Melatonin has gained in popularity as a sleep aid, especially for lessening the effects of jet lag. Unfortunately, the long-term effects of this naturally-occurring amino acid are unknown for humans, and many doctors warn against its continual use. However, initial research using lower mammals has promise for long-term human consumption. It is highly recommended to discuss the use of melatonin with a health care provider, especially because melatonin is not regulated by the FDA and commercial supplements may differ in regards to quality and purity.
Safety Uncertain
Melatonin is a safe, non-toxic supplement in the short-term, reports the National Institutes of Health, but human trials are few and far between for its long-term administration. Animal research indicates that the long-term use of melatonin is safe for rats and gerbils, although these findings are considered preliminary, according to a 1995 study published in the journal "Neuroreport." Bottom line: melatonin should not be used as a dietary supplement for long periods of time until more information is known about its long-term effects.
May Effect Organ Health
Because melatonin performs many regulatory functions for the body, including maintaining core temperatures and effecting hormonal levels, many doctors discourage the long-term use of melatonin. Animal research offers yet another clue. A 1995 study published in the "Indian Journal of Experimental Biology" determined that long-term use of melatonin in the Indian desert gerbil significantly increased the weight of the gerbil's adrenal gland, in particular the adrenal medulla. No ill effects were reported for the functioning of this organ, however.
No Reproductive Effects
One potential danger for melatonin is its effect on the reproductive system, given some initial research with animals suggesting it may decrease testosterone. However, a 2000 study published in the journal "Human Reproduction" found no ill-effects on the reproductive system for men who were treated with daily melatonin supplements for a month. The researchers warn that at higher doses, or at longer periods of times, men's sexual health may be compromised.
Desensitization as Sleep Aid
Lastly, the sleep-helping effect of melatonin may decrease with continual use as a dietary supplement. This is probably due to desensitization of the melatonin receptors in the brain, according to a 2004 study published in the journal "Biochemical Pharmacology." For sleep disorders that have symptoms lasting over a month, patients should consult a medical care provider.
References
- National Institutes of Health: Melatonin
- "Neuroreport": Effects of Long-term Administration of Melatonin and a Putative Antagonist on the Ageing Rat
- "Human Reproduction": Long-term Melatonin Administration Does Not Alter Pituitary-gonadal Hormone Secretion in Normal Men
- "Biochemical Pharmacology": Melatonin-mediated Regulation of Human MT(1) Melatonin Receptors Expressed in Mammalian Cells
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