You might only think about your digestive tract, or gut, when it’s feeling out of whack. But its influence extends far beyond your bowel habits. In fact, a healthy gut has whole-body effects: It can help protect against conditions like diabetes, obesity, and heart disease and may even improve your mental health.

How? It all comes down to bacteria. Known collectively as our microbiome, the bacteria that live in and on us play a major role in dictating health. And we’re not talking about just a few microbes. These bacteria outnumber the cells in our body by a factor of 10. All told, our microbiome contains as many as 500 bacteria species, comprising 2 million genes.

And gut microbes are particularly powerful. “The microbes in our gastrointestinal tract govern our whole world,” says Vermont-based nutritionist John Bagnulo, MPH, PhD.  Traditionally, it was thought that there are good bacteria (probiotics like lactobacillus acidophilus) and bad bacteria, also called pathogens, that cause immediate serious illness like food poisoning, strep throat, or pneumonia. But there are also bacteria species in your gut that—if they increase in number—may eventually make you more susceptible to chronic disease.

The good news: You have a lot of control over the types of bacteria that predominate in your gut. It’s as simple as what’s on your plate. Your mom was right: Eat your vegetables. More plant fiber means more diversity in your microbiome—and that’s a good thing. We asked Bagnulo, who teaches at the Center for Mind-Body Medicine’s Food As Medicine program, for his tips:

1. Boost the Bifidobacterium.

Bifidobacterium is one of the most important species of gut bacteria—one that nursing babies load up early on through breast milk. All strains of Bifidobacterium produce n-butyrate, a short-chain fatty acid that’s been shown to improve brain health and may also reduce the risk of colon cancer.

As we get older, however, our Bifidobacterium population plummets. And that can have negative effects. “The drop-off of Bifidobacterium has a linear relationship to disease,” Bagnulo notes.

Fortunately, you can boost your body’s amount of this beneficial bacterium by consuming more fermented dairy products like yogurt and some brands of sour cream and cottage cheese. But it’s a strain called Bifidobacterium 12 ( Bb12) that promotes a more drastic positive change in digestion, according to Bagnulo. While often found in European yogurt, Bb12 is less common in yogurt sold in the U.S. Read labels: Oregon-based Nancy’s is one brand that contains Bb12; Organic Valley’s sour cream also contains the strain.

2. Bulk up on fiber.  

Researchers have long known that a high-fiber diet can help reduce the risk of chronic conditions such as heart disease, gastrointestinal disorders, hypertension, obesity, and even certain cancers. That may be partly because a high-fiber diet feeds beneficial bacteria including (but not limited to) Ruminococcus. (Most of us already have Ruminococcus in our guts, but like many other bacteria, its populations flourish—or not—depending on our diet.)

The USDA’s Recommended Daily Allowance for fiber is 25 grams a day for women and 38 grams a day for men. However, the vast majority of Americans fall exceedingly short of these recommendations. To boost your fiber intake, eat a wide variety of fruits and vegetables, nuts, and whole grains (particularly barley, bulgur, oats, rye, and whole wheat). Ground flax seeds, chia seeds, and almonds with skins are good choices for people who can’t eat gluten or otherwise have trouble with grains.

3. Pick more polyphenols. 

Polyphenols, common antioxidants found in plant-based foods and beverages, play a role in helping prevent chronic diseases such as cancer, heart disease, and type 2 Diabetes. “Certain families of bacteria absolutely love polyphenols,” Bagnolo says. One of these is Akkermansia bacteria, which, in animal studies, seems to offer protection against metabolic syndromes like diabetes, heart disease, and obesity. On the other hand, low levels of Akkermansia bacteria in the gut correlate with gastrointestinal conditions such as irritable bowel syndrome, inflammatory bowel disease, and colon cancer.

You’ve probably heard that berries are rich in polyphenols—particularly elderberries, black currants, and blueberries. But cloves, peppermint, star anise, and dark chocolate actually contain the highest levels of polyphenols. Cinnamon, dried sage, oregano, rosemary, hazelnuts, pecans, and coffee are also rich in polyphenols.

4. Get a daily dose of good bacteria. 

Yogurt, which is full of good bacteria like Bifidobacterium and lactobacillus acidophilus, is essential for a healthy gut. If you don’t eat it already, make it a regular addition to your diet. (Just be sure it contains live, active cultures and not too much sugar.) “I’m all for eating more fruits and vegetables, but there is no equivalency for eating yogurt every day,” when it comes to gut health, Bagnolo says.

Kefir, probiotic sour cream, and fermented vegetables like kimchi (fermented cabbage), sauerkraut, carrots, and daikon radishes are also good additions to a healthy gut diet because they, like yogurt, contain probiotics. Bagnolo is less of a fan of kombucha, the popular fermented tea made with sugar, fruit, and a blob of beneficial bacteria. It usually doesn’t contain a complexity of probiotics that you’d get with vegetables or a protein like milk, he says.