Bodybuilders know the importance of growth hormone (GH) for building muscle and shedding fat. While virtually every bodybuilder 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 strategy for boosting 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 (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.
Alternately, if you are after a research-proven GH booster, I recommend GABA.
Taking GABA in the presence or absence of exercise is shown to provide a consistent, reliable increase in GH release.
Reference: 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.