Leucine is one of eight essential amino acids that must be obtained through the diet. Amino acids are found in a variety of foods and needed for proper growth and function of muscle tissue. Consult a health care provider before using any dietary supplements.
Identification
Leucine is considered one of three branched chain amino acids. Leucine, isoleucine and valine posses a unique branched-chain structure and therefore referred to as branched chain amino acids, according to The Biology Project at University of Arizona. Leucine is found in highest concentrations within muscle protein and the liver, reports The Journal of Nutrition.
Sources
Leucine can be found in various food sources such as soybeans, lentils, almonds and peanuts. Other dietary sources of the amino acid include eggs and dairy products. Animal products such as pork, beef and fish are also great food sources. Leucine can also be found in a variety of dietary supplements such as whey protein, soy protein and amino acid powders.
Muscle Synthesis
A review titled "The Role of Leucine in the Regulation of Protein Metabolism" in The Journal of Nutrition reported that leucine at a high dose can promote muscle anabolism. The results of the review showed that leucine enhances insulin sensitivity and induced muscle protein synthesis. Proteins are the building blocks of muscle tissue, therefore the the synthesis of muscle protein is the process of muscle growth, recovery and maintenance. Leucine was also reported to suppress protein breakdown within the muscle, or muscle catabolism. Leucine's physiological role in muscle synthesis has lead many researchers to study its effectiveness in sepsis patients or athletes but more research is needed before any recommendations can be made.
Exercise and Performance
A study titled "Leucine Supplementation and Intensive Training" in the Journal of Sports Medicine reported that leucine supplementation may be beneficial for athletes. A branched chain amino acid mixture containing 30 to 33 percent leucine was shown to improve mental and physical performance among athletes when taken before or during training. The leucine formula was also reported to spare muscle glycogen levels during exercise. Leucine supplementation was also shown to inhibit the decrease of leucine levels within skeletal muscle among strength athletes, according to the study in the Journal of Sports Medicine. A decrease of serum leucine levels in muscle is normally associated with high-intensity aerobic, anaerobic and strength exercises. The researchers concluded that further leucine supplementation research is still needed.
Protein Balance
Leucine's role in promoting protein synthesis and limiting protein degradation results in a positive net protein balance within the body. Individuals cycle from positive to negative protein balance depending on current food consumption, reports Jacob Wilson, researcher in the Department of Nutrition, Food, and Exercise Science at Florida State University. For example, fasting conditions bring forth a negative protein balance that results in a state of protein breakdown. Jacob Wilson recommends consuming a leucine-rich meal at every meal for exercise enthusiasts who wish to be at a positive protein balance.
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