The study examines the role of diet in supporting a healthy gastrointestinal microbiota

We know that eating a healthy diet affects body weight, cholesterol levels, and heart health. A new study from the University of Illinois focuses on another component: the role of diet in supporting a healthy gastrointestinal microbiota. The researchers conclude that according to the Dietary Guidelines for Americans (DGA) a gut microbiota composition that can support overall health is maintained.

“Currently, there is no definition of a ‘healthy’ microbiome. It is important that we understand how diet may affect the structure of the gut microbiome so that we can make recommendations for dietary approaches,” a says Alexis Baldeon, a doctoral student in the Division of Nutritional Sciences (DNS), part of the College of Agricultural, Consumer and Environmental Sciences at the U of I. Baldeon is lead author of the paper, published in The Journal of Nutrition.

The microbiota is made up of the trillions of microorganisms that live in the gastrointestinal tract. They contribute to many physiological processes, and a diverse gut microbiota may promote resilience to perturbations that may contribute to disease.

The researchers analyzed data from the American Gut Project, a large crowd-sourced database that includes fecal samples from thousands of people across the U.S. Their study focused on data from a subset of 432 healthy people divided into three groups according to how closely they followed the Healthy. Eating Index (HEI), which is based on the DGA.

The group with the highest overall HEI score had the highest gut microbiota diversity, indicating the strongest compliance with the DGA, as well as the presence of more bacteria that contribute beneficial functions such as fiber fermentation, says Baldeon.

“The gut microbiota is really good at breaking down fiber, which is important because humans can’t digest fiber. Study participants with higher diet quality had a greater abundance of bacteria in fiber metabolism,” he notes. .

Historically, questions regarding the microbiota have not been included in dietary guidelines and nutrient recommendations. But that could change in the future, says Hannah Holscher, associate professor in the Department of Food Science and Human Nutrition at U of I and co-author of the study.

Our work provides clues about specific microbes that may be relevant to monitoring microbial and overall health. Testing your microbiome composition is not currently part of a standard physical exam. Even if you went out and sequenced your microbiome today, your doctor or dietitian would not be able to give you strong evidence-based recommendations from your results. But as we understand more about the interaction of diet, microbes and health, some gut microbes may become targets for our dietary recommendations. Just as we currently make recommendations to reduce sodium to lower your blood pressure or to reduce saturated fat to lower your LDL cholesterol, our goal is to make dietary recommendations to support beneficial gut microbes.”

Hannah Holscher, Associate Professor, Department of Food Science and Human Nutrition at U of I

Health policy is also beginning to recognize the importance of the gut microbiome, the researchers say. Indeed, the latest scientific report to the DGA acknowledges that evidence from diet-microbiota studies should be considered in future dietary recommendations.

Holscher and Baldeon note that their study supports current DGA recommendations for a diet rich in fruits, vegetables and fiber. Following those guidelines, laid out in MyPlate, is the best strategy yet for your overall health, including nourishing your gut microbes.


University of Illinois College of Agricultural, Consumer and Environmental Sciences

Journal reference:

Baldeon, AD, et al. (2023). Diet Quality and the Fecal Microbiota in Adults in the American Gut Project. The Journal of Nutrition.

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