Arginine is a conditionally essential amino acid. This means that under normal circumstances, the body can synthesize arginine from other substances, but under certain conditions the body cannot keep up with the increased demand for arginine. In the body, arginine serves as raw material for the production of various vital substances. These substances include creatine, urea (the major waste product of protein metabolism), and nitric oxide (NO). The fact that arginine is the direct nutrient precursor for NO has led to its inclusion in various sports supplements touted to boost NO levels in the body. In years past, the major use of arginine for bodybuilding and athletic purposes has been to increase the secretion of human growth hormone (GH). The latter use of arginine is controversial, with some studies showing a definite GH-boosting effect, and others showing none. One reason why some studies show a nil effect of arginine in relation to GH-releasing abilities is that the use of other amino acids, such as the branched-chain amino acids (BCAA), which are popular among bodybuilders, decreases the level of a brain neurotransmitter called serotonin, which plays a role in GH release. In addition, during intense training conditions, the major use of arginine shifts towards catabolic conditions, such as the synthesis of urea from protein degraded during exercise. One way of overcoming the latter problem is through using another amino acid called ornithine, which can take the place of arginine in the urea cycle, thus sparing arginine for other uses, including promoting GH release after training.
A new study again looked at the relationship between supplemental arginine and ornithine and weight-training. The study involved 17 young male athletes, all with at least 5 years of training experience. They were divided into two groups, with one group ingesting arginine (3,000 milligrams) and ornithine (2,200 mgs) twice daily for 3 weeks. The other group received a placebo. Those in the arginine group took the first dose 2 hours after breakfast to prevent interference from other amino acids. This dose was ingested an hour before they trained. The second dose was ingested 2 hours after the last meal, but 30 minutes before bed. Both groups followed the same type of weight-training program for the three week course of the study.
The results showed post-training elevations of GH only in the arginine/ornithine group. The amino acid group also showed increased levels of IGF-1, a product of GH release, along with a lowering of the major binding protein of IGF-1 in the blood. While systemic release of IGF-1 isn't required for building muscle, the local release of IGF-1 in muscle is a vital player in the muscle hypertrophy process. The study authors argue that the increase level of unbound or free IGF-1 released as a result of the arginine/ornithine supplementation probably contributed to an increase of local IGF-1 in the muscle, thereby promoting a true anabolic effect.Arginine is thought to boost GH levels by inhibiting the major break on GH release, somatostatin. Other hormones, such as testosterone and cortisol, weren't affected by the amino acid usage in this study. The study authors suggest that arginine/ornthinine supplements for purposes of boosting GH should be only used short-term, since they body will readily adapt to chronic use, which would mean that the aminos would no longer work in this regard. They also note that ornithine is a precursor for another amino acid called proline. Proline, in turn, is a major amino acid found in the primary structural protein of connective tissue, collagen. This implies that by boosting collagen protein synthesis, ornithine may help prevent injuries and aid healing processes. There is also the NO effect of arginine, but that's another story.
Zajac A, et al. Arginine and ornithine supplementation increases growth hormone and insulin-like growth factor-1 serum levels after heavy-resistance exercise in strength-trained athletes.
J Strength Cond Res 2010: in press.
©,2012 Jerry Brainum. Any reprinting in any type of media, including electronic and foreign is expressly prohibited
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