Athletes know the importance of growth hormone (GH) for building muscle and shedding fat. While virtually every athlete I know takes supplements, most don’t realize that some supplements can actually blunt the GH response to exercise.
Melatonin (N-acetyl-5-methoxytryptamine), is a naturally occurring hormone that’s important for a number of biological functions and the regulation of the circadian rhythms. Supplementation with melatonin before sleep is a popular of strategy for boosting ‘youth’ hormones such as GH.
One recent study investigated the effects of heavy resistance training with the oral daytime ingestion of melatonin on some physiological responses such as testosterone and growth hormone (GH) release.
In a randomized and double-blind controlled manner 10 healthy male subjects undertook a whole body workout (3 sets of various exercises at 80% of their 1 rep max) on two occasions, after receiving either melatonin (6 mg) or placebo (6 mg) before each workout.
Blood samples were taken at several time points during the trials. Performance measures were completed (such as max jump height and 1 RM tests) in the days before and after the workouts.
The results were quite surprising.
Results showed there were no differences in the GH and testosterone concentrations at any time points between the groups but the area under the curve for GH during and after training was significantly lower after treatment with melatonin.
The findings suggest that supplementing with melatonin (6 mg) during the daytime before heavy resistance exercise may slightly decrease GH concentrations. Additionally, melatonin didn’t provide any performance-enhancing effect (the auto negative increase in max jump height or 1RM strength).
The message here is that if you use melatonin, don’t take it before a workout, not if you want an optimum GH response from your efforts.
A lot of bodybuilders still swallow free-form arginine to spike blood GH concentrations.
This information perpetuated on the back of intravenous studies done on the 1980’s that showed large doses of this amino acid (in free form) injected into the blood stream, promoted an increase in circulating GH.
One recent study investigated the combined effect of resistance training exercise and high dose free-form arginine supplementation on spontaneous GH release.
Eight healthy male subjects were studied randomly on four separate occasions (placebo; arginine 7 grams; placebo + exercise; arginine 7 grams + exercise). Subjects had blood sampled every 10 min for 3 and a half hours after a workout (3 sets of various exercises at 80% of their 1 rep max).
Results showed that the training produced a nice spike in GH after the workouts. Additionally, the dose of arginine without training also increased GH, but this was not as high as the GH-induced response to training.
Based on those two results you’d think that taking arginine before the workout would result in a double whammy – it didn’t. The combined effect of arginine before exercise didn’t provide as high a response that exercise alone did. The scientists suggest auto negative feedback loop possibly causes a refractory period such that when the two stimuli are presented there will be suppression of the GH somatotrope.
The take home message here is – don’t expect a GH boost from taking arginine before resistance training.
Alternately, if you are after a research-proven GH booster, I highly recommend GABA.
Taking GABA in the presence or absence of exercise is shown to provide a consistent, reliable increase in GH release.
References:
1. Effects of resistance exercise session after oral ingestion of melatonin on physiological and performance responses of adult men. Eur J Appl Physiol. 96:729-39, 2006.
2. Oral arginine attenuates the growth hormone response to resistance exercise. J Appl Physiol. 101:848-52, 2006.
