There’s been a lot of buzz in recent years about the microbiome — the collection of microorganisms, including bacteria, that live in and on your body, especially in your gastrointestinal (GI) tract. Gut bacteria play a major role in your digestive system, and research increasingly points to them having important effects in other areas of the body. But especially since there are so many different types of bacteria that haven’t been studied in depth, the role of the gut microbiome in health and disease is still somewhat veiled in mystery.
That veil has now been lifted, just a little, by a new study that looked at how a person’s gut microbiome is tied to their risk risk of developing certain health conditions. The results make it clearer than ever before that when it comes to predicting our risk for diabetes and other diseases, the kinds of bacteria we have in our body are just as important to consider as the genes in our own cells.
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First large study to chart microbiome in detail
The study, published in the journal Nature Medicine, was based on a subset of participants in the Personalized Responses to Dietary Composition Trial (PREDICT 1) study — which was designed to examine the relationship between food intake and health by tracking participants’ diets, as well as health measurements, over several years. The microbiome part of the study involved 1,098 participants.
As noted in a Harvard Gazette article on the study — which was conducted, in part, by researchers at Massachusetts General Hospital (MGH) — the PREDICT 1 study had already demonstrated a relationship between a healthy, plant-based diet and lower risks for obesity, type 2 diabetes and cardiovascular disease before a single person’s gut microbiome was sequenced. But by looking at the relationship between diet, gut bacteria and disease, the researchers gained a deeper understanding of how all three are related.
“This study demonstrates a clear association between specific microbial species in the gut, certain foods and risk of some common diseases,” explains co-senior author Andrew Chan, MD, a gastroenterologist at MGH, in the article. “We hope to be able to use this information to help people avoid serious health problems by changing their diet to personalize their gut microbiome.”
Overall, the researchers found that the makeup of a person’s gut bacteria was strongly tied to their dietary habits, and that levels of different gut bacteria were strong predictors of markers of disease such as blood glucose levels, cholesterol and triglyceride levels, and body-mass index (BMI, a measure of body weight that takes height into account). In fact, the composition of a person’s gut bacteria was more closely tied to these health measurements than a person’s own genes — showing that the bacteria in our bodies are as much an active part of us as our own human cells.
Certain specific types of gut bacteria were linked to certain outcomes. For example, having high levels of Prevotella copri and Blastocystis species was linked to maintaining more stable, lower blood glucose levels after meals. Other types of bacteria were linked to lower levels of blood fats and fewer markers of inflammation after eating. These links were so strong that the researchers believe sequencing a person’s gut bacteria could help determine a person’s risk of diabetes or cardiovascular disease even before there are any other signs of this disease risk.
The researchers note that they were actually surprised to see such large, clear groups of “good” and “bad” types of bacteria when it comes to their links to diabetes, obesity and cardiovascular disease. Some of these bacteria are so poorly studied that they don’t even have a name yet.
A personalized diet prescription?
While it may be possible in the future to get a personalized eating plan based on a scan of your microbiome, right now researchers don’t have such a detailed understanding of the relationship between individual foods and specific bacteria types. But in broad terms, the relationship between what you eat and levels of “good” and “bad” bacteria is already fairly clear.
Levels of “good” bacteria — those tied to the lowest risk for diabetes, cardiovascular disease and obesity — were highest in people who ate a variety of plant-based foods. You’ve probably read about the benefits of a healthy, plant-based diet before — but the study makes it strikingly clear how much our dietary choices affect what’s going on in our guts, and how critical these bacteria are when it comes to our health.
Want to learn more about the role of gut bacteria in health? Read “Diabetes and the Microbiome.”