How Your Gut Health Affects Almost Every System In Your Body

Your gastrointestinal tract is host to around 100 trillion microorganisms. Yes, that’s trillion with a T. And these gut bugs—primarily bacteria but also viruses, fungi and other microbes—make up about half of the cells in your body. Wild, right? We’re talking about your microbiome. You’ve heard that buzzword, of course, but what can be trickier to wrap your head around is how vital your gut health is to much more than your digestive system. 

“These microorganisms play a central role in your health, because they act as a chemical factory,” says gastroenterologist Will Bulsiewicz, M.D. “The food you put in your mouth, for example, comes in contact with these microbes, and the chemicals they produce influence so much of human health—your digestion, immune system, metabolism, mood, brain health, even the expression of your genetic code.”

A healthy diet rich in fruits, vegetables, beans and whole grains can help beneficial microorganisms flourish—in part by spurring them to produce health-promoting compounds called short-chain fatty acids. And that’s a good thing because short-chain fatty acids help reduce inflammation in the body, according to Sue-Ellen Anderson-Haynes, M.S., RDN, CDCES, a spokesperson for the Academy of Nutrition and Dietetics. Inflammation has been linked to a host of chronic diseases, including diabetes, heart disease and cancer, so keeping it in check is key. If you have an imbalance of microbes that favors the bad guys, it could increase your odds for all of the above conditions and more.  

Read on to find some of the ways your microbiome impacts many parts of your body and learn ways to support the beneficial bugs in your gut through the foods you eat.

The Connection Between Your Gut Health and …

Your Brain 

It might seem strange that microbes all the way down in your gut could impact your brain, influencing things like mood and cognition. But it’s true, thanks to what’s called the gut-brain axis. “It acts as a sort of superhighway between your gut and your brain,” says Anderson-Haynes. 

“There’s still a lot that we’re learning, and the microbiome isn’t the only thing that matters,” says Bulsiewicz. “But the science does suggest that the chemicals produced by your gut microbes, including short-chain fatty acids and neurotransmitters, cross the blood-brain barrier and influence mood and brain function.”

_{Research suggests that chemicals produced by your gut microbes cross the blood-brain barrier and can influence cognition.}

Your Mental Health

There are lots of factors that influence mental health—and many of them, like genetics, may be out of your control. That said, there is evidence that your gut health can directly impact not just mental health conditions—like clinical depression and anxiety—but also basic feelings of happiness, says Anderson-Haynes. In fact, research shows that more than 90% of your serotonin—a key brain chemical tied to mood—is found in your gut.

There’s also research showing that your microbiome might influence how you handle everyday stressors. And evidence suggests that following a gut-friendly diet, such as the Mediterranean diet, may reduce your risk of depression and anxiety by as much as 40%. “This is not an argument against antidepressant medication, because it can be important,” says Bulsiewicz. “This is about acknowledging the role that diet plays in our mood by affecting the microbiome.”

Your Cognitive Health

A growing body of research shows that your microbiome can influence cognitive health, as well, possibly by tamping down inflammation, which has been tied to neurodegenerative conditions such as Parkinson’s disease and Alzheimer’s disease. For instance, research has found that people with Alzheimer’s disease have less-diverse gut bacteria than healthy people. It’s still not known exactly if this triggers the disease. However, one theory is that an imbalance in gut bacteria may damage the intestinal lining, causing leaks that allow the release of harmful substances into the bloodstream, where they may travel to the brain, setting off a cycle of inflammation. 

According to the Parkinson’s Foundation, gut health and Parkinson’s disease are strongly linked. As with Alzheimer’s, people living with Parkinson’s disease also have differences in gut bacteria and increased intestinal permeability. There are also likely other mechanisms at play. For example, researchers have found that the same proteins that cause Parkinson’s-related clumps in the brain are also present in the GI tracts of people with Parkinson’s disease.

Your Heart

“Heart disease is the No. 1 cause of death in the United States. And if you look at the risk factors—high blood pressure, high cholesterol, diabetes, obesity—every one of them is a chronic illness connected back to your microbiome,” says Bulsiewicz.

Certain unhealthy species of gut bugs may contribute to heart disease by producing trimethylamine N-oxide (TMAO), a compound that can clog your arteries and increase your risk of heart attack or stroke. But research reveals that the reverse can also be true: A proliferation of friendly microbes can play an important role in promoting beneficial HDL cholesterol and keeping triglycerides in check—lowering the risk of heart disease.

