Discover the Function, Sources and Benefits of the Health Supplement Ingredient L-Leucine or 2-Amino-4-Methylpentanoic Acid
Leucine – also known as L-leucine and by its scientific name, 2-amino-4-methylpentanoic acid – is a branched-chain amino acid (BCAA). Because the human body cannot synthesize this essential amino acid, it must be obtained from food sources such as meat, dairy products and legumes. L-leucine is also available in natural dietary supplements, including health and bodybuilding supplements such as Ana-GH, DBol-GH, Cut and Ripped Plus, Amino Shooter and Chocolate Whey Protein.
Functions of L-Leucine
Branched-chain amino acids like L-leucine stimulate protein synthesis by triggering pancreatic islet cells to release insulin. This protein synthesis primarily takes place in skeletal muscle, but also occurs to a lesser extent in the liver and adipose (fat) tissue. It is believed that L-leucine may help prevent or reduce muscle damage, enhance anabolic muscle signaling, lower blood-glucose levels and avoid faulty message transmission in the brain cells of people with certain diseases. It may also decrease serotonin production by blocking tryptophan transport to the brain, thereby reducing feelings of drowsiness and fatigue.
Sources of L-Leucine
According to the United States Department of Agriculture (USDA), common dietary sources of L-leucine include beef, pork, fish, chicken, turkey, eggs, cheese and milk. Legumes are another good source – particularly beans, soy and peanuts – as are nuts and seeds (such as almonds and sunflower seeds) and grains (like wheat germ, oats, corn and rice). L-leucine may also be consumed directly as part of a natural dietary supplement.
Leucine Benefits and Uses
Because of L-leucine’s role in protein synthesis, it is often used in health and bodybuilding supplements that are designed to build muscle strength, increase exercise endurance, reduce muscle breakdown and promote muscle recovery. Its ability to inhibit serotonin production means that L-leucine may help prevent or delay fatigue during exercise. L-leucine has also been shown to stimulate the appetite – making it useful for athletes looking to gain mass and weight.
In addition, L-leucine appears to benefit individuals with specific medical conditions. For example, it may help to lower blood-glucose levels in diabetics, and it can improve the health and nutrition of patients experiencing loss of appetite due to hemodialysis, cancer treatments or anorexia. L-leucine has also been shown to diminish symptoms in manic patients, reduce involuntary movements in individuals with tardive dyskinesia, and improve muscle control and brain function in patients with advanced liver disease, including various forms of hepatic encephalopathy.
Side Effects of L-Leucine and Potential Interactions
L-leucine is generally considered safe when taken in normal doses, such as those found in food and most dietary supplements. However, excessive amounts can result in hypoglycemia or vitamin B3 and B6 deficiencies. Users are advised to adhere to supplement dosing information and avoid consuming more than 39 grams of L-leucine per day.
Few L-leucine side effects have been recorded, though some users have reported experiencing fatigue or decreased motor coordination. Individuals with certain medical conditions – including amyotrophic lateral sclerosis (ALS, or Lou Gehrig's disease), isovaleric acidemia, branched-chain ketoaciduria (maple syrup urine disease) and chronic alcoholism – should avoid L-leucine, as it can pose health risks in these patients. In terms of L-leucine interactions, it appears to decrease the effectiveness of levodopa. Conversely, it can have an additive effect when taken with diabetes medication, potentially resulting in hypoglycemia. Other medications – such as Diazoxide and corticosteroids – can decrease the effects of L-leucine on protein, while thyroid hormone medication can cause the body to break down L-leucine more slowly.
More detailed safety information on L-leucine side effects and interactions can be found on WebMD. As with any medication or health supplement, it is best to consult your physician before taking dietary supplements containing L-leucine.
L-Leucine Research and Studies
Scientists have researched L-leucine and other BCAAs to determine their benefits and practical uses, and numerous studies have indicated a positive effect on muscle strength, exercise endurance and muscle recovery. An article published in the European Journal of Applied Physiology reported that outrigger canoeists using leucine supplements displayed significantly improved endurance performance and upper-body power. In Applied Physiology, Nutrition, and Metabolism, researchers noted that well-trained male cyclists who took a leucine-protein supplement after intense training subsequently exhibited improved high-intensity endurance performance and lower perceived levels of tiredness. And according to the Journal of Sports Science & Medicine, resistance-trained males who consumed an energy drink with leucine (and other key ingredients) prior to their workout demonstrated a significant increase in the number of repetitions successfully performed.
Other studies examined the impact of L-leucine on protein synthesis. Research findings published in The American Journal of Clinical Nutrition indicated that increasing the concentration of leucine in an essential amino acid supplement consumed during steady-state exercise resulted in a greater muscle protein synthesis response during recovery. And in The Journal of Nutrition, researchers determined that insulin and leucine work in synergy, allowing skeletal muscles to coordinate protein synthesis with physiological state and dietary intake.
