Although no two people have identical microbiomes, the researchers hypothesized for their new study that elite athletes’ guts must contain similar bacterial species that help them perform and also recover.

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Great athletes not only have heart, they have guts — special guts. Boston Marathon runners and Olympic athletes have higher than usual amounts of Veillonella bacteria in their digestive tract following races, a new study finds. When mice consumed the Veillonella, their treadmill runs were better than those of mice not given the same bacterial diet, according to new research published Monday in the journal Nature Medicine.

Our digestive system, a group of organs that includes the stomach and colon, harbors nearly 100 trillion bacteria. Collectively known as the “gut microbiome,” these bacteria help our bodies break down complex carbohydrates and starches, while also producing vitamins and hormones. Gut flora, which collectively weigh up to four and a quarter pounds and contain more genes than our actual genome, have escaped observation until recently, when scientists began to study and sequence the 500 to 1,000 different species of bacteria that inhabit each of us.

Although no two people have identical microbiomes, the researchers hypothesized for their new study that elite athletes’ guts must contain similar bacterial species that help them perform and also recover.

Searching the ‘poo’ of athletes for answers

To test their theory, the researchers analyzed stool samples of 2015 Boston Marathon runners throughout the week before, as well as the week after the race, to identify possible fluctuations in bacterial species within the athletes’ microbiomes. Post-marathon, Veillonella genus bacteria increased substantially compared to other bacteria in the competitors’ guts, they found. The natural function of this bug is to break down lactic acid, which is produced by the body during intense exercise and is known to lead to muscle fatigue and soreness. Veillonella, then, could potentially help alleviate this soreness, the researchers believe.

Next, the researchers isolated a strain of Veillonella atypica from the athletes’ poo and fed it to mice. Treadmill tests showed this bacteria-enhanced diet boosted the animals’ performance by 13% compared to mice not given Veillonella. The lactate, produced when the mice exercised, was metabolized by the bacteria after which by-products of this chemical process crossed into the circulatory system and resulted in a performance boost, the new research showed.

A potential motivator — and conflict of interest — for the study scientists is their biotech company, FitBiomics Inc., which seeks to commercialize performance-enhancing probiotics based on bacterial “leads” they find hidden within the microbiomes of elite athletes.

Creating smart probiotics could not only improve the performance of next generation athletes but also improve the health of patients with certain metabolic disorders or diseases, such as diabetes, the researchers believe. They will continue their microbiome explorations as they work towards translating unique bacterial characteristics into probiotic treatments.

A skeptical view

Professor Timothy Read of Atlanta’s Emory University School of Medicine told CNN that previous studies have already shown that Veillonella exists in higher abundance in the stools of athletes. The new study takes this one step further by suggesting this bacterial species may be enriched “due to the breakdown of lactate in the gut produced by exercise,” said Read, who was not involved in the research.

A weakness of the study is the fact that the “only direct evidence” that Veillonella positively affects exercise potential are treadmill experiments in mice, noted Read. Add to that the proof of enhanced athletic performance being due to the metabolic properties of Veillonella comes from a small number of samples, he said. Though the study is “part of a trend of interesting papers” that illustrate striking effects of individual microbes, it only serves as a “preliminary” report and requires some skepticism, said Read.

“Life events such as diseases can change microbiomes,” said Read, who studies the role microbes play in the human body to affect health, either as pathogens or as members of the microbiome. How to permanently change our microbiome to improve our health is “an active area of research,” he said. “Our guts can vary to a certain extent at short time frames but there is certain resilience of individual patterns.”

Elizabeth Corwin, associate dean of research at Emory University School of Nursing, believes the new research is both “intriguing and comprehensive.” Corwin, who was not involved in the new study, said it indirectly relates to her own work with gut microbiomes of pregnant women.

Research has shown that the bacterial composition in the guts of women “adapts during a time of high energy demand — pregnancy — to more efficiently harvest calories from the mother’s diet,” she explained: Most women see a return “to the non-pregnant state after delivery, suggesting that various types of situations that increase energy utilization may stimulate changes in microbial composition.”