Abstract Veillonella atypica within the human gut converts lactate to propionate to improve marathoners’ endurance.

The study of the human gut microbiome and its symbiotic relationship with human health has often focused on various phyla of bacteria and their association with healthy and disease states. For example, the microbiomes of obese individuals have been found to differ in proportion of beneficial bacteria from those of lean people, and transplant of intestinal flora from obese to lean mice has been shown to trigger obesity. In this study, Scheiman et al. sought to study the microbiomes of athletes with exceptional endurance, specifically 15 individuals who completed the 2015 Boston Marathon.

Controlling for differences in diet, medications, weight, and other potential confounding factors, metagenomic analysis performed on daily stool samples demonstrated an increase in Veillonella bacteria in the days following completion of the marathon. Veillonella atypica was successfully cultured from the stool samples from the marathoners. Unlike other anaerobes, Veillonella atypica harbor a complete pathway for the metabolism of lactate through the tricarboxylic acid cycle to produce the short chain fatty acid propionate. Propionate can increase energy expenditure in individuals, even in a fasting state. Because the depletion of oxygen from muscle cells during a workout triggers a switch to anaerobic metabolism, the consumption of glucose results in the accumulation of lactate rather than carbon dioxide and water. In many athletes, lactate buildup is associated with discomfort.

To determine whether Veillonella atypica was enhancing athletic performance, a strain cultured from one of the runners was inoculated into mice via oral gavage. The authors observed improvements in the duration mice could run on a treadmill before exhaustion. They further showed that radiolabeled lactate was rapidly cleared from the serum of mice inoculated with Veillonella atypica. Finally, delivery of intrarectal propionate to mice without Veillonella atypica inoculation resulted in similarly improved treadmill run times.

Scheiman et al. concluded that the enrichment for Veillonella atypica is a consequence of selection for lactate-metabolizing bacteria in the low pH environment following anaerobic workouts. Although it is unlikely that fecal transplants would be considered as a performance-enhancing treatment of choice for elite athletes, the conversion of lactate to propionate emphasizes the importance of the Veillonella atypica—human symbiosis for endurance. Validation in the form of controlled studies would be needed to confirm whether intrarectal propionate directly improves athletic performance in humans.