The goal of bodybuilding is clear: gain muscle, lose fat. This can be done by burning the fat off, raising anabolic hormones for hypertrophy of muscle, and preventing muscle breakdown during the stress of dieting. Amazingly, there are studies that support melatonin's ability to promote all these things!
Melatonin, or N-acetyl-5-methoxytryptamine, is a hormone closely related to circadian rhythms and sleep. In studies where melatonin was put in the drinking water of rats, there were reductions in bodyweight and abdominal fat. Perhaps most intriguing about these studies is that melatonin's weight-loss effect was independent of any caloric restriction or exercise. In fact, melatonin may promote the recruitment of brown adipose tissue and raise basal metabolic rate through thermogenesis. Active brown adipose tissue has been identified in humans. However, extrapolating this data to human obesity has yet to be proven in any clinical trials.
Melatonin has been shown to have profound effects on the IGF-1 axis, thus it is intimately involved in muscle anabolism. One study by Oner et al. demonstrated fascinating results by comparing supplementation of melatonin to supplementation of testosterone in castrated rats. Castrating rats, similar to what happens in the New York Mafia, induces muscle atrophy by loss of the anabolic effect of testosterone produced by the testicle. In their study, the scientists found that melatonin or testosterone supplementation increased soleus (calf) muscle weight and fiber diameter while castration alone decreased these.The researchers noted that there was a strong IGF-1 presence within the treated muscles compared to the castrated without treatment group.This study concluded that melatonin is as effective as testosterone in the prevention of atrophy induced by castration through action on the IGF-1 axis. Furthermore, in a study in 2007, Willoughby and colleagues at Baylor University, showed that single 5-milligram dose of melatonin could affect the GH/IGF-1 axis.
Melatonin is also a versatile antioxidant. It is a hormone that can easily cross cell membranes including the very selective blood-brain barrier. Melatonin is a strong scavenger reactive oxygen species. Unlike many other antioxidants, melatonin does not recycle itself after performing its scavenging (redox cycling). Redox cycling is a catch-22 in that it may allow for other antioxidants (such as vitamin C) to act as pro-oxidants, counterintuitively promoting free radical production. Interestingly, once melatonin is oxidized it cannot be reduced to its former state. Thus, it can be referred to as a suicidal antioxidant.
If that wasn't enough, melatonin also has a role as an anti-inflammatory. In a recent 2011 study, Singh et al. were looking at inflammation of the esophagus due to acid reflux and melatonin was able to reduce tissue injury when given prior to induction of the esophagitis. The authors found a direct correlation to COX-2 inhibition by melatonin supplementation (albeit at high doses).
So what we know about melatonin is that it can protect against muscle atrophy, increase anabolic hormone production, protect tissues from inflammatory damage and stimulate fat loss... is this an ideal scenario for bodybuilders? Much of this data needs further substantiation in human randomized placebo-controlled studies, but is nonetheless interesting to us bodybuilding scientists out there. ?
By Victor R. Prisk, M.D.
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