They’re skinnier and swifter than most people. Now, a new study says marathoners may have different bugs in their stomachs that help them run.

Researchers from Boston’s Joslin Diabetes Center found that a bacteria, Veillonella, is present in the guts of elite runners that is not found in the guts of sedentary people.

They believe that the bacteria metabolizes the lactic acid produced by the muscles during exercise and converts it into propionate, a short chain fatty acid. The human body then utilizes that propionate to improve its exercise capacity, the center said in a statement.

The results, based on samples taken from both Boston Marathon runners and sedentary people in 2015, were reported recently in the journal Nature Medicine.


The researchers said they believed they had found a symbiotic relationship between microbes and their human hosts.

“It’s very clear. It creates this positive feedback loop. The host is producing something that this particular microbe favors. Then in return, the microbe is creating something that benefits the host,” Joslin researcher Aleksandar D. Kostic, a co-author of the paper, said in a statement. “This is a really important example of how the microbiome has evolved ways to become this symbiotic presence in the human host.”

Kostic said the research could one day lead to a probiotic supplement that will increase people’s “ability to do meaningful exercise and therefore protect them against chronic diseases including diabetes.”

Why not just take a pill full of propionate? Researchers said they believed it would be broken down by digestive juices before taking effect.

Kostic said in an e-mail that “based on our data, the composition of the microbiome might have an influence on exercise capacity, therefore ‘tuning’ your microbiome (for example, by taking a probiotic supplement of Veillonella) could increase your exercise capacity.”


He emphasized that the possible probiotic would be a “long-term goal or best-case scenario,” and it would take years for further testing to see whether such a probiotic would work.

Martin Finucane can be reached at martin.finucane@globe.com