What is Melatonin?
Melatonin is a hormone that helps regulate sleep. It also appears to influence other hormones in the body. Melatonin supplements have become popular as natural sleep aids.
The amount of melatonin we produce is determined by how dark or light our surroundings are. Our eyes have specialized light-sensitive receptors that relay this message to a cluster of nerves in the brain called the suprachiasmatic nucleus, or SCN. The SCN sets our internal biological clock, also called our circadian rhythm, which regulates a variety of body functions including sleep.
Melatonin is made from an amino acid called tryptophan. When our surroundings are dark, the SCN tells the pineal gland to produce melatonin, which is thought to trigger sleep. Some melatonin is also made in the stomach and intestines.
Melatonin levels were originally thought to decline with age. Early reports said that a person's melatonin levels peaked at age 20 and gradually decreased to 20% at age 80. This theory was used to explain why many older people have sleep difficulties. Melatonin supplements became marketed as a "youth hormone," contributing to its rise in popularity. Recent evidence, however, suggests that melatonin levels don't actually decline with age.
Health Benefits of Melatonin
Melatonin supplements are popular as natural sleep aids for the following sleep disorders:
1) Jet Lag
Travel across time zones disrupts the circadian rhythm. Evidence suggests that melatonin supplements can decrease jet-lag symptoms, particularly in people traveling eastward and/or crossing five or more time zones. Melatonin has been found to lessen the time it takes to fall asleep, reduce daytime tiredness, and boost alertness during the day.
The best results occur when melatonin supplements are started on the day of travel and taken at the desired bedtime at the destination. It is usually taken for several days. Melatonin doesn't work for everyone: Evidence suggests that approximately half of the people who take melatonin notice an improvement.
2) Shift Work
Although night shift work also disrupts the circadian rhythm, the evidence that melatonin can improve sleep after night shift work is less solid. It also hasn't been found to improve alertness during shift work. More research is necessary.
3) Insomnia in Older Adults
A number of studies have found that melatonin supplements taken between half an hour and two hours prior to the desired bedtime can shorten the time it takes older adults to fall asleep. It isn't clear, however, whether melatonin can help people stay asleep.
4) General Sleep Improvement
Melatonin appears to lessen the time it takes to fall asleep, promote sleepiness, and lengthen sleep time when taken by healthy people. Most studies have been small and short in duration, so more research is needed.
5) Delayed Sleep Phase Syndrome
Delayed sleep phase syndrome is a circadian rhythm disorder. People have trouble falling asleep until late at night and then have difficulty waking in the morning. Melatonin may help establish a regular sleep-wake cycle.
6) Sleep Problems in Children with Neuro-Psychiatric Disorders
There have been a number of well-designed studies and case reports on the use of melatonin in children with neuro-psychiatric disorders that result in sleep difficulties, such as autism, psychiatric disorders, visual impairment, or epilepsy. The studies conducted so far suggest that melatonin can shorten the time to fall asleep and lengthen sleep duration.
Although the evidence is unclear, melatonin has been studied for the following conditions:
- Withdrawal From Benzodiazepine Medications
- Sleep Problems due to Specific Conditions
- Electromagnetic Field Exposure
Melatonin has been studied for cancer, primarily using lab animals and human cells in test tubes. Although results have been promising, there isn't enough evidence to determine whether melatonin is safe or effective, and whether or not it might decrease the effectiveness of cancer therapies.
See my other articles on natural approaches to cancer.
There is some evidence that melatonin may help ease the withdrawal symptoms in people who are decreasing their use of benzodiazepine drugs, often used for sleep disorders and anxiety.
Preliminary evidence suggests that melatonin may improve sleep for people with specific conditions such as Alzheimer's disease, Parkinson's disease, bipolar disorder, attention deficit hyperactivity disorder (ADHD), and diabetes.
There is a theory that low-frequency electromagnetic fields (such as those in household appliances) may disrupt melatonin levels. Overall, studies with humans haven't supported this theory.
Melatonin Side Effects and Safety Concerns
Melatonin is generally considered safe when used short-term and within the recommended dosages. There is no research on the long-term effects of melatonin supplements, particularly in higher doses.
Some experts consider the doses commonly found in melatonin supplements, 3 to 5 milligrams, to be far too high and say that amounts in the range of 0.1 to 0.5 milligrams are more reasonable.
Melatonin side effects may include drowsiness, dizziness, confusion, headache, irritability, vivid dreams, and a temporary reduction in attention and balance. People shouldn't drive or use machinery for several hours after taking melatonin. Melatonin may cause abdominal cramps, nausea, and vomiting, lower blood pressure, and rarely, hallucinations or paranoia.
Melatonin may increase the risk of blood clotting, so it should not be used by people using warfarin (Coumadin), other medications that influence blood clotting, or by people with clotting disorders.