Melatonin: Therapeutic use

Last modified: Sunday, 31. May 2009 - 5:10 pm

Melatonin may be an effective treatment for several conditions. Studies suggest that it may be helpful in treating sleep disorders, jet lag, and even cancer. However, research on this topic is still very limited and experts have warned consumers that very little is known about the effectiveness or long-term safety of taking melatonin supplements.
Sleep disorders
While the popular press has publicized the usefulness of melatonin as a natural sleeping aid, the results of studies are often contradictory. Some studies suggest that melatonin is helpful in treating insomnia, while others have shown that it is absolutely useless.
Researchers still have not investigated melatonin’s effectiveness in treating insomnia in most age groups. As of 2000, only three studies had investigated the usefulness of melatonin in treating insomnia in people younger than 65 years of age.
While the effectiveness of melatonin in treating sleep disorders in most people remains unclear, research shows that it can be helpful for certain individuals. For example, many blind people have sleep disorders, and melatonin has been shown to help promote sleep in this population. Studies have also shown that it is helpful in treating sleep disorders in disabled children.
Jet lag/shift work
People and animals follow a natural circadian rhythm. Humans and many animals tend to be diurnal. They get up in the morning, are active during the day, and sleep at night. Disruptions in this natural cycle can be difficult. With the advent of air travel, people could travel halfway around the world, passing through several time zones. Their circadian rhythm can be very disrupted by the time differences. Besides having difficulties sleeping at the appropriate time, people with jet lag may also experience constipation and other digestive difficulties.
Shift workers have a similar difficulty in trying to stay awake at a time when they would normally be asleep. Nurses working an evening shift may start to get sleepy while they are still at work, while those on the morning shift may have a great deal of difficulty getting up well before dawn.
Melatonin may be helpful for both shift workers and air travelers trying to adjust to the local time. According to a paper published in 2002, nine out of 10 studies that investigated the effectiveness of melatonin in treating jet lag demonstrated that melatonin did help ease this condition. Individuals who had traveled across five or more time zones and then took melatonin close to the time they wanted to fall asleep were more easily able to make the adjustment to local time. Doses between 0.5 mg and 5 mg were effective, although the larger dose helped a bit more in promoting sleep. Larger doses did not provide any additional benefits. Reviewers suggested that melatonin was more effective when crossing more time zones and for eastbound travelers. The study review also indicated that time-release preparations or taking any form of melatonin earlier in the day was ineffective. Not only was it not helpful, but taking melatonin during the middle of day just made people sleepy and delayed their adjustment to the local time.
While more research is needed, a few studies indicate that melatonin can help people adjust to working the night shift. It can also help people readjust back to sleeping during the night and staying awake during the day when they discontinue working the night shift. In one study of 32 night workers published in 2002, those taking 0.5-3.0 mg of melatonin during the afternoon helped them sleep during the day before leaving for work.
In addition to questions concerning the effectiveness of melatonin for any condition, researchers still do not know enough about the long-term consequences of taking melatonin on a regular basis. Many experts caution that until melatonin has been proven to be safe and not cause serious side effects, using it as a therapeutic agent is too risky.
In the 1970s, researchers noticed that the amount of melatonin found in the blood of certain cancer patients was lower than in healthy individuals. Soon afterwards, other studies showed that the nighttime increase in melatonin, which occurs naturally in most humans, was markedly decreased in some cancer patients.
Experts are not sure how melatonin influences the development of cancer. A recent study published in 1999 in Cancer Research suggests that melatonin may help to starve cancer cells. Tumors use a type of fat called linoleic acid as a food source. Melatonin prevented the tumor cells in rats from being able to metabolize linoleic, but only when it was given to rats during the late afternoon. When it was given to the rats earlier in the day it did not have any effect.
Most of the research investigating the effectiveness of melatonin in treating cancer have been conducted in rats and mice, or in test tube samples of human cells. However, there have been several clinical trials that show that melatonin may be helpful as a therapy for different types of cancer. Again, timing of the dose is very important. Several other studies have shown that melatonin is not effective, or even promotes tumor growth, depending on when during the day it is given.
Other conditions
While melatonin is not currently being used to treat these conditions, research is currently underway investigating its role in preventing Alzheimer’s disease. A study published in Biochemistry in 2001 showed that melatonin can inhibit the development of amyloid beta, a toxic substance that has been linked to the development of Alzheimer’s. Other studies suggest that melatonin may be helpful in reducing the side effects caused by medications that are used to treat schizophrenia.

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