Scientists know that the billions of bacteria and other microbes that live in our gut play an important role in health, and this affects our risk of developing obesity, heart disease, type 2 diabetes and a wide range of other conditions. But now a large new international study has found that the composition of these microorganisms, known as our microbiomes, is largely shaped by what we eat.
By analyzing the diets, health and microbiomes of more than a thousand people, researchers have found that a diet rich in nutrient-dense, whole foods supports the growth of beneficial microbes that promote good health. But eating a diet full of highly processed foods with added sugars, salt and other additives had the opposite effect, promoting intestinal microbes linked to poorer cardiovascular and metabolic health.
The researchers found that what humans ate had a more powerful impact on the composition of their microbiomes than their genes. They also discovered that a variety of plant and animal foods are linked to a more favorable microbiome.
One critical factor was whether people ate foods that were heavily processed or not. People who tended to eat foods that were minimally processed, such as vegetables, nuts, eggs, and seafood, were more likely to contain beneficial intestinal bacteria. Consumption of large amounts of juices, sweetened beverages, white bread, refined grains and processed meats, on the other hand, was associated with microbes associated with poor metabolic health.
“It goes back to the age-old message of eating as much whole and unprocessed food as possible,” said Dr. Sarah E. Berry, a nutritionist at King’s College London and co-author of the new study, which has been published. Monday in Physical Medicine. “What this research shows for the first time is the relationship between the quality of the food we eat, the quality of our microbiome and ultimately our health outcomes.”
The findings could one day help doctors and nutritionists prevent or even treat some diseases related to diet, so that they can prescribe personalized diets to people based on their unique microbiome and other factors.
Many studies suggest that there is no uniform diet that works for everyone. For example, the new study found that while some foods were generally better for health than others, different people may have different metabolic responses to the same food, mediated in part by the types of microbes that live in their gut.
“What we found in our study was that the same diet in two different individuals does not lead to the same microbiome, and it does not lead to the same metabolic response,” said Dr. Andrew T. Chan, a co-author of the study and a professor of medicine at Harvard Medical School and Massachusetts General Hospital. “There’s a lot of variation.”
The new findings stem from an international study on personalized nutrition called Predict, which is the world’s largest research project designed to look at individual responses to food. The study, started in 2018 by British epidemiologist Tim Spector, followed more than 1,100 mostly healthy adults in the United States and Britain, including hundreds of identical and non-identical twins.
The researchers collected data on a wide range of factors that influence metabolism and disease risk. They analyzed the participants’ diets, microbiomes and body fat. They took blood samples before and after meals to look at their blood sugar, hormones, cholesterol and inflammation. They monitored their sleep and physical activity. And for two weeks, they had to wear continuous glucose monitors to track their blood sugar responses to different meals.
The researchers were surprised to discover that genetics played only a small role in the formation of a person’s microbiome. Identical twins were found to share only 34 percent of the same gut microbes, while unrelated people shared about 30 percent of the same microbes. It seems that the composition of each person’s microbiome is more driven by what they have eaten, and the types of microbes in their intestines have played a strong role in their metabolic health.
The researchers identified clusters of so-called good intestinal bugs, which are more common in people who eat a varied diet rich in high-fiber plants – such as spinach, broccoli, tomatoes, nuts and seeds – as well as minimally processed animal foods such as fish and full-fat yogurt. . They also found clusters of “bad” intestines that were common in people who regularly consumed a lot of processed foods. A common denominator among highly processed foods is that they contain very little fiber, a macronutrient that helps feed good microbes in the gut, the researchers said.
Among the ‘good’ strains of intestinal microbes were Prevotella copri and Blastocystis, both of which are associated with lower levels of visceral fat, the species that accumulate around internal organs and which increase the risk of heart disease. It appears that these microbes also improve blood sugar control, an indication of diabetes risk. Other beneficial microbes have been associated with reduced inflammation and lower increases in blood fat and cholesterol after meals, all of which play a role in cardiovascular health.
The new study was funded and supported by Zoe Global, a health science company, as well as by the Wellcome Trust, a UK non-profit organization, and various public health groups.
Dr. Berry said the findings suggest they can identify people at high risk of developing metabolic diseases by looking early at microbiome profiles. She and her colleagues are now planning a clinical trial that will test whether people can change specific foods in their diet, change the levels of good and bad microbes in their intestines and thus improve their health.
“We think there are very small changes that people can make that can have a huge impact on their health that can be mediated by the microbiome,” she said.