Researchers also found that consuming sugary drinks, snacking, eating a lot of carbohydrates, and drinking whole milk are correlated with a less diverse microbiome.
“In total we found 60 dietary factors that influence diversity,” said Alexandra Zhernakova, a researcher at the University of Groningen in the Netherlands and the first author on the study, in a statement. “But there is good correlation between diversity and health: greater diversity is better.”
Your microbiome is made of up of the community of mostly beneficial bacteria, fungi and viruses that live on and in your body.
Although these microscopic organisms do not share your DNA, you need them to help you process food and regulate your immune system.
In addition, recent studies suggest that the makeup of a person’s microbial community can also play a role in mood disorders, obesity, and other diseases including irritable bowel syndrome.
But the study of the microbiome is relatively new, and scientists are still working out exactly what a healthy microbiome looks like.
On Thursday, Zhernakova and her colleagues at the University of Groningen released the first results of a large-scale study that analyzed the microbial composition in the guts of more than 1,100 people.
The study, published in the journal Science, revealed 126 factors that are correlated with changes in the makeup of an individual’s microbial community. These include 60 dietary factors, 12 diseases, 19 drugs and 4 smoking categories.
“To our knowledge, this is the first study to systematically assess such a broad range of host and environmental factors in relation to gut microbiome and at such a large scale,” said Jingyuan Fu, an associate professor at the University of Groningen and one of the authors of the study.
The researchers analyzed stool samples of 1,135 Dutch participants in the Lifelines-DEEP study. All participants were from the northern part of the Netherlands.
The authors say one of the strengths of the study is the care they took to make sure all samples were handled in exactly the same way.
Participants in the study collected their own stool samples at home and then immediately put them in the freezer. No more than a few days later, the samples were transported to labs at the university by students who used dry ice to keep them cold. Once they were at the lab, the samples remained frozen until they were processed by researchers.
Fu explained that there were two advantages to this method: It ensured none of the bacteria had a chance to grow or change from the time the sample was collected to the time it made it to lab. Also, it ensured that all samples were processed the same way.
“In situations where samples are sent by post at room temperature, the time of the delivery for every sample is different,” she said. “That situation can lead to the growth of bacteria during transportation and adds additional ‘noise’ to the findings.”
After analyzing the samples and comparing them with other collected in the Lifelines-DEEP study, the scientists found that consuming fruits, vegetables and yogurt positively influenced microbial diversity in the gut.
In addition, drinking tea, wine, coffee and buttermilk was also correlated with more diversity.
On the flip side, sugary sodas and savory snacks were associated with lower levels of diversity. So was having irritable bowel syndrome and smoking during pregnancy.
The authors also report that women tend to have more microbial diversity than men, and older people have greater microbial diversity than younger people.
The study does not address exactly why certain foods and behaviors influence what microbes populate a person’s gut. However, the researchers report that people who eat a lot of yogurt and buttermilk had higher levels of the bacteria that are used in the making of those foods in their guts.
“For more complex food, such as fruits and vegetables, we don’t know the answer,” Fu said. “We can suggest that changes in fiber content and carbohydrate composition are playing a role, but this should be studied in detail in respect to every food item.”
Fu also outlined many areas of research that the group hopes to tackle next. She said they are hoping to expand the study to 10,000 participants. They also want to collect samples from the nose and throat, and are hoping to put a longitudinal study together.
She added that in the future, we might all be providing our doctors with stool samples to help better understand our health.
“It is becoming more and more clear that the gut microbiome serves as a sort of fingerprint that captures all kinds of signals about host health,” she said.