Melatonin helps us to wind down:it reduces our energy expenditure, and causes our temperature and blood pressure to drop. The pineal gland in our brain produces 12 times more sleep hormone at night than during the daytime.

There are also supplements that contain a milligram of melatonin or more, including tablets, teas and sprays. All forms boast the same promise: to help you fall asleep quickly and get better quality sleep. But is that true? Melatonin can help people who have difficulties falling and staying asleep. But for people suffering from insomnia with physiological causes, such as breathing or movement disorders, melatonin is unlikely to help.

There are lots of products on the market, but many of them aren't subject to regulation — the purity and effectiveness are not always certified. A manufacturer can say that its product helps you to sleep without any scientific proof. And melatonin products only help you to fall asleep — they don't guarantee better sleep.

What are the side effects?

Whether supplemented or produced naturally, melatonin is broken down by our bodies within an hour. That's why so many of the sleep products don't help. But there are slow-release capsules. These have the highest dose of melatonin and release it gradually to keep a steady level throughout the night.

Melatonin is mainly prescribed to people over 55 when natural hormone production decreases, or if stress or other medications are causing sleep problems. But caution is advised. It's better to start off with a small dose. It's also not a good idea to keep taking more tablets if you wake up in the night. In the worst case it can throw the entire sleep-wake cycle off.

Just because melatonin is produced naturally by the body, it doesn't mean it's free of side effects. Doctors advise not to use melatonin for more than three months without medical consultation. There are concerns that long-term use may cause damage to the liver and kidneys.