Growth Hormone Release L-Arginine Muscle Gain

L-Arginine – Mixed results on ergogenic effect, boost GH at rest

L-arginine is a conditionally essential amino acid and it plays an important role in cell division, immune function, the release of hormones and wound healing [1,2]. Arginine is the immediate precursor of nitric oxide (NO), urea, ornithine, and agmatine, it is also necessary for the synthesis of creatine.[1] It is found in red meat, poultry, fish, and dairy products.

L-Arginine as Performance Enhancer

L-arginine is broadly marketed (usually as arginine alphaketoglutarate [AAKG]) in order to promote widening of blood vessels by increasing nitric oxide (NO) production in muscles during exercise, improving strength, power and muscular recovery. However, studies contrast each other [3]. Many studies show no significant results with L-arginine as a performance enhancer [4-8] while some show beneficial effects [9-11].

Two more recent studies [20,21] both reported no effect of L-arginine on exercise performance or recovery in healthy individuals. Furthermore, L-arginine supplementation was unable to increase the effects of exercise on nitric oxide production in runners [22].

L-arginine supplementation only seems to aid in nitric oxide synthesis when a body is in L-arginine deficiency [12].

Effects on Human Growth Hormone

Orally supplemented L-arginine has been shown to cause a significant increment in resting growth hormone levels (by at least 100%) at doses from 5 to 9 grams [14]. A higher dose of 13 grams did not augment growth hormone response, probably due to intestinal distress which prevented absorption of the L-arginine [14]. In contrast to this study, Forbes and Bell [17] reported that neither high nor low dose or orally supplemented L-arginine was able to promote a significant increase in IGF-1, growth hormone, nitric oxide or insulin at rest.

A study measuring 24-hour growth hormone secretion reported no significant differences with two daily doses of 2 g [18]. This may be explained by modulatory effect on growth hormone known as the auto-negative feedback loop.

Both exercise and L-arginine have both been shown to independently augment growth hormone concentrations; however, their combined effect is controversial. The combination of oral arginine and exercise was reported to attenuated the growth hormone spike caused by exercise alone [13,15]. Exercise alone can increase growth hormone levels by 300-500%, while oral L-arginine plus exercise only increased growth hormone levels by around 200% [13]. This diminished response is seen in both younger and older individuals [14]; however, it seems to affect youth more than older persons [15].

In support of these findings, a more recent study by Forbes et al. [19] reported that L-arginine ingested prior resistance training attenuated plasma growth hormone in bodybuilders. Researchers also noted that growth hormone suppression was not due to a growth hormone or IGF-1 induced auto-negative feedback loop.

Possible L-Arginine Side Effects

Low oral doses are well tolerated and clinical side effects are rare in healthy subjects [3]. At high doses (13 grams) arginine was reported to cause considerable gastrointestinal distress [14]. Other side effects may include low blood pressure, diarrhea, abdominal pain,…


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