Researchers found that marathon runners have more bacteria that improves exercise ability.

The study found a bacterium called Veillonella changed the most before and after in human athletes that ran a marathon.

In another group of ultramarathon runners and Olympic trial rowers, the researchers found that the activity of Veillonella genes involved in processing lactate increased after exercise.

The Harvard University and Joslin Diabetes Center team gave a group of mice the Veillonella bacteria taken directly from the marathon runners. They gave another group of mice a different type of bacteria that can’t use lactate. Mice given the Veillonella ran on average 13% longer on a treadmill.

The researchers also showed that lactate injected into the bloodstream of mice crossed into the gut. This result suggests that gut bacteria would be able to access the excess lactate produced by exercise.

Lactate is produced by the body during exercise and Veillonella can use lactate as an energy source.

If lactate builds up in the bloodstream without being used as an energy source it causes muscles to feel weak and tired.

“Having increased exercise capacity is a strong predictor of overall health and protection against cardiovascular disease, diabetes, and overall longevity,” says Dr. Aleksandar D. Kostic at the Joslin Diabetes Center.

These findings suggest strategies, such as a probiotic supplement, that might help boost the ability to do meaningful exercise and therefore protect against chronic diseases.

Researchers say more studies are needed to understand how to use this information to alter metabolism to affect performance and health outcomes.