Scientists know that the trillions of bacteria and other microbes that live in our gut play an important role in health, affecting the 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 together as our microbiomes, is largely determined by what we eat.
Analyzing the diets, health and microbiomes of more than a thousand people, the researchers found that a diet rich in wholesome nutrients promotes 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, encouraging intestinal microbes that were linked to poorer cardiovascular and metabolic health.
One critical factor was whether people ate foods that were highly processed or not. People who tended to eat minimally processed foods 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 cereals and processed meats, on the other hand, is associated with microbes associated with poor metabolic health.
“This goes back to the age-old message of eating as many wholesome and unprocessed foods as possible,” said Dr. Sarah E. Berry, a nutritionist at King’s College London and co-author of the new study, published Monday in Nature Medicine. . “What this study shows for the first time is the relationship between the quality of the food we eat, the quality of our microbiomes, and ultimately our health outcomes.”
The findings may one day help doctors and nutritionists prevent or perhaps even treat certain diet-related diseases by allowing them to prescribe personalized diets to people based on the unique composition of their microbiomes and other factors.
Many studies show that there is no one-size-fits-all diet. The new study, for example, found that while some foods are generally better for health than others, different people may have wildly different metabolic responses to the same foods, mediated in part by the types of microbes that reside in their gut.
“What we found in our study is that the same diet in two different individuals does not lead to the same microbiome and does not lead to the same metabolic response,” said Dr. Andrew T. Chan, co-author of a teacher. and a professor of medicine at Harvard Medical School and Massachusetts General Hospital. “There are many variations.”
The new findings come from an international study of personalized nutrition called Predict, which is the world’s largest research project designed to look at individual food reactions. Launched in 2018 by British epidemiologist Tim Spector, the study followed more than 1,100 predominantly healthy adults in the United States and the United Kingdom, including hundreds of identical and non-identical twins.
Researchers have collected data on a wide range of factors that affect metabolism and disease risk. They analyzed participants’ diets, microbiomes and body fat. They took blood samples before and after meals to check their blood sugar, hormone, cholesterol and inflammation levels. They observed their sleep and physical activity. And for two weeks, they had them wear continuous glucose monitors that monitored their blood sugar responses to various meals.
Researchers were surprised to find that genetics played only a minor role in shaping a person’s microbiome. Identical twins have been found to share only 34 percent of the same gut microbes, while unconnected people share about 30 percent of the same germs. Instead, the composition of each person’s microbiome appears to be controlled more than what they eat, and the types of microbes in their gut play a strong role in their metabolic health.
Researchers have identified groups of so-called good gut bugs that 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 whole milk yogurt. They also found groups of “bad” intestinal bugs that are common in people who regularly consume foods that are highly processed. One common denominator among highly processed foods is that they usually contain very little fiber – a macronutrient that helps nourish good microbes in the gut, researchers say.
Among the “good” strains of intestinal microbes are Prevotella copri and Blastocystis, both associated with lower levels of visceral adipose tissue, which accumulates around internal organs and which increases the risk of heart disease. These microbes also improve blood sugar control, an indicator of diabetes risk. Other beneficial microbes are associated with reduced inflammation and lower spikes in blood fat and cholesterol levels after a meal, 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 the Wellcome Trust, a British non-profit organization, and several public health groups.
Dr Berry said the findings showed that by looking at microbiome profiles, they could identify people at high risk of developing metabolic diseases and intervene early. She and her colleagues are now planning a clinical trial that will test whether telling people to change certain foods in their diet can change the levels of good and bad germs in their gut and subsequently improve their health.
“We think there are a lot of small changes that people can make that can have a big impact on their health that can be mediated by the microbiome,” she said.