Most of the literature on the microbiome focuses on its contribution to illness and disease. We shouldn't forget bacteria have co-evolved with humans in symbiosis and are likely critical to health and wellness.

I came across an interesting study in Nature Medicine, Meta-omics analysis of elite athletes identifies a performance-enhancing microbe that functions via lactate metabolism. Researchers at Harvard linked a specific strain of gut bacteria to a 13% increase in athletic performance. Before you get too excited, the study was in mice. Here is what they did.

First, the scientists collected and compared the stool of Boston Marathon runners and sedentary individuals. Runners had higher levels of Veillonella than the non-runners. The marathon runners showed significant increases of Veillonella after exercise.

The scientists then transferred Veillonella from humans into mice. They introduced a different bacteria into other mice as controls. The mice receiving the Veillonella could run for 13% longer than the controls. Interesting!

What is the mechanism? While most gut bacteria ferment carbohydrates, Veillonella uses lactate as its "food source." Lactate, a by-product of energy production in the muscle (and elsewhere in the body), is produced during exercise. The body also produces large quantities of lactate during illness and injury. When the production of lactate exceeds elimination, lactate builds in the muscle, limiting performance. Interestingly, the enhanced athletic performance did not come from Veillonella serving as a lactate "sink." Instead, the benefits seem to derive from the production of propionic acid, a short-chain fatty acid.

The lactate produced during exercise crossed over from the circulation into the gut. The lactate was then converted into propionic acid by the Veillonella. The propionic acid then crossed back from the gut into the circulation. Propionic acid (and other short-chain fatty acids such as butyric acid) have many effects on the human body, including anti-inflammatory activity.

The impact and mechanism of action of Veillonella still has to be replicated in humans. The scientists conducting this study have already started a company to commercialize probiotic cocktails containing Veillonella. I am wary of probiotic supplements. Here is why.

After reading the study, several thoughts came to mind:

• Before the science is ironed out in humans, will athletes "dope" using Veillonella as a performance enhancer? Should (or can) the bacteria be detected in competitors (e.g., at the Olympics or Tour de France)?

• If microbial doping does take place, how long would the effect last? Knowing what I know about the microbiome, my suspicion is not long.

• Could Veillonella have a role in the treatment of sepsis and other critical illness? Although lactate is a by-product of a serious problem in critical illness (a sign, not the cause), it does have direct effects on physiology (e.g. impacting the contraction of the heart). Might Veillonella play a role in the management of critically ill patients?

Like all physiological processes, the story promises to be complicated. Veillonella is likely only a small piece of a much larger puzzle, but the preliminary findings are intriguing.