MONDAY, June 24, 2019 (HealthDay News) -- Elite athletes' grueling training regimens may pay off in an unexpected way: The exercise seems to boost levels of a type of gut bacteria that enhances athletic prowess.
Researchers found that the bacteria Veillonella were much more common in the guts of marathoners, compared to sedentary people. And the bugs rose in abundance soon after the runners finished a race.
To see what the bacteria might be doing, the researchers turned to a lab experiment. They fed mice pellets that contained Veillonella taken from one of the marathoners. The result? The bug boosted the animals' endurance on a treadmill run.
The research, published June 24 in Nature Medicine, is the latest to delve into the gut microbiome -- the vast collection of bacteria and other microbes that naturally dwell in the digestive tract.
A growing number of studies have linked the makeup of the gut microbiome to the risks of various health conditions, including asthma, type 1 diabetes, obesity, and even dementia. In general, research suggests, the more diverse your gut bacteria are, the better.
The new study took a different approach: It asked whether there's something unique about the gut bacteria of "ultra-healthy" people, said senior researcher Aleksandar Kostic, of Joslin Diabetes Center and Harvard Medical School, in Boston.
His team started with stool samples from 15 Boston Marathon runners, taken almost daily the week before and after the race. Samples were also taken from 10 sedentary people.
On average, the study found, the athletes harbored large amounts of Veillonella -- especially soon after the marathon.
The subsequent mouse study showed the bacteria improved the animals' stamina on a treadmill run by about 13% -- versus mice that were fed a different type of gut bacteria.
What's interesting about Veillonella, Kostic said, is that it uses lactic acid as its "preferred source" of energy. During strenuous exercise, the muscles produce lactic acid.
Kostic said his team suspects a "positive feedback loop" is at work: Elite athletes are constantly producing a lot of lactic acid, which sets up a friendly environment for Veillonella to thrive. The bacteria, in turn, support greater exercise capacity.
How, exactly, are the bugs doing that? The researchers found that a fatty acid called propionate might be key.
Veillonella bacteria, it seems, convert lactic acid into propionate. So Kostic's team tried infusing lab mice with the fatty acid, then running the treadmill test again. It turned out that propionate boosted the animals' endurance.
"To my knowledge, this is the first study showing a direct symbiotic mechanism between the microbiome and the host," Kostic said.
Dr. Emeran Mayer is a professor at the University of California, Los Angeles School of Medicine and author of the book "The Mind-Gut Connection."
He was impressed by the study's combination of human and lab data.
"These findings are pretty convincing," said Mayer, who wasn't involved with the study.
But they do not prove that athletes can gain anything from probiotic supplements of Veillonella -- which, Mayer noted, do not exist, to his knowledge.
Kostic agreed, saying that a clinical trial would be necessary to prove that. He said his primary interest is medical use: Could the bacteria improve exercise capacity in non-athletes -- enough to curb their risks of heart disease or other ills?
But Mayer sounded a cautionary note about probiotic supplements in general: Tinkering with levels of one bacteria in the gut might have unintended effects. The gut microbiome is complex and "does not act in isolation," he noted -- and instead seems to interact with systems throughout the body.
Mayer said it would be interesting to see whether particular diet factors -- along with exercise -- affect the natural abundance of Veillonella in the gut.
There is still a chicken-and-egg question, according to Mayer: Did elite athletes first gain their Veillonella abundance through hard training? Or did other factors -- such as genes or early-life environment -- give them a Veillonella boost, which helped their exercise capacity?
Kostic agreed that the answer isn't clear. But, he added, the two scenarios are not "mutually exclusive," and both could theoretically play a role in Veillonella abundance.
The American Gastroenterological Association has more on the gut microbiome.