TIME Research

Exercise Helps Your Gut Bacteria: Amazing, Overblown, or Plain Incorrect?

Debate over a new study looking at the difference in gut bacteria among athletes serves as a reminder of the delicacy of new fields of science

A new study out this week has experts in the field raising their eyebrows. After sampling the gut bacteria of 40 rugby players, researchers from the University College Cork in Ireland reported that exercise may improve the diversity of microbes that make up the microbiome. The microbiome is a relatively new area of scientific inquiry, and researchers think the bacteria that live in and on us may play a much larger role in our overall health that we currently have proof for. But even within the field, there’s concern that we might be getting a little ahead of ourselves.

In the latest research, scientists concluded this:

The results provide evidence for a beneficial impact of exercise on gut microbiota diversity but also indicate that the relationship is complex and is related to accompanying dietary extremes.

And in a section of their research explaining the significance of their findings, the authors write: “This is the first report that exercise increases gut microbial diversity in humans.”

The authors couch their finding by noting that diet is part of the relationship, but it’s the first part of their conclusion—that working out improves your gut bugs—that has skeptics taking to Twitter to express concern about the findings. At issue is the fact that diet likely plays a very large part in the findings, and it’s not news to scientists that what people eat affects their microbiome. When it comes to exercise, meanwhile, the connection was correlational—meaning the researchers found that rugby players both worked out a lot and happened to have diverse gut bugs when compared to a control group—but it did not in any way prove that one caused the other.

The backlash among science writers and researchers brings up an interesting debate about how we present many scientific findings, particularly in nascent fields like this one. “This is what I do. I love this type of work,” says Jonathan Eisen, a professor at University of California, Davis, focusing on evolution and ecology of microbes and genomes. “I just don’t want people to overstate what they are doing because I think that’s a longterm risk to the field.” Eisen runs a blog called “The Tree of Life” on which he fairly regularly gives out the “Overselling the Microbiome Award” (where TIME has been called out in the past). This week, that award went to the exercise study. Though he sees great promise in researching the microbiome, Eisen says it irks him when studies are blown out of portion both by scientists and the press.

Dr. Martin J. Blaser, author of the recent book ‘Missing Microbes’: How Antibiotics Can Do Harm, has a different take. “It’s kind of a brand new field,” says Blaser. “If you claim that the microbiome has cured cancer, that certainly would be hype,” he says. “But could it one day? Could our knowledge one day affect the treatments of many cancers and the preventions and diagnoses of many cancers? Yes.”

He adds: “Maybe nothing is ready for prime-time yet, but I won’t be surprised if research in this field changes medicine and healthcare dramatically.” Though Dr. Blaser does not hide his sincere excitement and optimism for the field, he acknowledges that we need to remember how new it is. “We are in the early stages of a scientific revolution. But it’s early stages,” he says. “We have to recognize that it’s all promise, but I think reasonable promise.”

I’m not sure how Eisen will rate this post, but as microbiome fervor continues to swell—and I expect it will—it’s worth taking a moment to be critical while still celebrating an area of science that’s honestly, pretty awesome.

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