Your Digestive System

When you digest food, the microbes in your GI tract secrete enzymes that influence gut motility—a fancy term for how food moves through your bowels. “When gut motility falls out of balance, you get constipation or diarrhea,” says Bulsiewicz. “It can also bring on or worsen inflammatory bowel diseases like Crohn’s and colitis.” 

Like those with Alzheimer’s and Parkinson’s, people with Crohn’s disease and ulcerative colitis have less-diverse gut bacteria as well as fewer inflammation-fighting gut microbes. In addition, they tend to harbor unusually large numbers of a specific bacterium linked to intestinal illness, called Mycobacterium avium paratuberculosis (MAP). While it’s premature to say that this bacterium causes Crohn’s, it may be involved in initiating the inflammatory response that sets off the disease.

And if you’re one of the 10% to 25% of Americans living with irritable bowel syndrome (IBS), your gut bacteria might be involved as well. Although this condition has many triggers, like diet, stress and infection, experts believe that unfavorable changes in gut bacteria may be an additional contributor.

Get the Recipe: Tropical Gut Healthy Smoothie

Your Immune System

Get this: An estimated 70% to 80% of your immune system is located in your gut. There, these microbes act like little sentinels—playing a crucial role in keeping out harmful intruders like viruses, infection and even allergens. “Your microbiome helps build a barrier within your GI tract. When that barrier is fortified, it protects your immune system,” says Bulsiewicz. “But if the microbes are out of balance, the barrier gets weak and porous—and that can trigger an immune response that fuels the diseases that are epidemic in the 21st century.” That means that if your gut barrier starts to weaken, you’re more prone not just to infectious diseases like colds and flu but also to chronic conditions such as heart disease, cancer, stroke and diabetes, to name a few. The encouraging news is that eating a gut-friendly diet can help you tighten that barrier to lock out many of these disease-causing substances by turning on genes that close tiny gaps in the gut and by helping intestinal cells grow and repair.

_{Your microbiome helps build a barrier within your GI tract that protects your immune system. But if the microbes are out of balance, the barrier gets weak and porous. Luckily eating a gut-friendly diet can help you tighten that barrier.}

Your Weight

A growing body of evidence suggests that people with obesity tend to have a lower diversity of gut microbiota. Your gut bacteria may also influence where you carry your weight, especially visceral fat. That’s the type of fat that collects around the midsection and has been linked to heart disease and other chronic conditions. One study of people with high amounts of visceral fat found that they had different species of gut microbes than those with low visceral fat levels. How can having fewer species of beneficial gut microbes impact your weight and fat distribution? It appears to alter certain weight-regulating hormones such as leptin and ghrelin and other substances that affect the way your body burns calories—impacting digestion, appetite, fat storage and inflammation.

What You Can Change About Your Gut Health—and What You Can’t

You inherit a certain amount of your microbiome—which is unique to you—when you’re born. Everyone’s microbiome is completely unique, and some of it comes down to genetics, which you can’t do so much about, says Bulsiewicz.  While your microbiome might not be the same as that of your friend who has never had GI issues or your cousin who seems to have a superhuman immune system, that doesn’t mean that your gut health is fixed for life. There are things you can do to help make yours the healthiest version that it can be. 

“Research shows that your microbiome is rapidly adaptable to your diet,” says Bulsiewicz. “The choices you make today will start to reshape your microbiome by tomorrow. And these changes are like a snowball. They start small, but with consistency, that snowball builds momentum and can become incredibly powerful.” Of course, lifestyle matters, too. “Other factors, like getting enough sleep, managing stress and being physically active also impact your microbiome. But diet plays a major role,” says Anderson-Haynes.

What dietary tweaks can you make to support your gut health? Here are six research-proven strategies:

1. Fall in Love with Fiber

“Fiber is exclusively digested by the microbes in your gut. It’s their preferred food source,” says Bulsiewicz. “Without enough of this nutrient, they get hangry.” And more than 90% of Americans don’t get the 28 to 34 grams of fiber they need each day. In addition to feeding your gut microbes—which in turn produce those good-for-you short-chain fatty acids—a high-fiber diet also promotes satiety and can support healthy weight management. 

“Resistant starches, in particular, are a type of fiber that are like a banquet for your good gut bacteria,” says Bonnie Taub-Dix, M.A., RDN, CDN, author of Read It Before You Eat It. “These include foods like underripe bananas, beans, chia seeds, some nuts, potatoes, and whole grains such as oats, sorghum and barley.”

