Family doctor

Overview:

• Melatonin is a hormone which is believed to help people go to sleep
• When taken as a drug it has a fast but mild sleep-inducing effect
• The drug melatonin has been shown to help with sleep in the elderly, shift workers and those with jet lag, however no large studies have been undertaken
• A 5 mg dose of melatonin is recommended for sleep disorders
• The long term safety of using melatonin has not been established

What is it?

Melatonin is a hormone of the pineal gland which is used to help people sleep. Melatonin is normally made at night and is considered to act as a signal of darkness to the body.

Melatonin appears to play a part in the sleep-wake rhythms among all life forms that have been studied. When taken by humans it has a fast, mild, sleep-inducing effect. It lowers alertness and body temperature during three hours after it has been taken.

Studies have shown it is able to shift people's body clock, depending on the time it is taken, so it has a role in helping shift workers and treating jet lag.

A study published in the British Medical Journal in 1989 found that melatonin could help restore normal sleeping patterns in weary travallers. The study of 20 people travelling to and from New Zealand and Britain found those taking 5 mgs of melatonin before, during and after the flights, returned to normal sleeping habits in just under three days compared to more than four days for those without treatment.

An improvement in sleep during the daylight and staying alert at night has been shown in two small studies of simulated night shift work.

One study of 20 men found melatonin decreased the time it takes to go to sleep, and increased the duration of sleep.

Melatonin has also been found to improve sleeping patterns among blind people and the elderly however, no large studies have been reported.

There is also controversy over the long-term use of melatonin because there have been no studies to prove its safety.

There have been claims that melatonin has anti-aging properties, can improve sexual dysfunction, cure AIDS, and Alzheimer's disease, but there is no evidence to support this.

Melatonin has been claimed to have antioxidant properties and to prevent the growth of cancer cells. However, it has been shown to promote melanoma in laboratory hamsters.

A study is currently being carried out into whether it is a useful combination with chemotherapy. It has also been investigated as a contraceptive at large doses (75-300 mg daily), and combined with a progestin mini pill. Side effects included abnormal bleeding and headache.

How is it taken?

Changing your body clock by the use of melatonin requires knowledge of your natural sleeping patterns. This is assessed by your normal time of going to sleep and the duration of sleep.

There has been no agreement on doses but studies so far suggest the use of 5 mgs of melatonin taken orally is better than lower doses for correcting sleep disorders.

The main side effect reported is a feeling of sleepiness after taking melatonin.

Other points

While melatonin supplements can be obtained without a prescription in other countries. In New Zealand and Britain it has been made a prescription medicine and must be prescribed by a doctor.

The safety of the long-term use of melatonin has yet to be established so care should be taken with regular use of melatonin. The effects of melatonin on pubescent teenagers, breastfeeding mothers, pregnant women and fetuses, are also unknown.