A compelling new study has found increased volumes of a certain species of gut bacteria in marathon runners following the completion of an event. This species was found to metabolize exercise-induced lactate into propionate, a compound that may increase exercise capacity, pointing the way to a potential performance-enhancing probiotic in the future.

The new research started off with an intriguing proposition. We know exercise can directly alter the composition of our microbiome, but can these bacterial alterations influence athletic performance?

The first step in the study was to investigate the microbiomes of elite athletes. Fifteen runners were recruited, all who were to take part in the Boston Marathon. The subjects delivered stool samples daily for a week leading up to the marathon, and for a week following the event.

Levels of one particular bacterial strain, called Veillonella atypica, were found to significantly increase in the runners' microbiomes following the marathon. Even more curiously, this specific bacterial species was detected in greater abundance in elite marathon runners in general, compared to sedentary individuals in a control group. The big detail that really piqued the researchers' interest, however, was that fact that Veillonella is a bacteria with a unique preference for lactic acid, or lactate, as its preferred energy source.

"This set up a hypothesis ... is it possible a bacteria in the gut is somehow using systemic lactate produced by the muscles during exercise," says Aleksandar Kostic, an author on the new study. "Is this the reason why it's blooming after a marathon? And is it possible this somehow has a beneficial effect?"

To investigate any potential performance-enhancing effects from the bacteria, a mouse treadmill study was set up, comparing animals propagated with Veillonella against animals propagated with a species of bacteria not known to metabolize lactate. Impressively, animals in the Veillonella group displayed a 13 percent increase in time-until-exhaustion on the treadmill compared to the control mice.

Kostic and his team did not think it was merely this straightforward clearing of lactate that accounted for the increase in athletic performance. Looking deeper it was discovered that Veillonella converts lactate into a compound called propionate. A subsequent mouse study administered propionate to a cohort of animals via enema, revealing propionate alone was enough to account for much of the increased exercise capacity seen in the animals colonized with Veillonella.

None of this means propionate is effectively a new secret performance-enhancer for athletes. When taken orally the compound is primarily metabolized in the liver, and Kostic suggests there is something unique about the way Veillonella produces propionate in relation to lactace produced by physical exercise that is key to the subsequent increase in exercise capacity.

"Propionate is a key short-chain fatty acid produced by the gut microbiota, Veillonella being just one human gut bug that produces it," Kostic explains to New Atlas in an email. "I think there is something important to Veillonella producing propionate 'at the right place and at the right time,' in the colon in response to an influx of propionate."

How this newly identified mechanism could be increasing exercise capacity and performance is perhaps the biggest question raised by this new study. Kostic readily admits this is still a mystery, but uncovering the details of this mechanism is the next step for the researchers.

"One hypothesis we have is that propionate is known to be a bioenergetic molecule for gut epithelial cells, so we want to test whether it could also fuel muscles," says Kostic. "Also, propionate is known to have anti-inflammatory effects, so we are also wondering whether it could directly reduce muscle inflammation and promote increased exercise that way."

So, is something like a performance-enhancing probiotic cocktail administered to athletes before exercise a realistic future proposition?

Kostic says this is certainly possible, and while his personal interest in the work is in the development of therapeutics that can enhance exercise capacity in patients at risk for diabetes and cardiovascular disease, some of his key collaborators on the study are looking more closely at how microbiome alterations could act to improve performance in elite athletes.

Kostic and other key members of the research team, including Jonathan Scheiman and influential geneticist George Church, have founded a company called FitBiomics. The company is more focused on developing commercial probiotic outcomes, so if future avenues for this research do prove successful, there could be a performance-enhancing probiotic on the market.

A lot more hurdles need to be cleared before this happens of course, not the least of which would be clear evidence that this potential performance-enhancing mechanism can be effectively manipulated in humans. So don't go hunting down Veillonella bacteria as your secret exercise enhancer just yet.

The new study was published in the journal Nature Medicine.