What comes to mind when you think of the relationship between nutrition and athletic performance? Perhaps protein for muscle development or carbohydrates for glycogen storage? You may consider fat for low-intensity activity and carbohydrates for high-intensity activity. You may focus more on hydration or total caloric intake and its relationship on hormone levels. But what about the gut microbiota and fiber? This recent paper highlights current evidence exploring the relationship between the gut microbiota and exercise (primarily aerobic).
The gut microbiota consists of approximately 40 trillion bacteria, viruses, archaea, and fungi. It plays a large role in our metabolic functions and immunity. We are starting to compile evidence that suggests it may influence our exercise capacity, tolerance, and performance. Observational studies show athletes have greater diversity, an enrichment of beneficial taxa, and more fecal short-chain fatty acids (which may benefit skeletal muscle metabolism). Any correlation can be bidirectional.
So, does exercise improve the gut microbiome, does a healthy gut improve exercise performance, or both? The evidence suggests the latter. Improved exercise capacity may be the result of boosted lactate metabolism. Our muscle fibers use lactate as a major fuel source during exercise. Oxidizing tissues use lactate to produce ATP and the remainder is converted to glucose by the liver, which can later be used as a glycolytic substrate for skeletal muscle. The gut microbiota may act as an additional lactate consumer site.
Glycogen storage capacity may be another benefit derived from a healthy gut. SCFAs may improve glucose uptake and glycogen repletion by increasing the expression of GLUT4. SCFAs can also assist with lipid and carb metabolism in the liver and muscle, supporting exercise demands.
So, how do you improve gut health? The easiest way is to eat a lot of whole foods, particularly those with fiber. You want both soluble and insoluble fiber, so keep your food options diverse and limit its processing.