Background
The Dietary Guidelines for Americans advise on dietary intake to meet nutritional needs, promote health, and prevent disease. Diet affects the intestinal microbiota and is increasingly linked to health. It is vital to investigate the relationships between diet quality and microbiota to better understand the impact of nutrition on human health.
Goals
This study aimed to investigate differences in fecal microbiota composition in adults from the American Gut Project based on their adherence to the Dietary Guidelines for Americans.
Methods
This study was a cross-sectional analysis of 16S sequencing and food frequency data from a subset of adults (n = 432; age = 18-60 years; 65% female, 89% white) participating in the American Gut Project of collective collaboration. The Healthy Eating Index-2015 evaluated compliance with the recommendations of the Dietary Guidelines. The cohort was divided into tertiles based on Healthy Eating Index-2015 scores, and differences in taxonomic abundance and diversity were compared between individuals with high and low scores.
Results
The mean total score of low-scoring adults (58.1 ± 5.4) was comparable to the reported score of the average American adult (56.7). People with high scores for the Total Score and components related to vegetables, grains, and dairy products had greater alpha diversity than people with low scores.
High scores on the fatty acid component had lower alpha diversity than low scores (95% CI: 0.35, 1.85). A positive log difference in the abundance of plant carbohydrate-metabolizing taxa in the families Lachnospiraceae and Ruminococcaceae was observed in the high-score tertiles for the total score components, vegetables, fruits, and grains (Benjamini-Hochberg; q < 0.05).
Conclusions
Adults with higher adherence to the Dietary Guidelines demonstrated greater diversity in their fecal microbiota and a greater abundance of bacteria capable of metabolizing complex carbohydrates, providing evidence for how the Dietary Guidelines support the gut microbiota.
Comments
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. Researchers conclude that following the Dietary Guidelines for Americans (DGA) promotes a gut microbiota composition that may support overall health.
“Currently, there is no definition of a ’healthy’ microbiome. Understanding how diet can influence the structure of the gut microbiota is important so we can make recommendations on dietary approaches,” says Alexis Baldeon, a doctoral student in the Division of Nutritional Sciences (DNS) , part of the Faculty of Agricultural Sciences, of Consumer and Environmental Studies at U of I. Baldeon is the lead author of the paper, published in The Journal of Nutrition .
The microbiota consists of trillions of microorganisms that live in the gastrointestinal tract. They contribute to many physiological processes, and a diverse gut microbiota may promote resilience to alterations that could contribute to disease.
The researchers analyzed data from the American Gut Project , a large collaborative database that includes fecal samples from thousands of people in the US . Eating Index (HEI), which is based on the DGA.
The group with the highest total HEI score, which indicates the highest compliance with the DGA, had the greatest diversity of gut microbiota, as well as a greater presence of bacteria that contribute to beneficial functions such as fiber fermentation, Baldeon says.
“The gut microbiota is really good at breaking down fiber, which is important because humans can’t digest fiber. “Study participants with a higher quality diet had a higher abundance of bacteria involved in fiber metabolism,” she notes.
Historically, dietary guidelines and nutrient recommendations have not included considerations for the microbiota. But that could change in the future, says Hannah Holscher , associate professor in the Department of Food Sciences and Human Nutrition and co-author of the study.
“Our work provides clues about specific microbes that may be relevant to monitoring microbiota health and overall health,” Holscher says. “Having your microbiome composition analyzed is currently not part of a standard physical exam. Even if you sequenced your microbiome today, your doctor or dietitian wouldn’t be able to give you solid evidence-based recommendations from your results. But as we understand more about the interaction of diet, microbiota, and health, some gut microbes may become targets for our dietary recommendations. "Just as we currently make recommendations to reduce sodium to lower blood pressure or reduce saturated fat to lower LDL cholesterol, our goal is to make dietary recommendations to nourish beneficial gut microbes."
Health policy is also beginning to recognize the importance of the gut microbiome, researchers say. In fact, the latest DGA scientific report recognizes that evidence from diet and 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, outlined on MyPlate , remains the best strategy for your overall health, including nourishing your gut microbes.
The article , "Diet quality and fecal microbiota in adults in the American Gut Project," is published in The Journal of Nutrition [DOI: 10.1016/j.tjnut.2023.02.018 ].
In addition to Baldeon and Holscher, authors include Daniel McDonald, Antonio González, and Rob Knight.
This work was supported in part by the USDA National Institute of Food and Agriculture under grant Nutrition and the Gut-Brain Axis: Implications for Development and Healthy Aging (2019-38420-28973) and Hatch Project 1009249 (HDH), as well as the Margin of Excellence Program, Division of Nutritional Sciences, University of Illinois.