For additional research related to L-leucine, refer to the PubMed site sponsored by the National Institutes of Health (NIH).
HGH.com Supplements With L-Leucine
Athletes, bodybuilders and fitness enthusiasts who wish to leverage the positive effects of L-leucine can find this essential amino acid in a variety of natural health and bodybuilding supplements from HGH.com:
Ana-GH – Each serving of Ana-GH contains 1.5 grams of L-leucine, which is blended with other branched-chain amino acids and active ingredients. This supplement is designed to jumpstart bulking cycles by promoting weight and mass gains while improving protein synthesis and contributing to joint and muscle repair.
Cut and Ripped Plus – Created to support cutting cycles and contest prep, Cut and Ripped Plus combines L-leucine with other active ingredients to help build muscle, increase strength and burn fat for a competition-ready physique. The capsules also help to boost energy and stamina, minimize pain, promote faster recovery and raise human growth hormone (HGH) levels.
DBol-GH – The proprietary blend of ingredients in DBol-GH includes L-leucine, which helps users to achieve lean mass and muscle growth, and also aids in muscle recovery. DBol-GH’s active ingredients are designed to stack and work together, delivering visible results and increasing HGH production.
Amino Shooter and Creatine Energy – Formulated to mix easily with cold water, Amino Shooter is used during intense workouts to protect and grow muscle. A single serving contains 3 grams of L-leucine, which supports protein synthesis and reduces muscle degradation.
Multi-Pro Chocolate Whey Protein – Each scoop of Multi-Pro Chocolate Whey provides 24 grams of protein and includes 2.16 grams of L-leucine. Fortified with vitamins and minerals, it provides a complete protein supplement for those looking to gain muscle and lose body fat.
References (Function, Sources, Benefits/Uses and Side Effects/Interactions):
Bruno, Gene. “A Primer on Branched Chain Amino Acids”; Smart Supplementation, published by Huntington College of Health Sciences; 2009. <http://www.hchs.edu/literature/BCAA.pdf>
Deuster, Patricia; Maier, Steven; et al. “Protein and Amino Acids Products – Branched Chain Amino Acids: Leucine, Isoleucine, Valine”; Dietary Supplements and Military Divers: A Synopsis for Undersea Medical Officers, published by Uniformed Services University of the Health Sciences; January 2004. <http://hprc-online.org/dietary-supplements/files/DietarySupplementUMO.pdf>
Memorial Sloan Kettering Cancer Center. “Leucine”; published under “About Herbs, Botanicals & Other Products” within Integrative Medicine area of website; last updated February 21, 2013. <http://www.mskcc.org/cancer-care/herb/leucine>
USDA Agricultural Research Service. “Leucine” search results in the National Nutrient Database for Standard Reference; accessed July 30, 2014. <http://ndb.nal.usda.gov/ndb/nutrients/index>
WebMD and Natural Medicines Comprehensive Database. “Branched Chain Amino Acids”; published under “Vitamins & Supplements”; accessed July 30, 2014. <http://www.webmd.com/vitamins-supplements/ingredientmono-1005-BRANCHED-CHAIN+AMINO+ACIDS.aspx?activeIngredientId=1005&activeIngredientName=BRANCHED-CHAIN+AMINO+ACIDS>
Crowe, Melissa J.; Weatherson, Jarrad N.; and Bowden, Bruce F. “Effects of Dietary Leucine Supplementation on Exercise Performance”; European Journal of Applied Physiology; August 2006. <http://www.ncbi.nlm.nih.gov/pubmed/16265600>
Gonzalez, Adam M.; Walsh, Allyson L.; et al. “Effect of a Pre-Workout Energy Supplement on Acute Multi-Joint Resistance Exercise”; Journal of Sports Science & Medicine; June 2011. <http://www.ncbi.nlm.nih.gov/pubmed/24149870>
Norton, Layne E. and Layman, Donald K. “Branched-Chain Amino Acids in Exercise: Leucine Regulates Translation Initiation of Protein Synthesis in Skeletal Muscle after Exercise”; The Journal of Nutrition; February 2006. <http://www.ncbi.nlm.nih.gov/pubmed/16424142>
Pasiakos, Stefan M.; McClung, Holly L.; et al. “Leucine-Enriched Essential Amino Acid Supplementation During Moderate Steady State Exercise Enhances Postexercise Muscle Protein Synthesis”; The American Journal of Clinical Nutrition; September 2011. <http://www.ncbi.nlm.nih.gov/pubmed/21775557>
Thomson, Jasmine S.; Ali, Ajmol; and Rowlands, David S. “Leucine-Protein Supplemented Recovery Feeding Enhances Subsequent Cycling Performance in Well-Trained Men”; Applied Physiology, Nutrition, and Metabolism; April 2011. <http://www.ncbi.nlm.nih.gov/pubmed/21609286>