Leucine is a branched-chain amino acid that serves as a building block for new proteins, and is a key signalling chemical for protein synthesis and blood sugar regulation. A study in Nutrition Metabolism, conducted by Columbia University in New York City, found that leucine improved blood sugar control in obese and diabetic mice. The mice were given leucine supplements in their drinking water for 8 months. Leucine stimulates insulin release by the pancreas and promotes the production of the amino acid glutamine, which is important for immune system health. Long-term supplementation of leucine improves the efficiency of insulin metabolism in people with type II diabetes.