Arginine and citrulline are both amino acids. The former is a conditionally essential amino acid you may need to obtain from your diet, while the latter is a nonessential amino acid your body can synthesize from other nutrients. These amino acids are interrelated in that they both contribute to the production of nitric oxide in your body --- an important chemical for heart health.
Sports Supplementation
L-arginine and citrulline are popular supplements in the sport of bodybuilding as well as other athletics. Manufacturers claim that these supplements are both capable of increasing your serum level of arginine. Based upon very little scientific evidence, these manufacturers claim that an increase in arginine will result in more blood flow to your muscles, thus delivering more oxygen and nutrients for muscle growth and performance.
Nitric Oxide Production
University of California professor Louis Ignarro received the Nobel Peace Prize in Medicine for his groundbreaking research on nitric oxide's effect in the human body. He notes that when nitric oxide contacts the cells in your arteries, it relaxes them and allows more blood to flow through the artery. While your body will absorb arginine and citrulline well, they are unlikely to increase the amount of nitric oxide in your body if you are healthy and already have normal nitric oxide production. This means that arginine and citrulline supplements probably do very little for an athlete.
Cardiovascular Health
Arginine and citrulline may not have an effect on your body when you are healthy, but they can be useful in boosting nitric oxide production if you have a condition that inhibits it, such as atherosclerosis. A 2005 study appearing in the journal "PNAS" examined the use of L-arginine, L-citrulline and antioxidant supplements in rabbits with atherosclerosis. After 12 weeks of taking the supplements orally, the rabbits had markedly increased blood flow and a reduction of lesions in their arteries.
Supplemental Doses
Both arginine and citrulline are amino acids that you consume on a daily basis from the proteins in your diet, so they are at least somewhat safe to consume on a regular basis. However, there is not a significant body of research clearly outlining what a safe or effective dose of either amino acid would be. Citrulline doses tend to be between 6 and 18 g daily, while arginine supplements is safe up to doses of 12 g per day. Speak to your physician before taking supplemental amino acids to ensure they will not produce any negative side effects.
References
- University of Arizona: Arginine
- New York University Langone Medical Center: Citrulline
- Huntington College of Health Sciences; Nitric Oxide Boosters; Gene Bruno, M.H.S.; 2009
- California State University; Evaluating Popular Sports Supplement; Ellen Coleman, M.A., M.P.H., R.D., C.S.S.D.; 2008
- "PNAS"; L-Citrulline and L-Arginine Supplementation Retards the Progression of High-Cholesterol-Diet-Induced Atherosclerosis in Rabbits; Toshio Hayashi, et al.; September 2005
- University of Southern California; How Nitric Oxide Maintains Health; Athan Bezaitis; February 2009
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