An essential amino acid -- one of the building blocks of proteins -- arginine makes up part of a healthful diet. Some people take arginine supplements in hopes of increasing muscle mass; however, research is still preliminary, and it conflicts on whether this is actually effective. Certain people should avoid these supplements, so speak with your doctor before taking supplemental arginine.
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People take arginine supplements to increase muscle growth because this amino acid is involved in producing creatine and growth hormone and increasing nitric oxide in the body, according to an article published in the "Journal of the International Society of Sports Nutrition" in 2004. All of these substances may increase muscle growth, hence the potential for increasing muscle growth by taking arginine supplements. However, the authors of this article note that there isn't enough evidence to support using arginine for this purpose.
Animal Study Results
Arginine supplements used in animal studies seem to be a promising way to increase muscle mass. For example, a study published in "Amino Acids" in May 2009 found that supplemental arginine may help increase muscle mass and decrease body fat in pigs. It also helped lower the pigs' triglyceride levels.
Human Study Results
The results from human studies don't look quite as promising as those from animal studies. A study published in February 2012 in "Applied Physiology, Nutrition and Metabolism" found that arginine supplements increased the blood volume in muscles but didn't help make the muscles any stronger. Another study, published in "The Journal of Nutrition" in December 2010, found that these supplements didn't increase either blood flow or the production of new muscle.
While it may sound safe to take arginine supplements because arginine is an amino acid used by your body, this isn't necessarily the case for everyone. Arginine can increase stomach acid production and heartburn and cause an upset stomach. People with liver disease or kidney disease should avoid taking supplemental arginine, as this could lead to elevated potassium levels. This supplement also can interact unpredictably with cholesterol medications and insulin, so people on these medications should also avoid taking arginine supplements.