Our guts are home to trillions of microbes that have a profound influence on our overall health. Now, a new study finds that — whether you're vegan, vegetarian or omnivore — the key to a healthy gut microbiome is the same: Eat lots of different plant-based foods.
Gut microbes break down food that your body can't digest and in turn, they produce chemical messengers that influence everything from your blood sugar levels to your immune system. Some of these messengers can boost health, others can hinder it. It all depends on what you feed your microbes.
"The microbiome modulates the effect of diet on our health. It basically decides our health status," says Nicola Segata, a professor at the University of Trento in Italy who studies the microbiome using advanced genome sequencing.
He and an international team of colleagues wanted to know how different diet patterns shape the kinds of microbes that dominate our guts. So they analyzed stool samples from more than 21,000 people in the U.S., the U.K., and Italy. The researchers not only knew whether participants were vegans, vegetarians or omnivores, but they also had detailed information about what these people ate for a couple of weeks at a time.
What they found is that the more plant-based foods people ate, the more gut bacteria they had that are linked with better health — such as less inflammation and a stronger immune system. Perhaps not surprisingly, these good bacteria were a hallmark of the microbiome of vegans.
As for omnivores, their gut microbiomes tended to have more bacteria associated with meat digestion, which makes sense. But they also had more bacteria linked to inflammatory bowel disease and a higher risk of colon cancer. That's the bad news.
But the good news for meat eaters is that, when it comes to having a healthy composition of good bacteria, their gut microbiomes looked a lot like those of vegans and vegetarians — so long as they ate an array of plant-based foods in large amounts.
"Omnivores who were eating a large diversity of vegetables were actually quite similar in terms of having the good microbes compared to vegans," Segata says.
That finding is important because it shows that "eating an array of plant-based foods is more important than strictly adhering to a vegan or vegetarian diet pattern," says Hannah Holscher, an associate professor of nutrition and microbiome researcher at the University of Illinois Urbana-Champaign who was not involved in the study.
In other words, it's the overall quality of the diet that counts, she says.
The study is one of the largest of its kind. Holscher, who is also a dietician, says it adds to existing evidence that supports advice nutritionists love to give: For better health, eat the rainbow — meaning lots of different types of colorful plant foods.
"Think tomatoes, butternut squash, pineapple, avocado, broccoli and kale, blueberries and eggplant. And really, don't forget about those whole grains, nuts, seeds and legumes," Holscher says.
Holscher points to a 2018 study that found that people who ate more than 30 different types of plant foods each week also had more gut microbes that produce chemical messengers known to boost health. But she says you don't have to aim for 30 to improve your health.
She says a simple goal is to eat five different plant-based foods every day. For example, consider making bean or lentil soups with lots of vegetables, or mixing up some pears or berries in your salad.
"Make some overnight oats before you go to bed," Holscher suggests. "When you're leaving for work in the morning, you're looking around. What can you toss into your bag? An apple, an orange, a banana?"
And as you try to diversify the plants in your diet, look for fiber-rich options, says Shana Spence, a registered dietician in Brooklyn, N.Y., because most Americans don't consume enough of this dietary-hero nutrient. One easy idea: Try adding seeds like chia seeds, pumpkin seeds or flax seeds, as an easy way to diversify your plant intake and boost the fiber content of any meal.
"They're so great to throw in yogurt and oatmeal and cereals in the morning," Spence says. "And they're shelf stable, which is great because we don't want to waste money, especially not in this economy."
Frozen foods — whether it's berries or vegetable medleys — are also a great option. "It's usually cheaper than buying fresh, and it's still just as healthy because you're still getting vitamins and minerals, antioxidants. The vegetables are picked at their peak, so they are still providing tons of nutrients," Spence says.
Give yourself as many opportunities as possible to snack on more plants every day, Spence advises. Instead of making goals to restrict certain foods, think of healthy eating as a matter of addition, she says. And try to add more nutrition to your diet every day.
Edited by Jane Greenhalgh
Copyright 2025 NPR
