Melatonin is a hormone that is released from the pineal gland. It reaches its peak at night to help maintain tissues in a youthful state of health. Secretion of melatonin declines significantly with age, as the pineal gland becomes calcified. It is naturally formed from the amino acid tryptophan. Melatonin production is inhibited by light and permitted by darkness. For this reason, it is known as the “hormone of darkness”. The level is the highest in the middle of the night and gradually decreases during the remainder of the night. When used several hours before sleep, the compound shifts the circadian clock earlier, thus promoting earlier sleep onset and morning awakening. The FDA classifies it as a dietary supplement because it is a natural substance.
Melatonin is commonly used for:
- Jet lag
- Delayed sleep phase disorders
- Shiftwork disorders
- Sleep enhancement
- Aggression and separation anxiety in dog
Oral melatonin often contains three to ten times the amount needed to produce physiologic nocturnal blood melatonin levels for a more rapid sleep onset. Studies suggest that smaller doses (for example 0.3 mg as opposed to 3 mg) are just as effective. It has also been shown that large doses of melatonin can even be counterproductive.
Melatonin appears to cause very few side-effects in the short term, up to three months, when healthy people take it at low doses. Studies have shown that there is evidence that melatonin is safe with short term use.
Some unwanted effects in some people, especially at high doses (~3 mg/day or more) may include: headaches, nausea, next-day grogginess or irritability, hormone fluctuations, vivid dreams or nightmares, and reduced blood flow.
Melatonin can cause drowsiness, and, therefore, caution should be shown when driving, operating machinery, etc.