There has been a lot of recent interest in arginine supplementation because it is the precursor to nitric oxide, which is a potent dilator of blood vessels. Thus, arginine may help vessels get bigger and lead to better blood flow to tissues like muscle. There has been some concern whether ingestion of arginine is absorbed and has any real biological effects. A study published in the Journal of Nutritional Biochemistry clearly indicates the answer is yes. Twelve subjects were provided with increasing doses of arginine for periods of one week. The doses were 3 g, 9 g, 21 g, and 30 g/day (divided into 3 doses per day). Blood arginine levels were significantly increased with 9 g/day and there was no further increase with 21 g/day. With the highest dose (30 g/day), there were quite a few minor side effects (dry mouth, nausea, etc.). The subjects showed quite a bit of variability in their response to the different doses but the results show that very high doses (>9 g/day) are not needed to increase blood arginine levels. This is good news because it means that relatively low doses of arginine can be ingested and still result in optimal absorption into the blood to have potentially favorable biological effects on blood vessel functioning.

Evans RW, Fernstrom JD, Thompson J, Morris SM Jr, Kuller LH. Biochemical responses of healthy subjects during dietary supplementation with L-arginine. J Nutr Biochem. 2004 Sep;15(9):534-9.