I took it once, got palpitations, never took it again. Please keep in mind that this is not a vitamin or mineral, it is a hormone. Hormones are compounds that cause/start reactions in the body. Taking a hormone is Hormone Replacement Therapy, which can lead to problems like the body making less to compensate, since the body is always trying to establish balance.

But taking it every now and again due to changing time zones and getting one's circadian rhythm off seems to be okay.

Here's a document on it, not very illuminating but people have only been supplementing Melatonin for less than a decade, so there's no way to know at this point what long-term ramifcations are.

Supplement Melatonin

Description Melatonin is a hormone produce by the pineal gland in the brain. It is synthesized from the amino acid tryptophan. Melatonin levels are lowest during midday and production peaks at night. In some animals, melatonin is necessary for regulation of light/dark cycle behavior like sleeping/waking, sexual maturation and waking. In humans, melatonin appears to have an inhibitory effect of early maturation.

Claims Promotes sleep
Reduced symptoms of jet-lag
Slows the aging process
Increases sex hormone secretion
Acts as an antioxidant


Theory In animals, melatonin seems to help regulate seasonal behaviors (mating, molting, hibernation), which are related to daily light/dark cycles. In humans, melatonin helps regulate our "internal clock". The onset of darkness results in an increased production of melatonin in the brain, while the light of morning tells the brain to stop producing melatonin. Melatonin levels are 10 times higher at night than during the day.

Scientific Support Melatonin supplementation has been shown to lower core body temperature, produce acute hypnotic effects and induce the onset of sleep in a variety of subjects including military pilots, jet-lagged travelers, elderly patients and individuals with delayed sleep disorder. Melatonin has also shown some benefit in helping to reset the biological clock of shift workers who tend to have peak melatonin levels during the day

As an antioxidant, melatonin has shown benefits in protecting cells against oxidative stress by scavenging hydroxyl radicals and preventing oxidative damage to DNA, lipids and cellular proteins. Melatonin is also thought to play a role in the regulation of human menstrual cycle, as evidenced by the finding that women with hypothalamic amenorrhea have melatonin levels 3X higher than normal. High-dose melatonin supplements have been used pharmacologically in studies to suppress ovulation for birth control purposes.



Safety The interactions of melatonin with other supplements or drugs is unknown, but some studies suggest that melatonin can induce or deepen Depression in susceptible individuals. Melatonin supplements may also be dangerous for people with cardiovascular risks, due to the possibility of vasoconstriction and increased blood pressure. The National Institutes of Health has warned about possible dangers of melatonin supplementation, including infertility, reduced sex drive in males, hypothermia, retinal damage and interference with hormone replacement therapy. Information regarding the long-term effects of melatonin supplements is unavailable.

Value Relatively inexpensive and non-addictive alternative to over the counter chemical sleep aids. Particularly useful as a short-term regulator of sleep/wake cycles in cases such as getting your body clock back on schedule after crossing several time zones (jet lag).

Dosage Studies of melatonin as a sleep aid or for relief of symptoms associated with let-lag have shown 1-10mg to be effective, depending on the degree of sleep disturbance. High dose melatonin supplements (~50mg) may disrupt female fertility and menstrual patterns and should be avoided except under the supervision of a reproductive physician.