USARIEM Scientists search for microscopic influencers of performance in the gut

Trillions of microbes in complex communities lie deep within our digestive systems. Despite being unable to be seen by the naked eye, we can feel and benefit from their influence constantly.

This is the gut microbiome, which impacts how people respond to diet, the environment and stress. From the brain to the respiratory tract and even down to the bone, the gut microbiome can influence the health and performance of Warfighters.

So, when Warfighters are traveling to austere environments, they may react differently based on the diversity within their individual gut microbiome. For example, a Warfighter may experience varying levels of leaky gut—a condition where waste products go into the bloodstream due to the gut’s weak intestinal walls—or acute mountain sickness—the body experiences distress when adjusting to higher altitudes—based on the types of microbes in their gut.

“What we eat shapes the gut microbiome. We know nutrition can improve health, and we know nutrition can improve performance and cognition, but not everyone responds the same way when exposed to the same diet or the same environment,” said Philip Karl, Ph.D., a Nutrition Physiologist in the Military Nutrition Division at the U.S. Army Research Institute of Environmental Medicine. “We want to know if individuality in the gut microbiome is one reason for that variability and whether we can manipulate that individuality and the diverse functions of the gut microbiome using nutrition.”

Karl and a team of researchers at USARIEM have been exploring how the gut microbiome may impact how Warfighters respond to military stressors such as physically and cognitively demanding training and environmental extremes like high-altitude. The goal is to use that information to develop nutrition interventions that improve performance within those environments.

“We know that certain microbes produce specific compounds that can impact health and possibly performance during military-relevant stressors,” Karl said. “If we can devise nutritional strategies to target those microbes to produce more or less of those compounds, then we may have an exciting and new way to improve Warfighter performance.”

Nutritional strategies that Karl and his team have considered derive from foods that many people already consume in their diets, but typically in low amounts such as probiotics—live beneficial microbes generally consumed in foods like yogurt—and prebiotics—compounds found in many plant foods or added to foods that feed beneficial microbes living in the gut. Prebiotics can be metabolized into health promoting compounds by resident microbes, whereas probiotics can produce some of those same compounds.

“What’s exciting here is that the genetic capacity of the gut microbiome far exceeds the genetic capacity of the human body,” said Karl. “This means that these microbes living in us give the human body numerous functions that the human body does not have. For example, humans cannot digest fiber. We rely on the bacteria in our gut to do the digesting for us. A byproduct of that relationship is the bacteria transform the fiber we cannot digest into a bunch of different healthy compounds that our bodies can use. It’s a win-win situation: we nourish the microbiota, and they nourish us.”

In previous studies, including one conducted at the High Altitude Research Laboratory at Pikes Peak, Colorado, Karl and his team showed an increase in gut leakiness at high altitude. More recently, the team used USARIEMs hypobaric chambers and created a nutrition bar—composed of prebiotics derived from fibers, cranberries, blueberries, cocoa, green tea leaves—with the DOD Combat Feeding Directorate to show that nourishing the gut microbiota with a combination of different prebiotics can help reduce the severity of gut leakiness in Soldiers exposed to high altitude.

“We hoped that the nutrition bar we developed would target beneficial microbes and help protect the gut from damage during environmental stress,” said Karl. “This is an exciting area of research that may help us develop new performance-optimizing nutrition interventions that leverage the diverse capabilities of our friendly resident gut microbes,” said Karl.

Ongoing research by Karl’s team is testing different types of prebiotics and probiotics for benefits on cognitive and physical performance. A long-term goal is to develop personalized nutrition interventions based on a Warfighter’s unique gut microbiome.

“We are always working to find new ways to help our Soldiers improve their performance and readiness,” Karl said.

USARIEM is a subordinate command of the U.S. Army Medical Research and Development Command under the Army Futures Command. USARIEM is internationally recognized as the DOD’s premier laboratory for Warfighter health and performance research and focuses on environmental medicine, physiology, physical and cognitive performance, and nutrition research. Located at the Natick Soldier Systems Center in Natick, Massachusetts, USARIEM’s mission is to provide solutions to optimize Warfighter health and performance through biomedical research.