Leucine is one of the building blocks of protein, particularly from animal foods, and it can be consumed through meat, dairy, soy, beans and other protein-rich sources. It's also widely sold as a dietary supplement.

Leucine or L leucine is an essential amino acid, which means the body cannot manufacture it and it must be ingested through dietary protein. Along with other essential amino acids, leucine helps maintain muscle mass -- which has made leucine-containing supplements a favorite of bodybuilders and athletes.

Subscribe to a FREE Supplement Research Update newsletter. Twice a month you will receive an email of several studies on various supplements and natural medicine topics, including amino acid leucine supplement information, and their practical interpretation by Ray Sahelian, M.D.

L Leucine and Muscle Tissue
A diet rich in the amino acid leucine might help prevent the muscle loss that typically comes with aging. French researchers found that a leucine-supplemented diet restored a more youthful pattern of muscle-protein breakdown and synthesis to elderly rats. The older animals had shown a tendency toward excessive protein breakdown before going on the leucine -rich diet, but the amino acid appeared to erase that imbalance. It's well known that after the age of 40 or so, people gradually lose muscle mass, and it's thought that an imbalance in muscle-protein synthesis and breakdown is involved. In younger people, this process is typically in balance. For example, research shows that after a meal, muscle-protein breakdown slows, whereas synthesis ramps up in response to the influx of amino acids from food. But in the new study, older rats did not show this post-meal dip in protein breakdown, whereas their younger counterparts did. A short time on the leucine -supplemented diet, however, restored a youthful pattern of protein breakdown in the elder rats. December, 2005 issue of the Journal of Physiology.

Amino Acid L Leucine questions
Q. Does a leucine supplement help with muscle mass as good as creatine does?
     A. I doubt if a l leucine supplement is as effective as creatine. Creatine is one of the most important supplements for muscle growth that I know of and would far surpass the effectiveness of leucine supplement.

Q. My friend gave me a bottle of leucine powder. What would this be used for?
     A. I don't really know why anyone would need to take a leucine powder supplement since I think all the amino acids are helpful for health and I don't see the need to take a leucine supplement by itself. However, having said this, I realize that there has been a study that a leucine supplement given to older rats was helpful for muscle tissue. But I think creatine or a general protein supplement would be preferable. Bulk leucine.