Leucine is an amino acid, or chemical unit, used to build proteins. As one of the eight essential amino acids, leucine is not produced by your body and must be obtained through the diet or through supplements. In addition to being involved with protein synthesis, leucine helps maintain nitrogen balance and promotes the repair of bones, skin and muscles. Leucine may also serve as an important ally for dieters; limited clinical studies support its ability to promote fat loss. Consult your doctor before taking leucine.
Features
Although Bodybuilding.com states that leucine only makes up 8 percent of your total amino acid count, it performs a wide range of important functions. Leucine helps preserve lean muscle tissue, lowers elevated blood sugar levels, assists with the production of hemoglobin, and works with the amino acids valine and isoleucine to provide energy for the muscles, especially when engaging in athletic activity. Supplement News states that the U.S. National Academy of Sciences recommends a daily allowance of 16 mg of leucine for every kg of body weight. Supplemental leucine is sometimes used to treat Parkinson's disease, muscular dystrophy and amyotrophic lateral sclerosis.
Dietary Sources
Leucine is found in all foods that contain protein and is particularly abundant in red meat, fish and poultry. A 3 1/2-oz serving of broiled flank steak contains 2.213 g of leucine, while an equivalent size serving of salmon provides 2.067 g. Shrimp, with 1.950 g per 3 1/2-oz serving is also a good source of leucine, as is cooked ham, with 1.661 g per serving. Good vegetarian sources of leucine include soybeans, with 1.355 g per 3 1/2-oz portion, as well as dry roasted peanuts, with 1.535 g. The amounts of leucine in vegetables are more modest; four spears of asparagus contain a mere 0.077 g.
Research
In an article published in 2006 in "The Journal of Nutrition," the authors reported the results of two separate weight loss trials in which obese subjects who consumed protein- and leucine-rich diets lost more body fat and maintained more lean muscle mass than those who followed the U.S. Department of Agriculture Food Guide Pyramid. Those who ate more leucine also maintained more stable blood glucose. The authors concluded that the beneficial effects of a higher protein diet included leucine's role in sparing muscle protein loss and enhancing glycemic control. This approach should be used in treating metabolic syndrome, a chronic condition characterized by elevated blood glucose, elevated triglycerides, low HDL cholesterol, abdominal obesity and high blood pressure.
Supplements
In addition to its medical applications, supplementary leucine is often used by bodybuilders and athletes to increase endurance and speed muscle recovery after workouts. Supplement News recommends taking the amino acids isoleucine and valine in conjunction with leucine, advising 2 mg each of leucine and valine for every milligram of isoleucine. The website cautions that taking high levels of leucine over a prolonged period of time could contribute to a deficiency of niacin -- or vitamin B-3 -- and tryptophan, a condition known as pellagra. Leucine may interact with prescription medications. Consult your doctor before taking leucine.
References
- USDA National Nutrient Database
- Vitamin and Health Supplements Guide; Leucine; Staff, 2006
- Supplement News; Supplement Reviews: Leucine; Staff; 2011
- Bodybuilding.com; Clayton's Health Facts: L-Leucine; Clayton South, S.P.A.; 2011
- "The Journal of Nutrition"; Potential Importance Of Leucine In Treatment Of Obesity And The Metabolic Syndrome; Donald K. Layman and Denise A. Walker; January 2006
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