Research suggests that drinking a leucine-enriched protein drink whist taking part in endurance exercise may boost muscle synthesis by up to a third. A team of researchers from the US Army Research Institute of Environmental Medicine, Tufts University, and Louisiana State University System gave 8 volunteers 10 grams of a protein drink containing either 1.87 grams or 3.5 grams of leucine during a cycling test. Results showed that consumption of the drink enriched with 3.5 grams of leucine was associated with a 33% increase in muscle synthesis, compared with consumption of the drink enriched with 1.87 grams of leucine. “These data indicate that increasing leucine availability during steady state exercise promotes skeletal muscle protein anabolism and spares endogenous protein,” wrote the authors. “Our findings indicate that increasing the leucine content of protein supplements provided for those populations susceptible to muscle loss, including proteolytic conditions – such as cachexia, sarcopenia, and calorie deprivation – may warrant further exploration.”