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Melatonin

Other benefits of melatonin include general neuroprotective effects, as melatonin is a powerful antioxidant

Neuroprotection:  Other benefits of melatonin include general neuroprotective effects, as melatonin is a powerful antioxidant. Melatonin also has several anti-cancer properties, and is currently being investigated for its role in fighting breast cancer.  “Both in vitro studies and in vivo studies have shown that melatonin is a potent scavenger of the highly toxic hydroxyl radical and other oxygen- centered radicals, suggesting that it has actions not mediated by receptors.31 In one study, melatonin seemed to be more effective than other known anti- oxidants (e.g., mannitol, glutathione, and vitamin E) in protecting against oxidative damage. There- fore, melatonin may provide protection against dis- eases that cause degenerative or proliferative changes by shielding macromolecules, particularly DNA, from such injuries. However, these antioxidant effects require concentrations of melatonin that are much higher than peak nighttime serum concentrations. Thus, the antioxidant effects of melatonin in humans probably occur only at pharmacologic concentrations….The decrease in nighttime serum melatonin concentrations that occurs with aging, together with its multiple biologic effects, has led several investigators to suggest that melatonin has a role in aging and age-related diseases. Studies in rats and mice suggest that diminished melatonin secretion may be associated with an acceleration of the aging process. Melatonin may provide protection against aging through attenuation of the effects of cell damage induced by free radicals or through immunoenhancement. However, the age-related reduction in nighttime melatonin secretion could well be a consequence of the aging process rather than its cause, and there are no data supporting an antiaging effect of melatonin in humans.”

A practical approach to circadian rhythm sleep disorders

Light suppresses melatonin while darkness stimulates its synthesis. Many people have trouble falling asleep. Delayed sleep phase syndrome results in late sleep onset, despite normal sleep architecture and total sleep duration. Melatonin has been shown to improve sleep latency (the time it takes to fall asleep) in several randomized controlled studies. Rather than immediately prior to sleeping, melatonin works best when given two hours before sleeping. Melatonin is also useful for jet lag, irregular sleep-wake rhythms, and shift work sleep disorder.  Exogenously administered melatonin has phase shifting properties, and the effect follows a phase- response curve (PRC) that is about 12 h out of phase with the PRC [phase response curve] of light Melatonin administered in the afternoon or early evening will phase advance the circadian rhythm, whereas melatonin administered in the morning will phase delay the circadian rhythm (Fig. 2). The magnitude of phase shifts is time-dependent, and the maximal phase shifts result when melatonin is scheduled around dusk or dawn. The effect of exogenous melatonin is minimal when administered during the night, at least during the first-half of the night.

Melatonin in nonapnea sleep disorders

Nonapnea sleep disorders:  Nonapnea sleep disorder In humans, melatonin secretion increases soon after the onset of darkness, peaks in the middle of the night (between 2 and 4 a.m.), and gradually falls during the second half of the night