Eating for You and Your Gut

The saying  “you are what you eat” highlights an important truth: good nutrition is key to health. Exciting research over the last 10 years adds that it’s not only “you” but “you and the trillions of microorganisms living in your gut” that are the key to connections between foods and health. This massive group of microorganisms in the gut, most of which are bacteria, is commonly known as the gut microbiota. The gut microbiota is involved in various bodily functions. These include functions from your intestines to your brain and have been associated with many diseases like heart disease, obesity, and cancer.

Many of the illnesses associated with the gut microbiota are also linked to poor diet. This means these microbial communities may play a role in how diet affects health. Diet-related diseases, such as heart disease, obesity, and diabetes, are very common in the USA. Most US adults are sick with at least one of these illnesses. On top of that, the leading causes of death stem from a poor diet. Therefore, there is great interest in understanding how to use diet to change the gut’s microbiota to treat and prevent disease.

         Long-term food habits are related to the overall structure of the gut microbiota. Still, short-term changes to food habits can also alter your gut microbiota. For instance, if you suddenly start eating only animal or vegetable products, you can cause microbiota changes  to appear within 24 hours. These microbiota changes result from the gut’s bacteria interacting with the nutrients found in the meals we eat. Some gut bacteria specialize in breaking down dietary fiber, a type of nutrient that humans cannot digest. When these gut bacteria break down dietary fibers, they produce molecules called short-chain fatty acids, or SCFAs. SCFAs provide energy for our intestinal cells and act as signals to other important organs. This is one example of how the gut microbiota regulates the effects of diet on health. 

         While it is valuable to understand the effect of single nutrients on the gut microbiota, it is also important to realize multiple nutrients are combined into foods that together form a meal. Nutrients are not consumed in isolation. It’s like listening to music — the chords from the guitar and the beat from the drums each play a role in the final product, but it’s the many instruments played together that create a song. Therefore, investigating the effects of everyday food choices is important. In fact, the Dietary Guidelines for Americans (DGA) are science-based recommendations to promote and sustain health, and they focus on the quality of food choices instead of individual nutrients. Studying food choices also makes it easier to make nutritional recommendations. This research is becoming increasingly important as scientists continue to understand the interactions between what we eat and our gut microbiota.

We conducted a study on how the gut microbiota of adults differs based on how well they follow the DGA. To do this, we selected 432 healthy adults from the American Gut Project. Healthy adults were defined as those not having a history of autoimmune, liver, or inflammatory bowel disease or diabetes. They also did not use any antibiotics in the past year. We chose healthy adults because they were less likely to have their microbiota altered by disease or antibiotics. This allowed us to investigate how diet was related to their gut microbiota without the influence of these other factors that are also known to impact the microbiota. We split the adults into three equal-sized groups according to how well their diet aligned with the DGA. One group of adults followed these guidelines the most (i.e., had the highest diet quality), another followed these guidelines the least (i.e., had the lowest diet quality), and one group was in the middle. The gut microbiota of the group with the highest diet quality was then compared to that of the group with the lowest diet quality. We hypothesized that we would find differences in their microbiota based on their differences in nutrition. In this study, adults with higher diet quality had greater gut microbiota diversity compared to those with lower diet quality. Greater gut microbiota diversity is important because scientists think that it may be a sign of healthy microbial communities. These results suggest that following the DGA may support a healthy gut microbiota.

Next, we wanted to know which bacteria were associated with diet quality. Identifying these bacteria helps paint a picture of what a gut microbiota could look like when you follow the DGA. Additionally, knowing how these bacteria are associated  with health and disease gives insight into the clinical implications of having more or less of these microorganisms in our gut. We found that the abundances of 19 bacteria were different between those that ate high vs. low-quality diets. Of these, 7 were more abundant in higher-diet-quality adults and 12 were more abundant in lower-diet-quality adults. Most of these bacteria belonged to the Lachnospiraceae and Ruminococcaceae families, which consume plant-based dietary fiber. This indicates that differences in the number of plant-based foods (e.g. fruits, vegetables, legumes, and nuts) consumed might be the driving force behind the difference in abundance of these microorganisms.

         The microbial inhabitants in our gut change based on our daily food choices and might play a role in the complex connections between diet and health. Our study showed that the gut microbiota of adults differed based on how closely they followed the Dietary Guidelines for Americans (DGA). The overlap in findings between our study and previous diet-microbiota research is encouraging. However, our work only looked at a single point in time. Therefore, we cannot know for certain if the gut microbiota differences were purely due to diet quality or if other factors also caused the differences we observed. Ultimately, more research is needed to reach a point where we can use food to modify the gut microbiota and improve people’s overall health. This work is more important now than ever due to the unfortunate landscape of health and nutrition in the United States today.

Written By: Alexis D. Baldeon & Dr. Hannah Holscher

Academic Editor: Biologist

Non-Academic Editor: Retiree 

Original Paper

• Title: Diet Quality and the Fecal Microbiota in Adults in the American Gut Project

• Journal: The Journal of Nutrition

• Date Published: 22 February 2023

Please remember that research is done by humans and is always changing. A discovery one day could be proven incorrect the next day. It is important to continue to stay informed and keep up with the latest research. We do our best to present current work in an objective and accurate way, but we know that we might make mistakes. If you feel something has been presented incorrectly or inappropriately, please contact us through our website.