Trillions of bacteria and other microbes live in the human digestive system. Together, they form a community that’s known as the gut microbiota.
Many bacteria in the microbiota play important roles in human health, helping to metabolize food, strengthen intestinal integrity, and protect against disease.
To help friendly bacteria in the gut thrive, new research presented at UEG Week 2019 suggests it may help to eat a Mediterranean-style diet that’s rich in plant-based foods, including fruits, vegetables, grains, legumes, and nuts, as well as fish.
When researchers from the University Medical Center Groningen in The Netherlands assessed the eating habits and gut bacteria of more than 1,400 participants, they found that a Mediterranean-style diet was linked to healthier gut microbiota. It was also associated with lower levels of inflammatory markers in stool.
This points to the role that a plant-rich diet might play in helping to protect against intestinal diseases, including inflammatory bowel disease (IBD).
“Connecting the diet to the gut microbiome gives us more insight into the relation between diet and intestinal disease,” Laura Bolte, lead investigator of the study and a dietitian who’s currently pursuing an MD and PhD in the field of nutrition, said in a statement.
“The results indicate that diet is likely to become a significant and serious line of treatment or disease management for diseases of the gut — by modulating the gut microbiome,” she added.
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Four groups of participants took part in Bolte’s study, including members of the general population and patients with Crohn’s disease, ulcerative colitis (UC), and irritable bowel syndrome (IBS).
Crohn’s disease and UC are forms of IBD that involve chronic inflammation in the intestines. IBS is another intestinal disease in which inflammation may play a role.
To identify potential links between diet, gut microbiota, and intestinal inflammation, the researchers administered a food frequency questionnaire and collected a stool sample from each participant.
They found multiple links between participants’ eating habits, gut microbiota, and markers of intestinal inflammation.
A Mediterranean-style diet rich in fruits, vegetables, legumes, grains, nuts, and fish was linked to greater abundance of friendly bacteria that help synthesize essential nutrients, produce fuel for cells in the colon, and reduce inflammation. This plant-rich eating pattern was also linked to lower levels of inflammatory markers in the stool.
In comparison, a diet rich in meat, refined sugar, or fast foods was linked to lower levels of friendly gut bacteria and higher levels of inflammatory markers.
“It’s not surprising that a diet pattern which has been connected to a lower risk of heart disease, cancer, and increased longevity is also associated with beneficial digestive effects,” Julie Stefanski, MEd, RDN, a spokesperson for the Academy of Nutrition and Dietetics, told Healthline.
“This study reinforces a growing body of data demonstrating that having a healthy intestine and pinpointing the right mix of bacteria needed for health may be key to tackling many chronic diseases,” she added.
This study adds to a large body of research that suggests Mediterranean-style diets and other plant-rich eating patterns have benefits for human health.
In addition to cardiovascular benefits and reduced risk of cancer, some research has linked plant-rich eating patterns to lower incidence of IBD. This new study might help explain why.
“We’ve known for some time that when you look at it at a country level, populations that take in less red meat and eat a more plant-based diet have lower incidence of inflammatory bowel disease, including Crohn’s and colitis,” Dr. Arun Swaminath, director of the inflammatory bowel disease program at Lenox Hill Hospital in New York City, told Healthline.
“I think the interesting addition here is that we didn’t know why that was true or really understand what the mechanism of that was,” he continued, “and the microbiome seems to be at least one of the ways that this association exists.”
To learn more about the potential relationship between diet, gut microbiota, and intestinal health, more research is needed. In particular, clinical trials are needed to test the links that identified in this cross-sectional study.
“Food frequency questionnaires can have hundreds of variables and microbiota data can have the same,” Swaminath explained, “and it’s hard to tell whether there’s really a meaningful signal or if it’s just part of the statistical noise.”
“So I think it’ll be interesting when we’re able to see more of the details of their data and methodology and then reproduce some of this in clinical trials,” he continued, “especially if people are put on these diets and we can see how the microbiota change moving forward in time.”
To follow up on their study, researchers at the University Medical Center Groningen are planning to conduct a trial to test the effects of a Mediterranean-style plant-rich eating pattern in people with Crohn’s disease.
Similar research is also underway in the United States, where investigators are comparing the effects of a Mediterranean-style diet and an eating pattern known as the Specific Carbohydrate Diet in adults with Crohn’s disease.
While research on gut microbiota and diet continues, Swaminath and Stefanski encourage patients with IBD to work with qualified health professionals to develop diet plans that works for them.
Some people with Crohn’s disease or UC develop strictures or narrowed segments in their intestines, which can make it difficult to pass bulky stools. Such patients might benefit from a low-fiber diet.
“Certain [foods] and ways of preparing them are better tolerated than others,” Stefanski said.
“Working with a [registered dietitian nutritionist] to personalize specific food choices is vital when trying to achieve more plant-based diets,” she added.
1. Written by Heather Cruickshank,
"The Mediterranean Diet Can Help Keep Your Gut Happy," Written 10/22/19,