From Ergo Log
A few years ago the EU banned supplements containing more than 0.3 mg melatonin. European regular melatonin users didn't need to lose any sleep over this, according to the man who discovered melatonin. His research suggests that the optimal melatonin dose is... 0.3 mg.
Richard Wurtman discovered in the 1950s that rats whose pineal gland had been removed developed sleep problems. He then worked out that this was because the pineal gland normally secretes melatonin before you go to sleep. Melatonin prepares the brain for sleep.
Melatonin is a simple compound which is produced in the body as a result of conversion of the amino acid L-tryptophan. Small quantities of melatonin are found in cherries, kiwis, tomatoes and bananas. If you consume small amounts of melatonin at the time when you usually fall asleep, the pineal reacts by producing extra melatonin itself. It needs to be dark for this to happen, as light inhibits the synthesis of melatonin.
In the 1990s Wurtman published a study in which he had given subjects a melatonin supplement at 9 o'clock in the evening, 2-4 hours before they went to sleep. On one occasion the supplement contained 0.3 mg melatonin, on the other it contained 1.0 mg. On another occasion Wurtman gave his subjects a placebo.
Melatonin reduced the amount of time the subjects needed to fall asleep once they'd gone to bed, as the figure below shows. The 0.3-mg dose worked best.
After ingesting this miniscule dose of melatonin the amount of melatonin in the blood of the subjects rose spectacularly. The bulk of the amount in the bloodstream probably came from the pineal gland.
The next day the researchers assessed how the subjects were feeling and tested their reaction speed. They discovered that the optimal dose of 0.3 mg did not make the subjects feel dopey, lethargic or sleepy.
Sleep. 1996 Jun;19(5):423-31.