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L-Arginine
Amino Acid
Used in VitalityMatrix to inhibit Somatostatin release. It is also a precursor for the production of L-proline, essential in collagen and cartilage. Arginine is a precursor for Nitric Oxide synthase, important to avoid erectile dysfunction.
Growth Horm IGF Res. 2005 Apr;15(2):136-9. Epub 2005 Jan 26. Links
Growth hormone responses to varying doses of oral arginine (VitalityMatrix).
Collier SR, Casey DP, Kanaley JA.
Department of Exercise Science, Syracuse University, 820 Comstock Avenue, Room 201, Syracuse, NY 13244, USA.
Intravenous (IV) arginine invokes an increase in growth hormone (GH) concentrations, however, little is known about the impact of oral arginine ingestion on the GH response.
OBJECTIVE: The purpose of this study was to determine the dose of oral arginine that elicits an optimal GH response and to determine the time course of the response.
DESIGN: Eight healthy males (18-33 years - 24.8+/-1.2 years) were studied on 4 separate occasions. Following an overnight fast at 0700 h, a catheter was placed in a forearm vein. Blood samples were taken every 10 min for 5 h. Thirty minutes after sampling was initiated, the subject ingested a dose of arginine (5, 9 or 13 g) or placebo (randomly assigned).
RESULTS: Mean resting GH values for the placebo, 5, 9 and 13 g day were 0.76, 0.67, 2.0 and 0.79 microg/L (n=6), respectively. Integrated area under the curve was not different with 13 g (197.8+/-65.7 min microg/L), yet it increased with 5 and 9 g compared with the placebo (301.5+/-74.6, 524.28+/-82.9 and 186.04+/-47.8 min microg/L, respectively, P<0.05). Mean peak GH levels were 2.9+/-0.69, 3.9+/-0.85, 6.4+/-1.3 and 4.73+/-1.27 microg/L on each day for the placebo, 5, 9 and 13 g days.
CONCLUSION: In conclusion, 5 and 9 g of oral arginine caused a significant GH response. A 13 g dose of arginine resulted in considerable gastrointestinal distress in most subjects without augmentation in the GH response. The rise in GH concentration started approximately 30 min after ingestion and peaked approximately 60 min post ingestion.
Growth hormone, arginine and exercise.
Curr Opin Clin Nutr Metab Care. 2008 Jan;11(1):50-4. links
Kanaley JA.
Department of Exercise Science, Syracuse University, Syracuse, New York, USA. jakanale@syr.edu
PURPOSE OF REVIEW: To describe the effect of an acute bout of exercise on growth hormone responses and to discuss the effect of L-arginine supplementation on growth hormone responses.
RECENT FINDINGS: Recent studies have shown that resting growth hormone responses increase with oral ingestion of L-arginine and the dose range is 5-9 g of arginine. Within this range there is a dose-dependent increase and higher doses are not well tolerated. Most studies using oral arginine have shown that arginine alone increases the resting growth hormone levels at least 100%, while exercise can increase growth hormone levels by 300-500%. The combination of oral arginine plus exercise attenuates the growth hormone response, however, and only increases growth hormone levels by around 200% compared to resting levels.
SUMMARY: Exercise is a very potent stimulator of growth hormone release and there is considerable research documenting the dramatic growth hormone rise. At rest oral L-arginine ingestion will enhance the growth hormone response and the combination of arginine plus exercise increases growth hormone, but this increase may be less than seen with exercise alone. This diminished response is seen in both in both younger and older individuals.
Effects of L-arginine supplementation on exercise metabolism.
Curr Opin Clin Nutr Metab Care. 2007 Jan;10(1):46-51. Links
McConell GK.
Department of Physiology, The University of Melbourne, Parkville, Victoria, Australia. mcconell@unimelb.edu.au
PURPOSE OF REVIEW: To describe the influence of acute and chronic administration of L-arginine on metabolism at rest and during exercise.
RECENT FINDINGS: There has been substantial examination of the effect of infusion and ingestion of L-arginine at rest. It has been clearly demonstrated that L-arginine administration improves endothelial function in various disease states. In addition, L-arginine infusion at rest increases plasma insulin, growth hormone, glucagon, catecholamines and prolactin. Such hormonal changes affect metabolism. There has, however, been very little examination of the effect of increases in L-arginine availability during exercise. This is important to study as there is preliminary evidence that L-arginine infusion, probably via increases in nitric oxide (NO), alters skeletal-muscle metabolism during exercise. There is a need for further research, especially to understand the mechanisms of how L-arginine affects exercise metabolism and also to determine whether the hormonal responses that occur in response to L-arginine at rest are also present to some extent during exercise.
SUMMARY: This line of research may have important therapeutic implications as there are indications that L-arginine augments the effects of exercise training on insulin sensitivity and capillary growth in muscles.
PMID: 17143054 [PubMed - indexed for MEDLINE]
Oral arginine attenuates the growth hormone response to resistance exercise.
J Appl Physiol. 2006 Sep;101(3):848-52. Epub 2006 Jun 1. Links
Collier SR, Collins E, Kanaley JA.
Dept. of Exercise Science, Syracuse University, Syracuse, NY 13244, USA.
This study investigated the combined effect of resistance exercise and arginine ingestion on spontaneous growth hormone (GH) release. Eight healthy male subjects were studied randomly on four separate occasions [placebo, arginine (Arg), placebo + exercise (Ex), arginine + exercise (Arg+Ex)]. Subjects had blood sampled every 10 min for 3.5 h. After baseline sampling (30 min), subjects ingested a 7-g dose of arginine or placebo (blinded, randomly assigned). On the exercise days, the subject performed 3 sets of 9 exercises, 10 repetitions at 80% one repetition maximum. Resting GH concentrations were similar on each study day. Integrated GH area under the curve was significantly higher on the Ex day (508.7 +/- 169.6 min.ng/ml; P < 0.05) than on any of the other study days. Arg+Ex (260.5 +/- 76.8 min.ng/ml) resulted in a greater response than the placebo day but not significantly greater than the Arg day. The GH half-life and half duration were not influenced by the stimulus administered. The GH secretory burst mass was larger, but not significantly, on the Arg, Ex, and Arg+Ex day than the placebo day. Endogenous GH production rate (Ex > Arg+Ex > Arg > placebo) was greater on the Ex and Arg+Ex day than on the placebo day (P < 0.05) but there were no differences between the Ex and Arg+Ex day. Oral arginine alone (7 g) stimulated GH release, but a greater GH response was seen with exercise alone. The combined effect of arginine before exercise attenuates the GH response. Autonegative feedback possibly causes a refractory period such that when the two stimuli are presented there will be suppression of the somatotrope.
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