Bulsiewicz suggests increasing fiber gradually in your diet: “A damaged microbiome struggles to perform its normal functions. But your gut is like a muscle that can be trained and made stronger,” he says. “So the right way to do it is to gently ease your body into it and give your microbiome a chance to adapt to increased fiber intake.” Start by adding a tablespoon of chia seeds to your morning smoothie or dipping cut-up veggies in our Easy Black Bean Dip for a midday snack.

2. Cook Up a Veggie-Packed Soup

“Different microbes enjoy different plants,” says Anderson-Haynes. And the more variety, the better. “Studies show that the people who consume the most variety of plants—specifically, at least 30 different types per week—are those with the healthiest guts,” says Bulsiewicz.16 Noshing on foods like vegetables, beans, fruits, whole grains, nuts and seeds will deliver the fiber your gut microbes need to thrive. Plus, plant foods also provide a range of health-promoting phytonutrients, including polyphenols—powerful antioxidants that Bulsiewicz says the friendly bugs in your gut can help unlock.

If the idea of eating 30 plants a week sounds daunting, think of a bountiful salad or a pot of soup like this Roasted Vegetable Soup. The satisfying soup features nine plants in a single bowl, getting you more than one-quarter of the way there in just one meal!

3. Explore the Wide World of Fermentation

Fermented and cultured foods like yogurt, kefir, kimchi, tofu, tempeh, sauerkraut and miso are filled with gut-friendly beneficial bacteria, says Anderson-Haynes. Research reveals that the compounds created during the fermentation process actually interact with the microorganisms in the GI tract, potentially improving gut health in both the short and long term. 17 For the biggest punch, start your day with probiotic-rich yogurt (there are so many ways to use it) or a Berry-Kefir Smoothie. Add Roasted Broccoli with Kimchi Vinaigrette to your dinner plan, or sip a glass of kombucha instead of soda.

Get the Recipe: Frozen Lemon-Blueberry Yogurt Bites

4. Stock Up on Gut-Healthy Snacks

What you don’t eat can be just as important as what you do eat. “There’s good evidence that [certain] ultra-processed items like chips, cookies and fast food—items that are high in added sugar, sodium and saturated fat, and low in nutritional value—can allow ‘bad’ gut bacteria to flourish and create inflammation in the body,” says Anderson-Haynes. “Plus, if you’re eating lots of highly processed foods, it tends to crowd out the healthier whole foods in your diet.” That doesn’t mean you have to completely eliminate processed foods from your diet: popcorn, roasted nuts and whole-grain crackers are all great options to stock in your pantry for snack time—and your gut will thank you for it.

5. Shake Up a Fabulous Mocktail

You’ve probably heard the recommendation to limit your alcohol consumption to no more than one to two drinks a day. That’s because as yummy as a glass of jammy cabernet can be, alcohol is a toxin. And it can damage your gut microbes if you consume too much. 

A good deal of the research on the link between alcohol and gut health has been done in people with alcohol use disorder. So, it’s not totally clear how moderate drinking may or may not impact your microbiome. There is evidence, though, that heavy drinking can cause what’s called dysbiosis, or an imbalance of levels of unfavorable microbes compared to beneficial ones, says Bulsiewicz. 

With all the amazing nonalcoholic options out there now—from our Watermelon-Lime Mocktail to hop seltzers—it’s easier than ever to trade booze for something equally as tasty.

6. Swap Out Some Saturated fat

“Polyunsaturated fats, including omega-3 fatty acids found in fish like salmon, [and in] walnuts and avocados, produce healthy gut microbes that may reduce the risk of a number of chronic diseases,” says Anderson-Haynes. She recommends replacing saturated fats, like butter and coconut oil, with healthier polyunsaturated ones, like nut and seed oils, when it makes sense. Since the American Heart Association recommends limiting saturated fat to a maximum of 6% of your daily calories, it’s also a good move for heart health. Try a Salmon Burger with Quick Pickles instead of a beef burger, cook with olive oil more often than with butter, and top your toast with avocado instead of cheese. Your friendly gut bugs will thank you.

Bottom Line

Gut health plays a crucial role in your overall health and wellbeing—and what you eat can profoundly impact it. Focusing on healthy foods like fiber-rich fruits, veggies, beans, nuts, seeds and whole grains, as well as lean protein such as omega-3-rich fish and cultured and fermented foods can shift the balance of good gut bacteria you have and may help protect your mental health, bolster immunity, keep weight in check and stave off conditions including heart disease and digestive issues.