French philosopher and scientist
René Descartes declared in the seventeenth century that the pineal
gland was the "seat of the soul." He didn't know the half of it.
The pea-sized gland in the brain produces melatonin, a hormone secreted
most profusely as darkness falls, to help regulate the body's sleep cycle.
If Descartes got on the World Wide Web and visited a melatonin home page
or joined a melatonin discussion group, he'd learn that this hormone is
all the rage. He'd also discover that, because his body appears to produce
less melatonin as he ages, he should take continuous supplemental doses
of this "magic potion," the "melatonin miracle." Melatonin
can not only give him a good night's sleep or reset his biological clock
and fix his jet lag, it may ward off depressive and panic disorders, the
common cold, cancer, even aging. He can pick up a bottle of pills at the
health-food store or from various Web purveyors. His physician might advise
him not to take a neurologically and endocrinologically active substance
manufactured without benefit of regulation, but maybe Descartes has melatonin
madness.
In "Melatonin Madness," an article in the journal Cell,
Steven M. Reppert and David R. Weaver ask, "Is all this excitement
really justified, or is it just hype?" Reppert and Weaver are professor
and associate professor of pediatrics, respectively, based at Massachusetts
General Hospital's Laboratory of Developmental Chronobiology.
"Melatonin does have therapeutic potential," says
Reppert, "but that potential is in the early stages of evaluation.
The oversell has tainted the remarkable research progress made in the past
five years."
"Melatonin administered orally to humans has been used
successfully to treat jet lag and some circadian-based sleep disorders,"
Reppert and Weaver write. Moreover, "there is good scientific evidence"
that melatonin can induce sleep in humans, and a very low-level dose will
do the trick. As to "the claim that the hormone can reverse aging,"
they write, "this assertion is scientifically unfounded and is based
on the results of a seriously flawed study performed in mice.The antioxidant
effect of melatonin has also been embellished, leading to claims that melatonin
is a wonder drug useful for treating everything from AIDS to Alzheimer's
disease." While melatonin does scavenge from the blood stream certain
free radicals that attack cells, these antioxidant effects require melatonin
concentrations a million times greater than any human would produce at any
time. Says Reppert, "The long-term consequences of taking melatonin
in such massive amounts are simply unknown."
