks every patient about their digestion, and many of them with mental health issues—and other chronic conditions—also have digestion complaints. This is in part because our guts (i.e. our gastrointestinal tract) do more than absorb the nutrients and liquids we put into our body: Our essential digestive organs are also connected to our brain. This explains why we use words like “gut feeling” and “gut-wrenching” to explain emotions and why constipation or an upset stomach can be linked to nerves or anxiety.
One way to think of the gut is as a type of switchboard, or communication hub, that connects back and forth from the brain via the vagus nerve—an essential cranial nerve that runs all the way from the brainstem to the colon. The vagus nerve sends sensory details from our skin and muscles to the brain; it also regulates motor functions like contractions that allow us to move food through the body. The brain and gut are constantly in communication with one another.
“Studies have shown that the bacteria in our gut can, in fact, influence our brain function,” says Megan Rossi, Ph.D., a registered dietitian, nutritionist, and author of the book Eat Yourself Healthy: An Easy-to-Digest Guide
to Health and Happiness from the Inside Out. She currently works as a research fellow investigating therapies in gut health at King’s College London.
“Back in 2017, a landmark study [published in BMC Medicine] came out, and what they did was they took people with clinical depression, and they put half of them on this gut-boosting diet. So super high in all these plant foods, which we know nourish the gut,” she says. “And after the 12-week intervention, they brought both groups back, and those who had the diet intervention had a significant improvement in their depression scores compared to the placebo group.” Rossi notes that while mental health is heterogeneous and complex, this was just one among several notable studies that have indicated that nourishing our bodies with fiber-rich nutrients can have “a powerful impact on the brain.”
Matluck notes that although there is ongoing research needed to fully understand the complexities of the bacteria living in our guts, research has confirmed that processed food or certain pharmaceuticals such as antibiotics and laxatives can have an unhealthy impact on our microbiome, and therefore negative consequences on our health. This buzzed-about scientific discovery, in part, explains why gut health has been tagged on Instagram more than 3 million times—and there’s a glut of online ads hawking probiotic vitamins or special bloat-resistant foods or drinks.
Matluck says that for the most part the wellness industry means well, but, even so, adding a single product or probiotic-rich foods like yogurt, sauerkraut, or kimchi to your diet is not a one-size-fits-all approach. If Matluck is working with a patient to improve their gut health—which, as a holistic health provider, she says can help with everything from digestion and fatigue to hormonal imbalances and anxiety or depression—she often will have them experiment with changes to their lifestyle or nutrition, like adding fruits and veggies, advising them to track how they feel week by week. However, Matluck primarily looks at what to eliminate in a diet, not add to it.
“At the end of the day, if you have a dairy sensitivity, or you’re eating too much sugar or drinking too much wine, and that’s what’s leading to bloating, you can take all the probiotic supplements or digestive enzymes, or try all the new latest and greatest products, but if you don’t remove the exposure, there’s no healing,” Matluck says. “Especially with gut stuff I always look at what you’re being exposed to that might be responsible, and it doesn’t require spending any money or require any products or services. It just requires you to do the work of cutting out something in your diet.”
Her aim? For her patients to have a healthy gut full of good bacteria that fights off the bad bacteria. Both Matluck and Rossi agree the first step to improving your own gut health bacteria involves paying attention to your digestion and what you’re regularly consuming. According to Matluck, eating foods high in fiber, adding probiotic foods to your diet such as yogurt or pickles, cutting back on sugar and carbs, and laying off gluten can not only help decrease inflammation in our gut—it can also improve our mood.
There’s a reason why ‘food is medicine’ has become a cliche after all. Matluck says, “By supporting your gut microbiome [with mindful nutrition], you can significantly change how your brain processes emotions.”
*This article was originally published in DoubleBlind Issue 5.
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