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Melatonin Research: Benefits and Side Effects
Produced by the pineal gland, melatonin is a remarkable hormone that works not only as a sleeping aid, but is a potent antioxidant, immune booster and guardian of our aging clock, says Dr. Geraldine Mitton in her Anti-Ageing Handbook. “It is produced in the dark while you sleep. If you get up during the night and put on a bright light, melatonin production stops immediately.”
Low melatonin levels are associated with premature aging. We know that seven hours’ sleep a night in a darkened room is anti-aging, whereas insomnia or lack of sleep is aging, says Dr. Mitton.
Melatonin as a Supplement
The Harvard Health Letter calls melatonin a natural sleeping pill that shifts the body clock into the desired direction. When taken between three and six p.m., melatonin tricks the body into thinking that dusk comes sooner so people become sleepy earlier, helping insomniacs fall asleep at 10 or 11 p.m. instead of tossing and turning all night.
Some studies support melatonin's reputation as a sleep aid. In one study, conducted by Dr. Richard J. Wurtman, professor of neuroscience at Massachusetts Institute of Technology, 20 young men with no sleep disorders were given various doses of melatonin or placebo, placed in a dark room at midday, and told to close their eyes for 30 minutes. The men on the placebo took 25 minutes to fall asleep, whereas those on melatonin took five or six minutes. In another study by this institute (2001), 30 people over age 50 took 0.3 milligrams of melatonin before bed for one week. The supplement restored normal sleep in those with insomnia.
In a double-blind, placebo-controlled, crossover study of 12 melatonin-deficient elderly subjects who complained of long-term insomnia, 2 milligrams of controlled-release melatonin, taken two hours before bedtime, improved sleep efficiency (sleep time as a percentage of time in bed) and decreased nocturnal awakenings. Melatonin was not found to decrease sleep latency or to increase total sleep time (time actually spent asleep).
A recent study from New Zealand found that 5 milligrams did not improve sleep quality in 20 older people with age-related sleep problems.
Leaving on a Jet Plane?
There's a good chance melatonin can ease jet lag by speeding the resynchronization of the body's time clock. A review of nine well-controlled studies concluded that nightly doses of 0.5 to 5 milligrams of melatonin reduced symptoms in air travelers crossing five or more time zones, especially eastward.
A landmark experiment by Professor Walter Pierpaoli in 1990 showed that when young mice and old mice surgically swapped pineal glands, the older mice looked and acted young and the young mice rapidly showed signs of advanced age. Another experiment by Pierpaoli involving melatonin supplements extended the lifespan of mice by 20 percent.
Rats do not necessarily react to hormones the way humans do. Therefore there's no proof melatonin can make you look younger or live longer. For example, melatonin signals rodents to become more active at night — just the opposite effect it has on humans. So when old rats dosed with melatonin live longer or their coats regain their youthful shine, that does not mean your life will be extended or your skin will become suppler if you take melatonin supplements.
Others claims include that the hormone melatonin can reduce cancer, high blood pressure, Alzheimer's disease, AIDS, coronary heart disease as well improve sexual vitality.
Separating melatonin myth from fact isn't easy. Consider the claim that melatonin improves sexual vitality. If melatonin has an effect on sex, it is probably more akin to that of a cold shower, says Cheryl Craft, head of the department of cell and neurobiology at the University of Southern California School of Medicine. Large doses are being tested in Europe as a contraceptive because the hormone acts to stop ovulation. And in her studies, it shrank hamsters' testicles.
Dr. Charles Czeisler warns that studies have yet to show if the supplements are safe. Cheryl Craft and other investigators are worried about hype, since the hormone could hurt rather than help. An animal study, for instance, showed that melatonin can narrow blood vessels in the heart and lungs, especially when there is underlying heart disease or asthma. If that turns out to be true for humans, older people particularly could be at high risk.
In general, the opinion of the scientific community can be summarized in the recent statement of the European Pineal Society: “Administration of melatonin is useful, when correctly timed, in certain types of human circadian rhythm disorder leading to sleep problems. There is insufficient scientific evidence for any other therapeutic uses in humans as yet. There is no information on possible harmful long-term side effects. Melatonin may be dangerous if incorrectly timed, and should not be taken without medical supervision.”
Doctors warn that people with kidney or liver disease shouldn't take melatonin; neither should those with a history of stroke, depression, or a neurological disorder. Women who wish to become pregnant should also avoid the use of melatonin.
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